고려대학교 생명과학대학 생명과학부/ 대학원 분자생명과학과

Ubiquitination is implicated in diverse cellular processes in higher plants. Arabidopsis contains at least 477 and 64 RING- and U-box-motif containing E3 ubiquitin (Ub) ligases, respectively. AtAIRP1 and AtAIRP2 encode cytosolic C3H2C3- and C3HC4-type RING E3 ligases, respectively, whose expressions were induced by ABA and dehydration stress. Both AtAIRP1- and AtAIRP2-overexpressing transgenic plants exhibited hyper-sensitive phenotypes to ABA in terms of stomatal movement. They were highly tolerant to severe drought stress. In contrast, atairp1 and atairp2 loss-of-function mutants showed opposite phenotypes in response to ABA and drought stress. The AtPUB22and AtPUB23 genes encode homologous U-box E3 ligases. Both AtPUB22- and AtPUB23-overexpressing transgenic plants exhibited hypersensitivity to drought stress. Contrastingly, loss-of-function atpub22 and atpub23 mutant plants were significantly tolerant to a severe drought stress, and an atpub22atpub23double mutant displayed even greater tolerance. Overall, possible cellular functions of RING and U-box E3 Ub ligases with respect to ABA-dependent and ABA-independent drought tolerance will be discussed.