Molecular characterization of OsPRP1 from rice, which is expressed preferentially in anthers

Abstract

A proline-rich protein-encoding cDNA encoded by a rice gene, OsPRP1, was isolated by PCR-mediated RNA subtraction hybridization strategy and rapid amplification of cDNA ends. The deduced protein consists of 224 amino acids with the highest level of proline residue (14.29%). Following the putative signal peptide, OsPRP1 contains two structural domains, of which the N-terminal domain lacks Pro-rich repetitive sequences, and the C-terminal domain has two repetitive proline-rich sequences of 18 amino acid residues with PEPK motifs. Southern blot and sequence analysis show that OsPRP1 exists as four copies in rice genome and is localized in rice chromosome 10. RT-PCR experiments reveal that OsPRP1 is expressed preferentially in spikelets and buds with lower levels in roots and leaves. In situ hybridization indicates that OsPRP1 transcripts are present at high levels in pollen mother cells (PMCs), meiotic PMCs, tapetal cells and vascular bundle cells of flower organs. The expression of OsPRP1 in anthers has temporal specificity. The transcripts are accumulated at high levels in PMCs, at the highest levels in meiotic PMCs and at undetectable levels in uninucleate pollen. In buds the transcripts are only detected in the epidermal cells of coleoptiles and leaf primordial.