Department of Breeding, Shandong Peanut Research Institute, Qingdao, China.
BMC Plant Biol. 2021 Nov 16;21(1):540. doi: 10.1186/s12870-021-03318-6.
Basic helix-loop-helix (bHLH) transcription factors (TFs) are one of the largest gene families in plants. They regulate gene expression through interactions with specific motifs in target genes. bHLH TFs are not only universally involved in plant growth but also play an important role in plant responses to abiotic stress. However, most members of this family have not been functionally characterized.
Here, we characterized the function of a bHLH TF in the peanut, AhHLH112, in response to drought stress. AhHLH112 is localized in the nucleus and it was induced by drought stress. The overexpression of this gene improves the drought tolerance of transgenic plants both in seedling and adult stages. Compared to wild-type plants, the transgenic plants accumulated less reactive oxygen species (ROS), accompanied by increased activity and transcript levels of antioxidant enzymes (superoxide dismutase, peroxidase and catalase). In addition, the WT plants demonstrated higher MDA concentration levels and higher water loss rate than the transgenic plants under drought treatment. The Yeast one-hybrid result also demonstrates that AhbHLH112 directly and specifically binds to and activates the promoter of the peroxidase (POD) gene. Besides, overexpression of AhHLH112 improved ABA level under drought condition, and elevated the expression of genes associated with ABA biosynthesis and ABA responding, including AtNCED3 and AtRD29A.
Drawing on the results of our experiments, we propose that, by improving ROS-scavenging ability, at least in part through the regulation of POD -mediated HO homeostasis, and possibly participates in ABA-dependent stress-responding pathway, AhbHLH112 acts as a positive factor in drought stress tolerance.
碱性螺旋-环-螺旋(bHLH)转录因子(TF)是植物中最大的基因家族之一。它们通过与靶基因中的特定基序相互作用来调节基因表达。bHLH TFs 不仅普遍参与植物生长，而且在植物应对非生物胁迫中也起着重要作用。然而，该家族的大多数成员尚未进行功能表征。
在这里，我们研究了花生 bHLH TF AhHLH112 对干旱胁迫的响应功能。AhHLH112 定位于细胞核内，受干旱胁迫诱导。该基因的过表达可提高幼苗期和成年期转基因植物的耐旱性。与野生型植物相比，转基因植物积累的活性氧（ROS）较少，抗氧化酶（超氧化物歧化酶、过氧化物酶和过氧化氢酶）的活性和转录水平升高。此外，与转基因植物相比，干旱处理下 WT 植物表现出更高的 MDA 浓度水平和更高的水分损失率。酵母单杂交结果也表明 AhbHLH112 直接并特异性地结合并激活过氧化物酶（POD）基因的启动子。此外，过表达 AhHLH112 可提高干旱条件下的 ABA 水平，并上调与 ABA 生物合成和 ABA 响应相关的基因表达，包括 AtNCED3 和 AtRD29A。
根据我们的实验结果，我们提出，通过提高 ROS 清除能力，至少部分通过调节 POD 介导的 HO 稳态，可能参与 ABA 依赖的应激响应途径，AhbHLH112 作为一个积极的因素在干旱胁迫耐受性。
