Superkiller 3 influences miR172 directed cleavage of the mRNA encoding the ethylene regulated transcription factor nodule number control 1 (NNC1), a negative modulator of the root nodule symbiosis

ZANETTI, MARIA EUGENIA

Colonia de Sacramento

Congreso; Congreso binacional de los Clubes del ARN de Argentina y Uruguay; 2022

Club Uruguayo y Argentino del RNA

Legumes and rhizobia establish a nitrogen-fixing symbiosis that involves the formation of a lateral root organ, the nodule, and the suppression of the immune response of the plant, which allows the rhizobia to infect the root tissue. The activation and coordination of these two genetic programs is accompanied by significant changes in gene expression that are regulated at the transcriptional and the post-transcriptional levels. We have previously showed that a transcript encoding the Subunit 3 of the Superkiller Complex (SKI), which acts along with the exosome in the 3´-5´ degradation of mRNAs, is required for nodule formation, bacterial survival, and induction of early nodulation genes during the symbiosis between the legume Medicago truncatula and its symbiotic partner Sinorhizobium meliloti. Here we present a degradome analysis that revealed that MtSKI3 affected the miR172-directed endonucleolytic cleavage of the Nodule Number Control 1 mRNA (MtNNC1), which encodes a transcription factor of the APETALA2 family that acts as a negative regulator of nodulation. Expression of MtNNC1 is down regulated at late stages of the symbiosis, and its expression is restricted to the nodule apex. Specific silencing of MtNNC1 enhanced nodule number and bacterial infection upon inoculation with S. meliloti.