植物肌醇半乳糖苷合酶的生理功能和调控机制

植物肌醇半乳糖苷合酶（galactinol synthase, GolS）是高等植物棉子糖类寡糖合成途径中的关键酶，为棉子糖系列寡糖提供活化的半乳糖基，调控植物体内棉子糖（raffinose, RFO）系列寡糖的生物合成与积累。编码该酶的基因属于糖基转移酶（glycosyltransferases, GTs）GT8基因家族的亚家族。GolS参与合成的最终产物棉子糖家族低聚糖（raffinose family oligosaccharides，RFOs）是植物中重要的碳水化合物存在形式，在细胞内可溶性强，可作为脱水保护剂；还能发挥稳定膜结构的作用。同时，GolS催化合成的直接产物肌醇半乳糖苷（galactinol）和RFOs都能作为羟基自由基捕获分子参与活性氧的清除。因此，GolS参与的代谢途径在植物碳同化物的贮存与运输、生物和非生物逆境响应、种子的脱水效应等生命过程中均发挥了重要作用。GolS基因结构差异与表达模式不同，导致不同GolS基因参与的生物学功能具有很大的差异。研究植物中不同GolS基因的结构特征，组织特异性表达特性及它们响应不同生长发育阶段、环境变化的表达特性，对了解GolS参与的生物学功能具有重要意义。同时，在分子生物学水平上，深入了解调控植物GolS基因的分子调控机制，为通过遗传工程或分子辅助育种等手段，利用GolS改良农林作物的经济性状提供理论支持。本文针对近年来植物中GolS基因的生理功能和调控机制的研究进行了综述。

Physiological Function and Regulation Mechanism of Galactinol Synthase in Plant

Plant galactinol synthase (GolS) is the key enzyme in the synthesis of raffinose (RFO) oligosaccharides biosynthesis pathway by providing activated galactosyl groups for RFO oligosaccharides in higher plants. Genes encoding GolS protein belongs to the subfamily of glycosyltransferases 8 (GT8) gene family. RFOs, the final product of biosynthesis pathway in which GolS were involved, is an important form of carbohydrates in high plants. They are characterized as compatible solutes, assisting in osmotic adjustments as well as in membrane stabilization. Galactinol, the direct product GolS catalyze, and raffinose can scavenge hydroxyl radicals to contact the accumulation of reactive oxygen species (ROS) under stress conditions. Therefore, GolS play important roles in transport and storage of carbon, response to biotic and abiotic stress conditions and desiccation effects during seed maturation. Gene structure and expression pattern of different GolS results in large different function for them. However, it is very important to characterize structure of GolS and their expression patterns in different tissues and to various environments. And, to elucidate molecular regulation mechanisms of different GolS also can provide theoretical support for the application of GolS to improve the economic traits of crops through genetic engineering or molecular-assisted breeding. In this paper, the physiological function and regulation mechanism of GolS gene in plants in recent years were reviewed.