Immunogold localization of LHC II proteins in chloroplasts with different degrees of grana stacking induced by SAN-9789.

The amount and distribution of proteins of the light-harvesting complex associated with photosystem II (PS II) were investigated using immunogold labelling of chloroplasts of wheat ( Triticum aestivum L. cv. Walde). The seedlings were grown in weak red light (16 mW m^?2) after imbibition of grains with SAN-9789 (Norflurazon, 0.028 to 28 mg I^?1). Chloroplasts of these plants exhibited thylakoids with different degrees of stacking. Thylakoids of untreated plants grown in a greenhouse had most gold particles per unit membrane length in both appressed and non-appressed regions compared to red light grown plants. The ratios of labelling between appressed and non-appressed membranes were fairly constant in red light- and greenhouse-grown plants. The labelling densities were 2.5–3 times higher in the appressed thylakoids compared to the non-appressed thylakoids. However, at a SAN concentration of 2.8 mg I^?1 there was a sharp decrease in thylakoid appressions and in labelling density of both appressed and non-appressed membranes. The total amount of particles per chloroplast was also much lower as compared to that at lower SAN concentrations. Plants treated with the highest concentration of SAN (28 mg I^?1) contained chloroplasts devoid of normal grana structures. In these plastids, the thylakoids were elongated and single. The labelling density in these membranes was ca 50% of that observed at 2.8 mg I^?1. This paper thus supports earlier observations that proteins of the light-harvesting complex of PS II (LHC II) are mainly localized in the appressed regions of the grana membranes, and may be involved in the formation of grana.