外源ABA对低温胁迫下玉米幼苗内源激素含量及Asr1基因表达的调节

Regulation on Contents of Endogenous Hormones and Asr1 Gene Expression of Maize Seedling by Exogenous ABA under Low-temperature Stress

脱落酸(ABA)是低温逆境下的重要信号因子,为了探讨外源ABA对低温胁迫下玉米幼苗的生长调节作用,以耐低温玉米品种久龙5号为试验材料,采用不同浓度(5、15、25、35 mg L–1)ABA于玉米三叶一心时喷雾于叶片,并进行低温梯次处理。分析处理后玉米叶片相对电导率、抗氧化酶活性及内源激素ABA、IAA的含量变化,并采用Real-time PCR明确Asr1基因表达水平变化。结果表明,低温胁迫下不同浓度外源ABA处理的玉米叶片相对电导率整体呈上升趋势,SOD和POD活性加强,15 mg L–1和25 mg L–1ABA处理的SOD活性均显著高于未应用ABA处理,玉米內源ABA和IAA合成水平上升,应用ABA后Asr1基因相对表达水平上调,其中5、15和25 mg L–1浓度处理基因表达上调显著。相关分析表明,ABA含量与Asrl基因相对表达量、SOD活性均表现为极显著正相关,与POD活性显著正相关。说明Asr1基因表达受ABA的介导调控,Asr1基因表达量的提升,也促进了内源ABA的合成,抗氧化酶活性加强,提升了应用ABA后玉米的抗低温能力。但外源ABA的介导调控具有一定浓度效应,表现为低促高抑。

Abscisic acid （ABA） is an important signal factor under low-temperature stress. This study aimed to investigate the effect of exogenous ABA on growth regulation of maize seedlings under low-temperature stress. Maize variety ＂Jiulong 5＂ resistant to low temperature was used with foliage spray of ABA （5, 15, 25, 35 mg L-1） at three-leaf period under varying degrees of low-temperature, to analyze relative electric conductivity, activities of autioxidant enzymes and contents variation of endogenous ABA and IAA of maize blades, as well as Asrl gene expression level by Real-time PCR. The relative electric conductivity of maize blades showed an increasing tendency, meanwhile, activities of SOD and POD were enhanced by exogenous ABA treatments among which SOD activity was significantly higher in ABA treatments of 15 mg L-1 and 25 mg L-1 than in the control under low-temperature stress. Also the synthesis of endogenous ABA and IAA were increased significantly. The expression level of dsrl gene significantly promoted in ABA treatments of 5, 15, and 25 mg L-1. ABA contant had a highly significant correlation with the relative expression ofAsrl gene and SOD activity and a significant correlation with POD activity. In conclusion the expression ofAsrl gene is mediated and regulated by ABA, the promotion ofAsrl gene expression also promotes the synthesis of endogenous ABA, and enhances antioxidant enzyme activities, resulting in improved maize resistance to low temperature. But the mediation and regulation of exogenous ABA have a concentration effect, showing promotion at low concentation and inhibition at high concentation.