Stage-specific reprogramming of gene expression characterizes Lr48-mediated adult plant leaf rust resistance in wheat

Abstract

Wheat genotype CSP44 carrying a recessive gene Lr48 exhibits adult plant resistance (APR; incompatible reaction) but gives a compatible reaction (susceptibility) at the seedling stage against leaf rust. A comparative gene expression analysis involving cDNA-amplified fragment length polymorphism (cDNA-AFLP) and quantitative PCR (qPCR) was carried out for incompatible and compatible reactions in the genotype CSP44. cDNA-AFLP analysis was conducted using RNA samples that were isolated from flag leaves following inoculation with leaf rust race 77-5 (the most virulent race) and also after mock inoculation. As many as 298 of a total of 493 expressed transcript-derived fragments (TDFs) exhibited differential expression (262 upregulated and 36 downregulated). Of these 298 TDFs, 48 TDFs were eluted from gels, re-amplified, cloned, and sequenced. Forty two of these 48 TDFs had homology with known genes involved in the following biological processes: energy production, metabolism, transport, signaling, defense response, plant-pathogen interaction, transcriptional regulation, translation, and proteolysis. The functions of the remaining six TDFs could not be determined; apparently, these represented some novel genes. The qPCR analysis for 18 TDFs (with known and unknown functions, but showing major differences in expression) was conducted using RNA isolated from the seedlings as well as from the adult plants. The expression of at least 11 TDFs was induced and that of 4 other TDFs attenuated or remained near normal in adult plants following leaf rust inoculations. The remaining three TDFs had non-specific/developmental stage-specific expression. Functional annotation of TDFs that were upregulated suggest that the APR was supported by transient recruitment and reprogramming of processes like perception and recognition of pathogen effector by receptors, followed by CDPK and MAPK signaling, transport, metabolism, and energy release.

De Novo Assembled Wheat Transcriptomes Delineate Differentially Expressed Host Genes in Response to Leaf Rust Infection

“…Moreover, many genes identified in this study are in concordance with the study carried out in Arachis diogoi challenged by late Leaf Spot Pathogen, Phaeoisariopsis personata [ 96 ]. In another study by our group, cDNA-AFLP (Amplified Fragment Length Polymorphism) was performed during compatible and incompatible leaf rust infection in wheat NILs carrying the recessive Lr48 gene [ 97 ]. As many as 298 transcripts exhibited differential expression, of which 42 transcripts had homology with genes involved in energy production, metabolism, transport, signaling, defense response, plant-pathogen interaction, transcriptional regulation, translation and proteolysis.…”