LcCCoAOMT8 from Liriodendron chinense positively regulates lignin synthesis and promotes secondary cell wall thickening in tobacco (Nicotiana tabacum)

Caffeoyl coenzyme A-O-methyltransferase (CCoAOMT) is engaged in plant secondary metabolism and stress response, influencing the synthesis of lignin. Liriodendron chinense is an excellent timber species, while the potential mechanisms of wood formation in L. chinense remains unclear. Here, we identified the CCoAOMT gene family within the L. chinense genome and analyzed the role of LcCCoAOMT8 in regulating lignin biosynthesis. In total, eight LcCCoAOMT genes were categorized into four distinct groups according to their phylogenetic characteristics. RNA-seq data analysis revealed that LcCCoAOMT1 , LcCCoAOMT3 , LcCCoAOMT5 , and LcCCoAOMT8 were highly expressed in the developing xylem of the stem (DXS). Further RT-qPCR results confirmed that LcCCoAOMT8 was most highly expressed in the stem. Moreover, overexpression of LcCCoAOMT8 in transgenic tobacco plants increased CCoAOMT activity and lignin content, promoted xylem development, and enhanced secondary cell wall (SCW) thickening. In summary, our results suggest that LcCCoAOMT8 positively regulates lignin synthesis in stem and promotes SCW thickening. • Eight CCoAOMT genes were identified in the Liriodendron chinense genome. • LcCCoAOMT8 was highly expressed in the developing xylem of the stem. • LcCCoAOMT8 positively regulates the lignin biosynthesis and secondary cell wall formation in transgenic tobacco.