L-Ascorbic acid (AsA) plays an important role in plants and animals.  In plants, GDP-D-mannose pyrophosphorylase (GMP) is essential in the AsA biosynthetic pathway.  However, little is known about the genes encoding GMP in soybean and here we report genetic and functional analysis of the GmGMP1 (Glycine max GDP-D-mannose pyrophosphorylase 1) gene in this species.  GmGMP1 encoded a GDP-mannose pyrophosphorylase and exhibited higher transcript levels in the leaf than in the root, stem, flower, and seed.  Transcript of this gene was ubiquitous in the vegetative and reproductive organs, and was induced by abiotic stress and light.  Increasing expression of GmGMP1 in Arabidopsis and soybean through an overexpressing approach caused pronounced enhancement of AsA content, and was implicated in lowering the superoxide anion radical content and lipid peroxidation levels in Arabidopsis, and conferring tolerance to osmotic and high salt stresses during seed germination.  The present study represents the first systematic determination of soybean genes encoding GDP-mannose pyrophosphorylase and provides useful evidence for the functional involvement of GmGMP1 in control of AsA content and conferring tolerance to osmotic and salt stress.

   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.

Phytophthora sojae Kanfman and Gerdemann (P. sojae) is one of the most prevalent pathogens and causes Phytophthora root rot, which limits soybean production worldwide. Development of resistant cultivars is a cost-effective approach to controlling this disease. In this study, 127 soybean germplasm were evaluated for their responses to Phytophthora sojae strain Pm28 using the hypocotyl inoculation technique, and 49 were found resistant to the strain. The hypocotyl of P1, P2, F1, and F2:3 of two crosses of Ludou 4 (resistant)×Youchu 4 (susceptible) and Cangdou 5 (resistant)×Williams (susceptible) were inoculated with Pm28, and were used to analyze the inheritance of resistance. The population derived from the cross of Ludou 4×Youchu 4 was used to map the resistance gene (designated as Rps9) to a linkage group. 932 pairs of SSR primers were used to detect polymorphism, and seven SSR markers were mapped near the resistance gene. The results showed that the resistance to Pm28 in Ludou 4 and Cangdou 5 was controlled by a single dominant gene Rps9, which was located on the molecular linkage group N between the SSR markers Satt631 (7.5 cM) and Sat_186 (4.3 cM).