β-galactosidases (EC 3.2.1.23) constitute a widespread family of glycosyl hydrolases in plants and are thought to be involved in metabolism of cell wall polysaccharides. A cDNA of the cotton (Gossypium hirsutum) β-g...β-galactosidases (EC 3.2.1.23) constitute a widespread family of glycosyl hydrolases in plants and are thought to be involved in metabolism of cell wall polysaccharides. A cDNA of the cotton (Gossypium hirsutum) β-galactosidase gene, designated GhGal1, has previously been identified and its transcripts are highly abundant at the elongation stage of the cotton fiber. To examine the temporal and spatial control of GhGal1 expression, a transcriptional fusion of the GhGal1 promoter region (1770 bp) with the β-glucuronidase (GUS) reporter gene was introduced into tobacco plants by the Agrobacterium infection method. The resulting transgenic plants showed higher GUS activity of fruit in the transgenic plants than that in the negative and positive controls. Histochemical localization of GUS activity demonstrated that the expression of the GUS gene could be found in the meristem zones of roots, cotyledons, vascular tissues, fruit and trichomes in transgenic tobacco plants. Additionally, se-quence analysis of the regulatory region also revealed several conserved motifs among which some were shared with previously reported fruit/seed-specific elements and the others were related with trichome expression. These results indicated the temporal and spatial expression characterization of the GhGal1 promoter in transgenic tobacco plants and provided an important insight into the roles of GhGal1 in cotton fiber development.展开更多
β-半乳糖苷酶具有将乳糖分解为半乳糖和葡萄糖的能力,也具有把半乳糖聚合成低聚半乳糖的能力。这两种能力在工业生产中具有不同的意义。通过点突变使β-galactosidase[Pyrococcus furiosus DSM 3638]415位天冬酰胺(Asn or N)突变为丝氨...β-半乳糖苷酶具有将乳糖分解为半乳糖和葡萄糖的能力,也具有把半乳糖聚合成低聚半乳糖的能力。这两种能力在工业生产中具有不同的意义。通过点突变使β-galactosidase[Pyrococcus furiosus DSM 3638]415位天冬酰胺(Asn or N)突变为丝氨酸(Ser or S),突变体构建于毕赤酵母表达质粒载体,并筛选以毕赤酵母为宿主细胞的工程菌种,以此制备β-半乳糖苷酶的突变体酶蛋白。研究发现,该突变体的β-半乳糖苷酶活性在95℃、p H5.5时达到最高酶活,为耐高温乳糖酶,且该突变体水解牛奶的能力较好,可用于低乳糖牛奶及其相关制品加工中。而突变后β-半乳糖苷酶的另一个活性,即产生低聚半乳糖的能力的活性也有所提高,但不够明显。因此该位点突变可用于乳制品的加工,但不能期盼产生更多的半乳糖寡聚体。展开更多
文摘β-galactosidases (EC 3.2.1.23) constitute a widespread family of glycosyl hydrolases in plants and are thought to be involved in metabolism of cell wall polysaccharides. A cDNA of the cotton (Gossypium hirsutum) β-galactosidase gene, designated GhGal1, has previously been identified and its transcripts are highly abundant at the elongation stage of the cotton fiber. To examine the temporal and spatial control of GhGal1 expression, a transcriptional fusion of the GhGal1 promoter region (1770 bp) with the β-glucuronidase (GUS) reporter gene was introduced into tobacco plants by the Agrobacterium infection method. The resulting transgenic plants showed higher GUS activity of fruit in the transgenic plants than that in the negative and positive controls. Histochemical localization of GUS activity demonstrated that the expression of the GUS gene could be found in the meristem zones of roots, cotyledons, vascular tissues, fruit and trichomes in transgenic tobacco plants. Additionally, se-quence analysis of the regulatory region also revealed several conserved motifs among which some were shared with previously reported fruit/seed-specific elements and the others were related with trichome expression. These results indicated the temporal and spatial expression characterization of the GhGal1 promoter in transgenic tobacco plants and provided an important insight into the roles of GhGal1 in cotton fiber development.
文摘β-半乳糖苷酶具有将乳糖分解为半乳糖和葡萄糖的能力,也具有把半乳糖聚合成低聚半乳糖的能力。这两种能力在工业生产中具有不同的意义。通过点突变使β-galactosidase[Pyrococcus furiosus DSM 3638]415位天冬酰胺(Asn or N)突变为丝氨酸(Ser or S),突变体构建于毕赤酵母表达质粒载体,并筛选以毕赤酵母为宿主细胞的工程菌种,以此制备β-半乳糖苷酶的突变体酶蛋白。研究发现,该突变体的β-半乳糖苷酶活性在95℃、p H5.5时达到最高酶活,为耐高温乳糖酶,且该突变体水解牛奶的能力较好,可用于低乳糖牛奶及其相关制品加工中。而突变后β-半乳糖苷酶的另一个活性,即产生低聚半乳糖的能力的活性也有所提高,但不够明显。因此该位点突变可用于乳制品的加工,但不能期盼产生更多的半乳糖寡聚体。
