OsZEP2基因沉默对2,2′,5-三氯联苯胁迫下水稻抗氧化反应的影响

Effects of OsZEP2 silencing on antioxidiative reaction against PCB18 stress in callus (Oryza sative L.)

载脂蛋白基因OsZEP2沉默突变株(mutation type,MT)和野生型(wide type,WT)的水稻愈伤组织被暴露于10、50、100μg·mL-1的2,2′,5-三氯联苯(PCB18)的培养基3 d后,通过比较两种水稻愈伤组织的生长、PCB18积累和抗氧化反应的变化情况,来探究水稻在多氯联苯胁迫下OsZEP2基因对水稻解毒响应机制的影响.实验发现,PCB18可以抑制WT和MT的生长,但PCB18的中浓度胁迫对两种愈伤组织生长的促进作用十分明显,即有"hormesis"效应.PCB18对MT生长的抑制高于WT,低浓度CB18(10μg·mL-1)胁迫抑制MT生长(4.5%),中浓度PCB18(50μg·mL-1)促进MT生长(8.3%),高浓度PCB18(100μg·mL-1)抑制MT生长(9.9%).OsZEP2基因沉默后促进了PCB18在愈伤组织的积累,并导致培养基中的PCB18去除效率提高.OsZEP2基因沉默降低类胡萝卜素含量,导致MT本身的氧化胁迫增强;并且在不同浓度PCB18胁迫下,MT的类胡萝卜素含量稳定,MT的抗氧化反应活性低与WT.在PCB18胁迫下,MT体内的SOD和CAT酶的活性都明显低于WT,这可能是导致膜脂过氧化程度显著升高的重要原因之一.另外,两种嫩弱的愈伤组织中的POD酶抗氧化活性较弱,但OsZEP2沉默可以促进POD酶活性升高.因此,OsZEP2基因沉默导致植物体内的PCB18积累增多,抗氧化反应减弱,不利于植物对PCB18毒性的抵抗.

To study the roles of rice′s OsZEP2 in polychlorinated biphenyls(PCBs)stress,10,50 and 100μg·mL-1 of 2,2′,5-trichlorobiphenyl(PCB18)were added into the media of OsZEP2 silenced(MT)and wild type(WT)rice callus during 3 d experiment period,respectively.The changes of callus growth,PCB18 contents and antioxidant reaction in MT and WT callus were compared in order to understand the response mechanism of plants against PCBs stress.The results demonstrated PCB18 inhibited the growth of MT and WT,but plants in 50μg·mL-1 PCB18 showed"Hormesis"effect.The growth of MT was inhibited 4.5%at low concentration PCB18(10μg·mL-1)and 9.9%at high concentration PCB18(100μg·mL-1),but promoted 8.3%at medium concentration PCB18(50μg·mL-1).After OsZEP2 silenced,the accumulation of PCB18 in MT callus and PCB18 removing efficiency from the culture media were enhanced.Total carotenoid contents were reduced in MT,and no response to PCB18 stress.Thus,the oxidative stress was stronger in MT than WT.Moreover,the activities of antioxiditive enzymes SOD and CAT were lower in MT than WT,which one of important reasons could result into the increase of lipid oxidation in MT.Although the activity of POD in callus was poor,OsZEP2 silencing could promote the activity of POD in MT.Therefore,after OsZEP2 silenced,PCB18 accumulation were enhanced in MT plants,and the resistance of MT plants to PCB18 toxicity was weak.