LEAF SIZE REGULATION BY miRNAs IN PLANTS

MARTIN MECCHIA; RAMIRO ESTEBAN RODRIGUEZ; JAVIER PALATNIK

Mar del Plata, Buenos Aires - Argentina

Congreso; XLIII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2007

SAIB

MicroRNAs (miRNAs) have been recognized as a novel mechanism to regulate gene expression in multicellular organisms. They are small RNAs of ~21 nt in length that recognize partially complementary sequences in target mRNAs and guide them to cleavage or translational arrest. They have been implicated in many key processes such as development and stress responses. In Arabidopsis thaliana the miR396 family includes two genes. These miRNAs regulate seven GRF transcription factors. The interaction between miR396 and the target site has near perfect complementarity, with a bulged base at position 7. We analyzed A. thaliana plants that overexpress the miR396b precursor. We also generated transgenic lines with a GRF version that is resistant to miR396 regulation (rGRF). From the morphological and molecular assays we concluded that the miR396/GRF system controls cell size and proliferation in leaves. To study the mechanism of miR396 action, we made translational fusions of GRF2 to the reporter gene GUS. We compared the wt version of GRF, rGRF and another version with perfect match to the miRNA. We found that miR396 regulates GRFs by two mechanisms, mRNA cleavage and translational repression.