The Protecive Role Of ABA In Celluar Oxidative Damage And Its Relation With MAPK In Maize Seedlings Under Drought Stress

Using abscisic acid(ABA) biosynthetic inhibitors,the role of ABA in drought stress-induced oxidative damage in leaves of maize(Zea mays L.) seedlings was investgated. The experimental results showed that drought stress led to significant increases in oxidative damage to lipids(expressed as malondialdehyde),proteins(in terms of carbonyl groups), and plasma membrane(expressed as leakage of electrolytes from cells).The oxidative damage was further enhanced by the pretreatment with the ABA biosynthetic inhibitor fluridone,but that could be alleviated by the pretreatment with 100μM ABA.These results clearly suggest that ABA plays an important protective role in cellular oxidative damage in maize leaves under drought stress.The role of exogenous ABA in oxidative damage induced by H₂O₂ and paraquat(PQ) in leaves of maize seedlings was also investgated.The experimental results showed that exogenous H₂O₂ and PQ could cause oxidative damage to lipids,proteins,and plasma membrane in maize seedlings.As a kind of protective hormone,exogenous ABA caused no oxidative damage to cells when was applied to maize plants alone,and the oxidative damage induced by H₂O₂ and PQ could be alleviated by ABA treatment.Besides,the contents of protein carbonyls decreased by ABA in maize leaves were mainly from 45-94kDa proteins. Those results suggest that exogenous ABA also has a procetive effect in cellular oxidative damage in maize leaves under oxidative stress.Using mitogen-activated protein kinase kinase(MAPKK) inhibitors,the effects of MAPK on oxidative damage induced by drought stress and oxidative stress in leaves of maize seedlings and its relation with ABA were investgated.As a result,drought stress,H₂O₂ and PQ stress led to significant increases in oxidative damage to lipids(expressed as malondialdehyde),proteins(in terms of carbonyl groups),and plasma membrane(expressed as the leakage of electrolytes from cells).But when pretreated the plants with the two MAPKK inhibitors PD98059 and U0126,the extent of oxidative damage in leaves under drought stress and oxidative stress became worse.Besides,the inhibitors also caused an enhancement in oxidative damage in the maize plants which were treated with exogenous ABA.Those data from above suggest that as a signal,ABA protects plants from oxidative damage through MAPK cascade in maize leaves exposed to drought stress and oxidative stress.