2020 Vol. 19 No. 11 Previous Issue    Next Issue

    Crop Science
    Plant Protection
    Animal Science · Veterinary Medicine
    Agro-ecosystem & Environment
    Food Science

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    Crop Science
    GraS is critical for chloroplast development and affects yield in rice 
    DU Zhi-xuan, HAO Hui-ying, HE Jin-peng, WANG Jian-ping, HUANG Zhou, XU Jie, FU Hai-hui, FU Jun-ru, HE Hao-hua
    2020, 19(11): 2603-2615.  DOI: 10.1016/S2095-3119(19)62859-5
    Abstract ( )   PDF in ScienceDirect  
    Leaf color has been considered an important agronomic trait in rice (Oryza sativa L.) for a long time.  The changes in leaf color affect the yield of rice.  In this study, a green-revertible albino (graS) mutant was isolated from a 60Co-gamma-irradiated mutant pool of indica cultivar Guangzhan 63-4S.  The fine mapping indicated that graS mutant was mapped to chromosome 1, and was located in a confined region between markers ab134 and InDel 8 with genetic distances of 0.11 and 0.06 cM, respectively.  Based on the annotation results, four open reading frames (ORFs) were predicted in this region.  Sequence analysis revealed that LOC_Os01g55974 had a 2-bp nucleotide insertion (AA) in the coding region that led to premature termination at the 324th base.  Sequence analysis and expression analysis of related genes indicated that LOC_Os01g55974 is the candidate gene of GraS.  We studied the genome and protein sequences of LOC_Os01g55974, and the data showed that GraS contains a deoxycytidine deaminase domain, which was expressed ubiquitously in all tissues.  Further investigation indicated that GraS plays an essential role in the regulation of chloroplast biosynthesis, photosynthetic capacity and yield.  Moreover, leaf color mutant can be used as an effective marker for the purity of breeding and hybridization.
    The wheat receptor-like cytoplasmic kinase TaRLCK1B is required for host immune response to the necrotrophic pathogen Rhizoctonia cerealis
    WU Tian-ci, ZHU Xiu-liang, LÜ Liang-jie, CHEN Xi-yong, XU Gang-biao, ZHANG Zeng-yan
    2020, 19(11): 2616-2627.  DOI: 10.1016/S2095-3119(20)63160-4
    Abstract ( )   PDF in ScienceDirect  
    Receptor-like cytoplasmic kinases (RLCKs) represent a large family of proteins in plants.  In Arabidopsis and rice, several RLCKs in subfamily VII (RLCKs-VII) have been implicated in pathogen-associated molecular pattern-triggered immunity and basal resistance against bacterial and fungal pathogens.  However, little is known about roles of RLCKs-VII of the important crop common wheat (Triticum aestivum) in immune responses.  Here, we isolated a RLCK-VII-encoding gene from wheat, designated as TaRLCK1B, and investigated its role in host immune response to infection of a necrotrophic fungus Rhizoctonia cerealis that is a major pathogen of sharp eyespot, a destructive disease of wheat.  RNA-sequencing and RT-qPCR analyses showed that transcriptional level of TaRLCK1B was significantly higher in sharp eyespot-resistant wheat cultivars than in susceptible wheat cultivars.  The gene transcription was rapidly and markedly elevated in the resistant wheat cultivars by R. cerealis infection.  The TaRLCK1B protein was closely related to OsRLCK176, a rice resistance-related RLCKs-VII, with 84.03% identity.  Virus-induced gene silencing plus wheat response to R. cerealis assay results indicated that silencing of TaRLCK1 impaired resistance to R. cerealis.  Meantime, silencing of TaRLCK1 significantly elevated both the content of H2O2 (a major kind of reactive oxygen species, ROS) and the transcriptional level of the ROS-generating enzyme-encoding gene RBOH, but repressed the expression of the ROS-scavenging enzyme-encoding gene CAT1 at 18 hours after inoculation (hai) with R. cerealis.  Taken together, these data suggested that TaRLCK1B was required for the early immune response of wheat to R. cerealis through modulating ROS signaling in wheat.
    Grain proteomic analysis reveals central stress responsive proteins caused by wheat-Haynaldia villosa 6VS/6AL translocation
    ZOU Rong, WU Ji-su, WANG Ruo-mei, YAN Yue-ming
    2020, 19(11): 2628-2642.  DOI: 10.1016/S2095-3119(19)62846-7
    Abstract ( )   PDF in ScienceDirect  
    Haynaldia villosa (2n=14, VV), a wild grass of the subtribe Triticeae, serves as potential gene resources for wheat genetic improvement.  In this study, the proteome characterization during grain development of Yangmai 5 and Yangmai 5-H. villosa 6VS/6AL translocation line was investigated by a comparative proteomic approach.  Two-dimensional electrophoresis identified 81 differentially accumulated proteins (DAPs) during five grain developmental stages in wheat-H. villosa translocation line.  These proteins were mainly involved in stress defense, storage protein, energy metabolism, protein metabolism and folding, carbon metabolism, nitrogen metabolism, and starch metabolism.  In particular, 6VS/6AL translocation led to significant upregulation of 36 DAPs and specific expression of 11 DAPs such as chitinase, thaumatin-like proteins, glutathione transferase, α-amylase inhibitor, heat shock proteins, and betaine aldehyde dehydrogenase.  These proteins mainly involved in biotic and abiotic stress responses.  Further analysis found that the upstream 1 500 promoter regions of these stress-responsive DAP genes contained multiple high-frequency cis-acting elements related to stress defense such as abscisic acid response element ABRE, methyl jasmonate (MeJA)-response element TGACG-motif and CGTCA-motif involved in oxidative stress and antioxidant response element (ARE).  RNA-seq and RT-qPCR analyses revealed the high expression of these stress-defensive DAP genes in the developing grains, particularly at the early-middle grain filling stages.  Our results demonstrated that 6VS chromosome of H. villosa contains abundant stress-defensive proteins that have potential values for wheat genetic improvement.
    Morpho-physiological traits contributing to better yield performance of japonica/indica hybrids over indica hybrids under input-reduced practices
    WEI Huan-he, MENG Tian-yao, GE Jia-lin, ZHANG Xu-bin, LU Yu, LI Xin-yue, TAO Yuan, DING En-hao, CHEN Ying-long, DAI Qi-gen
    2020, 19(11): 2643-2655.  DOI: 10.1016/S2095-3119(20)63251-8
    Abstract ( )   PDF in ScienceDirect  
    It is widely reported that japonica/indica hybrids (JIH) have superior grain yield over other main varietal groups such as indica hybrids (IH) under sufficient resource inputs.  To date, little attention has been paid to yield performance of JIH under input-reduced practices, and whether JIH could have better grain yield performance over IH under input-reduced practices.  In this study, three JIH varieties and three IH varieties were compared in grain yield and their related morpho-physiological traits under two cultivation modes, i.e., conventional high-yielding method (CHYM) and double reductions in nitrogen rate and planting density (DRNP).  Our results showed that JIH had 8.3 and 13.3% higher grain yield over IH under CHYM and DRNP, respectively.  The superior grain yield of JIH over IH under DRNP was mainly attributed to larger sink size and improved sink filling efficiency.  Three main morpho-physiological traits were concluded for better yield performance of JIH over IH under DRNP.  Firstly, JIH had the reduced unproductive tillers growth, indicated by a higher percentage of productive tillers and the percentage of effective leaf area index (LAI) to total LAI at heading stage.  Secondly, a synergistic increase in biomass accumulation and harvest index were achieved of JIH, supported by higher biomass accumulation and leaf area duration during the main growth periods, and improved non-structural carbohydrate (NSC) remobilization after heading.  Thirdly, JIH had an improved canopy structure, showing as higher leaf area of upper three leaves and lower light extinction coefficient.  Our results suggested that improved morpho-physiological traits of JIH could lead to better grain yield performance over IH under input-reduced practices.
    Growth, yield and water productivity of dry direct seeded rice and transplanted aromatic rice under different irrigation management regimes
    Muhammad ISHFAQ, Nadeem AKBAR, shakeel Ahmed ANJUM, Muhammad ANWAR-UL-HAQ
    2020, 19(11): 2656-2673.  DOI: 10.1016/S2095-3119(19)62876-5
    Abstract ( )   PDF in ScienceDirect  
    Sustainability of traditionally cultivated rice in the rice-wheat cropping zone (RWCZ) of Pakistan is dwindling due to the high cost of production, declining water resources and escalating labour availability.  Thus, farmers and researchers are compelled to find promising alternatives to traditional transplanted rice (TPR).  A field study was conducted in Punjab, Pakistan, in 2017 and 2018 to explore the trade-offs between water saving and paddy yield, water productivity and economics of two aromatic rice varieties under dry direct seeded rice (DDSR) and TPR.  The experiment was comprised of three irrigation regimes on the basis of soil moisture tension (SMT) viz., continuous flooded (>–10 kPa SMT), alternate wetting and drying (AWD) (–20 kPa SMT) and aerobic rice (–40 kPa SMT), maintained under TPR and DDSR systems.   Two aromatic rice verities: Basmati-515 and Chenab Basmati-2016 were used during both years of study.  In both years, DDSR produced higher yields (13–18%) and reduced the total water inputs (8–12%) in comparison to TPR.  In comparison to traditional continuous flooded (CF), AWD under DDSR reduced total water input by 27–29% and improved the leaf area index (LAI), tillering, yield (7–9%), and water productivity (44–50%).  The performance of AWD with regard to water savings and increased productivity was much higher in DDSR system as compared to AWD in TPR system.  Cultivation of DDSR with aerobic irrigation improved water savings (49–55%) and water productivity (22–30%) at the expense of paddy yield reduction (36–39%) and spikelet sterility.  With regard to variety, the highest paddy yield (6.6 and 6.7 t ha–1) was recorded in DDSR using Chenab Basmati-2016 under AWD irrigation threshold that attributed to high tiller density and LAI.  The economic analysis showed DDSR as more beneficial rice establishment method than TPR with a high benefit-cost ratio (BCR) when the crop was irrigated with AWD irrigation threshold.  Our results highlighted that with the use of short duration varieties, DDSR cultivation in conjunction with AWD irrigation can be more beneficial for higher productivity and crop yield.
    Effects of post-heading high temperature on some quality traits of malt barley
    NI sheng-jing, ZHAO Hui-fang, ZHANG Guo-ping
    2020, 19(11): 2674-2679.  DOI: 10.1016/S2095-3119(19)62878-9
    Abstract ( )   PDF in ScienceDirect  
    Global change is bringing barley with more frequency of suffering from high temperature.  However, little has been known about the influence of high temperature on malt quality traits.  In this study, we investigated the impact of 1-wk heat stress (32°C/26°C, day/night, 12 h/12 h) initiating from the 7th (HT7) and 14th (HT14) days after heading on some grain and malt quality traits of two barley cultivars.  In comparison with normal temperature (24°C/18°C, day/night, 12 h/12 h), heat stress significantly reduced kernel weight, seed setting rate and grains per spike: HT7 having a larger effect than HT14.  Meanwhile, total protein and β-glucan contents, and β-amylase and limit dextrinase activities were significantly increased under high temperature, with HT7-treated plants showing larger changes.  Moreover, the different changes of four protein fractions under heat stress were found in the two barley cultivars, indicating the possibility of breaking positive association between protein content and enzyme activity.
    Kernel crack characteristics for X-ray computed microtomography (μCT) and their relationship with the breakage rate of maize varieties
    DONG Peng-fei, XIE Rui-zhi, WANG Ke-ru, MING bo, HOU Peng, HOU Jun-feng, XUE Jun, LI Chao-hai, LI shao-kun
    2020, 19(11): 2680-2689.  DOI: 10.1016/S2095-3119(20)63230-0
    Abstract ( )   PDF in ScienceDirect  
    The most significant problem of maize grain mechanical harvesting quality in China at present is the high grain breakage rate (BR).  BR is often the key characteristic that is measured to select hybrids desirable for mechanical grain harvesting.  However, conventional BR evaluation and measurement methods have challenges and limitations.  Microstructural crack parameters evaluation of maize kernel is of great importance to BR.  In this connection, X-ray computed microtomography (μ-CT) has proven to be a quite useful method for the assessment of microstructure, as it provides important microstructural parameters, such as object volume, surface, surface/volume ratio, number of closed pores, and others.  X-ray computed microtomography is a non-destructive technique that enables the reuse of samples already measured and also yields bidimensional (2D) cross-sectional images of the sample as well as volume rendering.  In this paper, six different maize hybrid genotypes are used as materials, and the BR of the maize kernels of each variety is tested in the field mechanical grain harvesting, and the BR is used as an index for evaluating the breakage resistance of the variety.  The crack characteristic parameters of kernel were detected by X-ray micro-computed tomography, and the relationship between the BR and the kernel crack characteristics was analyzed by stepwise regression analysis.  Establishing a relationship between crack characteristic parameters and BR of maize is vital for judging breakage resistance.  The results of stepwise multiple linear regression (MLR) showed that the crack characteristics of the object surface, number of closed pores, surface of closed pores, and closed porosity percent were significantly correlated to the BR of field mechanical grain harvesting, with the standard partial regression coefficients of –0.998, –0.988, –0.999, and –0.998, respectively.  The R2 of this model was 0.999.  Results validation showed that the Stepwise MLR Model could well predict the BR of maize based on these four variables. 
    Giving maize an excited start – Effects of dopamine on maize germination
    CHENG Hang-yuan, WANG Xing, FENG Tian-yu, PENG Chuan-xi, WANG Wei, YANG Mu-yu, ZHOU Yu-yi
    2020, 19(11): 2690-2698.  DOI: 10.1016/S2095-3119(20)63252-X
    Abstract ( )   PDF in ScienceDirect  
    Dopamine (DA) is a neurotransmitter which takes charge of brain activities about memory and self-stimulation behavior in animals.  Interestingly, our results suggest that DA could also give maize an “excited state”.  The results showed that 1  mmol L–1 DA promoted maize germination by 23.2% significantly, and accelerated the growth rate of roots and shoots by 21.4 and 24.7%, respectively.  As we all known, abscisic acid (ABA) is the key hormone involved in seed dormancy.  In our research, ABA levels in roots and shoots dramatically decreased by 16.45 and 57.57%, respectively.  To further investigate how DA reduces the ABA level in budding seed, we studied ABA synthesis and catabolism pathway.  Specific expression of key ABA-synthesis genes, such as ZmNCED1, ZmNCED3 and ZmZEP were down-regulated by DA.  Simultaneously, the expression levels of ABA8OX1a and ABA8OX1b which are major transcripts of ABA 8´-hydroxylase in ABA catabolism were up-regulated at least 1.5- and 4.6-fold, respectively.  Our results enriched the functions of animal hormones in plants.
    Silencing the SLB3 transcription factor gene decreases drought stress tolerance in tomato
    WANG Zi-yu, bAO Yu-fang, PEI Tong, WU Tai-ru, DU Xu, HE Meng-xi, WANG Yue, LIU Qi-feng, YANG Huan-huan, JIANG Jing-bin, ZHANG He, LI Jing-fu, ZHAO Ting-ting, XU Xiang-yang
    2020, 19(11): 2699-2708.  DOI: 10.1016/S2095-3119(20)63350-0
    Abstract ( )   PDF in ScienceDirect  
    BRI1-EMS-SUPPRESSOR 1 (BES1) transcription factor is closely associated with the brassinosteroid (BR) signaling pathway and plays an important role in plant growth and development.  SLB3 is a member of BES1 transcription factor family and its expression was previously shown to increase significantly in tomato seedlings under drought stress.  In the present study,we used virus-induced gene silencing (VIGS) technology to downregulate SLB3 expression to reveal the function of the SLB3 gene under drought stress further.  The downregulated expression of SLB3 weakened the drought tolerance of the plants appeared earlier wilting and higher accumulation of H2O2 and O2·, decreased superoxide dismutase (SOD) activity, and increased proline (PRO) and malondialdehyde (MDA) contents and peroxidase (POD) activity.  Quantitative real-time PCR (qRT-PCR) analysis of BR-related genes revealed that the expression of SlCPD, SlDWARF and BIN2-related genes was significantly upregulated in SLB3-silenced seedlings under drought stress, but that the expression of TCH4-related genes was downregulated.  These results showed that silencing the SLB3 gene reduced the drought resistance of tomato plants and had an impact on the BR signaling transduction which may be probably responsible for the variation in drought resistance of the tomato plants. 
    The mitigation effects of exogenous dopamine on low nitrogen stress in Malus hupehensis
    LIU Xiao-min, GAO Teng-teng, ZHANG Zhi-jun, TAN ke-xin, JIN Yi-bo, ZHAO Yong-juan, MA Feng-wang, LI Chao
    2020, 19(11): 2709-2724.  DOI: 10.1016/S2095-3119(20)63344-5
    Abstract ( )   PDF in ScienceDirect  
    Dopamine plays numerous physiological roles in plants.  We explored its role in the regulation of growth, nutrient absorption, and response to nitrogen (N) deficiency in Malus hupehensis Rehd.  Under low N condition, plant growth slowed, and the net photosynthetic rates, chlorophyll contents, and maximal quantum yield of PSII (Fv/Fm) decreased significantly.  However, the application of 100 μmol L−1 exogenous dopamine significantly reduced the inhibition of low N stress on plant growth.  In addition to modifying root system architecture under low N supply, exogenous dopamine also changed the uptake, transport, and distribution of N, P, and K.  Furthermore, exogenous dopamine enhances the tolerance to low nitrogen stress by increasing the activity of enzymes (nitrate reductase, nitrite reductase, glutamic acid synthase and glutamine synthetase) involved in N metabolism.  We also found that exogenous dopamine promoted the expression of ethylene signaling genes (ERF1, ERF2, EIL1, ERS2, ETR1, and EIN4) under low N stress.  Therefore, we hypothesized that ethylene might be involved in dopamine response to low N stress in M. hupehensis.  Our results suggest that exogenous dopamine can mitigate low N stress by regulating the absorption of mineral nutrients, possibly through the regulation of the ethylene signaling pathway.
    Plant Protection
    A novel glycoside hydrolase 74 xyloglucanase CvGH74A is a virulence factor in Coniella vitis
    QIN Jia-xing, LI Bao-hua, ZHOU Shan-yue
    2020, 19(11): 2725-2735.  DOI: 10.1016/S2095-3119(20)63254-3
    Abstract ( )   PDF in ScienceDirect  
    Grape white rot is a destructive fungal disease occurring worldwide.  Recently, Coniella vitis was identified as the predominant pathogen causing this disease in China.  As the periderms of grape shoots are severely degraded by C. vitis, it was speculated that cell wall-degrading enzymes (CWDEs) might play a key role in the pathogenesis of this disease.  Therefore, this study aimed to examine the hydrolytic activity of the CWDEs of C. vitis.  The results showed that xylanase (Xy) and xyloglucanase (XEG) had high levels of hydrolytic activity both in vitro and in vivo.  Furthermore, a high-virulence fungal strain exhibited higher levels of Xy and XEG activities compared with a low-virulence strain.  The genome of the fungus was found to harbor two XEG-coding genes CvGH74A and CvGH74B, which belonged to the glycoside hydrolase (GH)74 family.  The expression level of CvGH74A was found to be high during pathogen infection.  CvGH74A gene deletion mutants were generated using the split-marker method.  The deletion of CvGH74A decreased both the hydrolytic activities of XEG and Xy and also the ability of the fungus to infect the grape leaves.  No differences in the hyphal growth, morphology of colonies, or conidiation were found between the ΔCvGH74A mutant strains and the wild-type strain.  Together, these results suggested that CvGH74A acted as an important virulence factor, and its enzymatic activity might regulate the virulence of the pathogen.  This study was novel in reporting that GH74 XEG acted as a virulence factor in C. vitis.
    Molecular diversity of barley yellow dwarf virus-PAV from China and the Czech Republic
    May Oo kHINE, brozenká MICHAELA, LIU Yan, Jiban kumar kUNDU, WANG Xi-feng
    2020, 19(11): 2736-2745.  DOI: 10.1016/S2095-3119(20)63241-5
    Abstract ( )   PDF in ScienceDirect  
    Wheat yellow dwarf disease (BYD), caused by different species of barley/cereal yellow dwarf viruses (B/CYDVs), is one of the most serious cereal diseases in China and the Czech Republic.  Because genetic diversity of the virus directly influences disease epidemiology, the molecular diversity and population structure of 24 Chinese isolates and 16 the Czech Republic isolates of BYDV-PAV from different regions in two countries were analyzed by sequencing their coat protein (CP) and readthrough protein (RTP) domain (RTD) genes and comparing the sequences with six CP and 16 RTP sequences of BYDV-PAV isolates from the NCBI database based on nucleotide identity position, phylogenetic analysis and nucleotide diversity.  Nucleotide identities between the Chinese and the Czech Republic isolates for the CP were 76.6–99.4%, 73.9–89.1% for RTD (ORF5), respectively.  The Chinese and the other country isolates showed 74.7–99.2% nucleotide identity for RTP (ORF3+ORF5).  Phylogenetic analysis of CP sequences showed that 20 Chinese isolates clustered in the same clade, but the other four Chinese isolates clustered in another clade with the isolates from the Czech Republic and other counties.  The population of BYDV-PAV in China had greater nucleotide variability and was more divergent than that in the Czech Republic.  Geographical and ecological factors but not hosts might contribute to the population differences in the two countries.
    Molecular characteristics and temperature tolerance function of the transient receptor potential in the native Bemisia tabaci AsiaII3 cryptic species
    JI Shun-xia, SHEN Xiao-na, LIANG Lin, WANG Xiao-di, LIU Wan-xue, WAN Fang-hao, Lü Zhi-chuang
    2020, 19(11): 2746-2757.  DOI: 10.1016/S2095-3119(20)63226-9
    Abstract ( )   PDF in ScienceDirect  
    Insects are poikilothermic animals, and temperature is one of the most important abiotic factors affecting their spread and distribution.  For example, differences in thermal tolerance may underlie the significant differences in geographical distributions between the native AsiaII3 and invasive MED (Mediterranean) cryptic Bemisia tabaci species in China.  Transient receptor potential (TRP) channels are key components of the insect temperature perception system and act as molecular thermometers since they can be activated by specific changes in temperature.  In this study, we cloned and characterized the AsiaII3 BtTRP gene and revealed its functions in the response to thermal stress.  The full-length cDNA of BtTRP was 3 821 bp, with a 3 501-bp open reading frame encoding a 132.05-kDa protein.  Comparing the deduced amino acid sequences of AsiaII3 BtTRP and MED TRP revealed five amino acid differences.  In situ hybridization indicated that BtTRP might be widely expressed throughout the AsiaII3 adult body.  BtTRP mRNA expression reached the highest levels after exposure to mild thermal stimuli (12 and 35°C), showing that BtTRP expression can be induced by temperature stress.  Furthermore, the thermal tolerance of AsiaII3 after BtTRP dsRNA feeding was significantly lower than that of the control.  Taken together, the present study highlights the importance of TRP channels for B.?tabaci thermal resistance, and allows us to infer that the differences in amino acids between AsiaII3 and MED might cause the differences in thermal tolerance of these two cryptic species.  This study provides a new direction for investigating geographic distribution differences between invasive and native insects.
    Pancreatic triglyceride lipase is involved in the virulence of the brown planthopper to rice plants
    YUAN Long-yu, HAO Yuan-hao, CHEN Qiao-kui, PANG Rui, ZHANG Wen-qing
    2020, 19(11): 2758-2766.  DOI: 10.1016/S2095-3119(20)63188-4
    Abstract ( )   PDF in ScienceDirect  
    The brown planthopper (BPH), Nilaparvata lugens, an important rice insect pest, can enhance its virulence to BPH-resistant rice within as short a span as several generations.  Here, we cloned a pancreatic triglyceride lipase (PTL) gene (NlPTL) in N. lugens, and found that its mRNA level was higher in the high virulence population (fed on variety Rathu Heenati, P-RH) than in the low virulence population (fed on variety Taichung Native 1, P-TN1).  Knocking down NlPTL caused BPH individuals to spend more time in non-penetration and the pathway phases and less time feeding on the phloem of rice plants; these changes consequently decreased food intake, lipid content, survival rate, and fecundity in the insects.  These findings reveal for the first time that PTL in BPH is involved in its virulence to rice plants.
    Animal Science · Veterinary Medicine
    Knockdown of the Meq gene in Marek’s disease tumor cell line MSB1 might induce cell apoptosis and inhibit cell proliferation and invasion
    ZHAO Chun-fang, LI Xin, HAN Bo, QU Lu-jiang, LIU Chang-jun, Jiu Zhou SONG, YANG Ning, LIAN Ling
    2020, 19(11): 2767-2774.  DOI: 10.1016/S2095-3119(20)63321-4
    Abstract ( )   PDF in ScienceDirect  

    Marek’s disease (MD), a highly cell-associated and contagious disease of chickens caused by Marek’s disease virus (MDV) can result in neural lesions, immunosuppression and neoplasia in chicken.  The Meq gene is an important oncogene in the MDV genome, and it is expressed highly in MD tumor tissues and MD T-lymphoblastoid cell lines.  An experiment was conducted to elucidate the role of Meq in MD tumor transformation.  RNA interference technology was used to block its expression, and then analyzed the biological effects of Meq knockdown on the MD tumor cell line MSB1.  A small interfering RNA with an interference efficiency of 70% (P<0.01) was transfected into MSB1 cells to knock down the expression of Meq gene.  The cell proliferation, cycle and apoptosis were detected post-Meq knockdown.  The results showed that MSB1 cell proliferation was downregulated remarkably at 48 h (P<0.01), 60 h (P<0.05) and 72 h (P<0.01) post-Meq knockdown.  The cell cycle was unaffected (P>0.05).  B-cell lymphoma 2 gene (BCL2) was anti-apoptotic and caspase-6 was the effector in the apoptosis pathway.  The activity of caspase-6 was upregulated (P<0.05) significantly and BCL2 gene expression was downregulated (P<0.05) significantly post-Meq knockdown, suggesting cell apoptosis might be induced.  MSB1 cell migration did not exhibit any obvious change (P>0.05) post-Meq knockdown, but the expression of two genes (matrix metalloproteinase 2 (MMP2) and MMP9) that are correlated closely to cell invasion was downregulated (P<0.05) remarkably post-Meq knockdown.  The Meq knockdown might affect the main features of tumorous cells, including proliferation, apoptosis, and invasion, suggesting that the Meq gene might play a crucial role in interfering with lymphomatous cell transformation.

    Effect of dietary calcium or phosphorus deficiency on bone development and related calcium or phosphorus metabolic utilization parameters of broilers from 22 to 42 days of age
    YANG Yun-feng, XING Guan-zhong, LI su-fen, SHAO Yu-xin, ZHANG Li-yang, LU Lin, LUO Xu-gang, LIAO Xiu-dong
    2020, 19(11): 2775-2783.  DOI: 10.1016/S2095-3119(20)63302-0
    Abstract ( )   PDF in ScienceDirect  
    This experiment was conducted to investigate the effect of dietary calcium (Ca) or phosphorus (P) deficiency on bone development and related Ca or P metabolic utilization parameters of broilers from 22 to 42 days of age based on our previous study, which indicated that dietary Ca or P deficiency impaired the bone development by regulating related Ca or P metabolic utilization parameters of broilers from 1 to 21 days of age.  A total of 504 one-day-old Arbor Acres male broilers were randomly assigned to 1 of 4 treatments with 7 replicates in a completely randomized design, and fed the normal control and Ca- or P-deficient diets from 1 to 21 days of age.  At 22 days of age, the broilers were further fed the normal control diet (0.90% Ca+0.35% non-phytate P (NPP)), the P-deficient diet (0.90% Ca+0.18% NPP), the Ca-deficient diet (0.30% Ca+0.35% NPP) or the Ca and P-deficient diet (0.30% Ca+0.18% NPP), respectively.  The results showed that dietary Ca or P deficiency decreased (P<0.05) tibia bone mineral density (BMD), bone breaking strength (BBS), ash content, tibia ash Ca content and serum P content on days 28 and 42, but increased (P<0.05) tibia alkaline phosphatase (ALP) activity of broilers on day 42 compared with the control group.  Furthermore, the broilers fed the P-deficient diet had the lowest (P<0.05) tibia BMD, BBS, ash content, serum P content and the highest (P<0.05) serum Ca content on day 28 compared with those fed the Ca-deficient or Ca and P-deficient diets.  The results from the present study indicated that the bone development and related Ca or P metabolic utilization parameters of broilers were the most sensitive to dietary P deficiency, followed by dietary Ca deficiency or Ca and P-deficiency; dietary Ca or P deficiency impaired the bone development possibly by regulating serum Ca and P contents as well as tibia Ca content and ALP activity of broilers from 22 to 42 days of age.
    Detection of antimicrobial resistance and virulence-related genes in Streptococcus uberis and Streptococcus parauberis isolated from clinical bovine mastitis cases in northwestern China
    ZHANG Hang, YANG Feng, LI Xin-pu, LUO Jin-yin, WANG Ling, ZHOU Yu-long, YAN Yong, WANG Xu-rong, LI Hong-sheng
    2020, 19(11): 2784-2791.  DOI: 10.1016/S2095-3119(20)63185-9
    Abstract ( )   PDF in ScienceDirect  
    The objectives of this study were to investigate antimicrobial resistance of Streptococcus uberis and Streptococcus parauberis isolated from cows with bovine clinical mastitis in China and to examine the distribution of resistance- and virulence-related gene patterns.  Antimicrobial susceptibility was determined by the E-test.  Genes encoding antimicrobial resistance and invasiveness factors were examined by PCR.  A total of 27 strains were obtained from 326 mastitis milk samples.  Streptococcus parauberis isolates (n=11) showed high resistance to erythromycin (90.9%), followed by tetracycline (45.5%), chloramphenicol (36.4%) and clindamycin (27.3%).  Streptococcus uberis isolates (n=16) were highly resistant to tetracycline (81.3%) and clindamycin (62.5%).  Both species were susceptible to ampicillin.  The most prevalent resistance gene in S. uberis was tetM (80.0%), followed by blaZ (62.5%) and ermB (62.5%).  However, tetM, blaZ, and ermB genes were only found in 27.3, 45.5, and 27.3%, respectively, of S. parauberis.  In addition, all of the isolates carried at least one selected virulence-related gene.  The most prevalent virulence-associated gene pattern in the current study was sua+pauA/skc+gapC+hasC detected in 22.2% of the strains.  One S. uberis strain carried 7 virulence-associated genes and belonged to the sua+pauA/skc+gapC+cfu+hasA+hasB+hasC pattern.  More than 59.3% of analysed strains carried 4 to 7 virulence-related genes.  Our findings demonstrated that S. parauberis and S. uberis isolated from clinical bovine mastitis cases in China exhibited diverse molecular ecology, and that the strains were highly resistant to antibiotics commonly used in the dairy cow industry.  The data obtained in the current study contribute to a better understanding of the pathogenesis of bacteria in mastitis caused by these pathogens, and the findings are relevant to the development of multivalent vaccines and targeted prevention procedures.
    Agro-ecosystem & Environment
    Effects of nitrogen application rates and irrigation regimes on grain yield and water use efficiency of maize under alternate partial rootzone irrigation
    QI Dong-liang, HU Tian-tian, SONG Xue
    2020, 19(11): 2792-2806.  DOI: 10.1016/S2095-3119(20)63205-1
    Abstract ( )   PDF in ScienceDirect  
    Faced with the scarcity of water resources and irrational fertilizer use, it is critical to supply plants with water and fertilizer in a coordinated pattern to improve yield with high water use efficiency (WUE).  One such method, alternate partial root-zone irrigation (APRI), has been practiced worldwide, but there is limited information on the performance of different irrigation regimes and nitrogen (N) rates under APRI.  The objectives of this study were to investigate the effects of varying irrigation regimes and N rates on shoot growth, grain yield and WUE of maize (Zea mays L.) grown under APRI in the Hexi Corridor area of Northwest China in 2014 and 2015.  The three N rates were 100, 200 and 300 kg N ha–1, designated N1, N2 and N3, respectively.  The three irrigation regimes of 45–50%, 60–65% and 75–80% field capacity (FC) throughout the maize growing season, designated W1, W2 and W3, respectively, were applied in combination with each N rate.  The results showed that W2 and W3 significantly increased the plant height, stem diameter, crop growth rate, chlorophyll SPAD value, net photosynthetic rate (Pn), biomass, grain yield, ears per ha, kernels per cob, 1 000-kernel weight, harvest index, evapotranspiration and leaf area index (LAI) compared to W1 at each N rate.  The N2 and N3 treatments increased those parameters compared to N1 in each irrigation treatment.  Increasing the N rate from the N2 to N3 resulted in increased biomass and grain yield under W3 while it had no impact on those under the W1 and W2 treatments.  The W3N3 and W2N2 and W2N3 treatments achieved the greatest and the second-greatest biomass and grain yield, respectively.  Increasing the N rate significantly enhanced the maximum LAI (LAI at the silking stage ) and Pn under W3, suggesting that the interaction of irrigation and fertilizer N management can effectively improve leaf growth and development, and consequently provide high biomass and grain yield of maize.  The W2N2, W2N3 and W3N3 treatments attained the greatest WUE among all the treatments.  Thus, either 60–65% FC coupled with 200–300 kg N ha–1 or 75–80% FC coupled with 300 kg N ha–1 is proposed as a better pattern of irrigation and nitrogen application with positive regulative effects on grain yield and WUE of maize under APRI in the Hexi Corridor area of Northwest China and other regions with similar environments.  These results can provide a basis for in-depth understanding of the mechanisms of grain yield and WUE to supply levels of water and nitrogen.
    Liming reduces soil phosphorus availability but promotes yield and P uptake in a double rice cropping system
    LIAO Ping, Mart B. H. ROS, Natasja VAN GESTEL, SUN Yan-ni, ZHANG Jun, HUANG Shan, ZENG Yong-jun, WU Zi-ming, Kees Jan VAN GROENIGEN
    2020, 19(11): 2807-2814.  DOI: 10.1016/S2095-3119(20)63222-1
    Abstract ( )   PDF in ScienceDirect  
    Liming is often applied to alleviate soil acidification and increase crop yield on acidic soils, but its effect on soil phosphorus (P) availability is unclear, particularly in rice paddies.  The objective of this study was to examine the effect of liming on rice production, yield and P uptake in a three-year field experiment in a double rice cropping system in subtropical China.  We also conducted an incubation experiment to investigate the direct effect of liming on soil available P and phosphatase activities on paddy soils in the absence of plants.  In the incubation experiment, liming reduced soil P availability (measured as Olsen-extractable P) by 14–17% and inhibited the activity of soil acid phosphatase.  Nonetheless, lime application increased grain yield, biomass, and P uptake in the field.  Liming increased grain yield and P uptake more strongly for late rice (26 and 21%, respectively) than for early rice (15 and 8%, respectively).  Liming reduced the concentration of soil available P in the field as well, reflecting the increase in rice P uptake and the direct negative effect of liming on soil P availability.  Taken together, these results suggest that by stimulating rice growth, liming can overcome direct negative effects on soil P availability and increase plant P uptake in this acidic paddy soil where P is not the limiting factor.
    Comparison of machine learning algorithms for mapping mango plantations based on Gaofen-1 imagery
    LUO Hong-xia, DAI Sheng-pei, LI Mao-fen, LIU En-ping, ZHENG Qian, HU Ying-ying, YI Xiao-ping
    2020, 19(11): 2815-2828.  DOI: 10.1016/S2095-3119(20)63208-7
    Abstract ( )   PDF in ScienceDirect  
    Mango is a commercial crop on Hainan Island, China, that is cultivated to develop the tropical rural economy.  The development of accurate and up-to-date maps of the spatial distribution of mango plantations is necessary for agricultural monitoring and decision management by the local government.  Pixel-based and object-oriented image analysis methods for mapping mango plantations were compared using two machine learning algorithms (support vector machine (SVM) and Random Forest (RF)) based on Chinese high-resolution Gaofen-1 (GF-1) imagery in parts of Hainan Island.  To assess the importance of different features on classification accuracy, a combined layer of four original bands, 32 gray-level co-occurrence (GLCM) texture indices, and 10 vegetation indices were used as input features.  Then five different sets of variables (5, 10, 20, and 30 input variables and all 46 variables) were classified with the two machine learning algorithms at object-based level.  Results of the feature optimization suggested that homogeneity and variance were very important variables for distinguishing mango plantations patches.  The object-based classifiers could significantly improve overall accuracy between 2–7% when compared to pixel-based classifiers.  When there were 5 and 10 input variables, SVM showed higher classification accuracy than RF, and when the input variables exceeded 20, RF showed better performances.  After the accuracy achieved saturation points, there were only slightly classification accuracy improvements along with the numbers of feature increases for both of SVM and RF classifiers.  The results indicated that GF-1 imagery can be successfully applied to mango plantation mapping in tropical regions, which would provide a useful framework for accurate tropical agriculture land management. 
    Food Science
    Phenolic extract of Morchella angusticeps peck inhibited the proliferation of HepG2 cells in vitro by inducing the signal transduction pathway of p38/MAPK
    LI Fu-hua, ZHENG Shao-jie, ZHAO Ji-chun, LIAO Xia, WU Su-rui, MING Jian
    2020, 19(11): 2829-2838.  DOI: 10.1016/S2095-3119(20)63322-6
    Abstract ( )   PDF in ScienceDirect  
    Morchella angusticeps Peck, one of the most popular edible mushrooms, has attracted great attention due to its delicious taste and healthy properties.  However, both its biological effects and the possible mechanism of action have not yet been known.  We investigated the anti-proliferative activity of the phenolic extract derived from Morchella angusticeps Peck (MPE) against HepG2 human hepatocellular carcinoma cells.  Results showed that MPE at non-cytotoxicity doses significantly inhibited the proliferation of HepG2 cells in a dose-dependent manner with inhibitory rates ranging from 18 to 90% (P<0.01).  The possible mechanism might be that MPE induced apoptosis through initiating the mitochondrial death pathway by regulating Bax, Bcl-2 and cleaved caspase-3.  On the other hand, MPE might trigger cell cycle arrest at G0/G1/S phases by managing p21, Cyclin D1, cyclin-dependent kinases-4 (CDK4) and proliferating cell nuclear antigen (PCNA).  Additionally, MPE downregulated TRAF-2 and p-p53, while upregulated p-ASK1 and p-p38.  Therefore, it could be inferred that MPE might induce the anti-proliferative function to HepG2 cells through the p38/MAPK signal transduction pathway.
    Comprehensive characterization of yam tuber nutrition and medicinal quality of Dioscorea opposita and D. alata from different geographic groups in China
    SHAN Nan, WANG Pu-tao, ZHU Qiang-long, SUN Jing-yu, ZHANG Hong-yu, LIU Xing-yue, CAO Tian-xu, CHEN Xin, HUANG Ying-jin, ZHOU Qing-hong
    2020, 19(11): 2839-2848.  DOI: 10.1016/S2095-3119(20)63270-1
    Abstract ( )   PDF in ScienceDirect  
    China is an important domestication center of yams, and two main yam species of Dioscorea opposita and D. alata are commonly cultivated in China.  However, the differences of nutritional and medicinal characteristics between the two species and their subgroups remain unclear, which would greatly affect the resource conservation and commercial utilization of yams.  In this study, typical yam resources including the species of D. opposita (wild and cultivated Ruichang yam from southern China, and Tiegun yam from northern China) and two landraces of D. alata (Longyan yam and Anyuan yam from southern China) were selected as materials.  Nutritional traits and medicinal characteristics were determined and analyzed respectively.  The results showed that there was no significant differences in the content of most nutrients between D. opposita and D. alata, but most cultivated Ruichang yam of D. opposita showed higher levels of starch, soluble sugar, sucrose, and ascorbate in tuber than that in yam from D. alata.  Moreover, an UPLC-MS method was developed for identification and determination of medicinal characteristics in the two species.  The results showed that allantoin can be detected in all selected samples.  Cultivated Ruichang yam of D. opposita possessed the highest allantoin content among the tested materials, and was significantly different with that in Tiegun yam and D. alata. Dioscin was not detected in D. alata. Overall, there was little difference in nutritional composition between D. opposita and D. alata, but the medicinal quality of D. opposita was better than that of D. alata.  Due to the outstanding comprehensive quality, the local variety of cultivated Ruichang yam can be further developed and utilized.