RNA-seq analysis of the tomato immune response identifies genes whose expression is induced by MAMPs and suppressed by type III effectors

ROSLI, HERNÁN GUILLERMO; FEI, ZHANGJUN; ZHEN, YI; COLLMER, ALAN; MARTIN, GREGORY

Congreso; IS-MPMI 2012 XV International Congress; 2012

Plants activate a variety of defense responses upon recognition of microbe-associated molecular patterns (MAMPs). This MAMP-triggered immunity (MTI) represents a first layer of defense and it can be suppressed by pathogens through the delivery of effectors into the cytoplasm. We used Illumina RNA-seq to perform a transcriptomic analysis of tomato leaves challenged with MAMPS (flg22, LPS, PGN), Pseudomonas syringae pv. tomato DC3000 and mutants (dhrcQ-U, dhrcQ-U/dfliC, d28, davrPto/davrPtoB), other Pseudomonas (P. fluorescens, P. putida) or Agrobacterium tumefaciens. An initial analysis of the treatments revealed the existence of two separate clusters: one that included mock, dhrcQ-U/dfliC, A. tumefaciens, LPS, PGN and DC3000, and the other containing the rest of the treatments. This distribution appears to be due to the perception or not of flagellin. Interestingly, wildtype DC3000, which expresses flagellin, clusters with the first group, indicating that the effectors delivered into the plant cell are largely involved in suppressing the transcriptional reprogramming that occurs upon flagellin perception. This large transcriptional suppression associated with delivery of the type III effectors is exemplified by the observation that of 2,600 genes induced by flg22, 1,600 are different when comparing DC3000 and the d28 "effector-less" mutant. We are currently focusing on this set of genes, especially those encoding protein kinases, whose expression appears to be targeted (directly or indirectly) by effectors, in order to identify novel genes involved in MTI.