Molecular cloning and characterization of a novel SNAP25-type protein gene OsSNAP32 in rice (Oryza sativa L.).

The SNAP25-type proteins belong to the superfamily of the SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors), and function as important components of the vesical trafficking machinery in eukaryotic cells. In this paper, we report the cloning and expression characterization of OsSNAP32 gene, and the subcellular localization of its encoded protein. The OsSNAP32 gene contains five exons and four introns, and is located between RFLP markers C12276S and S1917 on chromosome 2 in rice. The OsSNAP32 has a molecular weight of 31.3 kD, comprises 283 amino acid residues, and contains Qb-SNARE and Qc-SNARE domains in the N- and C-terminal, respectively. Multiple sequence alignment of the SNARE domains indicates that OsSNAP32 protein is homologous to HvSNAP34 and HvSNAP28 (63% and 55% of amino acid identity respectively) from barley. The transient expression method in onion epidermal cells, revealed that OsSNAP32 is located in the plasma membrane, like other SNAP25-type proteins. Semi-quantitative RT-PCR assay showed that the OsSNAP32 is highly expressed in leaves and culms, and low in roots of rice, while hardly detected in immature spikes and flowering spikes. The expression of OsSNAP32 was significantly activated in rice seedlings treated with H2O2, PEG6000, and low temperature or after inoculation with rice blast (Magnaporthe grisea strain Hoku 1). The results suggest that this gene belongs to a novel member of this gene family encoding SNAP25-type proteins, involved in the rice responses to biotic and abiotic stresses.