Modification of the Photosystem II light-harvesting chlorophyll [formula omitted] protein complex in maize during chill-induced photoinhibition

Abstract

The changes in the functional and molecular organization of the light-harvesting chlorophyll ab protein complex (LHC II), associated with Photosystem II (PS II), are examined when maize leaves are exposed to high light at 5°C for 6 h. Chlorophyll-fluorescence kinetic analyses of thylakoids isolated from mesophyll cells of stressed and control leaves demonstrate that the stress produces a reduction in energy transfer from LHC II to PS II. The polypeptide complements of thylakoids isolated from stressed leaves showed the accumulation of a 31 kDa polypeptide; no other changes in thylakoid polypeptides were observed between control and stress leaves. The 31 kDa polypeptide was a component of purified LHC II from stressed leaves and was immunologically related to the LHC II polypeptides. Differences in fluorescence emission spectra at 77 K of purified LHC II from control and stressed leaves suggested that the stress induces a perturbation of the environment of the chlorophyll species. The appearance of the 31 kDa polypeptide correlated with a modification of LHC II and its functional association with PS II. It is suggested that this polypeptide is a precursor of LHC II polypeptides and is inserted into the membrane prior to processing.