发根农杆菌附着植物细胞的离子效应

本文将光学显微镜、电镜技术和附着定量分析方法结合起来,研究了发根农杆菌各菌株附着烟草叶肉原生质体的离子效应。实验结果表明:发根农杆菌不同菌株对共培养基离子强度的敏感性有差异。菌株R1000附着植物细胞及其引起植物细胞的聚集对离子强度不敏感,而菌株A4和15834则非常敏感;农杆菌对植物细胞附着的多寡与其引起植物细胞的聚集程度有相关性;共培养基中Mg~(2 )、Mn~(2 )等二价刚离子(不包括Ca~(2 ))是农杆菌附着所必需的;植物凝集素ConA显著地促进了附着和植物细胞与细菌聚集团的形成。从菌株A4附着植物细胞的进程可以看出,附着至少是两步的过程:第一步主要是离子力的相互作用,是第二步附着发生的前提;第二步是位点专一的特异性附着,不可逆。发根农杆菌对植物细胞的附着机制不同于根癌农杆菌。

THE ION EFFECT IN ATTACHMENT OF AGROBACTE- R1UM RHIZOGENES TO PLANT CELLS

By using the photomicroscope, SEM and attachment assay techniques, we investigated and compared the effect of alterations in the ionic strengths (IS) and kinds (IK) of the co-cultivation medium on attachment to tobacco mesophyll protoplasts by different A. rhizogenes strains. The attachment of strain R 1000 and aggregation of cells by it were not strongly dependent on the IS of the medium. While the ability of some strains, such as A4 and 15834, to attach and aggregate plant cells was inhibited by much higher IS. Several divalent cations, like Mg2 or Mn2 but not Ca2 , could be required for attachment, although a role for other cations in the medium could not be excluded. The lectin ConA, whose activity de-pends on the presence of divalent cations, had greatly stimulated agglutination of 3-d protoplasts and attachment of bacteria. These results suggest the attachment of some A. rhizogenes strains, which are sensitive to alteration of IS and IK, may involve ionic interactions. From the kinetics of the attachment of strain A 4, we proposed that attachment might be a two step process. The first step was loose, reversible and sensitive to higher IS. The other step was tight, unreversible binding, occurred in 10 to 20 minutes after co-cultivation. Therefore, the differences in binding among different A. rhizogenes strains or their counterpart A. tumfaciens appeared to be due to different mechanisms.