Rossouw Debra, Bosch Sue, Kossmann Jens, Botha Frederik C, Groenewald Jan-Hendrik
Institute for Plant Biotechnology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.
Funct Plant Biol. 2007 Jun;34(6):490-498. doi: 10.1071/FP06214.
Suspension cultures were used as a model system to investigate sucrose metabolism in four sugarcane (Saccharum spp. interspecific hybrids) cell lines transformed with antisense neutral invertase (NI) constructs. Throughout a 14-day growth cycle two cell lines in which the antisense sequence was under the control of a tandem CaMV-35S: maize ubiquitin promoter showed a strong reduction in NI activity, as well as reduced hexose and increased sucrose concentrations in comparison to the control line. In lines where the antisense NI sequence was under the control of the weaker CaMV-35S promoter alone, changes in enzyme activity and sugar concentrations were intermediate to those of the more strongly inhibited lines and the control. In comparison to the control line, a higher sucrose to hexose ratio, i.e. increased purity, was obtained in all the lines with reduced NI activity. The in vivo rate of sucrose hydrolysis was reduced in the transgenic lines, suggesting a concomitant reduction in the flux through the 'futile cycle' of sucrose breakdown and re-synthesis. Differences between the transgenic cultures and the control were most pronounced during the early stages of the growth cycle and tapered off as the cultures matured. The transgenic cultures displayed impaired growth characteristics suggesting that the growth rate of these cells was retarded because of the reduced availability of hexoses for respiration.
悬浮培养物被用作模型系统，以研究用反义中性转化酶（NI）构建体转化的四种甘蔗（甘蔗属种间杂种）细胞系中的蔗糖代谢。在整个14天的生长周期中，与对照系相比，两个反义序列受串联CaMV-35S：玉米泛素启动子控制的细胞系显示NI活性大幅降低，己糖浓度降低，蔗糖浓度升高。在仅受较弱的CaMV-35S启动子控制的反义NI序列的细胞系中，酶活性和糖浓度的变化介于抑制较强的细胞系和对照之间。与对照系相比，所有NI活性降低的细胞系中蔗糖与己糖的比率更高，即纯度增加。转基因系中蔗糖水解的体内速率降低，表明通过蔗糖分解和再合成的“无效循环”的通量随之降低。转基因培养物与对照之间的差异在生长周期的早期最为明显，并随着培养物成熟而逐渐减小。转基因培养物显示出生长特性受损，表明这些细胞的生长速率因呼吸作用中己糖可用性降低而受到抑制。
