Altered methionine metabolism impacts phenylpropanoid production and plant development in Arabidopsis thaliana.
Altered methionine metabolism impacts phenylpropanoid production and plant development in Arabidopsis thaliana.
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DOI：
10.1111/tpj.16370
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发表时间：
2023-06
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影响因子：
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通讯作者：
Doosan Shin;Veronica C. Perez;Gabriella K. Dickinson;Haohao Zhao;Ru Dai;Breanna M Tomiczek;K. H. Cho;Ning Zhu;J. Koh;Alexander Grenning;Jeongim Kim
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作者：
Doosan Shin;Veronica C. Perez;Gabriella K. Dickinson;Haohao Zhao;Ru Dai;Breanna M Tomiczek;K. H. Cho;Ning Zhu;J. Koh;Alexander Grenning;Jeongim Kim
苯丙素类化合物是由苯丙氨酸衍生的特化代谢物。硫代葡萄糖苷是拟南芥中主要来源于蛋氨酸和色氨酸的防御化合物。此前已有研究表明，苯丙素途径和硫代葡萄糖甙的产生在代谢上存在联系。吲哚-3-乙醛肟（IAOx）的积累，前体的异硫氰酸葡萄糖苷，抑制苯丙烷类化合物的生物合成，通过加速降解苯丙氨酸氨裂解酶（PAL）。由于PAL在产生不可或缺的专门代谢物如木质素的苯丙素途径的入口点起作用，因此肟介导的苯丙素阻遏对植物存活是有害的。虽然甲硫氨酸衍生的芥子油苷在拟南芥中是丰富的，但衍生自脂肪族氨基酸如甲硫氨酸的脂肪族醛肟（AAOx）对苯丙素类产生的任何影响仍不清楚。在这里，我们调查的影响AAOx积累苯丙素生产使用拟南芥醛肟突变体，参考文献2和参考文献5。REF 2和REF 5将醛肟代谢为各自的腈氧化物，但具有不同的底物特异性。ref 2和ref 5突变体由于醛肟的积累而具有降低的类苯丙素含量。由于REF 2和REF 5分别对AAOx和IAOx具有高底物特异性，因此假定REF 2积累AAOx，而不是IAOx。我们的研究表明，ref 2积累AAOx和IAOx。去除IAOx部分恢复了ref 2中的苯丙素含量，但没有恢复到野生型水平。然而，当AAOx的生物合成被沉默时，在参考2中的苯丙素类化合物的产生和PAL活性完全恢复，这表明AAOx对苯丙素类化合物的产生具有抑制作用。进一步的饲养研究表明，通常在缺乏AAOx生产的拟南芥突变体中观察到的异常生长表型是甲硫氨酸积累的结果。
Phenylpropanoids are specialized metabolites derived from phenylalanine. Glucosinolates are defense compounds derived mainly from methionine and tryptophan in Arabidopsis. It was previously shown that the phenylpropanoid pathway and glucosinolate production are metabolically linked. The accumulation of indole-3-acetaldoxime (IAOx), the precursor of tryptophan-derived glucosinolates, represses phenylpropanoid biosynthesis through accelerated degradation of phenylalanine-ammonia lyase (PAL). As PAL functions at the entry point of the phenylpropanoid pathway which produces indispensable specialized metabolites such as lignin, aldoxime-mediated phenylpropanoid repression is detrimental to plant survival. Although methionine-derived glucosinolates in Arabidopsis are abundant, any impact of aliphatic aldoximes (AAOx) derived from aliphatic amino acids such as methionine on phenylpropanoid production remains unclear. Here, we investigate the impact of AAOx accumulation on phenylpropanoid production using Arabidopsis aldoxime mutants, ref2 and ref5. REF2 and REF5 metabolize aldoximes to respective nitrile oxides redundantly, but with different substrate specificities. ref2 and ref5 mutants have decreased phenylpropanoid contents due to the accumulation of aldoximes. As REF2 and REF5 have high substrate specificity toward AAOx and IAOx respectively, it was assumed that ref2 accumulates AAOx, not IAOx. Our study indicates that ref2 accumulates both AAOx and IAOx. Removing IAOx partially restored phenylpropanoid content in ref2, but not to the wild-type level. However, when AAOx biosynthesis was silenced, phenylpropanoid production and PAL activity in ref2 were completely restored, suggesting an inhibitory effect of AAOx on phenylpropanoid production. Further feeding studies revealed that the abnormal growth phenotype commonly observed in Arabidopsis mutants lacking AAOx production is a consequence of methionine accumulation.