Cytochrome P450 monooxygenase 704B (CYP704B), a member of the CYP86 clan, was found to be needed in Arabidopsis and rice to biosynthesize precursors of sporopollenin through oxidizing fatty acids. In the present study, we cloned and characterized a CYP704B gene in Panax ginseng, named PgCYP704B1. It shared high sequence identity (98-99%) with CYP704 of Arabidopsis, Theobroma cacao, and Morus notabilis. The phylogenetic comparison of ginseng and higher plants between the members of CYP86 clan revealed that ginseng CYP704 was categorized as a group of CYP704B with dicot plants. The expression of PgCYP704B1 is low in the stem, leaf, and fruit, and high in flower buds, particularly detected in the young gametic cell and tapetum layer of the developing anther. Arabidopsis plants overexpressing PgCYP704B1 improved plant biomass such as plant height, siliques and seed number and size. A cytological observation by transverse and longitudinal semi-thin sections of the siliques cuticles revealed that the cell length increased. Furthermore a chemical analysis showed that PgCYP704B1ox lines increased their cutin monomers contents in the siliques. Our results suggest that PgCYP704B1 has a conserved role during male reproduction for fatty acid biosynthesis and its overexpression increases cutin monomers in siliques that eventually could be used for seed production.
Keywords: Biomass; Cytochrome P450; Fatty acid; Overexpressing plants; Panax ginseng; PgCYP704B1; Reproduction; Seed yield.