紫花苜蓿甘氨酸脱羧酶H-蛋白基因MsGDC-H1功能分析

光呼吸通过清除2-磷酸乙醇酸（2-PG）使氧合光合作用成为可能，该过程对C₃植物至关重要。H-蛋白是光呼吸过程中将甘氨酸转化为丝氨酸的甘氨酸脱羧酶（GDC）的关键组成蛋白之一。本研究克隆了紫花苜蓿MsGDC-H1，该基因编码166个氨基酸，具有1个硫辛酰基附着位点保守结构域和1个N6-硫辛酰赖氨酸保守位点。进化分析表明，MsGDC-H1蛋白与双子叶植物的甘氨酸脱羧酶H-蛋白（GDC-H）亲缘关系近。表达模式分析表明，MsGDC-H1在苜蓿叶中表达丰度高，且受光诱导。为了探究MsGDC-H1基因对拟南芥生长的影响，分别使用光诱导的茎叶特异性启动子ST-LS1和组成型启动子CaMV 35S驱动MsGDC-H1（ST-LS1：：MsGDC-H1； CaMV 35S：：MsGDC-H1）在拟南芥中异源表达。检测过表达植株生物量、淀粉、可溶性糖含量以及光合速率。数据分析显示，CaMV 35S：：MsGDC-H1过表达拟南芥（G系列植株）生长受阻，淀粉含量比ST-LS1：：MsGDC-H1特异性表达拟南芥（GS系列植株）增加了34%~67%，比野生型（WT）增加了7.3%~33.7%；可溶性糖含量比GS系列降低了36%~38%，比WT增加了44.3%~49.7%；与WT相比，GS系列植株生长更快，淀粉含量无显著差异（P>0.05），可溶性糖含量显著增加（P<0.05）。试验结果表明，MsGDC-H1基因在调控拟南芥光合速率、碳水化合物合成以及生长等方面发挥重要作用，未来可作为提高苜蓿产量的基因工程育种候选基因。

Functional analysis of glycine decarboxylase H-protein gene MsGDC-H1 in Medicago sativa

Photorespiration is essential for C₃ plants， allowing oxygenated photosynthesis by removing 2-phosphoglycolate. H-protein is one of the key components of glycine decarboxylase （GDC）， which converts glycine to serine during photorespiration. The MsGDC-H1 gene was cloned from Medicago sativa. The cloned gene encoded 166 amino acids and had a conserved lipoyl-binding domain and a conserved N6-lipoyllysine site. Phylogenetic analysis showed that MsGDC-H1 was closely related to glycine decarboxylase H-protein （GDC-H） in other dicotyledons. The expression pattern analysis showed that MsGDC-H1 was highly expressed in leaves and was induced by light. To explore the effects of MsGDC-H1 on Arabidopsis thaliana growth， photoinduced stem-leaf specific promoter ST-LS1 and constitutive promoter CaMV 35S were used to drive MsGDC-H1 expression （ST-LS1：：MsGDC-H1； CaMV 35S：： MsGDC-H1）. MsGDC-H1 is heterogeneously expressed in A. thaliana. Biomass， starch and soluble sugar content and photosynthetic rate of overexpressed plants were evaluated. Data analysis showed that CaMV 35S：：MsGDC-H1 overexpression （G series） inhibited A. thaliana growth. The starch content of G series was increased by 34%-67% compared with A. thaliana in which ST-LS1：：MsGDC-H1 was overexpressed （GS series）， and was increased by 7.3%-33.7% compared with wild type （WT） A. thaliana； The soluble sugar content was decreased by 36%-38% compared with GS series and increased by 44.3%-49.7% compared with WT A. thaliana. Compared with WT， GS series plants grew faster， starch content was not significantly different （P>0.05）， and soluble sugar content was significantly increased （P<0.05）. The experiment results show that MsGDC-H1 plays an important role in regulating photosynthetic rate， carbohydrate synthesis and growth of A. thaliana， and can be used as a candidate gene in genetic engineering breeding to improve alfalfa yield in the future.