School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang, People's Republic of China.
Physiol Plant. 2020 Jan;168(1):98-117. doi: 10.1111/ppl.12978. Epub 2019 Jun 7.
WRKY transcription factors play a key role in the tolerance of biotic and abiotic stresses across various crop species, but the function of some WRKY genes, particularly in tomato, remains unexplored. Here, we characterize the roles of a previously unstudied WRKY gene, SlWRKY8, in the resistance to pathogen infection and the tolerance to drought and salt stresses. Expression of SlWRKY8 was up-regulated upon Pseudomonas syringae pv. tomato DC3000 (Pst. DC3000), abiotic stresses such as drought, salt and cold, as well as ABA and SA treatments. The SlWRKY8 protein was localized to the nucleus with no transcription activation in yeast, but it could activate W-box-dependent transcription in plants. The overexpression of SlWRKY8 in tomato conferred a greater resistance to the pathogen Pst. DC3000 and resulted in the increased transcription levels of two pathogen-related genes SlPR1a1 and SlPR7. Moreover, transgenic plants displayed the alleviated wilting or chlorosis phenotype under drought and salt stresses, with higher levels of stress-induced osmotic substances like proline and higher transcript levels of the stress-responsive genes SlAREB, SlDREB2A and SlRD29. Stomatal aperature was smaller under drought stress in transgenic plants, maintaining higher water content in leaves compared with wild-type plants. The oxidative pressure, indicated by the concentration of hydrogen peroxide (H O ) and malondialdehyde (MDA), was also reduced in transgenic plants, where we also observed higher levels of antioxidant enzyme activities under stress. Overall, our results suggest that SlWRKY8 functions as a positive regulator in plant immunity against pathogen infection as well as in plant responses to drought and salt stresses.
WRKY 转录因子在各种作物物种的生物和非生物胁迫耐受中发挥着关键作用，但一些 WRKY 基因的功能，特别是在番茄中，仍然未知。在这里，我们描述了一个以前未研究过的 WRKY 基因 SlWRKY8 在对病原体感染的抗性和对干旱和盐胁迫的耐受性中的作用。SlWRKY8 的表达在受到丁香假单胞菌 pv.番茄 DC3000（Pst. DC3000）、干旱、盐和冷等非生物胁迫以及 ABA 和 SA 处理后上调。SlWRKY8 蛋白定位于细胞核，在酵母中没有转录激活，但它可以在植物中激活 W-box 依赖性转录。番茄中 SlWRKY8 的过表达赋予了对病原体 Pst. DC3000 的更高抗性，并导致两个与病原体相关的基因 SlPR1a1 和 SlPR7 的转录水平增加。此外，转基因植物在干旱和盐胁迫下表现出萎蔫或黄化表型的减轻，胁迫诱导的渗透物质如脯氨酸水平较高，应激响应基因 SlAREB、SlDREB2A 和 SlRD29 的转录水平较高。在转基因植物中，气孔孔径在干旱胁迫下较小，与野生型植物相比，叶片中的水分含量较高。氧化压力，由过氧化氢（H2O2）和丙二醛（MDA）的浓度表示，也在转基因植物中降低，我们还观察到在胁迫下抗氧化酶活性水平升高。总的来说，我们的结果表明 SlWRKY8 作为植物对病原体感染的免疫以及对干旱和盐胁迫的反应中的正调控因子发挥作用。
