Light Stress Proteins in Viruses, Cyanobacteria and Photosynthetic Eukaryota

Abstract

Plants in Nature frequently perceive environmental extremes such as light stress. To maintain their physiol. functions under light stress conditions plants have developed different protection strategies that operate at morphol., anatomical and subcellular levels. The accumulation of light stress proteins from the light-harvesting complex (LHC)-like protein family can be considered to be a part of such photoprotective responses. LHC-like proteins are distant relatives of the chlorophyll a/b-binding proteins of photosystem I and II that accumulate only transiently in thylakoid membranes under certain physiol. stress conditions. Based on predicted secondary structure LHC-like family members are divided into three-helix ELIPs (early light-induced proteins), two-helix SEPs (stress-enhanced proteins) and one-helix OHPs (one-helix proteins), called also HLIPs (high light-induced proteins) or SCPs (small chlorophyll-binding-like proteins) in cyanobacteria and viruses. It is believed that these proteins play a protective role within the chloroplast under light stress conditions either by transient binding of free chlorophylls and preventing the formation of free radicals and/or by acting as sinks for excitation energy. Expanding functional genomics provided new tools for the identification of genes and proteins structurally and/or functionally related to LHC-like family members that escaped previous detection by classical mol. biol. or biochem. methods. This chapter provides an overview of "classical" LHC-like family members, discusses their evolution and photoprotective functions and introduces novel types of LHC-like proteins in algae and land plants. [on SciFinder(R)]