Abstract
Rubisco is the CO2 fixing enzyme in photosynthesis and the most abundant leaf protein in plants. Rubisco is composed of eight small subunits coded by RBCS in the nuclear genome and eight large subunits encoded by rbcL in the plastome. Although RBCS forms a multigene family, it is not known how each gene contributes to the amount of Rubisco in a leaf. To clarify this, four RBCS genes (OsRBCS2 to 5), which are highly expressed in a leaf, were individually knocked-down in rice (Oryza sativa L.) and their Rubisco contents were determined at different growth stages (seedling, vegetative, and reproductive stages). Rubisco content declined by 20-30% in RBCS2- and 3- knock-down transformants and by 5-20% in OsRBCS4- and 5- knock-down transformants. Similar trends were observed irrespective of growth stage. Thus, although the effects of individual knock-down of RBCS multigene family were quantitatively different, all RBCS genes were the determinant for the amount of Rubisco in leaves during the life span of rice plants.
