Overexpression of GmProT1 and GmProT2 increases tolerance to drought and salt stresses in transgenic Arabidopsis

The proline transporter protein (ProT) plays an important role in protective stress responses in various plants. However, its function in abiotic stress responses in soybean (Glycine max) remains obscure. In the present study, two soybean ProT genes, namely GmProT1 and GmProT2, were isolated by homologous cloning. GmProT1 and GmProT2 encode polypeptides of 435 and 433 amino acids, respectively. The GmProT1 and GmProT2 proteins showed high similarity to other ProT proteins. GmProT1 and GmProT2 transcripts were detected in different soybean tissues including roots, stems, leaves, flowers, and developmental seeds, and during diverse developmental stages. GmProT1 was strongly expressed in seeds 35 days after flowering. Quantitative real-time PCR analysis showed that the two genes were highly expressed in leaves and could be strongly induced in response to salt and drought conditions and ABA treatment. Transgenic Arabidopsis thaliana plants overexpressing the two genes were generated, which showed that GmProT genes attenuate damage from salt and drought stress. In addition, transgenic Arabidopsis plants accumulated proline in response to salt and osmotic stress. Transcription levels of salinity-responsive gene (RD29B and S0S3) and drought-induced gene (CDPK1) were higher in the transgenic lines than that of wild type plants. Our work provides evidence that GmProT genes function in the response to abiotic stresses and may affect the synthesis and response system of proline.