Isolation and characterization of a gene for a repetitive proline rich protein (OsPRP) down-regulated during submergence in rice (Oryza sativa)

Differential screening was performed on a cDNA library made from RNAs isolated from rice seedlings (variety Yukihikari) grown in submergence condition. A cDNA clone (OsPRP) encoding a repetitive proline-rich protein of 358 amino acids and molecular weight of 39 kDa was obtained. The C-terminal region of OsPRP contains proline (P) residues (40%), and high levels of glutamic acid (E) and lysine (K). The N-terminus was free from proline residues. Sequence analysis indicated that 40 distinct PEPK repetitive sequence motifs were present in the sequence along with other repetitive motifs. Furthermore, four phosphorylation sites were predicted from the sequence. The domain structure of OsPRP was compared with proline-rich proteins from other monocot species. The N-terminus of OsPRP is highly hydrophobic indicating the presence of a signal peptide. Southern blot data indicate that in the Yukihikari genome OsPRP is most likely encoded by a single gene. The expression of OsPRP was relatively uniform in the young seedlings. However, tissue-specific expression of OsPRP indicated that shoot tissue accumulates more mRNA, and the root has relatively low expression. In addition, OsPRP expression is regulated by various environmental factors and is down-regulated under submergence stress. Exogenous application of growth hormones, namely abscisic acid (ABA), methyl jasmonate (MeJ) and ethephon caused significant repression of the OsPRP transcript. The nucleotide sequence reported in this paper has been reported to the NCBI, GenBank under accession number AF 337054.