Arabinogalactan proteins (AGPs) are widely distributed in the plant kingdom and play a vital role during the process of plant sexual reproduction.  In this study, we performed a comprehensive identification of the PbrAGPs expressed in pear pollen and further explored their influences on pollen tube growth.  Among the 187 PbrAGPs that were found to be expressed in pear pollen tubes, 38 PbrAGPs were specifically expressed in pollen according to the RNA-seq data.  The PbrAGPs were divided into two groups of highly expressed and specifically expressed in pear pollen.  We further tested their expression patterns using RT-PCR and RT-qPCR.  Most of the PbrAGPs were expressed in multiple tissues and their expression levels were consistent with reads per kilobase per million map reads (RPKM) values during pollen tube growth, implying that PbrAGPs might be involved in the regulation of pear pollen tube growth.  We also constructed phylogenetic trees to identify the functional genes in pear pollen tube growth.  Therefore, 19 PbrAGPs (PbrAGP1 to PbrAGP19) were selected to test their influences on pollen tube growth.  Recombinant proteins of the 19 PbrAGP-His were purified and used to treat pear pollen, and 11 of the PbrAGP-His recombinant proteins could promote pear pollen tube growth.  Additionally, pollen tube growth was inhibited when the expression levels of PbrAGP1 and PbrAGP5 were knocked down using an antisense oligonucleotide assay.  PbrAGP1 and PbrAGP5 were localized in the plasma membrane and might not alter the distribution of pectin in the pollen tube.  In summary, this study identified the PbrAGPs expressed in pear pollen and lays the foundation for further exploring their functions in pollen tube growth.

The mutation of the gene encoding a stearoyl-acyl carrier protein fatty acid desaturase (ssi2) has been proved to enhance pathogen resistance in several plants, while it’s potential to regulate biotic and abiotic stresses in wheat is still unclear.  In this study, we cloned TaSSI2 gene in wheat and provided several evidences of its involvement in multiple biological functions.  By using barley stripe mosaic virus (BSMV)-induced gene silencing (VIGS) in wheat, it was found that TaSSI2 negatively regulated both powdery mildew and Fusarium head blight (FHB) resistance, which was consistent with the phenotype observed in knock-out mutants of Kronos.  The expression of TaSSI2 was down-regulated by in vitro treatments of methyl jasmonate (MeJA), but positively regulated by salicylic acid (SA) and abscisic acid (ABA), implying the cross-talk between different hormone signaling pathways involved in wheat to regulate biotic stresses is still to be elucidated.  Furthermore, the up-regulated expression of PR4 and PR5 indicated that TaSSI2 probably regulated FHB resistance by depressing the SA signaling pathway in wheat.  In addition, the over-expression of TaSSI2 increased the content of linolenic acid (18:3) and subsequently enhanced drought tolerance of transgenic Brachypodium.  This phenomenon might be associated with its subcellular localization in the whole cytosol, partly overlapping with Golgi apparatus and the secreted vesicles.  As a stearoyl-acyl carrier protein fatty acid desaturase, TaSSI2 was proposed to be involved in cell lipid metabolism and carried targets out of the cell from membrane or wax synthesis, resulting in enhanced drought tolerance in plant.

    The pleiotropic drug resistance (PDR) sub-family of adenosine triphosphate (ATP)-binding cassette (ABC) transporter had been reported to participate in diverse biological processes of plant. In this study, we cloned three novel PDR genes in Fusarium head blight (FHB) resistant wheat cultivar Ning 7840, which were located on wheat chromosomes 6A, 6B and 6D. In phylogeny, these genes were members of cluster I together with AePDR7 and BdPDR7. Subcellular localization analysis showed that TaPDR7 was expressed on the plasmalemma. The quantitative real time PCR (RT-PCR) analysis showed that this gene and its probable orthologues in chromosomes 6B and 6D were both up-regulated sharply at 48 h after infected by Fusarium graminearum and trichothecene deoxynivalenol (DON) in spike. When knocking down the transcripts of all TaPDR7 members by barely stripe mosaic virus-induced gene silencing (BSMV-VIGS) system, it could promote the F. graminearum hyphae growth and made larger pathogen inoculation points in Ning 7840, which suggested that TaPDR7 might play an important role in response to F. graminearum. Although salicylic acid (SA), methyl jasmonate (MeJA) and abscisic acid (ABA) had been reported to possibly regulate wheat FHB resistance, here, we found that the three members of TaPDR7 were negatively regulated by these three hormones but positively regulated by indoleacetic acid (IAA).

Fusarium head blight (FHB), caused primarily by Fusarium graminearum, is a destructive disease of wheat throughout the world. However, the mechanisms of host resistance to FHB are still largely unclear. Deoxynivalenol (DON) produced by F. graminearum which enhances the pathogen to spread could be converted into inactive form D3G by UDP-glycosyltransferases (UGTs). A DON responsive UGT gene, designated as TaUGT4, was first cloned from wheat in this study. The putative open reading frame (ORF) of TaUGT4 was 1 386 bp, encoding 461 amino acids protein. TaUGT4 was placed on chromosome 2D using a set of nulli-tetrasomic lines of wheat cultivar Chinese Spring (CS). When fused with eGFP at C terminal, TaUGT4 was shown to localize in cytoplasm of the transformed tobacco cells. The transcriptional analysis revealed that TaUGT4 was strongly induced by F. graminearum or DON in both of FHB-resistant cultivar Sumai 3 and susceptible cultivar Kenong 199, especially in Sumai 3 under DON treatment. Similar increase of TaUGT4 expression was observed in Sumai 3 and Kenong 199 in response to salicylic acid (SA) treatment. But interestingly, the transcripts level of TaUGT4 in Sumai 3 showed significantly higher than that in Kenong 199 after treated with methyl jasmonate (MeJA). According to the expression patterns, TaUGT4 might lead to different effects between FHB-resistant genotype and susceptible genotype in the process against F. graminearum inoculation. It had also been discussed in this paper that JA signaling pathway might play a significant role in the resistance against F. graminearum compared to SA signaling pathway.

Seven important grain traits, including grain length (GL), grain width (GW), grain perimeter (GP), grain area (GA), grain length/width ratio (GLW), roundness (GR), and thousand-grain weight (TGW), were analyzed using a set of 139 simple sequence repeat (SSR) markers in 130 hexaploid wheat varieties and 193 Aegilops tauschii accessions worldwide. In total, 1 612 alleles in Ae. tauschii and 1 360 alleles in hexaploid wheat (Triticum aestivum L.) were detected throughout the D genome. 197 marker-trait associations in Ae. tauschii were identified with 58 different SSR loci in 3 environments, and the average phenotypic variation value (R2) ranged from 0.68 to 15.12%. In contrast, 208 marker-trait associations were identified in wheat with 66 different SSR markers in 4 environments and the average phenotypic R2 ranged from 0.90 to 19.92%. Further analysis indicated that there are 6 common SSR loci present in both Ae. tauschii and hexaploid wheat, which are significantly associated with the 5 investigated grain traits (i.e., GA, GP, GR, GL, and TGW) and in total, 16 alleles derived from the 6 aforementioned SSR loci were shared by Ae. tauschii and hexaploid wheat. These preliminary data suggest the existence of common alleles may explain the evolutionary process and the selection between Ae. tauschii and hexaploid wheat. Furthermore, the genetic differentiation of grain shape and thousand-grain weight were observed in the evolutionary developmental process from Ae. tauschii to hexaploid wheat.

Expression profiles of ten pathogenesis-related (PR) genes during plant defense against Fusarium, Yellow dwarf virus (YDV) aphid-transmitted and Hessian fly (Hf) were compared temporally in both resistant and susceptible genotypes following pathogen infection or insect infestation. Quantitative real-time PCR (qRT-PCR) revealed that PR1, PR2, PR3, PR5, PR6, PR8, PR9, and PR15 appeared to be induced or suppressed independently in response to Fusarium, YDV aphid-transmitted or Hf during the interactions. The PR gene(s) essential to defense against one organism may play little or no role in defense against another pathogen or pest, suggesting the alternative mechanisms may be involved in different interactions of wheat- Fusarium, wheat-YDV aphid-transmitted and wheat-Hf. However, strong up- or down-regulation of PR12 and PR14 encoding low molecular membrane acting protein, defensin and lipid transfer protein (LTP), respectively, had been detected after either pathogen infection or insect infestation, therefore showed broad responses to pathogens and insects. It was postulated that low molecular proteins such as defensins and LTPs might play a role in the early stages of pathogenesis in the signaling process that informs plants about the attack from biotic stresses. In addition, a synergistic action between different PR genes might exist in plants to defense certain pathogens and insects on the basis of comprehensive expression profiling of various pathogenesis-related genes revealed by qRT-PCR in this study.