Overexpression of CiMYC2 Transcription Factor from Chrysanthemum indicum var. aromaticum Resulted in Modified Trichome Formation and Terpenoid Biosynthesis in Transgenic Tobacco.

Chrysanthemum indicum var. aromaticum (C. indicum var. aromaticum) is an important aromatic plant resource in the Chrysanthemum genus, and the main substance of its aroma is terpenoids. Myelocytomatosis 2 (MYC2) is essential for the JA response to the accumulation of secondary metabolites in several plants. However, there are few reports on the regulation of terpenoid secondary metabolism and the improvement of aromatic characters by Chrysanthemum MYC2 transcription factor. In this study, a C. indicum var. aromaticum MYC2 transcription factor, CiMYC2, was induced by methyl jasmonate and preferentially expressed in leaves. The overexpression of CiMYC2 in tobacco resulted in shorter plant height, darker leaf color, higher chlorophyll and carotenoid content, more long-handle trichomes and short-handle trichomes, and higher terpenes content compared with wild-type (WT) and empty vector (EV) lines. More importantly, some novel terpenes were detected in CiMYC2 transgenic tobacco lines, whereas no corresponding substances were detected in WT and EV lines. In addition, transcriptional analyses revealed that the expression levels of genes involved in the terpenoids biosynthesis pathways were higher in transgenic tobacco lines than those in the WT and EV lines. Results indicated that CiMYC2 may be a key regulator for terpenoids biosynthesis in C. indicum var. aromaticum plants. The research results will provide theoretical basis for creating high terpene aromatic materials and cultivating new varieties of aromatic chrysanthemum using transgenic engineering technology. [ABSTRACT FROM AUTHOR]