NO参与Spd诱导白三叶抗氧化酶活性及其基因表达

以‘拉丁诺’白三叶为试材,采用药理学实验,探讨一氧化氮(NO)信号在外源亚精胺(Spd)诱导抗氧化酶活性及其基因表达中的作用。研究结果显示,20 μmol/L的外源Spd可显著提高白三叶叶片硝酸还原酶(NR)和一氧化氮合酶(NOS)活性,诱导白三叶离体叶片NO积累,并且具有时间效应,在处理第2 h达到最大值;50 μmol/L NO清除剂牛血红蛋白(Hb)、5 mmol/L 硝酸还原酶(NR)抑制剂偏钒酸钠(NaVO₃)以及200 μmol/L一氧化氮合酶(NOS)抑制剂NG-硝基-L-精氨酸甲酯盐酸盐(L-NAME)处理均可不同程度地逆转Spd诱导的NO含量的升高。外源Spd亦可提高白三叶叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)的活性及其基因的相对表达量,而Hb、NaVO₃和L-NAME不同程度地抑制了Spd诱导的SOD、POD、CAT、APX酶活性及其基因表达。以上结果表明:Spd可能通过激活硝酸还原酶和一氧化氮合酶途径诱导产生NO,且NO信号参与了Spd调控白三叶叶片抗氧化酶活性及其基因表达。

The antioxidant enzyme activities and gene expression induced by spermidine in leaves of white clover

A pharmacological experiment was designed to investigate the function of nitric oxide (NO) in the spermidine-induced antioxidant enzyme activities and gene expression in white clover (Ladino). Treatment with exogenous spermidine (Spd) at 20 μmol/L significantly improved (P<0.05) the nitrate reductase (NR) and nitric oxide synthase (NOS) activities in leaves of white clover and NO content reached a maximum after 2 h of Spd treatment. However, treatments that included 50 μmol/L bovine hemoglobin (Hb) (NO-scavenger), 5 mmol/L partial sodium vanadate (NaVO₃) (a NR-inhibitor) and 200 μmol/L NG-nitro-L-arginine methyl ester hydrochloride (L-NAME) (a NOS-inhibitor) inhibited the accumulation of NO in Spd-treated white clover. Exogenous Spd treatment can also enhance the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbic acid peroxidase (APX) and the relevant gene expression in leaves. Hb, NaVO₃ and L-NAME inhibited the Spd-induced enzyme activities of SOD, POD, CAT, APX and gene expression to different degrees. These results suggest that Spd induced NO by enhancing antioxidant enzyme activities and expression of related genes in white clover, and that NO production is probably regulated from the NR and NOS pathways.