平邑甜茶延长根和吸收根抗凋亡基因的表达差异及其对2,4-D 的响应

 以3 年生平邑甜茶[Malus hupehensis（Pamp）Rehd. var. pinyiensis Jiang]盆栽树为材料，通过2,4-D 水溶液灌根处理，探讨了新根（延长根和吸收根）细胞死亡及其抗凋亡基因的表达特征。结果表明，在60 mg · L^-1 2,4-D 处理后的70 d 内，新根细胞死亡量和类caspase3/7（半胱天冬酶）活性先上升后下降，ATP 含量和根系活力的变化与之相反。平邑甜茶抗凋亡基因MhBAG、MhBI-1 与MhHSP70 在新根中均受2,4-D 诱导，随着2,4-D 处理时间的延长，MhBAG 基因的表达水平先下降后逐渐升高，MhBI-1 与MhHSP70 则先升高后下降。在2,4-D 处理下，吸收根细胞死亡量与根系活力的变化幅度明显高于延长根，吸收根MhBI-1 与MhHSP70 表达量的早期升高幅度大于延长根，表明吸收根细胞对2,4-D 的敏感性高于延长根；但在基因表达高峰时，延长根抗凋亡基因表达量的升高倍数明显高于吸收根，暗示延长根比吸收根有更强的抗凋亡能力。

Differential Expression of Anti-apoptotic Genes in Extensive and Absorbing Roots of Malus hupehensis and Their Response to 2,4-D

The three-year old potted trees of Malus hupehensis（Pamp）Rehd. var. pinyiensis Jiang were irrigated with water solution of 2,4-D to investigate the characteristics of cell death and the expression of anti-apoptotic genes of new roots（extensive roots and absorbing roots）. The result showed that the new roots’ cell death quantity and caspase-like 3/7 activity increased first and then fell in the 70 days after the treatment of 60 mg · L^-1 2,4-D，however，the ATP content and the root activity changed in the contrary trend. After the treatment，the expression of anti-apoptotic genes MhHSP70，MhBI-1，MhBAG were induced and the expression levels of MhBAG first decreased then increased，however MhHSP70 and MhBI-1 increased first，and then decreased later. At the same time，the change range of cell death quantity and caspase-like 3/7 activity and the rising range of MhHSP70 and MhBI-1 expression levels in absorbing roots were greater than that in extensive roots in the early stage of the 2,4-D treatment，which showed that absorbing roots had higher sensitivity to 2,4-D than extensive roots. When at peak value，the expression levels rising times of anti-apoptotic genes in extensive roots were significantly higher than that in absorbing roots，which indicated that the extensive roots had stronger anti-apoptotic ability than absorbing roots.