AUTHOR=Liu Miaomiao , Ma Yimian , Du Qing , Hou Xuemin , Wang Meizhen , Lu Shanfa 

TITLE=Functional Analysis of Polyprenyl Diphosphate Synthase Genes Involved in Plastoquinone and Ubiquinone Biosynthesis in Salvia miltiorrhiza

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00893

DOI=10.3389/fpls.2019.00893

ISSN=1664-462X

ABSTRACT=<p>Polyprenyl diphosphate synthase (PPS) plays important roles in the biosynthesis of functionally important plastoquinone (PQ) and ubiquinone (UQ). However, only few plant <italic>PPS</italic> genes have been functionally characterized. Through genome-wide analysis, two <italic>PPS</italic> genes, termed <italic>SmPPS1</italic> and <italic>SmPPS2</italic>, were identified from <italic>Salvia miltiorrhiza</italic>, an economically significant Traditional Chinese Medicine material and an emerging model medicinal plant. SmPPS1 and SmPPS2 belonged to different phylogenetic subgroups of plant trans-long-chain prenyltransferases and exhibited differential tissue expression and light-induced expression patterns. Computational prediction and transient expression assays showed that SmPPS1 was localized in the chloroplasts, whereas SmPPS2 was mainly localized in the mitochondria. SmPPS2, but not SmPPS1, could functionally complement the <italic>coq1</italic> mutation in yeast cells and catalyzed the production of UQ-9 and UQ-10. Consistently, both UQ-9 and UQ-10 were detected in <italic>S. miltiorrhiza</italic> plants. Overexpression of <italic>SmPPS2</italic> caused significant UQ accumulation in <italic>S. miltiorrhiza</italic> transgenics, whereas down-regulation resulted in decreased UQ content. Differently, <italic>SmPPS1</italic> overexpression significantly elevated PQ-9 content in <italic>S. miltiorrhiza</italic>. Transgenic lines showing a down-regulation of <italic>SmPPS1</italic> expression exhibited decreased PQ-9 level, abnormal chloroplast and trichome development, and varied leaf bleaching phenotypes. These results suggest that <italic>SmPPS1</italic> is involved in PQ-9 biosynthesis, whereas <italic>SmPPS2</italic> is involved in UQ-9 and UQ-10 biosynthesis.</p>