茶树镁转运子基因CsMGT6的表达和功能鉴定

Expression and Functional Identification of Magnesium Transporter Gene CsMGT6 in Camellia sinensis

为探究镁转运子(Magnesium Transporters,MGT)参与调控茶树镁元素吸收、转运的机制,从茶树品种‘鄂茶10号’中克隆了1个镁转运子基因CsMGT6(GeneBank登录号:ON934629),并分析其功能。CsMGT6位于茶树第3号染色体上,开放阅读框为1368 bp,编码455个氨基酸。多序列比对分析发现,CsMGT6含有2个跨膜结构域和1个保守的GMN基序。系统进化树显示,CsMGT6属于第5亚族,与山梨猕猴桃(Actinidia rufa)ArMGT6亲缘关系最近。亚细胞定位结果表明,CsMGT6定位在细胞质膜上。实时荧光定量PCR分析发现,镁缺乏条件下CsMGT6在茶树根和叶部的响应不同,且在不同茶树品种中的响应存在差异。沙门氏杆菌功能互补试验表明,CsMGT6属于低亲和镁转运子,可能在较高浓度镁存在的条件下参与镁元素的吸收和转运。结果表明CsMGT6可被镁缺乏诱导表达,可能参与维持茶树细胞质膜内外的镁稳态。

To understand how magnesium transporters regulate the uptake and translocation of magnesium,a magnesium transporter gene CsMGT6(GenBank Accession No.ON934629)was cloned from Camellia sinensis cultivar‘Echa 10’,which was distributed on the third chromosome of C.sinensis genome.The open reading frame of CsMGT6 gene was 1368 bp,encoding 455 amino acids.Multiple alignment analysis indicated that CsMGT6 contained two transmembrane domains and a conserved GMN motif.Phylogenetic tree analysis showed that CsMGT6 belonged to the five subfamily,which had the highest homology with Actinidia rufa ArMGT6.Subcellular localization assays confirmed that CsMGT6 was located in the plasma membrane in tobacco epidermal cells.Moreover,quantitative real-time PCR analysis indicated that CsMGT6 showed various response to magnesium deficiency in roots and leaves among five different tea plant cultivars.In addition,functional complementation tests in Salmonella typhimurium mutant strain MM281 proved that CsMGT6 was a low-affinity magnesium transporter,which might mediate the uptake and translocation of magnesium under high concentration of magnesium.These results implied that the expression of CsMGT6 could be induced by magnesium deficiency,and CsMGT6 might be involved in the maintenance of magnesium homeostasis in tea plant plasma membrane.