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bioRxiv · 10.1101/2020.03.02.972620

MiRNA and phasiRNAs-mediated regulation of TIR-NBS-LRR defense genes in Arabidopsis thaliana

Lopez-Marquez, D.·Del-Espino, A.·Lopez-Pagan, N.·Rodriguez-Negrete, E. A.·Rubio-Somoza, I.·Ruiz-Albert, J.·Bejarano, E. R.·Beuzon, C. R.
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Abstract

Plants encode large numbers of intracellular immune receptors known as resistance (R) proteins or nucleotide-binding (NB) leucine-rich repeat (LRR) receptors (NLRs), involved in perception of pathogen-derived effectors and activation of immunity. Here, we report a two-tiered regulatory network mediated by microRNA and secondary phased small RNAs (phasiRNA) that targets the silencing of dozens of NLR genes encoding yet uncharacterized members of the Toll/interleukin-1 (TIR)-NBS-LRR (TNLs) subfamily in Arabidopsis. We show that miR825-5p downregulates expression of Arabidopsis AT5G38850 gene (renamed as microRNA-silenced TNL 1 or MIST1) by targeting the sequence coding for a highly conserved functional amino acid motif (TIR2) within the TIR domain of the receptor. Further, we show that MIST1 functions as a regulatory hub, since miRNA825-5p triggers RDR6-mediated processing of MIST1 transcripts, to generate trans-acting phasiRNAs that in turn target, a wide network of TNL genes for gene silencing. Regulation through MIST1 affects disease resistance against the model bacterial pathogen Pseudomonas syringae, since altered levels of miRNA825-5p lead to changes in Arabidopsis ability to establish basal defenses against this pathogen. MiR825-5p is expressed in unchallenged adult leaves and its production is down regulated in response to PAMPs such as bacterial flagellin but also fungal chitin.

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Lopez-Marquez, D., Del-Espino, A., Lopez-Pagan, N., Rodriguez-Negrete, E. A., Rubio-Somoza, I., Ruiz-Albert, J., Bejarano, E. R., Beuzon, C. R.. 2020-03-03. MiRNA and phasiRNAs-mediated regulation of TIR-NBS-LRR defense genes in Arabidopsis thaliana. https://doi.org/10.1101/2020.03.02.972620

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