Functional Characterization of the 1-Deoxy-D-Xylulose 5-Phosphate Synthase Genes in Morus notabilis .

Terpenoids are considered to be the largest group of secondary metabolites and natural products. Studies have revealed 1-deoxy-D-xylulose 5-phosphate synthase (DXS) is the first and rate-limiting enzyme in the plastidial methylerythritol phosphate pathway, which produces isopentenyl diphosphate and its isoform dimethylallyl diphosphate as terpenoid biosynthesis precursors. Mulberry (MorusL.) is an economically and ecologically important perennial tree with diverse secondary metabolites, including terpenoids that protect plants against bacteria and insects and may be useful for treating human diseases. However, there has been relatively little research regardingDXSgenes in mulberry and other woody plant species. In this study, we cloned and functionally characterized threeMorus notabilis DXSgenes (MnDXS1,MnDXS2A, andMnDXS2B). Bioinformatics analyses indicatedMnDXS1belongs to clade 1, whereasMnDXS2AandMnDXS2Bare in clade 2. The three encoded MnDXS proteins are localized to chloroplasts. Additionally, substantial differences inMnDXSexpression patterns were observed in diverse tissues and in response to insect feeding and methyl jasmonate treatment. Moreover, overexpression ofMnDXS1inArabidopsis thalianaincreased the gibberellic acid content and resulted in early flowering, whereas overexpression ofMnDXS2Aenhanced root growth and increased the chlorophyll and carotenoid content. Our findings indicate thatMnDXSfunctions vary among the clades, which may be useful for further elucidation of the functions of theDXSgenes in mulberry.