Host factors underlying genetic susceptibility to Xanthomonas infection: a study of a neglected tropical disease in passion fruit (Passiflora alata)

Abstract

Abstract De novo RNA-Seq assembly facilitates the study of transcriptomes of non-model, underutilized crops, enabling researchers to capture the maximum number of genes expressed in plant tissues. We were able to describe the expression profiling of the sweet passion fruit (Passiflora alata) in response to Xanthomonas axonopodis pv. passiflorae(Xap) infection. The crop is appreciated for the typical aroma and characteristic flavor of its fruits. However, yield is impaired by Xap, whose effects are exacerbated by high temperature and humidity. Initially, we provided the P. alata transcriptome assemblies which were shown to have high completeness, based on the expected gene content for a de novo transcriptome assembly. A total of 1,329 were completed genes and 96.6% of the orthologs conserved across Embryophytes were represented in the assembled transcriptome. Genes involved in pathogen recognition such as PRRs, R genes and genes related to the signaling cascade, coding for specific transcription factors and secondary metabolites, were found to be upregulated after infection. P. alata is known to be susceptible to Xap, thus we were interested in identifying possible susceptibility (S) genes. Interestingly, both characterized S genes in other plant species i.e., SWEET10 and LOB1were found to be upregulated in P. alata, suggesting that an effector-triggered susceptibility was achieved through the interaction between Xap and P. alata. Our qPCR results corroborate the role played by these genes, which could potentially be targets for genome editing in order to produce disease-resistant cultivars.