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KMID : 0368420180610050330
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Journal of Plant Biology
2018 Volume.61 No. 5 p.330 ~ p.335
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Castasterone Can be Biosynthesized from 28-homodolichosterone in Arabidopsis thaliana
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Kim Sun-Young
Moon Jin-Young
Roh Jee-Hee
Kim Seong-Ki
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Abstract
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We recently demonstrated the biosynthesis of 24-ethylidene brassinosteroids in Arabidopsis thaliana. To determine the physiological role of biosynthesis of 24-ethylidene brassinosteroids, metabolism of 28-homodolichosterone as the end product of 24-ethylidene brassinosteroids biosynthesis was examined by a crude enzyme solution prepared from A. thaliana. In wild-type plants, dolichosterone and castasterone were identified as enzyme products on GC-MS analysis. In a mutant where DWARF1 was overexpressed (35S-DWF1), the conversion rate of 28-homodolichosterone to castasterone was significantly increased. These results indicate that conversion of 28-homodolichosterone to castasterone is mediated by dolichosterone in Arabidopsis. In the root growth assay, inhibitory activity was enhanced in the order of castasterone > dolichosterone > 28-homodolichosterone, demonstrating that conversion of 28-homodolichosterone to castasterone via dolichosterone is a biosynthetic reaction that increases BR activity in Arabidopsis. Compared to Arabidopsis grown under dark conditions, light-grown Arabidopsis showed up-regulated DWARF1 expression, resulting in an increased conversion rate of 28-homodolichosterone to castasterone, suggesting that light is an important regulatory factor for the biosynthetic connection of 24-ethylidene brassinosteroids and 24-methyl brassinosteroids in A. thaliana. Consequently, 24-ethylidene brassinosteroids biosynthesis to generate 28-homodolichosterone is a lightregulated alternative route for synthesis of the biologically-active BRs, castasterone and brassinolide in Arabidopsis plants.
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KEYWORD
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Arabidopsis thaliana, Biosynthesis of 24-ethylidene brassinosteroids, Biosynthetic connection of C28- Brassinosteroids and C29-brassinosteroids, Metabolism of 28-homodolichosterone, Synthesis of castasterone
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