Chemical identification of 18-hydroxycarlactonoic acid as an LjMAX1 product and in planta conversion of its methyl ester to canonical and non-canonical strigolactones in Lotus japonicus
Chemical identification of 18-hydroxycarlactonoic acid as an LjMAX1 product and in planta conversion of its methyl ester to canonical and non-canonical strigolactones in Lotus japonicus
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DOI：
10.1016/j.phytochem.2020.112349
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发表时间：
2020-06-01
期刊：
影响因子：
3.8
通讯作者：
Akiyama, Kohki
中科院分区：
文献类型：
--
作者：
Mori, Narumi;Sado, Aika;Akiyama, Kohki
独脚金内酯（SL）是一类植物脱辅基类胡萝卜素，是丛枝菌根真菌和根寄生植物的根际信号分子。它们还作为植物激素调节植物结构。模式豆科植物百脉根（Lotus corniculatus的同义词）产生典型的5-脱氧独脚金醇（5DS）和非典型的莲花内酯（LL）。这两种SL的生物合成途径仍然难以捉摸。在这项研究中，我们表征了L。日本莲MAX 1同源物LjMAX 1，在日本莲基因组组装构建2.5中发现。洛杉矶LORE 1插入突变体的5DS和LL合成缺陷。在酵母微粒体中表达的重组LjMAX 1蛋白通过卡拉酮酸（CLA）将卡拉酮（CL）转化为18-羟基卡拉酮酸（18-OH-CLA）。通过使用LCMS/MS比较MAX 1产物的甲酯衍生物与化学合成的18-羟基己酸甲酯（18-OH-MeCLA），确认了18-OH-CLA的同一性。japonicas. C-13标记的CL、CLA和18-OH-MeCLA在使用L.山茱萸这些结果表明，LjMAX 1是百脉根SL生物合成的关键酶，18-羟基carlactonoates可能是百脉根SL生物合成的前体。japonicas.
Strigolactones (SLs) are a group of plant apocarotenoids that act as rhizosphere signaling molecules for both arbuscular mycorrhizal fungi and root parasitic plants. They also regulate plant architecture as phytohormones. The model legume Lotus japonicas (synonym of Lotus corniculatus) produces canonical 5-deoxystrigol (5DS) and non-canonical lotuslactone (LL). The biosynthesis pathways of the two SLs remain elusive. In this study, we characterized the L. japonicas MAX1 homolog, LjMAX1, found in the Lotus japonicas genome assembly build 2.5. The L. japonicas maxi LORE1 insertion mutant was deficient in 5DS and LL production. A recombinant LjMAX1 protein expressed in yeast microsomes converted carlactone (CL) to 18-hydroxycarlactonoic acid (18-OH-CLA) via carlactonoic acid (CLA). Identity of 18-OH-CLA was confirmed by comparison of the methyl ester derivative of the MAX1 product with chemically synthesized methyl 18-hydroycarlactonoate (18-OH-MeCLA) using LCMS/MS. (11R)-CL was detected as an endogenous compound in the root of L. japonicas. C-13-labeled CL, CLA, and 18-OH-MeCLA were converted to [C-13]-5DS and LL in plant feeding experiments using L. japonicas WT. These results showed that LjMAX1 is the crucial enzyme in the biosynthesis of Lotus SLs and that 18-hydroxylated carlactonoates are possible precursors for SL biosynthesis in L. japonicas.