The Oryza sativa no pollen (Osnop) gene plays a role in male gametophyte development and most likely encodes a C2-GRAM domain-containing protein

Abstract

Phenotype screens of Ds insertional lines identified a male sterile Orysa sativa no pollen (Osnop) mutant with a pollen-less phenotype at the flowering stage. The mutant phenotype showed linkage to Ds insertion into Osnop gene region. This mutant contained a deletion of 65 kb chromosomal region at the site of Ds insertion containing 14 predicted genes. Out of these deleted genes, Delegen 5-7, 9-10 were redundant, as two or three copies were present with 100% homology in other regions of rice genome. RT-PCR analysis showed that Delegen 5-7 were expressed not only in wild type plants but also in the mutant plants. In addition to this, Delegen 8-10 transcripts could not be detected under normal growth conditions, and Delegen 12 was expressed only in roots, thus deletion of these genes may not affect the pollen development. Our data and analysis also ruled out the possibility of delegen 1-4, 11, and 13 as candidates contributing to the pollen-less phenotype. Further investigation showed that the delegen 14 was expressed only in late stage of pollen development with the highest expression at the stage of pollen release and germination by RT-PCR, Northern blotting, in situ hybridization, and promoter-GUS transgenic plants. Thus, the delegen 14 gene is the best candidate for Osnop, corresponding to the pollen-less phenotype in the mutant. Our data suggest that delegen 14 may play an important role during late stage of pollen development and its germination. Since the delegen 14 gene has both C2 and GRAM domains, it can be assumed that this gene cross-links both calcium and phosphoinositide signaling pathways. This is the first report to suggest possible functions for this gene in plant development. © Springer 2005.