Zhao Xun, Yang Xuanwen, Pei Shengqiang, He Guo, Wang Xiaoyu, Tang Qi, Jia Chunlin, Lu Ying, Hu Ruibo, Zhou Gongke
Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, PR China.
Gene. 2016 Jul 15;586(1):158-69. doi: 10.1016/j.gene.2016.04.028. Epub 2016 Apr 13.
NAC (NAM, ATAF1/2, and CUC2) transcription factors are known to play important roles in responses to abiotic stresses in plants. Currently, little information regarding the functional roles of NAC genes in stress tolerance is available in Miscanthus lutarioriparius, a promising bioenergy plant for cellulosic ethanol production. In this study, we carried out the functional characterization of MlNAC9 in abiotic stresses. MlNAC9 was shown to act as a nuclear localized transcription activator with the activation domain in its C-terminus. The overexpression of MlNAC9 in Arabidopsis conferred hypersensitivity to abscisic acid (ABA) at seed germination and root elongation stages. In addition, the overexpression of MlNAC9 led to increased seed germination rate and root growth under salt (NaCl) treatment. Meanwhile, the transgenic Arabidopsis overexpressing MlNAC9 showed enhanced tolerance to drought and cold stresses. The expression of stress-responsive marker genes was significantly increased in MlNAC9 overexpression lines compared to that of WT under ABA, drought, salt, and cold stresses. Correspondingly, the activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were significantly increased and the malondialdehyde (MDA) content was lower accumulated in MlNAC9 overexpression lines under drought and salt treatments. These results indicated that the overexpression of MlNAC9 improved the tolerance to abiotic stresses via an ABA-dependent pathway, and the enhanced tolerance of transgenic plants was mainly attributed to the increased expression of stress-responsive genes and the enhanced scavenging capability of reactive oxygen species (ROS).
NAC（NAM、ATAF1/2和CUC2）转录因子在植物对非生物胁迫的响应中发挥重要作用。目前，关于NAC基因在耐盐芒（一种有潜力用于生产纤维素乙醇的生物能源植物）胁迫耐受性中的功能作用的信息还很少。在本研究中，我们对MlNAC9在非生物胁迫中的功能进行了表征。结果表明，MlNAC9是一种核定位转录激活因子，其激活结构域位于C端。MlNAC9在拟南芥中的过表达使其在种子萌发和根伸长阶段对脱落酸（ABA）超敏感。此外，MlNAC9的过表达导致在盐（NaCl）处理下种子萌发率提高和根生长加快。同时，过表达MlNAC9的转基因拟南芥对干旱和寒冷胁迫的耐受性增强。与野生型相比，在ABA、干旱、盐和寒冷胁迫下，MlNAC9过表达株系中胁迫响应标记基因的表达显著增加。相应地，在干旱和盐处理下，MlNAC9过表达株系中抗氧化酶超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）的活性显著增加，丙二醛（MDA）含量积累较低。这些结果表明，MlNAC9的过表达通过ABA依赖途径提高了对非生物胁迫的耐受性，转基因植物耐受性的增强主要归因于胁迫响应基因表达的增加和活性氧（ROS）清除能力的增强。
