Martín Ignacio, Dopico Berta, Muñoz Francisco J, Esteban Rocío, Oomen Ronald J F J, Driouich Azeddine, Vincken Jean-Paul, Visser Richard, Labrador Emilia
Departamento de Fisiología Vegetal, Centro Hispano Luso de Investigaciones Agrarias, Universidad de Salamanca, Plaza Doctores de la Reina s/n, Campus Miguel Unamuno, Spain.
Plant Cell Physiol. 2005 Oct;46(10):1613-22. doi: 10.1093/pcp/pci177. Epub 2005 Aug 2.
We report the generation of Solanum tuberosum transformants expressing Cicer arietinum betaIII-Gal. betaIII-Gal is a beta-galactosidase able to degrade cell wall pectins during cell wall loosening that occurs prior to cell elongation. cDNA corresponding to the gene encoding this protein was identified among several chickpea beta-galactosidase cDNAs, and named CanBGal-3. CanBGal-3 cDNA was expressed in potato under the control of the granule-bound starch synthase promoter. Three betaIII-Gal transformants with varying levels of expression were chosen for further analysis. The transgenic plants displayed no significant altered phenotype compared to the wild type. However, beta-galactanase and beta-galactosidase activities were increased in the transgenic tuber cell walls and this affected the potato tuber pectins. A reduction in the galactosyl content of up to 50% compared to the wild type was observed in the most extreme transformant, indicating a reduction of 1,4-beta-galactan side-chains, as revealed by analysis with LM5 specific antibodies. Our results confirm the notion that the pectin-degrading activity of chickpea betaIII-Gal reported in vitro also occurs in vivo and in other plants, and confirm the involvement of betaIII-Gal in the cell wall autolysis process. An increase in the homogalacturonan content of transgenic tuber cell walls was also observed by Fourier transform infrared spectroscopy (FTIR) analysis.
我们报道了表达鹰嘴豆βIII-半乳糖苷酶的马铃薯转化体的产生。βIII-半乳糖苷酶是一种β-半乳糖苷酶，能够在细胞伸长之前发生的细胞壁松弛过程中降解细胞壁果胶。在几种鹰嘴豆β-半乳糖苷酶cDNA中鉴定出了与编码该蛋白的基因相对应的cDNA，并将其命名为CanBGal-3。CanBGal-3 cDNA在颗粒结合淀粉合酶启动子的控制下在马铃薯中表达。选择了三个表达水平不同的βIII-半乳糖苷酶转化体进行进一步分析。与野生型相比，转基因植物没有表现出明显改变的表型。然而，转基因块茎细胞壁中的β-半乳聚糖酶和β-半乳糖苷酶活性增加，这影响了马铃薯块茎果胶。在最极端的转化体中观察到半乳糖基含量比野生型降低了50%，这表明1,4-β-半乳聚糖侧链减少，如用LM5特异性抗体分析所揭示的。我们的结果证实了体外报道的鹰嘴豆βIII-半乳糖苷酶的果胶降解活性在体内和其他植物中也存在的观点，并证实了βIII-半乳糖苷酶参与细胞壁自溶过程。通过傅里叶变换红外光谱（FTIR）分析还观察到转基因块茎细胞壁中同型半乳糖醛酸聚糖含量增加。
