Matamoros Manuel A, Clemente Maria R, Sato Shusei, Asamizu Erika, Tabata Satoshi, Ramos Javier, Moran Jose F, Stiller Jiri, Gresshoff Peter M, Becana Manuel
Department of Botany, University of Queensland, Brisbane, Australia.
Mol Plant Microbe Interact. 2003 Nov;16(11):1039-46. doi: 10.1094/MPMI.2003.16.11.1039.
The thiol tripeptides, glutathione (GSH) and homoglutathione (hGSH), perform multiple roles in legumes, including protection against toxicity of free radicals and heavy metals. The three genes involved in the synthesis of GSH and hGSH in the model legume, Lotus japonicus, have been fully characterized and appear to be present as single copies in the genome. The gamma-glutamylcysteine synthetase (gamma(ecs)) gene was mapped on the long arm of chromosome 4 (70.0 centimorgans [cM]) and consists of 15 exons, whereas the glutathione synthetase (gshs) and homoglutathione synthetase (hgshs) genes were mapped on the long arm of chromosome 1 (81.3 cM) and found to be arranged in tandem with a separation of approximately 8 kb. Both genes consist of 12 exons of exactly the same size (except exon 1, which is similar). Two types of transcripts were detected for the gshs gene, which putatively encode proteins localized in the plastids and cytosol. Promoter regions contain cis-acting regulatory elements that may be involved in the plant's response to light, hormones, and stress. Determination of transcript levels, enzyme activities, and thiol contents in nodules, roots, and leaves revealed that gamma(ecs) and hgshs are expressed in all three plant organs, whereas gshs is significantly functional only in nodules. This strongly suggests an important role of GSH in the rhizobia-legume symbiosis.
硫醇三肽，即谷胱甘肽（GSH）和高半胱甘肽（hGSH），在豆科植物中发挥多种作用，包括抵御自由基和重金属的毒性。模式豆科植物百脉根中参与GSH和hGSH合成的三个基因已得到充分表征，并且在基因组中似乎以单拷贝形式存在。γ-谷氨酰半胱氨酸合成酶（γ(ecs)）基因定位于4号染色体长臂（70.0厘摩[cM]）上，由15个外显子组成，而谷胱甘肽合成酶（gshs）和高半胱甘肽合成酶（hgshs）基因定位于1号染色体长臂（81.3 cM）上，发现它们串联排列，间隔约8 kb。这两个基因均由12个大小完全相同的外显子组成（外显子1除外，其相似）。gshs基因检测到两种类型的转录本，推测它们编码定位于质体和细胞质中的蛋白质。启动子区域包含可能参与植物对光、激素和胁迫响应的顺式作用调控元件。对根瘤、根和叶中转录本水平、酶活性和硫醇含量的测定表明，γ(ecs)和hgshs在所有三个植物器官中均有表达，而gshs仅在根瘤中有显著功能。这有力地表明GSH在根瘤菌 - 豆科植物共生关系中具有重要作用。
