Project description:Aim:To characterise a recently discovered stem rust resistance locus on wheat chromosome 7AL. Transcriptome analysis by RNA-sequencing, in association with microscopic observations, was used to compare responses to the Puccinia graminis f. sp. tritici pathogen of the susceptible line Columbus, and two independent backcrossed resistant lines containing the locus, Columbus-NS765 and Columbus-NS766. Results: Microscopic observations of infected leaves revealed that the resistance conferred by the 7AL resistance locus was initiated by two days post-inoculation, upon the entry of the stem rust fungus into the plant through the stoma. Death of guard and epidermal cells adjacent to the fungal points of entry was observed to be clearly more frequent in resistant lines than in the susceptible genotype, suggesting that the resistance response is similar in all genotypes, but enhanced in the resistant lines. Transcriptomic analysis, combined with assignment of genes to wheat chromosomes, revealed a disporportionately high number of differentially expressed genes were located on chromosomes 7AL and 6A. A number of genes annotated as cysteine-rich receptor-like kinases were located on chromosome 7AL. Closer investigation indicated that the encoded proteins were in fact putative receptor-like cytoplasmic kinases (RLCKs). One of the putative RLCK genes contained a SNP marker previously shown to co-segregate with the 7AL resistance locus. The large number of differentially expressed genes on chromosome 6A indicated the presence of a large introgression on this chromosome that co-segregated with stem rust resistance in the two independent resistant lines, but its role in the resistance response is currently unclear. Conclusions: This study represents the first transcriptome analysis of responses to stem rust in wheat, and the first investigation of the resistance conferred by the newly-discovered wheat 7AL stem rust resistance locus. Microscopy showed the resistance response was associated with pre-haustorial cell death. Results of the RNA-seq, which has the resolution to discriminate between homeologous wheat genes, along with assignment of differentially expressed genes to wheat chromosomes, suggested putative receptor-like cytoplasmic kinases linked to the 7AL locus as candidate resistance genes for further investigation.
Project description:Stem rust of wheat is a deleterious fungal disease across the globe causing severe yield losses. Although, many stem rust resistance genes (Sr) are being used in wheat breeding programs, new emerging stem rust pathotypes are a challenge to important Sr genes. In recent years, multiple studies on leaf and yellow rust molecular mechanism have been done, however, for stem rust such studies are lacking. Current study investigated stem rust induced response in the susceptible wheat genotype C306 and its Near Isogenic Line (NIL) for Sr24 gene, HW2004, using microarray analysis to understand the transcriptomic differences at different stages of infection. Results showed that HW2004 has higher basal levels of several important genes involved in pathogen detection, defence, and display early activation of multiple defence mechanisms. Further Gene Ontology (GO) and pathway analysis identified important genes responsible for pathogen detection, downstream signalling cascades and transcription factors (TFs) involved in activation and mediation of defence responses. Results suggest that generation of Reactive Oxygen Species (ROS), cytoskeletal rearrangement, activation of multiple hydrolases, and lipid metabolism mediated biosynthesis of certain secondary metabolites are collectively involved in Sr24-mediated defence in HW2004, in response to stem rust infection. Novel and unannotated, but highly responsive genes were also identified, which may also contribute towards resistance phenotype. Furthermore, certain DEGs also mapped close to the Sr24-linked marker on Thinopyrum elongatum translocated fragment on wheat 3E chromosome, which advocate further investigations for better insights of the Sr24-mediated stem rust resistance.
Project description:Purpose: Next-generation sequencing (NGS) has revolutionized systems-based analysis of cellular pathways. The goals of this study are to compare NGS-derived Triticum aestivum transcriptome (RNA-seq) profiling methods and to evaluate genotypes associated with resistance against the Wheat dwarf virus. Methods: Triticum aestivum mRNA profiles of genotypes associated with resistance against the Wheat dwarf virus were generated by deep sequencing, in four replicates, using Illumina. The sequence reads that passed quality filters were analyzed at the transcript isoform level with two methods: Burrows–Wheeler Aligner (BWA) followed by ANOVA (ANOVA) and TopHat followed by Cufflinks. qRT–PCR validation was performed using TaqMan and SYBR Green assays. Conclusions: Our study represents the first detailed analysis of Triticum aestivum transcriptomes, with biologic replicates, generated by RNA-seq technology. The optimized data analysis workflows reported here should provide a framework for comparative investigations of expression profiles. Our results show that NGS offers a comprehensive and more accurate quantitative and qualitative evaluation of mRNA and miRNA content within a cell or tissue. We conclude that RNA-seq based transcriptome characterization would expedite genetic network analyses and permit the dissection of complex biologic functions.
Project description:The RNA sequencing analysis was undertaken to investigate the transcriptomic changes in adult wheat inoculated with Puccinia graminis f. sp. tritici the causal agent of stem rust disease. The project firstly aims to compare gene expression in one susceptible wheat line with two wheat lines exhibiting adult plant resistance to the stem rust. Secondly, the project aims to examine the temporal changes in gene expression in wheat after inoculation. Wheat plants was grown until maturity under greenhouse conditions. Plants were inoculated with Puccinia graminis f. sp. tritici and the flag leaf sheath sampled for RNA sequencing. The project aims to give essential insight into the adult plant resistance response in wheat to Puccinia graminis f. sp. tritici inoculation.
Project description:To improve our understanding of the organization and evolution of the wheat gene space, we established the first map of genes of the wheat chromosome 1BL by hybridizing the newly developed INRA GDEC Triticum aestivum NimbleGen 12x40k unigenes microarray (A-MEXP-2314) with BAC pools from the 1BL physical map as well as with genomic DNA of the sorted chromosome 1BL. By hybridizing the BAC pools with the wheat NimbleGen 40K unigenes chip we managed to map almost 1615 unigenes on the wheat chromosome 1BL BACs. By hybridizing the genomic DNA of the 1BL sorted chromosome and by comparison with 454 sequences from the sorted chromosome 1BL, we confirmed the assignation of 1223 unigenes in individual BACs from the chromosome 1BL. This data allowed us to study the organization of the wheat gene space along chromosome 1BL. The sequences of the unigenes helped to perform synteny and evolutionary analyses of these unigenes.