干旱胁迫对紫花苜蓿黄酮类化合物含量及其合成途径关键酶活性的影响

Flavonoids Contents and Flavonoids Synthetic Key Enzyme Activities in Alfalfa under Drought Stress

以3个紫花苜蓿(Medicago sativa)品种为试验材料,利用不同浓度(0、5%、10%、15%、20%、25%)的PEG-6000溶液模拟干旱胁迫,探究干旱胁迫对不同品种紫花苜蓿黄酮类化合物合成上游3个关键酶活性以及黄酮类化合物含量的影响。结果表明:(1)随着PEG-6000胁迫浓度的增加,3种紫花苜蓿叶片中PAL(苯丙氨酸解氨酶)、C4H(肉桂酸-4-羟基化酶)和4CL(4-香豆酸辅酶A连接酶)活性均呈先升高后降低的趋势,但不同酶类之间响应存在差异,即PAL活性在10%PEG-6000胁迫浓度下最高,C4H和4CL活性则在15%PEG-6000胁迫浓度下最高,且均显著高于相应对照。(2)3种紫花苜蓿植株地上部总黄酮含量和8种黄酮类化合物含量均随着PEG-6000胁迫浓度的增加呈先上升后下降的趋势,且均在10%~15%PEG-6000胁迫浓度时达到最高值,并显著高于相应对照。(3)各品种紫花苜蓿叶片黄酮类化合物含量与其关键酶活性呈不同程度的相关性,即紫花苜蓿黄酮类化合物合成途径上游3个关键酶活性与其地上部黄酮类化合物含量存在密切的关系。研究认为,不同程度的干旱胁迫可以通过促进黄酮类化合物合成途径上游关键酶活性的变化来调节紫花苜蓿植株中黄酮类化合物的合成,且适度干旱胁迫能显著促进相关酶活性增强和黄酮类化合物含量增加。

Drought stress was simulated with different concentrations(0,5%,10%,15%,20%,25%)of PEG-6000 solution.We used three cultivars of alfalfa(Medicago sativa)to clarify the effects of drought stress on the activities of three key enzymes as well as the accumulation of flavonoids.Results revealed that:(1)with the increase of PEG-6000 simulated drought stress concentration,the activities of PAL(phenylalanine ammonia lyase),C4H(cinnamic acid-4-hydroxylase)and 4CL(4-coumaric acid coenzyme A ligase)in the three alfalfa cultivar leaves increased first and then decreased but there were differences among different enzymes.PAL reached the maximum under 10%PEG stress,whereas,C4H and 4CL reached the maximum under 15%PEG stress and significantly higher than the corresponding control.(2)Compared with the control,with the increase of PEG-6000 simulated drought stress concentration,the content of flavonoids in three cultivars of alfalfa increased first and then decreased,and the content of flavonoids was the highest under the stress of 10%to 15%PEG-6000 and significantly higher than the corresponding control.(3)The activities of three key enzymes in the upstream synthesis of flavonoids in alfalfa leaves are closely related to the content of flavonoids and the content of flavonoids in the leaves of three alfalfa cultivars are related to their key enzyme activities to varying degrees.The results showed that different degrees of drought stress can increase the synthesis of flavonoids in alfalfa plants by promoting the accumulation of key enzyme activities upstream of flavonoids in alfalfa and moderate drought stress can significantly increase the related enzyme activities to promote the content of flavonoids.