Molecular Cloning and Characterisation of Genes Coding for Glycine- and Proline-Rich Proteins (GPRPs) in Soybean

Genes encoding glycine- and proline-rich proteins (GPRPs) are widely distributed in land plants, but these have been rarely characterised. In this study, a total of six GPRPs (GmGPRP1 to 6) have been identified in the soybean genome database, and full-length complementary DNA and genomic DNA sequences of GmGPRP3 and GmGPRP4 have been cloned. GmGPRP1-6 genes encoded a set of small predicted proteins (<185aa) with molecular mass of 12.35?C19.67?kDa and isoelectric point of 6.79?C10.22. GmGPRP1-5 contained three exons and two introns with fixed occurring sites, whereas GmGPRP6 only has two exons and one intron. In the deduced GmGPRP1-5 sequences, six amino acids (glycine, proline, histidine, alanine, lysine and tyrosine) account for more than 75% of the total protein composition. GmGPRPs showed high similarity to other known GPRPs at amino acid level. Most of GPRPs had three conserved regions, including an N-terminal XYPP-repeat domain, a central hydrophobic domain containing several uninterrupted alanine residues and a C-terminal HGK-repeat region. The transcripts of GmGPRP1, 3 and 4 appeared in different organs including seedling leaves, stems and roots, flowers and developing seeds, but every gene showed a unique organ-specific expression pattern. Furthermore, the expression of GmGPRP1, 3 and 4 was significantly induced by drought, salt and cold, but repressed by abscisic acid. In silico analysis of promoter regions of these genes revealed the presence of putative abiotic-stress regulatory elements. Our data suggest GmGPRPs encoding a class of conservative XYPP-repeat proteins probably play an important role in plant development as well as in response to abiotic stresses.