转ipt和反义ACO基因番茄的叶片衰老相关特性

以ipt和反义ACO转化的两类转基因番茄纯系为材料,研究在植株不同生长发育阶段,不同叶位中,与叶片衰老相关的生理生化指标.结果表明:两类基因导入番茄后,均可增强内源iPA和IAA表达水平,增加或保持番茄叶片的叶绿素含量、提高光合效率,进而明显地延缓植株的叶片衰老,提高单株果实产量.但它们调控叶片衰老的途径不同,ipt主要通过提高CTK的水平延缓叶片衰老,而反义ACO则主要是通过抑制乙烯生成,间接提高IAA的水平来实现.

Characteristics Related to Leaf Senescence in Tomatoes with Transgenic ipt and anti-ACO Genes

Several physiological and biochemical characteristics of phytohormones, photosynthesis and senescence of leaves in tomato were investigated on plants of two homozygous transgenic tomato lines, one contains the ipt(isopentenyl transferase gene)driven by leaf senescence-specific promoter P SAG12 (ipt1 and ipt2), and the other carrying an antisense ACO (ACC oxidase gene) (B2) driven by CaMV35S promoter. The results show that plants of both transgenic lines express higher levels of IAA and iPA (Fig.1), higher chlorophyll content (Fig.4), and higher photosynthesis rates (Fig.5) than the wild type plants, especially in the older leaves. The declining rates of hormones and chlorophyll in certain leaves in transgenic plants were lower than those in the wild type (Figs.2,4B). Leaf senescence was slower and higher yields of tomato fruit were obtained from transgenic plants (Table 1). There were also some differences in the manners of the regulation of the leaf senescence between these two transgenic lines. The ipt transgenic plants produced higher levels of iPA to delay leaf senescence (Fig.2A). In the line of B2, leaf senescence was delayed mainly through the direct inhibition of ethylene evolution and indirect improvement of IAA level (Figs.2B, 3A).