大豆细胞周期G1/S期阻滞对镉胁迫的应答调控机制

Response Mechanism of Cell Cycle G1/S Phase Arrest Regulation under Cadmium Stress in Soybean(Glycine max)

选取对Cd抗性不同的两个大豆品种为试验材料,采用培养皿双层滤纸法培养幼苗,分别添加不同Cd浓度溶液处理,Cd浓度设为0~2.5 mg/L处理4 d,通过对幼苗根尖细胞周期和相关基因表达的研究,旨在探讨Cd胁迫下大豆细胞周期G1/S期阻滞调控的应答机制。结果表明,不同的Cd浓度处理均能引起大豆幼苗根尖DNA的损伤,造成基因组的不稳定性,Cd处理后‘辽豆10号’细胞周期阻滞在G1/S期,而‘沈农豆20’则是阻滞在G2/M期;DNA损伤检验点基因ATM和ATR的表达量与Cd浓度呈明显的倒U型剂量-效应关系;DNA错配修复基因MSH2和MSH6的表达量与Cd浓度呈明显的倒U型剂量-效应关系。Cd胁迫引起DNA损伤被MRN蛋白复合体识别,从而诱导ATM激活,然后ATM通过磷酸化p21抑制CDK在cyclin-Cdk/PCNA复合体中磷酸化,使转录活化因子E2Fa不能脱离Rb控制,失去转录活化因子的作用,从而使细胞被阻断在G1/S期。

The two varieties of Glycine max which have different resistance of Cd were used as tested plants in this study.The soybean seedlings were grown on petri dish with double-layer filter paper,which was containing cadmium(Cd) of 0~2.5 mg/L for 4 d.By studying the expression of root length and morphology index,apical cell cycle and related genes,we aim to discuss the effects of cell cycle arrest regulation in soybean under Cd stress and screen the biomarkers of G2/M phase arrest cell cycle with Cd exposure in soybean.The results showed that DNA damage could be induced under Cd stress at different concentrations of Cd,resulting in the instability of the genome.Cd-stress could induce G1/S cell cycle arrest in ’Liaodou10’ roots,however,Cd-stress could induce G2/M cell cycle arrest in ’Shennongdou20’ roots.It was inverted U-shaped dose-effect relationships in ATM/ATR DNA damage checkpoints expression and Cd expose.According to the inverted U-shaped dose-effect relationships in MSH2/MSH6 expression and Cd expose.Cd-induced DNA stress could be sensed by MRN complex,leading to activation of ATM.Then ATM inhibited that phosphorylating of CDK in cyclin-Cdk/PCNA complex by phosphorylating p21,which made the transcriptional activator E2Fa unable separated from Rb control and lost its function,finally causing the cell cycle arrest in G1/S phase.