Correlation between pigment composition and apoproteins of the light-harvesting complex II (LHC II) in wheat (Triticum aestivum)

Seedlings of wheat (Triticum aestivum L. cv. Walde, Weibull) grown in continuous weak red light (16 mW m⁻²) with or without SAN-9789, contained significantly lower amounts of chlorophylls and carotenoids compared to untreated plants grown in a greenhouse. The Chl alb ratios were 3.6 in the greenhouse-grown plants, 5.1 in untreated and ca 16 in SAN-treated plants grown in weak red light, respectively. The main difference in polypeptide composition of thylakoids isolated from red light-grown plants, compared to those grown in the greenhouse, was a lower amount of proteins of the light-harvesting complex (LHC) II. The amount of apo-LHC and LHC were correlated to the xanthophyll to β-carotene ratios in these plants. The absence of grana and the absence of proteins of the light-harvesting complex 11 in SAN-treated plants, support the general dogma that these proteins are involved in the formation of grana. Since the amount of apo-LHC and LHC could be correlated to the presence of carotenoids as well as the chlorophylls, it is concluded that the carotenoids are necessary for the correct assembly and stabilization of the apoproteins of LHC II in the thylakoid membranes.