Regulation of hormone pathways in wheat infested by Blumeria graminis f. sp. tritici.

BACKGROUND: Wheat powdery mildew is an obligate biotrophic pathogen infecting wheat, which can pose a serious threat to wheat production. In this study, transcriptome sequencing was carried out on wheat leaves infected by Blumeria graminis f. sp. tritici from 0 h to 7 d. RESULTS: KEGG and GO enrichment analysis revealed that the upstream biosynthetic pathways and downstream signal transduction pathways of salicylic acid, jasmonic acid, and ethylene were highly enriched at all infection periods. Trend analysis showed that the expressions of hormone-related genes were significantly expressed from 1 to 4 d, suggesting that 1 d-4 d is the main period in which hormones play a defensive role. During this period of time, the salicylic acid pathway was up-regulated, while the jasmonic acid and ethylene pathways were suppressed. Meanwhile, four key modules and 11 hub genes were identified, most of which were hormone related. CONCLUSION: This study improves the understanding of the dynamical responses of wheat to Blumeria graminis f. sp. tritici infestation at the transcriptional level and provides a reference for screening core genes regulated by hormones.

Identification of Key Modules and Candidate Genes for Powdery Mildew Resistance of Wheat-Agropyron cristatum Translocation Line WAT-2020-17-6 by WGCNA

As one of the serious diseases of wheat, powdery mildew (Blumeria graminis f. sp. tritici) is a long-term threat to wheat production. Therefore, it is of great significance to explore new powdery mildew-resistant genes for breeding. The wild relative species of wheat provide gene resources for resistance to powdery mildew breeding. Agropyron cristatum (2n = 4x = 28, genomes PPPP) is an important wild relative of wheat, carrying excellent genes for high yield, disease resistance, and stress resistance, which can be used for wheat improvement. To understand the molecular mechanism of powdery mildew resistance in the wheat-A. cristatum translocation line WAT2020-17-6, transcriptome sequencing was performed, and the resistance genes were analyzed by weighted gene co-expression network analysis (WGCNA). In the results, 42,845 differentially expressed genes were identified and divided into 18 modules, of which six modules were highly correlated with powdery mildew resistance. Gene ontology (GO) enrichment analysis showed that the six interested modules related to powdery mildew resistance were significantly enriched in N-methyltransferase activity, autophagy, mRNA splicing via spliceosome, chloroplast envelope, and AMP binding. The candidate hub genes of the interested modules were further identified, and their regulatory relationships were analyzed based on co-expression data. The temporal expression pattern of the 12 hub genes was verified within 96 h after powdery mildew inoculation by RT-PCR assay. In this study, we preliminarily explained the resistance mechanism of the wheat-A. cristatum translocation lines and obtained the hub candidate genes, which laid a foundation in the exploration of resistance genes in A. cristatum for powdery mildew-resistant breeding in wheat.

Development and identification of an elite wheat-Hordeum californicum T6HcS/6BL translocation line ND646 containing several desirable traits.

Hordeum californicum (H. californicum, 2n=2X=14, HcHc), one of the wild relatives of wheat (Triticum aestivum L.), harbors many desirable genes and is a potential genetic resource for wheat improvement. In this study, an elite line ND646 was selected from a BC4F5 population, which was developed using 60Co-γ irradiated wheat-H. californicum disomic addition line WJ28-1 (DA6Hc) as the donor parent and Ningchun 4 as the recurrent parent. ND646 was identified as a novel wheat-H. californicum 6HcS/6BL translocation line using genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), and H. californicum-specific expressed sequence tag (EST) markers. Further evaluation revealed that ND646 had excellent performance in several traits, such as a higher sedimentation value (SV), higher water absorption rate (WAR), and higher hardness index (HI). More importantly, it had more kernels per spike (KPS), a higher grain yields (GY), and good resistance to powdery mildew, leaf rust, and 2,4-D butylate (2,4-D). Its excellent phenotypic performance laid the foundation for further investigation of its genetic architecture and makes ND646 a useful germplasm resource for wheat breeding.

Genome-wide identification of the jumonji C domain- containing histone demethylase gene family in wheat and their expression analysis under drought stress.

Methylation and demethylation of histone play a crucial role in regulating chromatin formation and gene expression. The jumonji C (JmjC) domain-containing proteins are demethylases that are involved in regulating epigenetic modification in plants. In our study, the JmjC genes in Triticum aestivum L., Triticum turgidum L., Triticum dicoccoides L., Triticum urartu L., and Aegilops tauschii L. were identified. Phylogenetic relationship and colinearity analysis revealed that the wheat JmjC genes were conserved in A, B, and D subgenomes during evolution. Cis-acting elements analysis showed that elements related to stress response, hormone response, and light response were found in wheat JmjC genes. The expression of JmjC genes was affected by tissue types and developmental stages, and members of the same subfamily tended to have similar expression patterns in wheat. They also showed a unique expression pattern in root during PEG (Polyethylene glycol) treatment. In conclusion, comprehensive analysis indicated that three members (Tr-1A-JMJ2, Tr-1B-JMJ2, and Tr-1D-JMJ2) might be regulated by several hormones and function in the early stages of drought stress, while eight members (Tr-1B-JMJ3, Tr-4B-JMJ1, Tr-7A-JMJ1, etc.) displayed a significantly high expression after 24 h of PEG treatment, indicating a role in the later stages of drought stress. This research presents the first genome-wide study of the JmjC family in wheat, and lays the foundation for promoting the study of their functional characterization in wheat drought resistance.