Role of small RNAs in the systemic response against pathogens in Arabidopsis

LUCIANO MARTIN QUEVEDO; HERNÁN RAMIRO LASCANO; DAMIÁN ALEJANDRO CAMBIAGNO

Mendoza

Congreso; LVIII Reunión Anual de la Sociedad Argentina de Investigaciones Bioquímicas y de Biología Molecular (SAIB); 2022

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

When plants are exposed to pathogens, they induce both local and systemic defenses to evade them. After pathogen recognition in aerial tissues by extra and or intracellular receptors, the activation of MAPKs-dependent signaling, accumulation of ROS, and accumulation of Salicylic Acid (SA) induce local resistance. Moreover, the spreading of mobile signals such as SA and Pipecolic Acid (PIP), among others, trigger the systemic response called systemic acquired resistance (SAR). SAR is characterized by the establishment of a primed condition, which prepares the plant for a faster and/or more robust activation of defenses in further infections. In both local and systemic tissue, the stress-responsive genes are subject to a fine-tuning of their transcription and stability of their mRNAs for proper defense activation. In this process, miRNAs trigger post-transcriptional gene silencing of many defense-master genes. The miRNA precursors are transcribed by RNAP-II. At the co-transcriptional level, Dicer-Like1 degrades precursors to generate mature miRNAs. Its recruitment to chromatin is allowed by HASTY. Then, mature miRNAs are loaded in AGO1, exported to the cytoplasm, and directed to their target molecule. Interestingly, both HST and AGO1 also modulate the systemic mobilization of miRNAs.We are interested in knowing how the biogenesis/activity of miRNAs controls the systemic responses and priming in Arabidopsis. To this end, we evaluated the ability to induce systemic defenses in mutants affected in different components of the miRNA biogenesis pathway. Either wild type or mutants were treated with Mock, PIP, SA, or Pseudomonas syringe pv tomato (Pst) AvrRpt2 to induce systemic responses. In contrast to ago1 mutant plants, hst were more resistant to Psm than wild type. Interestingly, both hst and ago1 were unable to induce systemic responses after PIP treatment as wild type plants did. Interestingly, both mutants respond to SA and Pst-AvrRpt2 treatment for systemic defense induction. By the analysis of mRNA-seq of wild-type plants with SAR or treated with systemic inductors as well as sRNA-seq of hst and ago1 and RT-qPCR, we found four miRNA candidates to modulate systemic resistance and/or priming. Our current studies are directed to understand how HST and AGO1 modulate PIP- but not SA-systemic signaling, focusing on a potential general modulation of miRNA systemic mobilization and/or the activity of specific miRNAs in the triggering of this response.