Successful Fertilization Requires the Presence of at Least One Major O-Acetylserine(thiol)lyase for Cysteine Synthesis in Pollen of Arabidopsis
Successful Fertilization Requires the Presence of at Least One Major O-Acetylserine(thiol)lyase for Cysteine Synthesis in Pollen of Arabidopsis
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DOI：
10.1104/pp.113.221200
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发表时间：
2013-10-01
期刊：
影响因子：
7.4
通讯作者：
Hell, Ruediger
中科院分区：
文献类型：
--
作者：
Birke, Hannah;Heeg, Corinna;Hell, Ruediger
半胱氨酸（Cys）的合成是植物初级代谢的主控开关，协调硫通量与碳氮代谢。在拟南芥中，有九个基因编码 O-乙酰丝氨酸（硫醇）裂解酶（OAS-TL）样蛋白，其中主要亚型 OAS-TL A、OAS-TL B 和 OAS-TL C 分别通过在细胞质、质体和线粒体中结合 O-乙酰丝氨酸和硫化物来催化半胱氨酸的形成。到目前为止，单个 OAS-TL 样酶的重要性尚未解决。所有主要 OAS-TL 双功能丧失突变体的生成与放射性标记示踪剂研究相结合表明，OAS-TL 蛋白的亚细胞定位对于有效 Cys 合成比叶子中总细胞 OAS-TL 活性更重要。定向杂交后 oastl 三倍胚的缺失表明三个主要 OAS-TL 合成半胱氨酸的排他性，并排除了其他 OAS-TL 样蛋白的替代硫固定。对 oastlABC 花粉的分析表明，至少一种功能性 OAS-TL 亚型的存在对于雄配子体的正常功能至关重要，尽管组氨酸、赖氨酸和色氨酸的合成在花粉中是可有可无的。对来自遗传不同的亲本植物组合的 oastlABC 花粉进行比较，使我们能够区分花粉中半胱氨酸和谷胱甘肽的不同功能，并揭示谷胱甘肽对花粉萌发的额外作用。相比之下，雌性配子发生不受主要 OAS-TL 缺失的影响，这表明半胱氨酸从母本植物显着转运到发育中的胚珠中。
The synthesis of cysteine (Cys) is a master control switch of plant primary metabolism that coordinates the flux of sulfur with carbon and nitrogen metabolism. In Arabidopsis (Arabidopsis thaliana), nine genes encode for O-acetylserine(thiol)lyase (OAS-TL)-like proteins, of which the major isoforms, OAS-TL A, OAS-TL B, and OAS-TL C, catalyze the formation of Cys by combining O-acetylserine and sulfide in the cytosol, the plastids, and the mitochondria, respectively. So far, the significance of individual OAS-TL-like enzymes is unresolved. Generation of all major OAS-TL double loss-of-function mutants in combination with radiolabeled tracer studies revealed that subcellular localization of OAS-TL proteins is more important for efficient Cys synthesis than total cellular OAS-TL activity in leaves. The absence of oastl triple embryos after targeted crosses indicated the exclusiveness of Cys synthesis by the three major OAS-TLs and ruled out alternative sulfur fixation by other OAS-TL-like proteins. Analyses of oastlABC pollen demonstrated that the presence of at least one functional OAS-TL isoform is essential for the proper function of the male gametophyte, although the synthesis of histidine, lysine, and tryptophan is dispensable in pollen. Comparisons of oastlABC pollen derived from genetically different parent plant combinations allowed us to separate distinct functions of Cys and glutathione in pollen and revealed an additional role of glutathione for pollen germination. In contrast, female gametogenesis was not affected by the absence of major OAS-TLs, indicating significant transport of Cys into the developing ovule from the mother plant.