Leaf C40.4: a carotenoid‐associated protein involved in the modulation of photosynthetic efficiency?

Publisher Website
Google Scholar
Abstract
Summary: Comparative analysis by differential RNA display (DDRT–PCR) of the expression patterns of potato plants induced and non‐induced to tuberize, led to the isolation of a cDNA clone, C40.4, that is strongly upregulated in the leaves of tuberizing plants. Leaf expression of this transcript was shown to be light‐dependent, with increased levels of mRNA and protein being detected during the light hours. Sequence analysis revealed near complete identity to potato CDSP34, a thylakoid protein induced by drought stress, and strong homology to the carotenoid‐associated proteins fibrillin, ChrB and PAP from pepper fruit, and CHRC from cucumber flowers. By using an antibody against pepper fibrillin, we were able to demonstrate a chloroplastic location of the C40.4 protein in association with the thylakoid membranes. Two‐dimensional analysis of thylakoid pigment–protein complexes showed a specific association of the protein with the photosystem II (PSII) multi‐subunit complex. Antisense plants with reduced levels of accumulation of C40.4 showed a stunted growth and decreased tuber yield and exhibited reduced values of non‐photochemical quenching of chlorophyll a fluorescence. Altogether, these results indicate a preferential association of the C40.4 protein with the light harvesting complex of photosystem II (LHCII) antenna pigment complexes, and suggest a functional role of this protein in photosynthesis, by modulating photosynthetic efficiency and dissipation of excess absorbed light energy within the antenna complex.