Drought leads to reductions in plant growth and crop yields. Arbuscular mycorrhizal fungi (AMF), which form symbioses with the roots of the most important crop species, alleviate drought stress in plants. In the present work, we identified 14 GH3 genes in apple (Malus domestica) and provided evidence that MdGH3-2 and MdGH3-12 play important roles during AM symbiosis. The expression of both MdGH3-2 and MdGH3-12 was upregulated during mycorrhization, and the silencing of MdGH3-2/12 had a negative impact on AM colonization. MdGH3-2/12 silencing resulted in the downregulation of five genes involved in strigolactone synthesis, and there was a corresponding change in root strigolactone content. Furthermore, we observed lower root dry weights in RNAi lines under AM inoculation conditions. Mycorrhizal transgenic plants showed greater sensitivity to drought stress than WT, as indicated by their higher relative electrolytic leakage and lower relative water contents, osmotic adjustment ability, ROS scavenging ability, photosynthetic capacity, chlorophyll fluorescence values, and abscisic acid contents. Taken together, these data demonstrate that MdGH3-2/12 plays an important role in AM symbiosis and drought stress tolerance in apple.

中文翻译：

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沉默苹果中的 MdGH3-2/12 通过调节 AM 定殖降低抗旱性

干旱导致植物生长和作物产量减少。丛枝菌根真菌 (AMF) 与最重要的作物物种的根形成共生体，可缓解植物的干旱胁迫。在目前的工作中，我们确定了 14GH3苹果中的基因（海棠) 并提供证据证明MdGH3-2和MdGH3-12在 AM 共生过程中发挥重要作用。两者的表达MdGH3-2和MdGH3-12在菌根化过程中被上调，并且沉默MdGH3-2/12对 AM 定植产生了负面影响。MdGH3-2/12沉默导致参与独脚金内酯合成的五个基因下调，并且根独脚金内酯含量发生相应变化。此外，我们观察到在 AM 接种条件下 RNAi 系的根干重较低。菌根转基因植物对干旱胁迫的敏感性高于野生型，表现为其较高的相对电解泄漏和较低的相对含水量、渗透调节能力、ROS清除能力、光合能力、叶绿素荧光值和脱落酸含量。综上所述，这些数据表明MdGH3-2/12在苹果 AM 共生和干旱胁迫耐受性中起重要作用。