Examining the functions of the LHC proteins and their relatives

Abstract

The LHC supergene family encodes the not only the light-harvesting chlorophyll a/b-binding proteins; other family members, PsbS, ELIP and some newly identified proteins seem to have a role in high-light protection rather than light-harvesting and. In this seminar, recent data obtained by biochemical and spectroscopic studies on wild type, mutant and antisense Arabidopsis plants will be reviewed. The polypeptide composition of the antenna in different light conditions and thylakoid subcompartments is highly variable. Analysis of Lhca2, Lhca3, Lhca4 antisense Arabidopsis plants have revealed spectroscopic features, subunit interactions and flexibility in the PS I antenna. Lhcb4 (CP29), Lhcb5 (CP26) and Lhcb6 (CP24) antisense plants have shown that these proteins seem to be pure antenna proteins and not directly involved in non-photochemical quenching (NPQ). This suggests that PsbS, identified as the essential protein for NPQ, is really the quenching site. Antisense plants completely devoid of LHC II trimers have been analysed to pinpoint the functions of peripheral LHC II. We have also studied the regulation of the PsbS gene in the field, and shown that lack of NPQ reduces fitness with 40% under natural conditions.