Evolutionary analysis of the small heat shock proteins in five complete algal genomes.
Small heat shock proteins (sHSPs) are chaperones that are crucial in the heat shock response but also have important nonstress roles within the cell. sHSPs are found in all three domains of life (Bacteria, Archaea, and Eukarya). These proteins are particularly diverse within land plants and the evolutionary origin of the land plant sHSP families is still an open question. Here we describe the identification of 17 small sHSPs from the complete genome sequences of five diverse algae: Chlamydomonas reinhardtii, Cyanidioschyzon merolae, Ostreococcus lucimarinus, Ostreococcus tauri, and Thalassiosira pseudonana. Our analysis indicates that the number and diversity of algal sHSPs are not correlated with adaptation to extreme conditions. While all of the algal sHSPs identified are members of this large and important superfamily, none of these sHSPs are members of the diverse land plant sHSP families. The evolutionary relationships among the algal sHSPs and homologues from bacteria and other eukaryotes are consistent with the hypothesis that the land plant chloroplast and mitochondrion sHSPs did not originate from the endosymbionts of the chloroplast and mitochondria. In addition the evolutionary history of the sHSPs is very different from that of the HSP70s. Finally, our analysis of the algal sHSPs sequences in light of the known sHSP crystal structures and functional data suggests that the sHSPs possess considerable structural and functional diversity.
Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-4614, USA. ewaters@sciences.sdsu.edu
Elizabeth R
ER
Waters
Ignatius
I
Rioflorido
D020418:Algal Proteins / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000235:genetics; D000460:Chlorophyta / Q000235:genetics; D017377:Diatoms / Q000235:genetics; D056890:Eukaryota / Q000145:classification / Q000235:genetics*; D019143:Evolution, Molecular; D016678:Genome; D050888:Heat-Shock Proteins, Small / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D000461:Rhodophyta / Q000235:genetics; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D013045:Species Specificity
D020418:Algal Proteins; D050888:Heat-Shock Proteins, Small