耐酸性紫花苜蓿的研究进展

Progress of the Research on Alfalfa with Acidity Tolerance

紫花苜蓿要在占到世界可耕地面积的40%的酸性土壤上推广和利用,就必须培育耐酸性品种。现已获得的转基因苜蓿在耐酸性和耐铝性方面都有了很大的提高。主要是通过导入特定花椰菜花叶病毒35S作为启动子,引起苹果酸脱氢酶(MDH)和烯醇式丙酮酸羧化酶(PEPC)超表达,结果表明与非转基因苜蓿相比较,MDH的量增加1.6倍时,转基因苜蓿根尖有机酸的浓度增加了4.2倍,而柠檬酸、草酸、苹果酸、琥珀酸和醋酸在根部的分泌量增加了7.1倍;但是PEPC的超表达对增加苜蓿根部有机酸的分泌没有贡献。通过转基因苜蓿根际周围增加的有机酸来螫合铝元素,从而减轻酸性土壤中铝毒对苜蓿生产的限制。

It is indispensable to breed Alfalfa （ Medicago sativa） with acid tolerance in order to extend and utilize on the range of acid soil which make up about 40% worldwide arable land. Reported transgenic alfalfa using nodule-enhanced forms of malate dehydrogenase and phosphoenolpyruvate carboxylase cDNAs under the control of the constitutive cauliflower mosaic virus 35S promoter enhanced remarkably alfalfa tolerances of soil acidity and Al toxicity. It was reported that a 1.6-fold increase in malate dehydrogenase enzyme specific activity in root tips of selected transgenic alfalfa led to a 4. 2-fold increase in root concentration as well as a 7.1-fold increase in root exudation of citrate, oxalate, malate, succinate, and acetate compared with untransformed control alfalfa plants. Overexpression of phosphoenolpyruvate carboxylase enzyme specific activity in transgenic alfalfa did not result in in- creased root exudation of organic acids. Addition of organic acids exuded roots of transgenic alfalfa alleviates Al toxicity by means of chelating Al in acid soil.