Regulation of cell proliferation by microRNA families in Arabidopsis thaliana

RAMIRO ESTEBAN RODRIGUEZ; HEIKE WOLLMANN; MARTIN MECCHIA; CARLA SCHOMMER; NICOLAS BOLOGNA; JERÔME BOISBOUVIER; DETLEF WEIGEL; JAVIER PALATNIK

Sunshine Coast, Australia

Congreso; Seventh Human Frontier Science Program Awardees Meeting; 2007

MicroRNAs are small RNAs of ~21 nt that regulate gene expression in animals and plants. They recognize complementary sequences in other longer RNAs and guide them to degradation or translational arrest. In general, animal microRNAs recognize multiple target sites with low complementarity that are located in the 3’UTR of target mRNAs and inhibit their translation. Plant microRNAs have usually better complementarity to their targets than their animal counterparts and in most cases recognize only one target sequence located within the coding sequence of the target mRNAs and guide them to degradation. Most of the genes controlled by conserved microRNAs in plants are involved in the regulation of transcription and hormone signaling. We have previously identified 5 TCP transcription factors as targets of miR319a using an experimental approach. These transcription factors inhibit cell proliferation and are required to maintain the flat structure of the leaf. Overexpression of miR319a causes increased degradation of TCP transcription factors, excess of cell proliferation and changes in leaf morphogenesis making them turn crinkly. Target predictions for miR319a include also several MYB transcription factors that are required for stamen development. Interestingly, these MYBs are also targeted by another microRNA, miR159. We have developed a method to differentiate between MYB-targeting by miR319 and miR159 in vivo. Our results have shown that miR319 can target both TCPs and MYBs in plants, but due to the low abundance of this miRNA compared to miR159, the regulation of the MYBs by miR319a plays at most a minor role in vivo. The abundant miR159 is therefore the mayor microRNA involved in MYB regulation, while miR319 is required for the control of the TCPs and leaf morphogenesis. We have characterized other miRNA systems of Arabidopsis thaliana that affect leaf development. Modification of their levels can alter the number and size of the cells in the leaf, while they can have different effects on the organ shape. Our results suggest that different microRNAs may be acting coordinately at different hierarchical levels or pathways during leaf development. We have characterized other miRNA systems of Arabidopsis thaliana that affect leaf development. Modification of their levels can alter the number and size of the cells in the leaf, while they can have different effects on the organ shape. Our results suggest that different microRNAs may be acting coordinately at different hierarchical levels or pathways during leaf development. We have characterized other miRNA systems of Arabidopsis thaliana that affect leaf development. Modification of their levels can alter the number and size of the cells in the leaf, while they can have different effects on the organ shape. Our results suggest that different microRNAs may be acting coordinately at different hierarchical levels or pathways during leaf development. We have characterized other miRNA systems of Arabidopsis thaliana that affect leaf development. Modification of their levels can alter the number and size of the cells in the leaf, while they can have different effects on the organ shape. Our results suggest that different microRNAs may be acting coordinately at different hierarchical levels or pathways during leaf development. in vivo. Our results have shown that miR319 can target both TCPs and MYBs in plants, but due to the low abundance of this miRNA compared to miR159, the regulation of the MYBs by miR319a plays at most a minor role in vivo. The abundant miR159 is therefore the mayor microRNA involved in MYB regulation, while miR319 is required for the control of the TCPs and leaf morphogenesis. We have characterized other miRNA systems of Arabidopsis thaliana that affect leaf development. Modification of their levels can alter the number and size of the cells in the leaf, while they can have different effects on the organ shape. Our results suggest that different microRNAs may be acting coordinately at different hierarchical levels or pathways during leaf development.