The sumoylation pathway is involved in a variety of processes in C. elegans including gonadal and vulval fate specification, cell cycle progression, maintenance of chromosome structure and chromosome segregation. In a targeted RNAi screen to identify genes regulating cell invasion, we have found that several components of the sumoylation pathway are required for normal anchor cell (AC) invasion, such as the E2 SUMO-conjugating enzyme
ubc-9, the SUMO E3 ligase
gei-17 or the SUMO ortholog
smo-1. It is also known that many proteins are sumoylated during the epithelial to mesenchymal transition (EMT), highlighting the importance of the sumoylation pathway in cell invasion. Since many transcription factors crucial for normal development are modified by SUMO, studying the exact role of this posttranslational modification with respect to specific targets is a challenging question. Therefore, we have developed the tools to block sumoylation in a tissue-specific and temporally controlled manner to study how loss of sumoylation affects vulval development and AC invasion. For this purpose, we are using the auxin-inducible tissue-specific protein degradation system to down-regulate degron-tagged components of the sumoylation pathway (such as the E3 ligase
gei-17) in the AC or vulval precursor cells (VPCs). To this aim, we generated animals expressing the modified Arabidopsis thaliana TIR1 protein (component of the E3 ubiquitin ligase complex) under the VPC specific
bar-1 or the AC-specific
cdh-3 promoters. The degradation of GEI-17 in these different somatic tissues resulted in defects in AC positioning, basement membrane breaching and utse formation. Moreover, VPC-specific inhibition of sumoylation perturbs vulval toroid formation. In further experiments we will examine specific transcription factors that require sumoylation for proper vulval morphogenesis and AC invasion.