The relative contribution of genes operating in the S-methylmethionine cycle to methionine metabolism in Arabidopsis seeds
The relative contribution of genes operating in the S-methylmethionine cycle to methionine metabolism in Arabidopsis seeds
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DOI：
10.1007/s00299-017-2124-1
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发表时间：
2017-05-01
影响因子：
6.2
通讯作者：
Amir, Rachel
中科院分区：
文献类型：
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作者：
Cohen, Hagai;Salmon, Asaf;Amir, Rachel
在s -甲基蛋氨酸循环中工作的酶对种子中蛋氨酸的合成有不同的贡献。此外，种子中s -甲基蛋氨酸循环与天冬氨酸家族通路存在相互作用。蛋氨酸是一种含硫氨基酸，是植物细胞的重要代谢物。先前的证据表明，s -甲基蛋氨酸（SMM）循环有助于种子中蛋氨酸的合成，其中非种子组织中产生的蛋氨酸转化为SMM，然后通过韧皮部运输到种子中。然而，s -甲基转移酶在种子中这一循环中的相对调控作用尚不完全清楚。在本研究中，我们制备了三种同型半胱氨酸s -甲基转移酶（hmt）和蛋氨酸s -甲基转移酶（MMT）表达改变的转基因拟南芥种子，并分析了它们的转录和代谢变化。结果表明，AtHMT1和AtHMT3是在种子中起作用的主要酶，而不是AtHMT2和AtMMT，这两个基因的表达改变影响了转基因种子中蛋氨酸和SMM的水平。他们的操作导致了通过SMM和天冬氨酸家族途径参与蛋氨酸合成的基因的适应表达水平。综上所述，我们的研究结果为SMM循环的调控作用和两种蛋氨酸生物合成途径之间存在的相互作用提供了新的见解，突出了蛋氨酸和SMM在种子中代谢的复杂性。
Key message Enzymes operating in the S-methylmethionine cycle make a differential contribution to methionine synthesis in seeds. In addition, mutual effects exist between the S-methylmethionine cycle and the aspartate family pathway in seeds.Abstract Methionine, a sulfur-containing amino acid, is a key metabolite in plant cells. The previous lines of evidence proposed that the S-methylmethionine (SMM) cycle contributes to methionine synthesis in seeds where methionine that is produced in non-seed tissues is converted to SMM and then transported via the phloem into the seeds. However, the relative regulatory roles of the S-methyltransferases operating within this cycle in seeds are yet to be fully understood. In the current study, we generated transgenic Arabidopsis seeds with altered expression of three HOMOCYSTEINE S-METHYLTRANSFERASEs (HMTs) and METHIONINE S-METHYLTRANSFERASE (MMT), and profiled them for transcript and metabolic changes. The results revealed that AtHMT1 and AtHMT3, but not AtHMT2 and AtMMT, are the predominant enzymes operating in seeds as altered expression of these two genes affected the levels of methionine and SMM in transgenic seeds. Their manipulations resulted in adapted expression level of genes participating in methionine synthesis through the SMM and aspartate family pathways. Taken together, our findings provide new insights into the regulatory roles of the SMM cycle and the mutual effects existing between the two methionine biosynthesis pathways, highlighting the complexity of the metabolism of methionine and SMM in seeds.