Control of biomass accumulation in plants by miR396

DEBERNARDI, JUAN MANUEL; SABATINI, MARTIN; MECCHIA, MARTIN; PALATNIK, JAVIER F; RODRIGUEZ VIRASORO, RAMIRO ESTEBAN

Mar del Plata

Congreso; Reunión Argentina de Fisiología Vegetal.; 2012

Sociedad Argentina de Fisiología Vegetal

The development and growth of plants organs is based on a common general pattern. After primordia initiation, a stage of cell proliferation occurs in which new cells of small size and limited differentiation are produced. Later, cell expansion and differentiation shape their final size and function. We have identified and characterized in Arabidopsis thaliana a regulatory module consisting of a family of transcription factors and a microRNA that controls post-embryonic growth in plants by regulating cell proliferation in developing organs. The family of transcription factors GROWTH-REGULATING FACTORS (GRF) is composed of nine members and defined by the presence of two conserved domains, the QLQ and WRC. The WRC domain has a functional nuclear localization signal and a conserved DNA binding motif consisting of three cysteines and one histidine. The QLQ domain mediates the interaction of these transcription factors with proteins belonging to the GRF-INTERACTING FACTORS family. MicroRNAs are small RNAs of 21 nucleotides that negatively regulate gene expression by inhibiting translation or promoting degradation of target mRNAs. In particular, miR396 regulates 7 out of 9 GRFs present in Arabidopsis. By manipulating this regulatory module we have increased the size of multiple organs and biomass accumulation in plants. Specifically, transgenic Arabidopsis plants transformed with a version of a GRF insensitive to regulation by miR396 have larger leaves and stems with a greater accumulation of dry weight. A detailed analysis at the cellular level indicates that the enlarged size is due to increased cell number. Finally, we show that GRFs also exist in crop species where they operate in a similar way.