AUTHOR=Wei Hui  , Xu Chen  , Movahedi Ali , Sun Weibo , Li Dawei , Zhuge Qiang  

TITLE=
Characterization and Function of 3-Hydroxy-3-Methylglutaryl-CoA Reductase in Populus trichocarpa: Overexpression of PtHMGR Enhances Terpenoids in Transgenic Poplar

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.01476

DOI=10.3389/fpls.2019.01476

ISSN=1664-462X

ABSTRACT=<p>In the mevalonic acid (MVA) pathway, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) is considered the first rate-limiting enzyme in isoprenoid biosynthesis. In this study, we cloned a full-length cDNA from <italic>Populus trichocarpa</italic> with an open reading frame of 1,734 bp. The deduced PtHMGR sequence contained two HMG-CoA motifs and two NADPH motifs, which exhibited homology with HMGR proteins from other species. Subsequently, truncated PtHMGR was expressed in <italic>Escherichia coli</italic> BL21 (DE3) cells, and enzyme activity analysis revealed that the truncated PtHMGR protein could catalyze the reaction of HMG-CoA and NADPH to form MVA. Relative expression analysis suggests that <italic>PtHMGR</italic> expression varies among tissues and that <italic>PtHMGR</italic> responds significantly to abscisic acid (ABA), NaCl, PEG<sub>6000</sub>, hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>), and cold stresses. We used polymerase chain reaction (PCR) analysis to select transgenic Nanlin 895 poplars (<italic>Populus× euramericana</italic> cv.) and quantitative reverse-transcription PCR (qRT-PCR) to show that <italic>PtHMGR</italic> expression levels were 3- to 10-fold higher in transgenic lines than in wild-type (WT) poplars. qRT-PCR was also used to determine transcript levels of methylerythritol phosphate (MEP)-, MVA-, and downstream-related genes, indicating that overexpression of <italic>PtHMGR</italic> not only affects expression levels of MVA-related genes, but also those of MEP-related genes. We also measured the content of terpenoids including ABA, gibberellic acid (GA), carotenes, and lycopene. <italic>PtHMGR</italic> overexpression significantly increased ABA, GA, carotene, and lycopene content, indicating that PtHMGR participates in the regulation of terpenoid compound synthesis.</p>