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2020 Vol. 19 No. 6 Previous Issue    Next Issue

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Special Focus: Physiology and interaction of insects with environmental factors
Crop Science
Horticulture
Animal Science · Veterinary Medicine


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Green peach aphid Myzus persicae is a widely distributed agricultural pest causing great economic loss of Rosaceae plants and vegetables by ingesting plant sap for nutrition and transmitting viral diseases. The asexual production with high reproductive capacity can promote the aphid outbreak. Cover photo shows the principle feeding sites of M. persicae on radish seedlings, including the young stems (left) and blade surface (right), which was provided by Prof. LI Hu from China Agricultural University. See pages 1447–1457 for more details.


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Special Focus: Physiology and interaction of insects with environmental factors

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Editorial- Physiology and interaction of insects with environmental factors FENG Qi-li 2020, 19(6): 1411-1416.  DOI: 10.1016/S2095-3119(20)63200-2 Abstract ( )   PDF in ScienceDirect   Annual loss of crop yields due to agricultural insect pests are approximately 10%.  Effective and safe management of insect pests would reduce the loss of crop production.  Insects live in an environment where they need to deal with biological and non-biological factors that impact their physiological and developmental activities to survive and expand their population.  These environmental factors include, but not limited to, phytochemicals in the host plants they feed on, toxic compounds, such as insecticides sprayed by human, parasitoid, microbes, temperature and drought stress.  In the long-term evolution, insects have developed sophisticated strategies to adapt the harmful factors against them.  For example, to feed on different host plants, insects develop effective and comprehensive olfactory and gustatory receptor systems and detoxification enzyme systems to deal with the secondary toxic phytochemicals.  These olfactory and gustatory receptor and detoxification enzyme systems contain multiple superfamilies of proteins and enzymes, such as cytochrome P450s, glutathione S-transferases (GSTs) and esterases, together to form multiple preventive and protection barriers along with the regulation and function of the endocrine systems, which synthesize and secrete hormones and neuropeptides circulating to the different target tissues and organs to guarantee the normal growth and development.  On the other hand, insects also adjust their feeding behaviors and metabolism pathways, as well as even the nutrient components in the host plants by changing the expression patterns of related genes to promote the nutrient intake and utilization.  Insects and their host plants ultimately establish a cooperative and antagonistic relationship during evolution.  Insect development is coordinated by various hormones and neuropeptides.  The steroid hormone 20-hydroxyecdysone (20E) activates molting and metamorphosis, while juvenile hormone (JH) maintains larval status (Riddiford 1996; Riddiford et al. 2003).  These two hormones are the most critical hormones that regulate and balance the processes of growth, development and maturation of insects depending on their titers.  They often counteract each other in most of physiological events, but sometimes they also cooperate to regulate some activities, such as reproductive maturation.  20E and JH also involve in insect behavior, for example, feeding behavior, in which high level of 20E suppresses feeding, whereas high level of JH enhances feeding.  Insulin, along with JH, promotes larval growth by feeding more food and 20E opposes insulin and JH functions to initiate metamorphosis (Pan et al. 2018).  These three signal transduction pathways work together to maintain the growth and development on the right track.  Any interference on the intermediate steps in these pathways may result in arrest of the insect growth and development.  Neuropeptides are a group of small protein molecules, usually synthesized and secreted from nervous systems to cells of the target tissues and organs, where they bind specific membrane receptors, for example, the G-protein-coupled receptors and initiate second-message cascades and then the distinct molecular responses.  It has been found that insect neuropeptides play crucial roles in feeding behavior, growth regulation, locomotor activity and sleep, ethanol sensitivity, learning and memory, aggression, courtship and reproduction, phase switch, osmotic and metabolic stress and hormone release (Nässel and Wegener 2011). . . .

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Progress in understanding hormonal regulation during the post-embryonic development of Helicoverpa armigera ZHAO Xiao-fan 2020, 19(6): 1417-1428.  DOI: 10.1016/S2095-3119(19)62860-1 Abstract ( )   PDF in ScienceDirect   Lepidoptera, with 0.16 million species, is the second largest order of insecta.  This order includes silk worms, butterflies, and many agricultural pests.  The cotton bollworm, Helicoverpa armigera (Hübner) is one of the pests in Lepidoptera that seriously harms cotton plant and other crops in China and other countries.  This pest develops resistance to chemical insecticides rapidly.  Bacillus thuringiensis (Bt) transgenic cotton plants are developed to control H. armigera population in the field.  However, during the past years, the rapid evolution of Bt toxin resistance is observed in H. armigera in transgenic cotton fields.  New approaches for the development of new environmentally friendly insecticides to control H. armigera have become necessary, and the molecular mechanisms underlying the development and physiological processes of this species need to be further understood.  Considerable progress in the study of H. armigera development and physiology has been achieved in the last decade.  This mini-review summarizes the main findings on the molecular mechanisms of hormonal regulation of the development of H. armigera to present new target genes for developing new approaches to control the pest.

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Structure and function of neuropeptide F in insects CUI Hong-ying, ZHAO Zhang-wu 2020, 19(6): 1429-1438.  DOI: 10.1016/S2095-3119(19)62804-2 Abstract ( )   PDF in ScienceDirect   Insect neuropeptides are a group of brain neuro-regulatory factors, which plays very important roles in growth and development, molting and metamorphosis, as well as mating and reproduction.  The neuropeptide F (NPF), a multi-functional neuropeptide, is one of neuropeptides identified in numerous insect species, which plays important roles in feeding, metabolism, courtship, reproduction, aggression, ethanol sensitivity, locomotor circadian rhythms, learning and stress responses.  These roles of NPF are implemented through NPF receptors (NPFR).  The NPFR1, a G protein-coupled receptor with 7 transmembrane domains, is one of these receptors and is found to be important for NPF regulation.  The NPF usually is consisted of around 36–40 amino acid residues, but the short neuropeptide F (sNPF) consisted of 7–16 amino acid residues have also been found in some insects.  In this review, the structure and function of both NPF and sNPF in insects are discussed.

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BmApontic is involved in neurodevelopment in the silkworm Bombyx mori MENG Miao, YU Qi, WANG Qin, LIU Chun, LIU Zhao-yang, REN Chun-jiu, CUI Wei-zheng, LIU Qing-xin 2020, 19(6): 1439-1446.  DOI: 10.1016/S2095-3119(19)62787-5 Abstract ( )   PDF in ScienceDirect   The nervous system of the silkworm is vital for the development of organisms.  It achieves and maintains normal life activities by regulating the function of the organs and all kinds of physiological processes in the silkworm.  BmApontic (BmApt), as an important bZIP transcription factor, is required for the formation of pigmentation in the silkworm.  However, the function of BmApt in the development of the nervous system of the silkworm remains unclear.  Here, we showed that amino acid sequence of BmApt was evolutionarily conserved in its Myb/SANT motif and basic DNA binding domain.  BmApt was expressed in the nervous system at the embryonic stage.  Knockdown of Bmapt by RNA interference resulted in abnormal development of axons.  Moreover, the expression of BmnetrinA, BmnetrinB and Bmfrazzled was decreased in the Bmapt knockdown embryos.  These results demonstrate that BmApt controls neurodevelopment by activating the expression of Bmnetrin and Bmfrazzled.

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Reproductive polyphenism and its advantages in aphids: Switching between sexual and asexual reproduction YAN Shuo, WANG Wan-xing, SHEN Jie 2020, 19(6): 1447-1457.  DOI: 10.1016/S2095-3119(19)62767-X Abstract ( )   PDF in ScienceDirect   Reproductive polyphenism, which allows one genotype to produce sexual and asexual morphs, is an extreme case of phenotypic plasticity and is commonly observed in aphids.  Aphids are typical species that switch these reproductive modes, and the pathway orientation is triggered by the environmental conditions (mainly photoperiod and temperature).  The typical annual life of aphids includes a succession of parthenogenetic generations during the spring and summer and a single sexual generation in autumn.  In this review, we describe how the environmental cues orientate the reproductive mode of aphids from photoperiodic perception to endocrine regulation, and how juvenile hormones may act on the target cells (oocytes) to initiate the gametogenesis and embryogenesis in sexual and asexual reproduction.  We also discuss the paradox of sex, especially the advantages of sexual reproduction in aphids.  With the recent development of genomic resources in aphids, many potential genes involved in the reproductive polyphenism will enter the public’s awareness.  In particular, we describe a novel RNAi method in aphids, which may provide a molecular technique for determining the developmental fate and multiple reproductive strategies.

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Morphological traits for sex identification of the oriental armyworm, Mythimna separata (Lepidoptera: Noctuidae) CHEN Lin, PAN Qin-jian, Muhammad Saad WAQAS, LIU Tong-xian 2020, 19(6): 1458-1463.  DOI: 10.1016/S2095-3119(19)62862-5 Abstract ( )   PDF in ScienceDirect   The oriental armyworm, Mythimna separata (Lepidoptera: Noctuidae) is a harmful pest which causes heavy loss in agricultural crops.  Sex identification of M. separata is very important for understanding the biology and management of this pest.  Development of fast and convenient methods to identify M. separata female and male is the necessary prerequisite for conducting gender-related studies.  In this study, new methods to differentiate sex of M. separata at pupal and adult stages were investigated.  Our results showed that posterior abdominal segments containing genital organs which are morphological traits to differentiate female and male.  Genital openings are important characters for the female and male pupae differentiation.  For female pupa, it locates on the ventral side of eighth and ninth abdominal segments and appears as a visible longitudinal suture; for male pupa, it locates on the ventral side of the ninth abdominal segment and appears as a short slit surrounded by a pair of visible semicircular lumps.  Bristle numbers are another indicator for sex differentiation of adults.  Each female has three-bristled frenulum and each male has one bristled-frenulum near the base of hind wing of each side of moth body.  We confirmed the two sex differentiation methods manually by dissecting genitalia of adults and found their genger was as same as what we examined the sex of pupae and adults using the morphological methods.

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Physiology and defense responses of wheat to the infestation of different cereal aphids LIU Fang-hua, KANG Zhi-wei, TAN Xiao-ling, FAN Yong-liang, TIAN Hong-gang, LIU Tong-xian 2020, 19(6): 1464-1474.  DOI: 10.1016/S2095-3119(19)62786-3 Abstract ( )   PDF in ScienceDirect   Cereal aphids are major insect pests of wheat, which cause significant damages to wheat production.  Previous studies mainly focused on the resistance of different wheat varieties to one specific aphid species.  However, reports on the physiology and defense responses of wheat to different cereal aphids are basically lacking.  In this work, we studied the feeding behavior of three cereal aphids: the grain aphid, Sitobion avenae (Fabricius), the greenbugs, Schizaphis graminum (Rondani), and the bird cherry-oat aphid, Rhopalosiphum padi (Linnaeus) on winter wheat, and the physiology and defense responses of wheat to the infestation of these cereal aphids with focus on how these cereal aphids utilize divergent strategies to optimize their nutrition requirement from wheat leaves.  Our results indicated that S. graminum and R. padi were better adapted to penetrating phloem tissue and to collect more nutrition than S. avenae.  The harm on wheat physiology committed by S. graminum and R. padi was severer than that by S. avenae, through reducing chlorophyll concentration and interfering metabolism genes.  Furthermore, cereal aphids manipulated the plant nutrition metabolism by increasing the relative concentration of major amino acids and percentage of essential amino acids.  In addition, different cereal aphids triggered specific defense response in wheat.  All of these results suggested that different cereal aphids utilize divergent strategies to change the physiological and defense responses of their host plants in order to optimize their nutrition absorption and requirement.  These findings not only extend our current knowledge on the insect–plant interactions but also provide useful clues to develop novel biotechnological strategies for enhancing the resistance and tolerance of crop plants against phloem-feeding insects.

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Feeding effects of dsNPF interference in Ostrinia furnacalis CUI Hong-ying, WANG Yuan, PENG Xin, WANG Yi-tong, ZHAO Zhang-wu 2020, 19(6): 1475-1481.  DOI: 10.1016/S2095-3119(19)62788-7 Abstract ( )   PDF in ScienceDirect   The corn borer is a world-wide agricultural pest.  In this study, a high-efficiency RNAi method was explored to knock down the neuropeptide F (NPF) to determine if NPF regulates larval feeding in the Asian corn borer, Ostrinia furnacalis.  Results showed that the expression peaks of npf mRNA in both midgut and fat body are at 28 h of early 5th instar larvae.  When NPF was knocked down either by feeding dsNPF-containing artificial diet or direct dsNPF injection into the 5th instar larvae, npf expression was effectively inhibited in the midgut.  Larval feeding, body weight and development time were significantly impacted.  In contrast, the expression of the npf receptors npfr1 and npfr2 in fat body of 5th instar larvae was significantly increased by dsNPF injection.  These results indicate that NPF can be effectively knocked down in O. furnacalis, and dsNPF by injection is an effective and fast way to silence npf expression.  This study provides a critical basis for further exploration in mechanism of feeding regulation in O. furnacalis.

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Proboscipedia and Sex combs reduced are essential for embryonic labial palpus specification in Bombyx mori ZHANG Ru, ZHANG Zhong-jie, YU Ye, HUANG Yong-ping, QIAN Ai-rong, TAN An-jiang 2020, 19(6): 1482-1491.  DOI: 10.1016/S2095-3119(19)62785-1 Abstract ( )   PDF in ScienceDirect   Hox genes of proboscipedia (pb) and Sex combs reduced (Scr) and their cofactors are required for determination of insect mouthpart identity and play important roles in insect organ morphogenesis.  However, in the lepidopteran insects, including many agricultural and forest pests, the roles of these genes in determination of mouthpart morphogenesis are unclear.  Here we report that both BmPB (Gene ID: 101740380) and BmSCR (Gene ID: 692761) are essential for labial palpus specification in a lepidopteran model insect, the silkworm, Bombyx mori.  During embryonic morphogenesis, CRISPR/Cas9-mediated mutagenesis of BmPB induced transformation of labial palpus into thoracic leg and BmSCR mutation transformed labial palpus into maxilla.  Mutagenesis of Hox-related cofactor extradenticle (BmEXD; Gene ID: 692478) and its nuclear localization factor homothorax (BmHTH; Gene ID: 576938425) also induced distortion of embryonic labial palpus.  Furthermore, mutagenesis of each of the four genes induced severe degeneration of spigot morphogenesis, an important part of spinneret structure.  Quantitative real-time PCR analysis further revealed that the transcriptional interaction among these genes.  Our data thus provide novel evidence for Hox gene regulation of insect embryonic patterning.

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Expression, regulation and binding affinity of fatty acid-binding protein 2 in Spodoptera litura WEN Liang, GAO Gui-ping, HUANG Zhi-qiang, ZHENG Si-chun, FENG Qi-li, LIU Lin 2020, 19(6): 1492-1500.  DOI: 10.1016/S2095-3119(20)63167-7 Abstract ( )   PDF in ScienceDirect   Fatty acid-binding proteins (FABPs) are a family of lipid chaperones, which contribute to systemic metabolic regulation through diverse lipid signalings.  In this study, a midgut-specific FABP gene (Slfabp2) was cloned from Spodoptera litura.  RT-PCR and Western blot analysis indicated that RNA and protein levels of SlFABP2 gradually increased and reached a peak at the prepupal stage and maintained a high level during the pupal stage.  The expression of SlFABP2 protein was induced by starvation treatment.  In vitro binding assay revealed that the recombinant SlFABP2 had high affinities of binding long-chain fatty acids, such as palmitic acid, arachidonate and oleic acid.  The results suggest that SlFABP2 may have a unique function that transports intracellular fatty acids and can regulate the metabolism of lipids in metamorphosis.  This work provides experimental clues for understanding the potential function of SlFABP2 in fatty acid metabolism in S. litura.

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Comparative analysis of the ecological fitness and transcriptome between two genotypes of the brown planthopper Nilaparvata lugens LIU Kai, CHEN Zhan, SU Qin, YUE Lei, CHEN Wei-wen, ZHANG Wen-qing 2020, 19(6): 1501-1511.  DOI: 10.1016/S2095-3119(19)62768-1 Abstract ( )   PDF in ScienceDirect   Insect quantity is an important index for determining the degree of damage to plants.  The brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most important rice pests in Asia.  Here, we used two genotypes of BPH, a high-fecundity genotype (HFG) and a low-fecundity genotype (LFG), to measure their ecological fitness and to explore possible causes for genotype differentiation by transcriptome sequencing.  Our results showed that there were significant differences in body weight, egg hatching rate and honeydew secretion between the HFG and LFG, particularly, the number of eggs laid per female was more significant.  Transcriptional analysis showed that a total of 1 966 differentially expressed genes (DEGs) were mainly involved in energy metabolism, carbohydrate and lipid synthesis, insect hormone synthesis and fecundity-related pathways.  Moreover, we found that the phosphorylation levels of AMPK, AKT and FoxO and the synthesis of ecdysone were different between the two genotypes of BPH.  These findings may partially explain the difference in the ecological fitness between HFG and LFG.  This study is the first to compare the differences between two genotypes of BPH and to provide transcriptomic evidence to further understand the fecundity of BPH.

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Characteristics and roles of cytochrome b5 in cytochrome P450-mediated oxidative reactions in Locusta migratoria LIU Jiao, ZHANG Xue-yao, WU Hai-hua, MA Wen, ZHU Wen-ya, Kun-Yan ZHU, MA En-bo, ZHANG Jian-zhen 2020, 19(6): 1512-1521.  DOI: 10.1016/S2095-3119(19)62827-3 Abstract ( )   PDF in ScienceDirect   Cytochrome b5 (Cyt-b5) is a small heme protein and known to be involved in a wide range of biochemical transformations, including cytochrome P450 monooxygenase (CYP)-mediated metabolism of endogenous and exogenous compounds.  Studies on Cyt-b5 are more concentrated in mammals, but are relatively rare in insects.  The characteristics and function of Cyt-b5 from Locusta migratoria have not been described yet.  We sequenced the full-length cDNA sequence of Cyt-b5 from L. migratoria (LmCyt-b5) by reverse transcription-PCR (RT-PCR) based on locust transcriptome database.  The phylogenetic analysis showed that LmCyt-b5 was closely related to the Cyt-b5 from Blattodea.  LmCyt-b5 was highly expressed in ovary, Malpighian tubules, midgut, gastric caeca, and fat bodies.  Silencing of LmCyt-b5 had no effect on the susceptibility of L. migratoria to four different insecticides.  Suppression of LmCyt-b5 or silencing of both LmCyt-b5 and LmCPR did not significantly change the total CYP activity toward the substrate 7-ethoxycoumarin (7-EC).  However, coexpression of LmCYP6FD1 with LmCPR and LmCyt-b5 together in Sf9 cells by using Bac-to-Bac baculovirus expression system significantly increased the catalytic activity of LmCYP6FD1 toward 7-EC as compared with the coexpression of LmCYP6FD1 with cytochrome P450 reductase (LmCPR) or LmCyt-b5 separately.  These results suggest that LmCyt-b5 plays an important role in the catalytic reaction of LmCYP6FD1 toward 7-EC in our in vitro experiments.  Further study is needed to clarify the role of LmCyt-b5 in CYP-mediated catalytic reactions in L. migratoria.

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Molecular cloning and expression patterns of two small heat shock proteins from Chilo suppressalis (Walker) SONG Jie, LU Ming-xing, DU Yu-zhou 2020, 19(6): 1522-1529.  DOI: 10.1016/S2095-3119(19)62808-X Abstract ( )   PDF in ScienceDirect   Small heat shock proteins (sHSPs) are a very complex protein superfamily that increase insect temperature tolerance.  In order to deeply understand the function and role of sHSPs in Chilo suppressalis (Walker), this study isolated and identified two CsHSP genes lacking introns from C. suppressalis, Cshsp23.9 and Cshsp27.3.  The cDNA full-length of Cshsp23.9 and Cshsp27.3 were 909 and 1 036 bp encoding 220 and 242 amino acids, respectively.  Alignment with homologs and phylogenetic analysis indicated Cshsp23.9 and Cshsp27.3 were two new types of Cshsps in C. suppressalis.  Real-time quantitative PCR (qPCR) revealed that Cshsp23.9 had the highest relative expression in hindgut compared with other tissues (head, epidermis, foregut, midgut, fat body, Malpighian tubules, and hemocytes), while Cshsp27.3 expressed the highest in fat body content.  When exposed to thermal stress from –11 to 43°C for 2 h, two genes showed different expression patterns.  Cshsp23.9 did not respond to low temperature, but could be up-regulated by high temperature and the highest expression temperature was at 36°C.  Cshsp27.3 could only be induced by mild temperature, with the highest expression at 15 and 30°C.  In conclusion, Cshsp23.9 and Cshsp27.3 existed in different tissues/organs of C. suppressalis, and played different important roles in C. suppressalis to resist temperature stress and regulate physiological activities.

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Role of TRP channels and HSPs in thermal stress response in the aphid parasitoid Aphelinus asychis (Hymenoptera: Aphelinidae) LIU Xiang, KANG Zhi-wei, YU Xing-lin, LI Fan, LIU Tong-xian, LI Qiang 2020, 19(6): 1530-1542.  DOI: 10.1016/S2095-3119(19)62869-8 Abstract ( )   PDF in ScienceDirect   Aphelinus asychis is an important aphid endoparasitoid.  Under field and greenhouse conditions, high temperature is one of the factors limiting the application of A. asychis for biological pest control.  To explore the potential role of transient receptor potential (TRP) channels and heat shock proteins (HSPs) in this process, we identified 11 genes encoding TRP channels and nine genes encoding HSPs.  Three proteins (AasyTRPA5, AasyPyrexia, AasyPainless) that belong to transient receptor potential ankyrin (TRPA) subfamily and nine HSPs are involved in the response to high temperature.  We also investigated the survival of A. asychis and the response of the identified TRP channels and HSPs to high temperature.  The results showed that the maximum temperature that allowed A. asychis survival was approximately 41°C; females had higher survival rates than that of the males at 40 and 41°C.  Short-term heat-shock resulted in increased expression of Aasyshsp in males, and Aasyhsp40, Aasyhsp68, Aasyhsp70-4, Aasyhsp70-5 and Aasyhsp90 were upregulated and then downregulated, whereas Aasyhsp70-3 was upregulated at 41°C.  Moreover, Aasyhsp40 and Aasyhsp90 showed higher expression levels in females, while Aasyshsp and Aasyhsp70-3 presented opposite expression patterns.  At temperature above 35°C, expression of AasyPyrexia in females was significant higher than that in males, whereas AasyPainless and AasyTRPA5 presented higher expression in males at 40 and 41°C, respectively.  Altogether, these results indicate that protection against thermal stress in A. asychis is coordinated by TRP channels and HSPs.  These findings provide a basis for understanding the potential mechanism of A. asychis in response to high temperatures.

Crop Science

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dCAPS markers developed for nitrate transporter genes TaNRT2L12s associating with 1 000-grain weight in wheat HUANG Jun-fang, LI Long, MAO Xin-guo, WANG Jing-yi, LIU Hui-min, LI Chao-nan, JING Rui-lian 2020, 19(6): 1543-1553.  DOI: 10.1016/S2095-3119(19)62683-3 Abstract ( )   PDF in ScienceDirect   Nitrate transporters (NRTs) are regulators of nitrate assimilation and transport.  The genome sequences of TaNRT2L12-A, -B and -D were cloned from wheat (Triticum aestivum L.), and polymorphisms were analyzed by sequencing.  TaNRT2L12-D in a germplasm population was highly conserved.  However, 38 single nucleotide polymorphisms (SNPs) in TaNRT2L12-A coding region and 11 SNPs in TaNRT2L12-B coding region were detected.  Two derived cleaved amplified polymorphic sequences (dCAPS) markers A-CSNP1 and A-CSNP2 were developed for TaNRT2L12-A based on SNP-351 and SNP-729, and three haplotypes were identified in the germplasm population.  B-CSNP1 and B-CSNP2 were developed for TaNRT2L12-B based on SNP-237 and SNP-1 227, and three haplotypes were detected in the germplasm population.  Association analyses between the markers and agronomic traits in 30 environments and phenotypic comparisons revealed that A-CSNP2-A is a superior allele of shorter plant height (PH), length of penultimate internode (LPI) and peduncle length (PL), B-CSNP2-G is a superior allele of higher grain number per spike (GNS).  Hap-6B-1 containing both superior alleles B-CSNP1-C and B-CSNP2-A is a superior haplotype of 1 000-grain weight (TGW).  Expression analysis showed that TaNRT2L12-B is mainly expressed in the root base and regulated by nitrate.  Therefore, TaNRT2L12 may be involved in nitrate transport and signaling to regulate TGW in wheat.  The superior alleles and dCAPS markers of TaNRT2L12-A/B are beneficial to genetic improvement and germplasm enhancement with molecular markers-assisted selection.

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The effect of amylose on kernel phenotypic characteristics, starch-related gene expression and amylose inheritance in naturally mutated high-amylose maize ZHANG Xu-dong, GAO Xue-chun, LI Zhi-wei, XU Lu-chun, LI Yi-bo, ZHANG Ren-he, XUE Ji-quan, GUO Dong-wei 2020, 19(6): 1554-1564.  DOI: 10.1016/S2095-3119(19)62779-6 Abstract ( )   PDF in ScienceDirect   High-amylose maize starch has great potential for widespread industrial use due to its ability to form strong gels and film and in the food processing field, thus serving as a resistant starch source.  However, there is still a substantial shortage of high-amylose maize due to the limitation of natural germplasm resources, although the well-known amylose extender (ae) gene mutants have been found to produce high-amylose maize lines since 1948.  In this context, high-amylose maize lines (13 inbreds and 18 hybrids) originating from a natural amylose mutant in our testing field were utilized to study the correlation between amylose content (AC) and phenotypic traits (kernel morphology and endosperm glossiness), grain filling characteristics, gene expression, and amylose inheritance.  Our results showed that AC was negatively correlated with total starch content but was not correlated with grain phenotypes, such as kernel fullness, kernel morphology and endosperm glossiness.  Maize lines with higher amylose had a greater grain filling rate than that of the control (B73) during the first 20 days after pollination (DAP).  Both starch debranching enzyme (DBE) groups and starch branching enzyme IIb (SBEIIb) groups showed a greater abundance in the control (B73) than in the high-amylose maize lines.  Male parents directly predicted AC of F1, which was moderately positively correlated with the F2 generation.

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Increased BnaMFT-transcript level is associated with secondary dormancy in oilseed rape (Brassica napus L.) LIU Lei, FAN Wen-qi, LIU Fu-xia, YI Xin, TANG Tang, ZHOU Ying, TANG Zi-wei, CHEN Gui-min, ZHAO Xiang-xiang 2020, 19(6): 1565-1576.  DOI: 10.1016/S2095-3119(19)62684-5 Abstract ( )   PDF in ScienceDirect   Brassica napus cultivars have little or no primary dormancy; however, they are prone to secondary dormancy induction.  Secondary dormant seeds can produce volunteer plants, which can result in genetic contamination, reduced quality and biosafety issues.  However, information regarding the molecular mechanism underlying secondary dormancy is limited.  The MOTHER OF FT AND TFL1 (MFT) gene, which is evolutionarily conserved in the plant kingdom, acts in a complex gene network in the seed dormancy or germination processes.  In this study, we identified four B. napus genes that share high homology with AtMFT, named as BnaMFT.  Analyses of cis-acting elements showed that BnaMFT promoters contain multiple seed-specific regulatory elements, and various stress- and hormone-responsive elements.  Further experiments validated that BnaMFTs were specifically expressed during seed maturation and in the dry seed, with peaks at 35–42 days after pollination.  BnaMFTs were not sufficient for primary dormancy; however, they were significantly enhanced by secondary dormancy induction with PEG6000 treatment.  Moreover, BnaMFT transcripts were elevated by treatment with abscisic acid (ABA), which is known to be accumulated during secondary dormancy.  These results collectively suggest that increased BnaMFT transcription levels are associated with secondary dormancy induction in an ABA-dependent manner in B. napus.

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The effects of intraspecific competition and light transmission within the canopy on wheat yield in a wide-precision planting pattern LIU Xin, WANG Wen-xin, LIN Xiang, GU Shu-bo, WANG Dong 2020, 19(6): 1577-1585.  DOI: 10.1016/S2095-3119(19)62724-3 Abstract ( )   PDF in ScienceDirect   The wide-precision planting pattern has become widely used in the North China Plain as a practice for increasing wheat yield.  However, the effects of tillering development and light transmission within canopy on wheat yield under different sowing widths have not been clearly described.  Therefore, a two-year experiment was conducted, including four different seeding widths (6 cm, W6; 8 cm, W8; 10 cm, W10; 12 cm, W12) and the traditional planting pattern with seeding width of 4 cm (W4).  The results indicated mainly positive effects by the reduced intraspecific competition, specifically all three yield components of W6 and W8 were higher than those for W4.  The configurations with more than 10-cm seeding width were mainly affected by the negative effect of a relative homogeneous canopy, leading to the weakened light transmission, leaf senescence, and reduced grain number per spike.  Finally, the yields of W6 and W8 were significantly higher than that of W4, whereas the yield in W12 was lower (though not significantly) than W4.  In wheat production, therefore, the appropriate seeding width of 6–8 cm is recommended for farmers, whereas the too wide seeding width, with more than 10 cm, should be avoided.

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Effects of urea mixed with nitrapyrin on leaf photosynthetic and senescence characteristics of summer maize (Zea mays L.) waterlogged in the field REN Bai-zhao, HU Juan, ZHANG Ji-wang, DONG Shu-ting, LIU Peng, ZHAO Bin 2020, 19(6): 1586-1595.  DOI: 10.1016/S2095-3119(19)62725-5 Abstract ( )   PDF in ScienceDirect   Waterlogging is one of the major abiotic stresses in agricultural crop production.  However, the application of 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin) can effectually mitigate the losses of nitrogen efficiency and grain yield of summer maize induced by waterlogging.  In order to explore its role to alleviate waterlogging stress on leaf antioxidative system and photosynthetic characteristics of summer maize, a field experiment was executed to research effects of nitrapyrin application on leaf photosynthetic and senescent characteristics of waterlogged summer maize Denghai 605 (DH605) and Zhengdan 958 (ZD958).  Experimental treatments consisted of waterlogging treatment that was applying only urea (WL), waterlogging treatment that was applying urea mixing with nitrapyrin (WL-N), and no waterlogging treatment that was only applying urea (NWL).  Results showed that WL significantly decreased leaf area index (LAI), SPAD, photosynthetic rate (Pn), and protective enzyme activities, accelerated leaf aging, eventually led to a remarkable yield reduction by 38 and 42% for DH605 and ZD958, respectively, compared to NWL.  However, the application of nitrapyrin was useful for relieving waterlogging damages on leaf photosynthetic ability.  LAI, SPAD and Pn of WL-N for DH605 were 10, 19 and 12–24% higher, and for ZD958 were 12, 23 and 7–25% higher, compared to those of WL, respectively.  Moreover, application of nitrapyrin effectually relieved waterlogging losses on antioxidative enzyme activities.  Leaf superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities of WL-N were averagely increased by 24, 15 and 30%, respectively, while malondialdehyde (MDA) content was averagely decreased by 13%, compared to those of WL.  Visibly, nitrapyrin application could improve leaf photosynthetic characteristics and retard leaf aging induced by waterlogging, thereby leading to a yield increase of waterlogged maize.

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Effects of subsoiling depth, period interval and combined tillage practice on soil properties and yield in the Huang-Huai-Hai Plain, China WANG Yun-xia, CHEN Shu-ping, ZHANG Dong-xing, YANG Li, CUI Tao, JING Hui-rong, LI Yu-huan 2020, 19(6): 1596-1608.  DOI: 10.1016/S2095-3119(19)62681-X Abstract ( )   PDF in ScienceDirect   Compaction layers are widely distributed in the Huang-Huai-Hai Plain, China, which restrict root growth and reduce yields.  The adoption of subsoiling has been recommended to disrupt compacted soil layers and create a reasonable soil structure for crop development.  In this paper, the effects of subsoiling depth (30, 35 and 40 cm), period interval (2 or 3 years) and combined pre-sowing tillage practice (rotary cultivation or ploughing) on soil condition improvement was studied on a tidal soil in the Huang-Huai-Hai Plain.  Seven tillage patterns were designed by combining different subsoiling depths, period intervals and pre-sowing.  The evaluation indicators for soil condition improvement were as follows: thickness of the plough layer and hard pan, soil bulk density, cone index, soil three-phase R values, alkali nitrogen content, crop yield, and economic benefits.  The results showed that subsoiling can significantly improve the soil structure and physical properties.  In all subsoiling treatments, the depth of 35 or 40 cm at a 2-year interval was the most significant.  The thickness of the plough layer increased from 13.67 cm before the test to 21.54–23.45 cm in 2018.  The thickness of the hard pan decreased from 17.68 cm before the test to 12.09–12.76 cm in 2018, a decrease of about 40.07%.  However, the subsoiling combined pre-sowing tillage practice, that is, rotary cultivation or ploughing, was not significant for soil structure and physical properties.  For all subsoiling treatments, the soil bulk density, cone index and soil three-phase R values of the 15–25 cm soil layer were significantly lower compared to single rotary cultivation.  Subsoiling was observed to increase the soil alkaline nitrogen and water contents.  The tillage patterns that had subsoiling at the depth of 35–40 cm at a 2-year interval combined with rotary cultivation had the highest alkali nitrogen and water contents, which increased by 31.08–34.23% compared with that of the single rotary cultivation.  Subsoiling can significantly increase the yield both of wheat and corn, as well as the economic benefits.  The treatment of subsoiling at the depth of 35 cm at an interval of 2 years combined with rotary cultivation had the highest annual yield and economic benefits.  For this treatment, the annual yield and economic benefits increased by 14.55 and 62.87% in 2018, respectively.  In conclusion, the tillage patterns that involved subsoiling at a depth of 35 cm at a 2-year interval along with rotary cultivation are suitable for the Huang-Huai-Hai Plain.

Horticulture

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Genome-wide identification and expression analysis of StPP2C gene family in response to multiple stresses in potato (Solanum tuberosum L.) WANG Yi-fan, LIAO Yu-qiu, WANG Ya-peng, YANG Jiang-wei, ZHANG Ning, SI Huai-jun 2020, 19(6): 1609-1624.  DOI: 10.1016/S2095-3119(20)63181-1 Abstract ( )   PDF in ScienceDirect   The plant protein phosphatase 2Cs (PP2Cs) play an essential role in response to stress and abscisic acid (ABA) signaling pathway.  However, to date, no systemic characterization of the PP2Cs has yet been conducted in potato (Solanum tuberosum L.).  In the study, a comprehensive research was performed on genome-wide identification and expression analysis of StPP2C genes in potato.  A total of 78 potato StPP2C genes were identified based on specific structure of PP2C domain, which were distributed across 11 out of 12 potato chromosomes and divided into 12 (A–L) phylogenetic branches.  The result from gene duplication analysis showed that 14 StPP2Cs were involved in gene tandem duplication and 8 genes formed fragment duplication events, which indicated that both tandem and fragment duplication contributed to the expansion of the gene family in evolution.  Exon–intron structural analysis showed that they had a wide range of exon numbers.  Analysis of protein conservative motif demonstrated that StPP2Cs contained more similar motif structures in the same phylogenetic branches.  The cis-elements in StPP2C gene promoter regions were mainly responded to light, phytohormone and abiotic stress.  Most of them exhibited tissue-specific expression patterns, and some members could differentially express under abiotic stress.  The evidence suggested that StPP2C genes may contribute to different functions in several physiological stress and environmental stress conditions.  This study could provide new insights to further investigate StPP2C functional characteristics responding to various stresses in potato.

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Pearprocess: A new phenotypic tool  for stone cell trait evaluation in pear fruit XUE Yong-song, XU Shao-zhuo, XUE Cheng, WANG Run-ze, ZHANG Ming-yue, LI Jia-ming, ZHANG Shao-ling, WU Jun 2020, 19(6): 1625-1634.  DOI: 10.1016/S2095-3119(20)63193-8 Abstract ( )   PDF in ScienceDirect   The content of stone cells is an important factor for pear breeding as a high content indicates severely reduced fruit quality in terms of fruit taste.  Although the frozen-HCl method is currently a common method used to evaluate stone cell content in pears, it is limited in incomplete separation of stone cell and pulp and is time consuming and complicated.  Computer-aided research is a promising strategy in modern scientific research for phenotypic data collection and is increasingly used in studying crops.  Thus far, we lack a quantitative tool that can effectively determine stone cell content in pear fruit.  We developed a program, Pearprocess, based on an imaging protocol using computer vision and image processing algorithms applied to digital images.  Using photos of hand-cut sections of pear fruit stained with phloroglucin-HCl (Wiesner’s reagent), Pearprocess can extract and analyze image-based data to quantify the stone cell-related traits measured in this study: number, size, area and density of stone cell.  We quantified these traits for 395 pear accessions by Pearprocess and revealed large variation in different pear varieties and species.  The number of stone cells varied greatly from value of 138 to 2 866, the density of stone cells ranged from 0.0019 to 0.0632 cm2 cm–2, the distribution of stone cell area ranged from 0.06 to 2.02 cm2, and the stone cell size was between 2e-4 and 1e-3 cm2.  Moreover, trait data were correlated with fruit taste data.  We found that stone cell density is likely the most important factor affecting the taste of pear fruit.  In summary, Pearprocess is a new cost-effective web-application for semi-automated quantification of two-dimensional phenotypic traits from digital imagery using an easy imaging protocol.  This simpler, feasible and accurate method to evaluate stone cell traits of fruit is a promising new tool for use in evaluating future germplasms for crop breeding programs.

Animal Science · Veterinary Medicine

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Investigating structural impact of a valine to isoleucine substitution on anti-Müllerian hormone in silico and genetic association of the variant and AMH expression with egg production in chickens DANG Li-ping, LIU Rui-fang, ZHAO Wen-yan, ZHOU Wen-xin, MIN Yu-na, WANG Zhe-peng 2020, 19(6): 1635-1643.  DOI: 10.1016/S2095-3119(20)63176-8 Abstract ( )   PDF in ScienceDirect   Anti-Müllerian hormone (AMH) acts in maintaining orderly cyclic recruitment of early follicles, suggesting that it is a promising candidate for influencing animal reproductive efficiency.  This study aimed to elucidate the effect of a missense mutation of Val566Ile on the structure of AMH protein and the genetic association of Val566Ile and AMH expression with egg production in chickens.  Structural perturbations of Val566Ile were predicted by homology modeling.  The association of the variant with the number of eggs was tested using a quantitative trait transmission disequilibrium test model. AMH expression in granulosa cells in Lueyang black-boned chickens was compared with that in Nick chickens.  The Val566 of AMH is a non-conservative amino acid among mammals and birds, but its hydrophobicity is completely conservative.  The substitution of Val566 for Ile566 potentially disrupted hydrogen bonds and solvent accessibility of 22 residues and created a short α-helix in the C terminus of AMH.  Despite having striking structure-disrupting potential, the variant was not statistically associated with the number of eggs (P>0.05) in the Lueyang black-boned chickens.  We did not detect differential expression of AMH between Lueyang black-boned chickens and Nick chickens (P>0.05).  These results confirmed the structural impact of Val566Ile, but suggested that Val566Ile and AMH expression might not be the major genetic determinants for egg production in Lueyang black-boned chickens.

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Effects of different molecular weights of chitosan on methane production and bacterial community structure in vitro TONG Jin-jin, ZHANG Hua, WANG Jia, LIU Yun, MAO Sheng-yong, XIONG Ben-hai, JIANG Lin-shu 2020, 19(6): 1644-1655.  DOI: 10.1016/S2095-3119(20)63174-4 Abstract ( )   PDF in ScienceDirect   As a new feed additive, chitosan has been shown in recent years to have a certain role in reducing methane emissions from the gastrointestinal tracts of ruminants.  However, the effects of chitosan with different molecular weights on rumen fermentation, methane production and bacterial community structure are not yet clear.  A basal diet without chitosan served as the control (CTL), and the treatment diets were supplemented with chitosan with different molecular weights: 1 000 (1K), 3 000 (3K), 5 000 (5K), 50 000 (5W) and 200 000 (20W) dry matter (DM).  Six fermentation units per treatment were established.  Gas chromatography was used to measure the concentrations of methane, H2 and volatile fatty acids (VFAs).  The bacterial 16S rRNA genes were sequenced with an Illumina MiSeq platform and analysed to reveal the relative abundances of bacterial community taxa.  The results showed that the propionate proportion was significantly increased by the addition of chitosan with different molecular weights (P<0.05), while methane production and the acetate proportion were significantly decreased (P<0.05).  The relative abundances of Rikenellaceae_RC9_gut_group and Prevotellaceae_UCG_003 were significantly increased in the 3K chitosan group compared with the CTL group, whereas the relative abundance of Ruminococcaceae_NK4A214_group was significantly decreased (P<0.05).  Correlation analyses of the relative abundances of the bacterial genera showed that Prevotella was positively related to propionate production (P<0.05).  In conclusion, 3K chitosan could reduce methane production by replacing fibrolytic bacteria (Firmicutes and Fibrobacteres) with amylolytic bacteria (Bacteroidetes and Proteobacteria) in the bacterial community structure.

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Molecular detection of virulence genes in Campylobacter species isolated from livestock production systems in South Africa Bongekile NGOBESE, Oliver Tendayi ZISHIRI, Mohamed Ezzat EL ZOWALATY 2020, 19(6): 1656-1670.  DOI: 10.1016/S2095-3119(19)62844-3 Abstract ( )   PDF in ScienceDirect   Campylobacter species are a major cause of foodborne bacterial infections in both developed and developing countries worldwide.  Campylobacter jejuni is responsible for the majority of infections.  This study was conducted to identify virulence-associated genes in Campylobacter species isolated from livestock production systems in South Africa.  A total of 250 fecal samples consisting of cattle (n=50), chickens (n=50), goats (n=50), sheep (n=50) and pigs (n=50) were randomly collected from livestock in Eastern Cape and KwaZulu-Natal provinces of South Africa between April and October 2018.  The samples were analyzed for the presence of virulence genes in Campylobacter species using molecular PCR-based methods.  It was found that 77 and 23% of Campylobacter jejuni and Campylobacter coli respectively were isolated from all the livestock samples.  There were positive significant (P<0.05) correlations amongst all the virulence genes that were investigated.  Chi-square and Fisher’s exact tests were implemented to test for the effect of livestock species on the presence or absence of virulence genes.  The study demonstrated that most of livestock species can potentially cause zoonotic infections and food poisoning due to the high prevalence of Campylobacter.  The high prevalence of virulence genes highlights the significance of Campylobacter in livestock production systems in South Africa.  This requires the implementation of one-health approaches to reduce the impact of foodborne and zoonotic diseases for the welfare of human and animal health.