Data_Sheet_1_Strigolactone alleviates the salinity-alkalinity stress of Malus hupehensis seedlings.docx

Salinity-alkalinity stress can remarkably affect the growth and yield of apple. Strigolactone (SL) is a class of carotenoid-derived compounds that functions in stress tolerance. However, the effects and mechanism of exogenous SL on the salinity-alkalinity tolerance of apple seedlings remain unclear. Here, we assessed the effect of SL on the salinity-alkalinity stress response of Malus hupehensis seedlings. Results showed that treatment with 100 μM exogenous SL analog (GR24) could effectively alleviate salinity-alkalinity stress with higher chlorophyll content and photosynthetic rate than the apple seedlings without GR24 treatment. The mechanism was also explored: First, exogenous GR24 regulated the expression of Na+/K+ transporter genes and decreased the ratio of Na+/K+ in the cytoplasm to maintain ion homeostasis. Second, exogenous GR24 increased the enzyme activities of superoxide, peroxidase and catalase, thereby eliminating reactive oxygen species production. Third, exogenous GR24 alleviated the high pH stress by regulating the expression of H+-ATPase genes and inducing the production of organic acid. Last, exogenous GR24 application increased endogenous acetic acid, abscisic acid, zeatin riboside, and GA3 contents for co-responding to salinity-alkalinity stress indirectly. This study will provide important theoretical basis for analyzing the mechanism of exogenous GR24 in improving salinity-alkalinity tolerance of apple.

盐碱胁迫可显著影响苹果的生长与产量。独脚金内酯（Strigolactone, SL）是一类类胡萝卜素衍生的化合物，在胁迫耐受过程中发挥作用。然而，外源SL对苹果幼苗盐碱胁迫耐受性的作用及分子机制仍不明确。本研究以湖北海棠（Malus hupehensis）幼苗为材料，探究了SL对其盐碱胁迫响应的调控效应。结果显示，施加100 μM外源SL类似物（GR24）可有效缓解盐碱胁迫：相较于未施加GR24的苹果幼苗，处理组幼苗的叶绿素含量与光合速率均显著更高。本研究进一步解析了其作用机制：其一，外源GR24可调控Na+/K+转运蛋白基因的表达，降低细胞质内Na+/K+比值，维持离子稳态；其二，外源GR24可提升超氧化物歧化酶、过氧化物酶与过氧化氢酶的酶活性，从而清除活性氧积累；其三，外源GR24通过调控H+-ATP酶基因的表达并诱导有机酸合成，缓解高pH胁迫；最后，外源GR24处理可提升幼苗内源乙酸、脱落酸、玉米素核苷与赤霉素3（GA3）的含量，间接响应盐碱胁迫。本研究可为解析外源GR24提升苹果盐碱胁迫耐受性的机制提供重要理论依据。