RNAseq analysis of cassava reveals similar plant responses upon infection with pathogenic and non-pathogenic strains of Xanthomonas axonopodis pv. manihotis

Abstract: Cassava bacterial blight, a disease caused by the gram-negative bacterium Xanthomonas axonopodis pv. manihotis (Xam), is a major limitation to cassava production worldwide and especially in developing countries. The molecular mechanisms underlying cassava susceptibility to Xam are currently unknown. To identify host genes and pathways leading to plant susceptibility, we analyzed the transcriptomic responses occurring in cassava plants challenged with either the non-pathogenic Xam strain ORST4, or strain ORST4(TALE1) which is pathogenic due to the major virulence transcription activator like effector TALE1. Both strains triggered similar responses, i.e., induction of genes related to photosynthesis and phenylpropanoid biosynthesis, and repression of genes related to jasmonic acid signaling. Finally, to search for TALE1 virulence targets, we scanned the list of cassava genes induced upon inoculation of ORST4(TALE1) for candidates harboring a predicted TALE1 effector binding element in their promoter. Among the six genes identified as potential candidate targets of TALE1 a gene coding for a heat shock transcription factor stands out as the best candidate based on their induction in presence of TALE1 and contain a sequence putatively recognized by TALE1. Key message: An RNAseq-based analysis of the cassava plants inoculated withXamallowed the identification of transcriptional upregulation of genes involved in jasmonate metabolism, phenylpropanoid biosynthesis and putative targets for a TALE.