Deciphering critical regulators in wheat rust immunity (SAUNDERS_J27DTP)
Successful plant pathogens hijack plant metabolism and biosynthetic pathways to enrich nutrient availability. However, exploiting host physiology creates changes in metabolites that plants can sense and interpret as indicators of pathogen infection. This includes branched chain amino acids (BCAAs), which represent important energy sources for pathogens, yet BCAA accumulation in plants also increases levels of the defence compound salicylic acid (SA), which plays a central role in directing immune signaling against biotrophic pathogens. We previously showed in bread wheat (Triticum aestivum), that infection by the biotrophic yellow rust pathogen (Puccinia striiformis f. sp. tritici; Pst) upregulates the gene for BCAA AMINOTRANSFERASE 1 (TaBCAT1), which modulates catabolism of BCAAs to prevent BCAA accumulation and promote Pst colonisation. In contrast, disrupting TaBCAT1 function leads to hyperaccumulation of BCAAs and SA, resulting in reduced susceptibility to Pst. Furthermore, we found that BCAA-mediated SA accumulation is dependent on a MYB/SANT transcription factor (TF), termed TaASIL1, which represses expression of TaSIZ1, a SUMO E3 ligase that is a key negative regulator of SA homeostasis. However, how BCAA accumulation enhances TaASIL1 activity remains to be resolved.
The aim of this proposal is to elucidate how BCAA availability activates SA-mediated defence and/or modulates metabolic signalling in plants, by: (i) resolving the unknown link between BCAA accumulation and activation of TaASIL1 function, and (ii) characterising additional BCAA-dependant gene targets of TaASIL1. This research will ultimately determine how MYB TFs mediate environmental signals, such as BCAAs, to modulate metabolic signalling in plants and provide critical new insight into basal plant defence responses in wheat.
The student will be embedded in the Saunders Lab at the John Innes Centre, which is a multidisciplinary research lab, providing the opportunity to develop extensive skills in a breadth of areas, including plant pathology, wheat genetics, molecular biology, and bioinformatics.