Hwang Sung Min, Kim Dae Won, Woo Min Seok, Jeong Hyeong Seop, Son Young Sim, Akhter Salina, Choi Gyung Ja, Bahk Jeong Dong
Division of Applied Life Sciences (BK21+), Graduate School of Gyeongsang National University, Jinju, 660-701, Korea; Research Center for Biobased Chemistry, Korea Research Institute of Chemical Technology, Deajeon, 305-600, Korea.
Plant Cell Environ. 2014 May;37(5):1202-22. doi: 10.1111/pce.12228. Epub 2013 Dec 8.
Although heat-shock transcription factors are well characterized in the heat stress-related pathway, they are poorly understood in other stress responses. Here, we functionally characterized AtHsfA6a in the presence of exogenous abscisic acid (ABA) and under high salinity and dehydration conditions. AtHsfA6a expression under normal conditions is very low, but was highly induced by exogenous ABA, NaCl and drought. Unexpectedly, the levels of AtHsfA6a transcript were not significantly altered under heat and cold stresses. Electrophoretic mobility shift assays and transient transactivation assays indicated that AtHsfA6a is transcriptionally regulated by ABA-responsive element binding factor/ABA-responsive element binding protein, which are key regulators of the ABA signalling pathway. Additionally, fractionation and protoplast transient assays showed that AtHsfA6a was in cytoplasm and nucleus simultaneously; however, under conditions of high salinity the majority of AtHsfA6A was in the nucleus. Furthermore, at both seed germination and seedlings stage, plants overexpressing AtHsfA6a were hypersensitive to ABA and exhibited enhanced tolerance against salt and drought stresses. Finally, the microarray and qRT-PCR analyses revealed that many stress-responsive genes were up-regulated in the plants overexpressing AtHsfA6a. Taken together, the data strongly suggest that AtHsfA6a acts as a transcriptional activator of stress-responsive genes via the ABA-dependent signalling pathway.
尽管热休克转录因子在热应激相关途径中已得到充分表征，但在其他应激反应中的了解却很少。在此，我们对外源脱落酸（ABA）存在以及高盐和脱水条件下的AtHsfA6a进行了功能表征。AtHsfA6a在正常条件下的表达非常低，但受到外源ABA、NaCl和干旱的高度诱导。出乎意料的是，AtHsfA6a转录本水平在热应激和冷应激下没有显著变化。电泳迁移率变动分析和瞬时反式激活分析表明，AtHsfA6a受ABA反应元件结合因子/ABA反应元件结合蛋白转录调控，而这些蛋白是ABA信号通路的关键调节因子。此外，分级分离和原生质体瞬时分析表明，AtHsfA6a同时存在于细胞质和细胞核中；然而，在高盐条件下，大多数AtHsfA6A存在于细胞核中。此外，在种子萌发和幼苗阶段，过表达AtHsfA6a的植物对ABA高度敏感，并表现出对盐胁迫和干旱胁迫的耐受性增强。最后，微阵列和qRT-PCR分析表明，许多应激反应基因在过表达AtHsfA6a的植物中上调。综上所述，这些数据强烈表明AtHsfA6a通过ABA依赖的信号通路作为应激反应基因的转录激活因子。
