The plant sHSP superfamily: five new members in Arabidopsis thaliana with unexpected properties.
The small heat shock proteins (sHsps), which are ubiquitous stress proteins proposed to act as chaperones, are encoded by an unusually complex gene family in plants. Plant sHsps are classified into different subfamilies according to amino acid sequence similarity and localization to distinct subcellular compartments. In the whole Arabidopsis thaliana genome, 19 genes were annotated to encode sHsps, of which 14 belong to previously defined plant sHsp families. In this paper, we report studies of the five additional sHsp genes in A. thaliana, which can now be shown to represent evolutionarily distinct sHsp subfamilies also found in other plant species. While two of these five sHsps show expression patterns typical of the other 14 genes, three have unusual tissue specific and developmental profiles and do not respond to heat induction. Analysis of intracellular targeting indicates that one sHsp represents a new class of mitochondrion-targeted sHsps, while the others are cytosolic/nuclear, some of which may cooperate with other sHsps in formation of heat stress granules. Three of the five new proteins were purified and tested for chaperone activity in vitro. Altogether, these studies complete our basic understanding of the sHsp chaperone family in plants.
Siddique
Masood
M
Molecular Cell Biology, Johann Wolfgang Goethe University, Biocenter N200, Max-von-Laue-Strasse 9, Frankfurt am Main, Germany. msiddiqu@biochem2.uni-frankfurt.de
Gernhard
Sascha
S
von Koskull-Döring
Pascal
P
Vierling
Elizabeth
E
Scharf
Klaus-Dieter
KD
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D017930:Genes, Reporter; D006360:Heat-Shock Proteins / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D006358:Hot Temperature; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D046912:Multiprotein Complexes / Q000737:chemistry; D016366:Open Reading Frames / Q000235:genetics; D010802:Phylogeny; D017510:Protein Folding; D011523:Protoplasts; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological / Q000235:genetics; D013347:Subcellular Fractions / Q000378:metabolism; D014026:Nicotiana
D029681:Arabidopsis Proteins; D006360:Heat-Shock Proteins; D046912:Multiprotein Complexes; D011993:Recombinant Fusion Proteins