(+)-Sesamin, a furofuran class lignan, is widespread in vascular plants and represented by
Sesamum
spp. (+)-Sesamin has been of rapidly growing interest because of its beneficial biological effects in mammals, but its biosynthesis and physiological roles in plants remain to be clarified. It is speculated to be synthesized from (+)-pinoresinol by means of (+)-piperitol by formation of two methylenedioxy bridges mediated by two distinct
Sesamum indicum
cytochrome P450 (SiP450) proteins. Here, we report an SiP450, CYP81Q1, that alone catalyzes (+)-sesamin biosynthesis from (+)-pinoresinol by means of (+)-piperitol by forming two methylenedioxy bridges. The CYP81Q1 gene expression profile was temporally consistent with the accumulation pattern of (+)-sesamin during seed development. The CYP81Q1-GFP chimera protein was colocalized with an endoplasmic reticulum (ER)-targeting chimera protein, indicating that (+)-sesamin biosynthesis occurs on the ER cytoplasmic surface. Moreover, we isolated two CYP81Q1 homologs from other
Sesamum
spp.
Sesamum radiatum
CYP81Q2 showed dual (+)-piperitol/(+)-sesamin synthetic activity. CYP81Q2, as well as CYP81Q1, therefore, corresponds to a (+)-piperitol/(+)-sesamin synthase in lignan biosynthesis. In contrast,
Sesamum alatum
CYP81Q3 showed no activity, in accord with (+)-sesamin being deficient in
S. alatum
. Our findings not only provide insight into lignan biosynthesis but also unravel a unique mode of cytochrome P450 action.
(+)-Sesamin是一种
呋喃呋喃类
木脂素,在血管植物中广泛存在,并由芝麻属(Sesamum spp.)代表。由于其对哺乳动物有益的
生物效应,因此已经引起了快速增长的兴趣,但其在植物中的
生物合成和生理作用仍需澄清。据推测,它是通过两个不同的Sesamum indicum细胞色素P450(SiP450)蛋白介导的两个甲氧基桥的形成,从(+)-pinoresinol合成的。在此,我们报道了一个SiP450,CYP81Q1,它单独通过形成两个甲氧基桥,通过(+)-piperitol从(+)-pinoresinol合成(+)-sesamin。CYP81Q1
基因表达谱与(+)-sesamin在种子发育过程中的积累模式时间上一致。CYP81Q1-GFP嵌合蛋白与内质网(ER)靶向嵌合蛋白共定位,表明(+)-sesamin的
生物合成发生在ER细胞质表面。此外,我们从其他芝麻属(Sesamum spp.)中分离出两个CYP81Q1同源物。 Sesamum radiatum CYP81Q2显示双重(+)-piperitol/(+)-sesamin合成活性。因此,CYP81Q2和CYP81Q1对应于
木脂素生物合成中的(+)-piperitol/(+)-sesamin合酶。相反,Sesamum alatum CYP81Q3没有活性,这与S. alatum中缺乏(+)-sesamin相一致。我们的发现不仅提供了
木脂素生物合成的见解,而且揭示了一种独特的细胞色素P450作用模式。