干旱是影响南方夏季蔬菜生产的主要逆境，油菜素内酯（BR）可促进叶绿体能量代谢平衡防御作物干旱光抑制。研究表明BR诱导了辣椒叶片线粒体AOX基因表达，而AOX途径增强可有效防御作物逆境光抑制发生；但BR诱导AOX表达的信号通路，以及BR如何通过AOX途径防御干旱光抑制的作用机制尚不清楚。为此，本项目以辣椒为材料，利用叶绿素荧光、生化和分子生物学手段，探索BR诱导AOX表达的信号通路；并从AOX途径通过苹果酸-草酰乙酸穿梭调控叶绿体能量代谢这一角度出发，在探明干旱胁迫下AOX途径对辣椒叶片光抑制、苹果酸-草酰乙酸穿梭及叶绿体能量代谢影响研究的基础上，开展BR诱导AOX途径增强对干旱光抑制、苹果酸-草酰乙酸穿梭、叶绿体能量代谢影响的研究，阐明干旱胁迫下BR通过诱导线粒体AOX途径以调控叶绿体能量代谢防御干旱光抑制的作用机制。研究为利用BR提高作物抗性提供理论和实践指导，具有重要的科学和现实意义。

Drought is the major limiting factor of vegetable crops production in summer in southern China. Brassinosteroid (BR) has shown been alleviated drought-induced photoinhibition by optimizing chloroplast energy balance in crop leaves. BR would up-regulate the expression of mitochondrial AOX gene. It has been suggested that AOX appears to contribute to protection against photoinhibition in plants. However, the signal pathway of BR-induced up-regulation of AOX gene expression, and the defense mechanisms from drought photoinhibition have yet to be deterimined. In this project, we will investigate the signal pathway of BR induced AOX gene expression in pepper leaves. Then, we will examine the changes of alternative respiration, chloroplast energy metabolize, malate/oxaloacetate shuttle, and photoinhibition in pepper leaves with or without inhibitors of alternative respiration under drought treatment. The objective of these studies is to explore the signal pathway of BR induced AOX gene expression, and to address the defense mechanism of BR in the protection of drought-induced photoinhibition in pepper leaves by BR-induced up-regulation of AOX pathway.