Small RNA bidirectional crosstalk during the interaction between wheat and Zymoseptoria tritici

Abstract

Cross-kingdom RNAi has been shown to play important roles during plant pathogen interactions. But this cross-kingdom RNAi was still unexplored in the wheat-Zymoseptoria tritici pathosystem. Here we performed a detailed analysis of the sRNA bidirectional crosstalk between wheat and Z. tritici. Using a combination of sRNA-seq and mRNA-seq we were able to identify known and novel sRNAs and study their expression and their action on putative targets in both wheat and Z. tritici. We predicted the target genes of all the sRNAs in either wheat or Z. tritici transcriptome and used degradome analysis to validate the cleavage of these gene transcripts. We could not find any clear evidence of a cross-kingdom RNAi in this pathosystem. We also found that the fungal sRNA enrichment was lower in planta than during in vitro growth, probably due to the lower expression of the only Dicer gene of the fungus during plant infection. However, we found a downregulation of specific wheat sRNAs during the fungal infection, leading to a boost expression of wheat defense related genes, which may be enhancing the plant defense ability against the pathogen. Additionally, the fungal infection also induced sRNAs regulating the expression of specific wheat genes, including auxin related genes, as an immune response. These results confirm the role of sRNAs in the regulation of wheat defenses during Z. tritici infection. Our findings contribute to improve our understanding of the interactions between wheat and Z. tritici.