Characterization And Protein Subcellular Location Of Two GmSBP Protein And Their Response To Abiotic Stress In Soybean [Glycine Max(L.)Merr.]

Through photosynthesis, plants produce sucrose and other carbohydrates. Once these carbohydrates were synthesized, they are partitioned throughout the plant where they can be used as an energy source, regulating cell metabolism and playing important role in gene expression. And the regulation of sucrose transport throughout the plant has a tremendous impact on plant growth and development. Transporters are needed during sucrose movement across the plasma membrane and distribution in plants. Sucrose-binding protein was identified because of its strong affinity for a sucrose analog,6 deoxy-6’-(4-azido-2-hydroxy)-benzamido-sucrose, which competitively inhibited the influx of radiolabeled sucrose into protoplasts from developing soybean cotyledons. It can transport sucrose independently and belonging to storage protein family. Due to its high protein (about 40%) and high oil content (about 20%), HTH stress (high temperature and humidity stress) can result in seed deterioration during seed growth and seed storage.Through differention protemics, we found that GmSBP showed down-regulated expression patterns in response to HTH stress in the seeds of Xiangdou No.3. In order to further understand their function in stress response, we had identified resistance varieties of soybean seeds and separated two genes sequence of GmSBP protein gene:GmSBP2 and GmSBPL. Bioinformatic and expression profile analyses and subcellular localization were conducted to futher understand the two genes.The full ORF sequence of GmSBP2 was 1467 bp and encoded a protein with 489 amino acids which was hydrophilic protein and located in cytoplasm and cell membrane through subcellular location. The full ORF sequence of GmSBPL was 1512 bp and encoded a protein with 504 amino acids which was also hydrophilic protein. GmSBPL protein might locate in cell membrane and cytoplasm too. Real-time quantitative PCR analysis showed that GmSBP2 and GmSBPL were expressed in root, stem, leaf, flower and young pod and especially high in young leaf and flower. Both of them had higher expression in mid-leaf than in young leaf particularly in Xiangdou No.3. During seed germination, the expression of GmSBP2 and GmSBPL were reduced gradually. In seed developmental processes, two genes present unimodal change in expression and had peak value at 30 d. Real-time quantitative (RT-PCR) analysis revealed that the expression of two genes was significantly induced by HTH treatment in developing seeds of seed deterioration resistant cultivar Xiangdou No.3 and sensitive cultivar Ningzhen No.1. Meanwhile the levels of sucrose and soluble sugar in developing seeds of both the cultivars were affected under HTH stress. Two genes all could be induced by hormone. Especially to GA, GmSBP2 had a strong reaction.Meanwhile, transient expression of the GmSBP2:GFP and GmSBPL:GFP proteins in onion epidermal cells showed that they all localized in cytoplasm and cell membrane. The results suggested that GmSBP2 and GmSBPL genes may play roles in abiotic resistance pathways.