Molecular Cloning and Functional Analysis of 1-Deoxy-D-Xylulose 5-Phosphate Reductoisomerase from <i>Santalum album</i>

• Main Authors: Yueya Zhang, Haifeng Yan, Yuan Li, Yuping Xiong, Meiyun Niu, Xinhua Zhang, Jaime A. Teixeira da Silva, Guohua Ma
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Genes
• Subjects: 1-deoxy-D-xylulose 5-phosphate reductoisomerase; chlorophylls and carotenoids; MEP pathway; <i>Santalum album</i>; sandalwood sesquiterpenoids
• Online Access: https://www.mdpi.com/2073-4425/12/5/626

Sandalwood (<i>Santalum album</i> L.) heartwood-derived essential oil contains a high content of sesquiterpenoids that are economically highly valued and widely used in the fragrance industry. Sesquiterpenoids are biosynthesized via the mevalonate acid and methylerythritol phosphate (MEP) pathways, which are also the sources of precursors for photosynthetic pigments. 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) is a secondary rate-limiting enzyme in the MEP pathway. In this paper, the 1416-bp open reading frame of <i>SaDXR</i> and its 897-bp promoter region, which contains putative conserved <i>cis</i>-elements involved in stress responsiveness (HSE and TC-rich repeats), hormone signaling (abscisic acid, gibberellin and salicylic acid) and light responsiveness, were cloned from 7-year-old <i>S. album</i> trees. A bioinformatics analysis suggested that <i>SaDXR</i> encodes a functional and conserved DXR protein. <i>SaDXR</i> was widely expressed in multiple tissues, including roots, twigs, stem sapwood, leaves, flowers, fruit and stem heartwood, displaying significantly higher levels in tissues with photosynthetic pigments, like twigs, leaves and flowers. <i>SaDXR</i> mRNA expression increased in etiolated seedlings exposed to light, and the content of chlorophylls and carotenoids was enhanced in all <i>35S::SaDXR</i> transgenic <i>Arabidopsis thaliana</i> lines, consistent with the <i>SaDXR</i> expression level. <i>SaDXR</i> was also stimulated by MeJA and H₂O₂ in seedling roots. α-Santalol content decreased in response to fosmidomycin, a DXR inhibitor. These results suggest that <i>SaDXR</i> plays an important role in the biosynthesis of photosynthetic pigments, shifting the flux to sandalwood-specific sesquiterpenoids.