果胶甲基酯酶PME参与调控大麦根尖铝毒敏感性

Involvement of PME activity in regulation of Al toxic sensitivity in the root tips of barley

利用大麦耐铝品种和敏感品种来分析根尖果胶甲基酯酶(PME)在大麦铝毒敏感性中的调控作用.通过对耐铝性差异极其显著的2个大麦明品种2000-2与沪麦16经铝处理后的Morin荧光检测,观察到2000-2根尖荧光明显比沪麦16强,铝试剂比色法测定结果进一步表明,敏感品种根尖细胞壁上铝积累量比耐铝品种高,达到极显著差异(p<0.05或0.01).对根尖PME活性分析结果表明,与对照相比,铝处理4 h的2000-2根尖PME活性显著上升,但处理24 h后PME活性又显著下降;而沪麦16的PME活性与对照相比无显著性差异.这些结果表明细胞壁上铝积累与PME活性变化有密切的相关性,证实PME活性参与调控大麦铝毒敏感性.

It has been proposed that Aluminum（Al） accumulation on cell walls of root tips is the primary prerequisite of toxic effects of Al on root tips in plants.In this study,pectin methylesterase（PME） regulation of Al toxicity sensitivity and Al accumulation on cell walls were investigated in the root tips of two barley cultivars significantly different in Al resistance.Morin fluorescent staining showed that the fluorescence signal of root tips was much stronger in Al-sensitive cultivar 2000-2 than in Al-resistant Humai 16 after Al treatments,indicating that more Al was accumulated on the root tip of cv.2000-2 than cv.Humai 16.Aluminon spectrophotometric assay further confirmed that the Al content in primary root tips was significantly higher in the Al-sensitive cultivar than in the Al-resistant one（t-test,p0.05 or 0.01）.Compared with individual controls,a significant increase of PME activity in root tips was observed in cv.2000-2 after 4 h Al treatments,but after 24 h Al treatments,its PME activity significantly decreased.However,in cv.Humai 16,the significant alteration of PME activity was not observed over Al treatments.These data together demonstrate that there exists a close correlation between Al accumulation and the change in PME activity on cell walls of the root tip,and therefore PME activity is involved in the regulation of Al sensitivity in the root tips of barley.