#Srdx repressor Activator#

Based on phylogenetic analysis and their distribution in the plant kingdom, WOX genes have been classified into three clades: modern/WUS (found in seed plants), intermediate (found in vascular plants including lycophytes), and ancient (found in vascular and nonvascular plants, including mosses and green algae) ( 1, 8). In Arabidopsis, the WOX family consists of 15 members, including the founding member WUSCHEL ( WUS) and WOX1–WOX14 ( 3), which are involved in the regulation of key developmental processes, including stem cell maintenance in shoot and root meristems, embryo apical-basal polarity patterning, and development of lateral organs ( 1, 4– 7). The WUSCHEL related homeobox ( WOX) genes form a plant-specific family of the eukaryotic homeobox transcription factor superfamily ( 1, 2). These results suggest that modern clade WOX genes have evolved for repressor activity through acquisition of the WUS-box. Furthermore, we found that fusion of either the WUS-box or an exogenous repressor domain to WOX7 or to members of intermediate and ancient WOX clades results in a gain-of-function ability to complement lam1 blade outgrowth. Consistent with this, all members of the modern clade except WOX7 can complement the lam1 mutant when expressed using the STF promoter, but members of the intermediate and ancient clades cannot. With the exception of WOX7, the WUS-box is conserved in the modern clade WOX genes, but is not found in members of the intermediate or ancient clades. These results indicate that transcriptional repressor activity mediated by the WUS-box of STF acts to promote blade outgrowth.

#Srdx repressor Activator#

Fusion of an exogenous repressor domain to STFm1 restores complementation, whereas fusion of an exogenous activator domain to STFm1 enhances the narrow leaf phenotype. We found that the introduction of mutations into the WUS-box of STF (STFm1) reduces its ability to complement the lam1 mutant. Using the classical bladeless lam1 mutant of Nicotiana sylvestris as a genetic tool, we examined the function of the Medicago truncatula WOX gene, STENOFOLIA ( STF), in controlling leaf blade outgrowth. WOX genes have been categorized into three clades-ancient, intermediate, and modern/WUS-based on phylogenetic analysis, but a functional basis for this classification has not been established. The WUSCHEL related homeobox ( WOX) genes play key roles in stem cell maintenance, embryonic patterning, and lateral organ development.