Abscisic acid (ABA) is an important plant hormone that mediates abiotic stresses in plant growth and development. A number of E3 ligases have been reported to be involved in ABA signaling pathway. In this study, we identified a C3H2C3 RING-type E3 ligase, Arabidopsis thaliana Tόxicos en Levadura 61 (ATL61), which regulated drought stress in planta. Enzyme assay in vitro demonstrated that ATL61 had E3 ubiquitin ligase activity, while point mutation of ATL61^{H109A, H122A} (mATL61) abolished its E3 ubiquitin ligase activity. ATL61 overexpression plants exhibited ABA hypersensitivity and were more tolerant to drought, while the atl61 mutant plants were insensitive to ABA. Moreover, mATL61 overexpression lines exhibited similar ABA-related phenotypes with wild type (WT) plants. The transcript abundances of ABA-mediated drought stress-related genes RD20 and RD22 were higher in ATL61 overexpression plants than those in WT, atl61, and mATL61 plants. Our results indicated that ATL61 acted as a positive regulator in the ABA-mediated drought stress response.

脱落酸（ABA）是一种重要的植物激素，可介导植物生长发育中的非生物胁迫。据报道许多E3连接酶参与ABA信号传导途径。在这项研究中，我们确定了一个C3H2C3 RING型E3连接酶，拟南芥（Arabidopsis thalianaTόxicosen Levadura 61）（ATL61），它调节了植物的干旱胁迫。体外酶试验表明，ATL61具有E3泛素连接酶活性，而ATL61 ^{H109A，H122A}（mATL61）的点突变消除了其E3泛素连接酶活性。ATL61过表达植物表现出ABA超敏性，并且更耐干旱，而atl61突变植物对ABA不敏感。此外，mATL61过表达系与野生型（WT）植物表现出相似的ABA相关表型。ATL61过表达植物中ABA介导的干旱胁迫相关基因RD20和RD22的转录本丰度高于野生型，atl61和mATL61植物。我们的结果表明，ATL61在ABA介导的干旱胁迫反应中起正调控作用。