The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, School of Life Sciences, Shandong University, Jinan, Shandong, China.
Shandong Province Administration of Work Safety, Jinan 250100, Shandong, China.
Plant Cell Physiol. 2017 Oct 1;58(10):1764-1776. doi: 10.1093/pcp/pcx111.
MYB-type transcription factors (MYB TFs) play diverse roles in plant development and stress responses. However, the mechanisms underlying the actions of MYB TFs during stress response remain unclear. In this study we identified a R2R3-MYB TF in soybean (Glycine max), denoted GmMYB84, which contributes to drought resistance. Expression of GmMYB84 was induced by drought, salt stress, H2O2 and ABA. Compared with the wild type (WT), GmMYB84-overexpressing soybean mutants (OE lines) exhibited enhanced drought resistance with a higher survival rate, longer primary root length, greater proline and reactive oxygen species (ROS) contents, higher antioxidant enzyme activities [peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD)], a lower dehydration rate and reduced malondialdehyde (MDA) content. We also found that ROS could induce SOD/POD/CAT activity in OE lines. In particular, we found that the optimal level of ROS is required for GmMYB84 to modulate primary root elongation. Some ROS-related genes were up-regulated under abiotic stress in GmMYB84 transgenic plants compared with the WT. Furthermore, electrophoretic mobility shift assay and luciferase reporter analysis demonstrated that GmMYB84 binds directly to the promoter of GmRBOHB-1 and GmRBOHB-2 genes. Based on this evidence, we propose a model for how GmMYB84, H2O2 and antioxidant enzymes work together to control root growth under both optimal and drought stress conditions.
MYB 型转录因子（MYB TFs）在植物发育和应激反应中发挥着多样化的作用。然而，MYB TFs 在应激反应中的作用机制仍不清楚。在这项研究中，我们鉴定了大豆中的一个 R2R3-MYB TF，命名为 GmMYB84，它有助于抗旱。GmMYB84 的表达受干旱、盐胁迫、H2O2 和 ABA 的诱导。与野生型（WT）相比，GmMYB84 过表达的大豆突变体（OE 系）表现出增强的抗旱性，存活率更高，主根更长，脯氨酸和活性氧（ROS）含量更高，抗氧化酶活性[过氧化物酶（POD）、过氧化氢酶（CAT）和超氧化物歧化酶（SOD）]更高，脱水率更低，丙二醛（MDA）含量更低。我们还发现 ROS 可以诱导 OE 系中 SOD/POD/CAT 的活性。特别是，我们发现 ROS 的最佳水平是 GmMYB84 调节主根伸长所必需的。在 GmMYB84 转基因植物中，一些与 ROS 相关的基因在非生物胁迫下的表达水平高于 WT。此外，电泳迁移率变动分析和荧光素酶报告基因分析表明，GmMYB84 直接结合到 GmRBOHB-1 和 GmRBOHB-2 基因的启动子上。基于这些证据，我们提出了一个模型，说明 GmMYB84、H2O2 和抗氧化酶如何在最佳和干旱胁迫条件下协同作用控制根的生长。
