The Subunit 3 of the Superkiller complex (SKI3) mediates regulation of AP2/NNC1 transcription factor during symbiosis.

MILAGROS YACULLO; MAURICIO REYNOSO; MAUREEN HUMMEL; JULIA BAILEY-SERRES; FLAVIO BLANCO; MARÍA EUGENIA ZANETTI; SOLEDAD TRAUBENIK

Congreso; XXXIII Argentinian meeting of Plant Physiology (RAFV2021); 2021

SOCIEDAD ARGENTINA DE FISIOLOGÍA VEGETAL

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 requires the reprogramming of root cells, which is accompanied by significant changes in the profiles of gene expression at both the transcriptional and the post-transcriptional levels. Previous studies identified transcripts that change their association to the translational machinery at early stages of symbiosis between the legume Medicago truncatula and its symbiotic partner Sinorhizobium meliloti. A transcript encoding the Subunit 3 of the Superkiller Complex (SKI), designated as MtSKI3, was differentially up regulated at the translational level. The SKI complex acts along with the exosome in the 3´-5´ degradation of mRNAs. Functional analysis revealed that MtSKI3 is required for nodule formation, bacterial survival, and induction of early nodulation genes such as ENOD40 (https://doi.org/10.1105/tpc.19.00647). Recently, a degradome analysis showed that MtSKI3 affected the miR172-directed endonucleolytic cleavage of the APETALA 2/ Nodule Number Control 1 mRNA (referred to as MtNNC1). Analysis of publicly available expression data showed that MtNNC1 is down regulated at late stages of the symbiosis, and its expression is restricted to the nodule apex. We are currently using different reverse genetic approaches to elucidate the biological function of MtNNC1. The results will allow a better understanding of the mechanisms by which MtNNC1 exerts its activity during the agronomically important process of nitrogen-fixing symbiosis.