CHLOROPLAST RESPONSE IN DUNALIELLA SALINA TO IRRADIANCE STRESS - EFFECT ON THYLAKOID MEMBRANE PROTEIN ASSEMBLY AND FUNCTION

摘要

The chloroplast response in the green alga Dunaliella salina to irradiance stress was investigated. Cells were grown under low light (LL) at 100 mu mol photons m(-2) s(-1) or high light (HL) at 2000 mu mol photons m(-2) s(-1) incident intensity. LL-grown cells had allow chlorophyll (Chi) a/b ratio, an abundance of light-harvesting complex II proteins (LHC-II), and a large Chi antenna size. HL-grown cells had a higher Chi a/b ratio, relatively fewer LHC-II, and a small Chi antenna size. The more abundant higher molecular mass subunits of the LHC-II (approximately 31 kD) were selectively depleted from the thylakoid membrane of HL-grown cells. Light-shift experiments defined the kinetics of change in the subunit composition of the LHC-II and suggested distinct mechanisms in the acclimation of thylakoids to HL or LL conditions. The results showed that irradiance exerts a differential regulation on the expression of various Lhcb genes. The specific polyclonal antibodies used in this work, raised against the purified LHC-II, cross-reacted with a polypeptide of approximately 20 kD in HL-grown samples. In this work we examined the dynamics of induction of this novel protein and discuss its function in terms of a chloroplast response to the level of irradiance. [References: 38]