Function and diversity of oomycetous and fungal small RNAs suppressing host plant immunity
Metabolism, Biochemistry and Genetics of Microorganisms
Final Report Abstract
In a previous proof of principle study, the discovery was made that the fungal plant pathogen B. cinerea secretes BcsRNA effectors that hijack the plant`s RNAi pathway to suppress important host immunity genes. This virulence strategy has been termed ckRNAi. The exchange of sRNAs between fungal pathogens and host plants has been reported to be bidirectional, as plants use sRNAs to fight back against infecting fungi. In this study, we discovered for the first time that an oomycete plant pathogen uses sRNA effectors to colonize host plants. Oomycetes and fungi are phylogenetically far distant; thus, this discovery expands the concept of ckRNAi to diverse plant pathogens. Moreover, we identified at least two functional sRNA effectors of the obligate biotroph pathogen H. arabidopsidis to suppress genes in its host plant A. thaliana. Both B. cinerea and H. arabidopsidis sRNA effectors bind to the plant AGO1 to induce host gene silencing. Moreover, a recent study reports that rhizobial bacterial sRNA effectors load into the AGO1 of soybean to achieve root nodule symbiosis. These examples of ckRNAi are remarkable discoveries from the point of view, that representatives of different microbial kingdoms and lifestyles evolved strategies to deliver sRNAs into their hosts and to manipulate plant gene expression. The pathogen H. arabidopsidis forms haustoria to parasite plant cells. Through these haustoria, not only sRNAs are possibly released, but also protein effectors. We here have shed light on an unexplored class of non-RxLR, apoplastic effectors, named the HaCRs, to explore their role in host infection. In future, it will be interesting to elucidate how plant pathogens orchestrate sRNA and protein effectors to colonize their host species and what are the plants` defence strategies to resist those.
Publications
- (2020) Oomycete small RNAs bind to the plant RNA-induced silencing complex for virulence. eLife
Dunker F., Trutzenberg A., Rothenpieler J.S., Kuhn S., Pröls R., Schreiber T., Tissier A., Hückelhoven R., Weiberg A.
(See online at https://doi.org/10.7554/eLife.56096) - (2021) An Arabidopsis downy mildew non-RxLR effector suppresses induced plant cell death to promote biotroph infection. J Exp Bot 72, 718-732
Dunker F., Oberkofler L., Lederer B., Trutzenberg A., Weiberg A.
(See online at https://doi.org/10.1093/jxb/eraa472) - (2021) Plant ARGONAUTE protein immunopurification for pathogen cross kingdom small RNA analysis. Bio Protocol 11, e3911
Dunker F., Lederer B., Weiberg A.
(See online at https://doi.org/10.21769/bioprotoc.3911)
