Functional analysis of psbp-like protein 1 (PPL1) in arabidopsis

Abstract

Higher plants have a number of PsbP homologs (PsbP-like proteins: PPLs, PsbP-domain proteins: PPDs) in addition to the authentic PsbP in the oxygen-evolving complex of photosystem II (PSII). Among the PsbP homologs, the PPL1 protein is most homologous to a cyanobacterial PsbP (cyanoP), and we previously reported that PPL1 is required for the efficient repair of photo-damaged PSII under high light conditions [Ishihara et al. (2007) Plant Physiol. 145: 668-679]. However, functional role of PPL1 in the PSII repair cycle has not been clarified yet. In this study, we further investigated molecular function of PPL1 by characterizing the phenotypes of the PPL1 knockdown plants (ppl1i) in which PPL1 expressions were differently suppressed. Although growth of the ppl1i mutants under low intensity light was comparable with that of wild type plants, PSII activity of the ppl1i mutants was more sensitive to high intensity light and the extent of photoinhibition was correlated with the levels of the knocked-down PPL1. The possible functional role of PPL1 in PSII repair is discussed.