Abstract
One of Dof transcription factors of Arabidopsis, Dof5.8, is expressed in provascular cells of leaf primordia. We previously showed that the provascular expression of Dof5.8 is regulated by auxin and MONOPTEROS (MP/ARF5). Here we show functional analysis of Dof5.8. Co-expression of Dof5.8 with MP in Arabidopsis protoplasts resulted in strong suppression of MP-mediated activation of Dof5.8 promoter. Similar suppression was observed when transcriptional activation domain of VP16 was fused to Dof5.8, suggesting that Dof5.8 may function as a transcriptional repressor and represses its own expression. To gain insights into the function of Dof5.8 in planta, we generated transgenic lines overexpressing Dof5.8 in provascular cells. These lines exhibited narrow leaves and lacked the marginal parts of secondary veins and the higher-order veins. Overexpression of Dof5.8 fused to a transcriptional repression domain of SUPERMAN resulted in similar phenotype. These results suggest that Dof5.8 represses the formation of vascular network through its transcriptional repressor activity.
