Glutaredoxins (GRXs) are essential for reactive oxygen species (ROS) homeostasis in responses of plants to environment changes. We previously identified several drought-responsive CC-type GRXs in cassava, an important tropical crop. However, how CC-type GRX regulates ROS homeostasis of cassava under drought stress remained largely unknown. Here, we report that a drought-responsive CC-type GRX, namely MeGRXC3, was associated with activity of catalase in the leaves of 100 cultivars (or unique unnamed genotypes) of cassava under drought stress. MeGRXC3 negatively regulated drought tolerance by modulating drought- and abscisic acid-induced stomatal closure in transgenic cassava. It antagonistically regulated hydrogen peroxide (H₂O₂) accumulation in epidermal cells and guard cells. Moreover, MeGRXC3 interacted with two catalases of cassava, MeCAT1 and MeCAT2, and regulated their activity in vivo. Additionally, MeGRXC3 interacts with a cassava TGA transcription factor, MeTGA2, in the nucleus, and regulates the expression of MeCAT7 through a MeTGA2-MeMYB63 pathway. Overall, we demonstrated the roles of MeGRXC3 in regulating activity of catalase at both transcriptional and post-translational levels, therefore involving in ROS homeostasis and stomatal movement in responses of cassava to drought stress. Our study provides the first insights into how MeGRXC3 may be used in molecular breeding of cassava crops.

中文翻译：

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CC 型谷氧还蛋白 MeGRXC3 与过氧化氢酶结合并负向调节木薯 (Manihot esculenta Crantz) 的耐旱性

谷氧还蛋白 (GRXs) 对于植物对环境变化的反应中的活性氧 (ROS) 稳态至关重要。我们之前在木薯（一种重要的热带作物）中发现了几种对干旱敏感的 CC 型 GRX。然而，CC 型 GRX 如何调节木薯在干旱胁迫下的 ROS 稳态仍然在很大程度上未知。在这里，我们报告了一种干旱响应的 CC 型 GRX，即 MeGRXC3，与干旱胁迫下 100 个木薯品种（或独特的未命名基因型）叶片中的过氧化氢酶活性相关。MeGRXC3通过调节转基因木薯中干旱和脱落酸诱导的气孔关闭来负向调节耐旱性。它拮抗调节过氧化氢 (H ₂ O ₂) 在表皮细胞和保卫细胞中积累。此外，MeGRXC3 与木薯的两种过氧化氢酶 MeCAT1 和 MeCAT2 相互作用，并在体内调节它们的活性。此外，MeGRXC3 与细胞核中的木薯 TGA 转录因子 MeTGA2 相互作用，并通过 MeTGA2-MeMYB63 通路调节MeCAT7的表达。总的来说，我们证明了MeGRXC3在转录和翻译后水平上调节过氧化氢酶活性的作用，因此涉及木薯对干旱胁迫的响应中的 ROS 稳态和气孔运动。我们的研究首次深入了解了 MeGRXC3 如何用于木薯作物的分子育种。