Molecular cloning and characterization of a novel gene MsKMS1 in Medicago sativa

Vacuole membrane proteins play a critical role in the regulation of plant physiological processes including normal growth and development, and responses to stresses. The killing me slowly 1 (KMS1) gene that encodes a soluble N-ethylmaleimide-sensitive fusion attachment receptor (SNARE) domain-containing vacuole membrane protein was first reported in Arabidopsis. Currently, the function of KMS1 in other plants under stress is poorly understood. In this study, we report cloning, expression, and characterization of a novel KMS1 gene in alfalfa (Medicago sativa L.), designated MsKMS1 (GenBank accession No. JX467688). The full-length cDNA of MsKMS1 was 1 396 bp and contained a complete open reading frame of 1 257 bp, which encoded a putative protein of 418 amino acids. The BLASTp analysis showed that MsKMS1 shared high amino acid sequence similarities with KMS1 from other plants such as Medicago truncatula (99 %), Cicer arietinum (89 %), Glycine max (77 %), Prunus mume (76 %), Ricinus communis (72 %), Populus euphratica (72 %), Theobroma cacao (72 %), and Arabidopsis thaliana (67 %). Transient transformation of onion (Allium cepa) bulb scale epidermal cells by biolistic bombardment showed that MsKMS1 was localized to the plasma membrane. Quantitative real-time PCR revealed that MsKMS1 expression was upregulated under different abiotic stresses (200 mM NaCl, 20 % (m/v) polyethylene glycol 6000] and 10 mg dm-3 abscisic acid. Transgenic tobacco plants were obtained via Agrobacterium-mediated transformation and treated with 200 mM NaCl. Reverse-transcription PCR data showed that MsKMS1 was successfully transcribed and expressed in the leaves of transgenic plants. The MsKMS1-overexpressors showed a lower malondialdehyde content and maintained a higher relative water content and proline content compared with non-transgenic controls under salt stress. These results indicate that the introduction of the MsKMS1 gene could improve salt stress resistance in tobacco plants. This study reveals the role of MsKMS1 in the regulation of plant responses to abiotic stress and provides evidence for further functional studies of the KMS1 family in alfalfa.