香蕉叶片发育过程中不同甲酯化程度果胶的变化

采用免疫荧光标记技术,利用5种识别不同甲酯化程度聚半乳糖醛酸(HGs)果胶及香蕉果胶甲酯酶(PME)的单克隆抗体,对不同株龄香蕉叶片中PME及不同甲酯化程度的HGs定位、相对含量以及PME活性的变化进行分析,为探讨HGs和PME在香蕉生长发育及抵抗逆境过程中的功能和生理机制奠定基础。结果显示:(1)PME主要在组培苗的叶肉和保卫细胞中表达,其表达量及其酶的活性均随着香蕉株龄的增长而呈现下降趋势。(2)叶肉细胞也是各类不同甲酯化程度HGs的主要分布区域,其含量随着香蕉株龄的增长有不同程度的下降,但不同HGs在叶肉细胞中的含量以及在表皮、保卫细胞及叶脉中的分布模式不尽相同,保卫细胞中HGs的甲酯化程度较高。研究表明,香蕉的叶肉细胞是PME及这5种不同甲酯化程度HGs的主要分布场所,且这些HGs在香蕉发育过程中的含量变化趋势与PME相似。

Changes in Homogalacturonans at Different Esterification Degrees during the Development of Banana (Musa spp. AAA) Leaves

For better understanding the functions and mechanism of PMEs and HGs in the growth and development of banana and in the defense of banana to the stresses, we traced the spatial and temporal abundance and distribution of banana pectin methylesterases (PMEs) and five homogalacturonans (HGs) at different methyl esterification degrees (MDs) in banana leaves at different developmental stages using immuno fluorescence labeling techniques. In addition, enzyme activity of PMEs was also tested. The results indicated that: (1) PMEs located mainly in the mesophyll and guard cells in tissue cultured banana seedlings. Both the level and activity of PMEs decreased with the development of the plant. (2) HGs at different MDs also mainly appeared in mesophyll cells in tissue cultured plants and their contents reduced gradually with the development of plants, though the speed varied with each other. However, the distribution of these HGs in the epidermis, the guard cells and the vein of banana leaves showed differential patterns. The MDs of HGs present in the guard cells was relatively high. These results indicated that PMEs and five tested HGs were mainly present in the mesophyll. During the development of banana leaves, the levels of these HGs showed similar trend to that of PMEs.