Characterization of SP1, a Stress-Responsive, Boiling-Soluble, Homo-Oligomeric Protein from Aspen

• Published in: Plant physiology (Bethesda) Vol. 130; no. 2; pp. 865 - 875
• Main Authors: Wang-Xia Wang, Dan Pelah, Tal Alergand, Shoseyov, Oded, Altman, Arie
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.10.2002; American Society of Plant Physiologists
• Subjects: Abscisic Acid - pharmacology; Adaptation, Physiological - genetics; Adaptation, Physiological - physiology; Amino Acid Sequence; Amino acids; Antibodies; Base Sequence; Biological and medical sciences; Blotting, Northern; Cell biochemistry; Cell physiology; Cloning, Molecular; Complementary DNA; Cycloheximide - pharmacology; Dehydration; DNA, Complementary - chemistry; DNA, Complementary - genetics; Electrophoresis, Gel, Two-Dimensional; Environmental Stress and Adaptation; Fundamental and applied biological sciences. Psychology; Gels; Genes. Genome; Mannitol - pharmacology; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Oligomers; Oxidative stress; Peptide Mapping; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plantlets; Plants; Populus - drug effects; Populus - genetics; Populus - metabolism; Proteins; Sequence Alignment; Sequence Analysis, DNA; Sodium Chloride - pharmacology; Water - pharmacology; Water - physiology; Cold; Nucleotide sequence; Desiccation; Populus tremula; Environmental factor; Oligomer; Water stress; Thermal stability; Salicaceae; Salinity; Characterization; Heat; Gene; Dicotyledones; Sesquiterpenes; Angiospermae; Abscisic acid; Plant growth substance; Isolation; Hardwood forest tree; Spermatophyta; Molecular cloning; Aminoacid sequence
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.002436

sp1 cDNA was isolated from aspen (Populus tremula) plants by immunoscreening an expression library using polyclonal antibodies against BspA protein. BspA, which is a boiling-stable protein, accumulates in aspen plants in response to water stress and abscisic acid application (Pelah et al., 1995). The sp1 cDNA was found to encode a 12.4-kD generally hydrophilic protein with a hydrophobic C terminus, which is different from the BspA protein and was termed SP1 (stable protein 1). Northern-blot analysis revealed that sp1 encodes a small mRNA (about 0.6 kb) that is expressed in aspen plants under non-stress conditions and is accumulated after salt, cold, heat, and desiccation stress, and during the recovery from stress. The SP1 detected in plants remained soluble upon boiling, migrated both as a 12.4-kD band and a much higher mass of 116 kD on a 17% (w/v) Tricine-sodium dodecyl sulfate-polyacrylamide gel. Comparative protease digestion patterns, amino acid analyses, and the N-terminal sequences of the 12.4- and 116-kD proteins revealed that SP1 is homo-oligomeric. Furthermore, gel filtration chromatography analysis indicated that SP1 exists in aspen plants as a complex, composed of 12 subunits of 12.4 kD. A large number of sequences deduced from expressed sequence tags and genomic sequences of other organisms with unknown function show high homology to SP1. Thus, SP1 may represent a new protein family. Here, we present the first report on this putative protein family: the cloning, isolation, and characterization of SP1, a stress-responsive, boiling-soluble, oligomeric protein.