Molecular characterization of a novel soybean gene encoding a neutral PR-5 protein induced by high-salt stress

• Published in: Plant physiology and biochemistry 2009, Vol.47 (1), p.73-79
• Main Authors: Tachi, Hiroyuki, Fukuda-Yamada, Kumiko, Kojima, Toshio, Shiraiwa, Masakazu, Takahara, Hidenari
• Format: Article
• Language: English
• Subjects: Acetates - pharmacology; Amino Acid Sequence; Biological and medical sciences; Cicer arietinum; Cyclopentanes - pharmacology; Fundamental and applied biological sciences. Psychology; Gene Expression - drug effects; Gene Expression Regulation, Plant; Glycine max; Glycine max - genetics; Glycine max - metabolism; High-salt stress; Homology modeling; Methyl jasmonate; Molecular Sequence Data; Oxylipins - pharmacology; Pathogenesis-related protein; Phylogeny; Plant Growth Regulators - pharmacology; Plant physiology and development; Plant Proteins - genetics; Protein Conformation; Protein Isoforms - chemistry; Protein Isoforms - classification; Protein Isoforms - isolation & purification; Salicylic acid; Salicylic Acid - pharmacology; Salt Tolerance - genetics; Sequence Analysis, Protein; Soybean Proteins - genetics; Soybean Proteins - metabolism; Thaumatin-like protein
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2008.09.012

In this study, we characterized a novel soybean gene encoding a neutral PR-5 protein and compared it to two acidic isoforms of soybean PR-5 protein. This gene, designated as Glycine max osmotin-like protein, b isoform ( GmOLPb, accession no. AB370233), encoded a putative protein having the greatest similarity to chickpea PR-5b (89% identity). Unlike the two acidic PR-5, GmOLPa and P21, the protein had a C-terminal elongation responsible for possible vacuolar targeting and after maturation showed a calculated molecular mass of 21.9 kDa with p I 6.0. The 3D models, predicted by the homology modeling, contained four α-helixes and 16 β-strands and formed three characteristic domains. The two acidic PR-5 proteins also showed a 3D structure very similar to GmOLPb, although the electrostatic potential on molecular surface of each PR-5 was significantly different. In the study of the gene expression under conditions of high-salt stress, GmOLPb was highly induced in the leaves of the soybean, particularly in the lower part of a leaf. The expression started at 2 h after initiation of the stress and was highly induced between 18–72 h. Gene expression of P21e (protein homologous to P21) was transiently induced by high-salt stress, but took place earlier than the gene expressions of GmOLPa and GmOLPb. Such differential expression was observed also under investigation with methyl jasmonate and salicylic acid. These results suggested that each soybean PR-5 might play a distinctive role in the defensive system protecting the soybean plant against high-salt stress, particularly in the leaves of the soybean.