高浓度细胞分裂素诱导棉花悬浮细胞程序性死亡的发生

High concentration of cytokinin induces programmed cell death of cotton suspension cultures

棉花悬浮细胞经高浓度细胞分裂素(2 mg·L-1KT或4 mg·L-1KT)处理后第4天大量死亡,培养物呈褐黑色;抽提总DNA,进行琼脂糖胶电泳,结果表明:2和4 mg·L-1KT两处理中有明显的大小为140～180 bp及其倍增量片段的DNA'梯'(DNA Ladder).进行PI和FDA染色显微观察可以看到:2 mg·L-1KT处理中大部分细胞的细胞核较小,核质浓缩,呈棒形或弯月形;胞质浓缩,出现了不对称的质壁分离,且丧失了FDA染色活性.这些结果表明由高浓度细胞分裂素处理引起的棉花悬浮细胞大规模死亡是一种PCD.不同的生理状态(UCSA和BAE)和不同生长时期(指数增长期和静止期)的棉花悬浮细胞对高浓度细胞分裂素的诱导反应表现出差异.

Large-scale cell death occurred when cotton suspension cells were treated with high concentration of cytokinin （2 mg·L^-1 KT or 4 mg·L^-1KT）, and the suspension cultures turned brown-black. Agarose gel electrophoresis of genomic DNA showed that apparent DNA fragmentations of multimers of 140 - 180 bp existed in the cells treated with high concentration of cytokinin （2 mg·L^-1 KT or 4 mg·L^-1 KT）. Cytological studies also revealed that this kind of cell death was accompanied by such morphological characters as chrornatin condenses, the maintaining of membrane continuity and condensed cytoplasm （shrinkage of the plasma membrane away from cell wall） .These results supported that cell death induced by high concentration of cytokinin was a kind of PCD. In the experiment, we also found that cells in different physiological states（UCSA or BAE） and cells in various growth-phases （the exponential growth-phase or the quiescent phase） responded differentially to high concentration of cytokinin. The UCSA cells and the cells in exponential growth-phase were more sensitive to the induer.