Cloning And Expression Of Sucrose Phosphate Synthase Gene From Sugar Beet (Beta Vulgaris L.) And Its Genetic Transformation

Sugar beet is an important economic crop. It is necessary to study those enzymes which are correlative with sugar synthesis for the reason that the yield of sugar in sugar beet is one of the important standards for strain selection of sugar beet. Sucrose Phosphate Synthase (SPS) is believed to represent a key enzyme in controlling sucrose biosynthesis. SPS plays an important role in regulating the partition of photoproduct and sucrose accumulation in sink cell. Our studies focus on SPS gene as follows:1. A cDNA clone encoding a sucrose phosphate synthase from sugar beet (BvSPS 1) has been isolated from tap root of sugar beet. Analysis of the nucleotide sequence indicated that the cDNA of BvSPS1 was 3138 bp in length with an open reading frame encoding 1045 amino acids corresponding to a protein with a predicted molecular weight of 118 kDa. There was a transmembrane domain between Val561-Val593 . Sequence comparison of the predicted amino acid sequence with deduced SPS protein sequences from grape and tobacco showed that SPS proteins were highly conserved. The identity of SPS from sugar beet and SPS from grape and tobacco were 75.45 % and 74.59% respectively.2. RT-PCR result showed that BvSPS1 was expressed most predominant in tap root and was expressed in an organ-specific manner. The highest amounts of SPS transcript was observed in tap roots, which the same result was found in assays of Enzyme activity. The study on the factors that can influence expression of BvSPS1 showed that glucose can enhance the expression of BvSPS1 with accumulation of time.3. A genetic transformation system has been established by the study of regeneration of petioles from sugar beet. We found that the most effective medium for regeneration with 6-BA 1.0 mg/L, IAA 0.3 mg/L, which the regeneration ratio reached 14.0% . Based on the studies, we transferred BvSPS1 into sugar beet using agroinfection and obtained positive transgenic plants which have been confirmed by PCR.We made conclusions on characterization and function of BvSPS1 gene at molecular level. Meanwhile, we hope that we could make further research on BvSPS1 gene by obtaining transgenic plants.