Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou, 510650, China.
University of Chinese Academy of Sciences, Beijing, 100039, China.
Sci Rep. 2021 Jan 13;11(1):1082. doi: 10.1038/s41598-020-80268-3.
Sandalwood (Santalum album L.) is famous for its unique fragrance derived from the essential oil of heartwood, whose major components are santalols. To understand the mechanism underlying the biosynthesis of santalols, in this study, we cloned two related genes involved in the mevalonate pathway in S. album coding for acetyl-CoA C-acetyl transferase (AACT) and 3-hydroxy-3-methyglutary-CoA synthase (HMGS). These genes were characterized and functionally analyzed, and their expression profiles were also assessed. An AACT gene designated as SaAACT (GenBank accession No. MH018694) and a HMGS gene designated as SaHMGS (GenBank accession No. MH018695) were successfully cloned from S. album. The deduced SaAACT and SaHMGS proteins contain 415 and 470 amino acids, and the corresponding size of their open-reading frames is 1538 bp and 1807 bp, respectively. Phylogenetic trees showed that the SaAACT protein had the closest relationship with AACT from Hevea brasiliensis and the SaHMGS proteins had the highest homology with HMGS from Siraitia grosvenorii. Functional complementation of SaAACT and SaHMGS in a mutant yeast strain deficient in these proteins confirmed that SaAACT and SaHMGS cDNA encodes functional SaAACT and SaHMGS that mediate mevalonate biosynthesis in yeast. Tissue-specific expression analysis revealed that both genes were constitutively expressed in all examined tissues (roots, sapwood, heartwood, young leaves, mature leaves and shoots) of S. album, both genes showing highest expression in roots. After S. album seedlings were treated with 100 μM methyl jasmonate, the expression levels of SaAACT and SaHMGS genes increased, suggesting that these genes were responsive to this elicitor. These studies provide insight that would allow further analysis of the role of genes related to the sandalwood mevalonate pathway in the regulation of biosynthesis of sandalwood terpenoids and a deeper understanding of the molecular mechanism of santalol biosynthesis.
檀香（Santalum album L.）以其独特的香气而闻名，这种香气源自心材中的精油，其主要成分是檀香醇。为了了解檀香醇生物合成的机制，本研究克隆了檀香中与甲羟戊酸途径相关的两个基因，它们分别编码乙酰辅酶 A C-乙酰转移酶（AACT）和 3-羟基-3-甲基戊二酰辅酶 A 合酶（HMGS）。对这些基因进行了特征分析和功能分析，并评估了它们的表达谱。从檀香中成功克隆了一个命名为 SaAACT（GenBank 登录号为 MH018694）的 AACT 基因和一个命名为 SaHMGS（GenBank 登录号为 MH018695）的 HMGS 基因。推导的 SaAACT 和 SaHMGS 蛋白分别含有 415 和 470 个氨基酸，相应的开放阅读框大小分别为 1538 bp 和 1807 bp。系统发育树显示，SaAACT 蛋白与巴西橡胶树的 AACT 蛋白关系最密切，SaHMGS 蛋白与三叶木通的 HMGS 蛋白同源性最高。在这些蛋白缺失的酵母突变体中，SaAACT 和 SaHMGS 的功能互补证实了 SaAACT 和 SaHMGS cDNA 编码的 SaAACT 和 SaHMGS 是酵母甲羟戊酸生物合成的功能蛋白。组织特异性表达分析表明，这两个基因在檀香的所有检测组织（根、边材、心材、幼叶、成熟叶和嫩枝）中均为组成型表达，两个基因在根中表达量最高。在檀香幼苗用 100 μM 茉莉酸甲酯处理后，SaAACT 和 SaHMGS 基因的表达水平增加，表明这些基因对该诱导剂有反应。这些研究为进一步分析檀香甲羟戊酸途径相关基因在檀香萜类化合物生物合成调控中的作用提供了深入了解檀香醇生物合成的分子机制。
