DIFFERENTIAL REGULATION OF microARN miR398 TARGETS IN Arabidopsis

ANA PAULA MARTIN; ANABELLA LODEYRO; NESTOR CARRILLO; JAVIER PALATNIK

San Miguel de Tucumán

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

MicroRNAs (miRNAs) are a class of regulatory RNAs of ~21 nucleotides thatposttranscriptionally regulate eukaryotic gene expression by directing mRNA cleavage ortranslational inhibition. They are involved in diverse physiological processes like development,differentiation and metabolism.MiRNA miR398 targets two closely related Cu/Zn superoxide dismutases (cytosolic CSD1and chloroplastic CSD2) that can detoxify superoxide radicals; and a subunit of Cytochrome COxidase, COX5b1. All these proteins bind Cu as a cofactor.Copper deficiency in the growth media induces miR398, which causes the degradation ofits targets, so that the available copper is re-directed to essential proteins. It has been observedthat miR398 exhibits differential activity to its targets, being CSD1 and CSD2 more sensitive thanCOX5b1 to the miRNA levels. Interestingly, genes regulated by miR398 have target sites withspecific sequences that have been conserved throw evolution. To study this complex system weprepared transgenic plants that act as sensors of miR398 activity by overexpressing CSD2 andCOX5b1 fused to GFP. Next, we introduced specific mutations in the miRNA target site of thesensors to study the mechanisms underlying miR398 activity. The action mechanism of miR398will be discussed.