Potato E3 ubiquitin ligase PUB27 negatively regulates drought tolerance by mediating stomatal movement

The ubiquitin-proteasome system (UPS) is one of the main ways of eukaryotic protein degradation and post-translational modification. It has proven as an essential process for plants to respond to abiotic stresses. Plant U-box (PUB) protein acts as a ubiquitin ligase, which recognizes and ubiquitinates the target proteins. Many PUBs have been involved in water stress in Arabidopsis and rice, but similar comprehensive studies in potato remained limited. In this study, the overexpressed and interfered transgenic potato plants of StPUB27 were obtained and their performances were evaluated under osmotic stress. The result showed that overexpression of StPUB27 accelerated the dehydration of detached leaves companied with greater stomatal conductance, while the down-regulated StPUB27 expression by RNA interference (RNAi) showed a smaller stomatal conductance and a lower rate of water loss in detached leaves, thus showing higher tolerance to osmotic stress. In addition, no significant changes in the proline content were observed between StPUB27 overexpressed and RNAi potato plants. The result demonstrated that potato E3 ubiquitin ligase PUB27 may negatively regulate drought tolerance by mediating stomatal conductance.