记者从中科院华南植物园获悉，该园生物技术育种研究组发现铁皮石斛中GDP—甘露糖焦磷酸化酶基因调控了富含甘露糖的多糖的生物合成，并与种子萌发与植株生长过程中的抗逆性有关。相关研究日前发表在Scientific Reports上。

铁皮石斛属于兰科石斛属植物，是传统名贵中药材。以甘露糖和葡萄糖等单糖为主组成的多糖被认为是铁皮石斛中的主要功效成分之一，在自然界的所有植物中，铁皮石斛中水溶性的多糖含量是最高的。另外，在种植过程中，铁皮石斛还表现出很强的抗逆性。

为了深入了解铁皮石斛这些重要性状形成的机制，该研究组何春梅博士在段俊研究员的指导下，对参与多糖合成过程中的关键酶基因GDP—甘露糖焦磷酸化酶基因进行了克隆分析，发现该基因上游1000bp的调控区内含有ABRE、HSE、LTR、TC—rich repeats和MBS等多个响应非生物逆境的顺式作用元件。通过转化拟南芥进行转基因功能验证的结果表明，转基因植株的水溶性多糖和水溶性多糖中甘露糖含量大幅度增加，在盐胁迫的条件下，转基因植株种子的萌发率和生长情况均好于野生型。（来源：中国科学报 朱汉斌 周飞）

DoGMP1 from Dendrobium officinale contributes to mannose content of water-soluble polysaccharides and plays a role in salt stress response

Abstract  GDP-mannose pyrophosphorylase (GMP) catalyzed the formation of GDP-mannose, which serves as a donor for the biosynthesis of mannose-containing polysaccharides. In this study, three GMP genes from Dendrobium officinale (i.e., DoGMPs) were cloned and analyzed. The putative 1000 bp upstream regulatory region of these DoGMPs was isolated and cis-elements were identified, which indicates their possible role in responses to abiotic stresses. The DoGMP1 protein was shown to be localized in the cytoplasm. To further study the function of the DoGMP1 gene, 35S:DoGMP1 transgenic A. thaliana plants with an enhanced expression level of DoGMP1 were generated. Transgenic plants were indistinguishable from wild-type (WT) plants in tissue culture or in soil. However, the mannose content of the extracted water-soluble polysaccharides increased 67%, 96% and 92% in transgenic lines #1, #2 and #3, respectively more than WT levels. Germination percentage of seeds from transgenic lines was higher than WT seeds and the growth of seedlings from transgenic lines was better than WT seedlings under salinity stress (150 mM NaCl). Our results provide genetic evidence for the involvement of GMP genes in the biosynthesis of mannose-containing polysaccharides and the mediation of GMP genes in the response to salt stress during seed germination and seedling growth.

原文链接：http://www.nature.com/articles/srep41010