PLANT PHYSIOLOGY , Vol 107, Issue 3 885-893, Copyright © 1995 by American Society of Plant Biologists
Chloroplast Response in Dunaliella salina to Irradiance Stress (Effect on Thylakoid Membrane Protein Assembly and Function)
M. R. Webb and A. Melis
Department of Plant Biology, University of California, Berkeley, CA 94720-3102
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 a low chlorophyll (Chl) a/b ratio,
an abundance of light-harvesting complex II proteins (LHC-II), and a large
Chl antenna size. HL-grown cells had a higher Chl a/b ratio, relatively
fewer LHC-II, and a small Chl 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.