微管骨架在苔藓植物适应干旱胁迫应答中的功能研究

植物体通过一系列生理生化反应的改变来适应干旱胁迫。对干旱/复水及秋水仙素处理后再干旱/复水的仙鹤藓(Atrichum undulatum)原丝体细胞中微管骨架的动态变化进行了研究，发现干旱处理后细胞内微管骨架从有规律排列的较细的丝状形式转换为无规律排列的较粗的微管束；复水后微管骨架的结构和分布与对照细胞中无明显区别；秋水仙素处理后再干旱/复水的细胞中，微管骨架呈分散的棒状或点状分布，而且原丝体丧失了干旱胁迫后正常复水的能力，进而导致细胞不能恢复正常的生理活动。因此认为，微管骨架在仙鹤藓原丝体适应干旱逆境的过程中起着重要作用。

The Role of Cortical Microtubules in Moss Protonemal Cells During Dehydration/rehydration Cycle

Plant cells response to water deficit through a variety of physiological processes. In this work, we studied the function of microtubule cytoskeleton during dehydration/rehydration cycle in moss ( Atrichum undulatum ) protonemal cells as a model system. The morphological and cytological change of protonemal cells during dehydration and rehydration cycle were first investigated. Under normal conditions, protonemal cells showed bright green colour and appeared wet and fresh. Numerous chloroplasts distributed regularly throughout the cytoplasm in each cell. After dehydration treatment, protonemal cells lost most of their chlorophylls and turned to look yellow and dry. In addition, dehydration caused plasmolysis in these cells. Upon rehydration, the cells could recover completely from the dehydrated state. These results indicated that moss had a remarkable intrinsic ability to survive from the extreme drought stress. Microtubule, an important component of cytoskeleton, is considered to play crucial roles in the responses to some environmental stresses such as cold and light. To see if it is also involved in the drought tolerance, dynamic organization of microtubules in protonemal cells of Atrichum undulatum subjected to drought and rehydration were examined by indirect immunofluorescence combined with confocal lasersharp scanning microscopy. The cortical microtubules were arranged into a fine structure with a predominant orientation parallel to the long axis of the cells in the control cells. After dehydration, the microtubule organization was remarkablly altered and the fine microtubule structure disappeared whereas some thicker cables formed. When the cells were grown under rehydration conditions, the fine microtubule arrays reappeared. These results provided a piece of evidence that microtubules play a role in the cellular responses to drought stress in moss. Furthermore, we analyzed the effects of the microtubule disrupting agent colchicine on the morphology recovery of the protonemal cells during rehydration process. The cells were incubated with colchicine, followed by drought stress treatment and rehydration in the presence of colchicine to prevent recovery of microtubule organization. Results from immunofluorescence showed that microtubule arrays were broken down into smaller fragments. Compared to the cells treated with drought stress alone, the cells treated with drought stress in the presence of colchicine could not recover after rehydration treatment. The morphology resembled those of the drought treated cells, with obvious plasmolysis phenomena and loss of chlorophyll content. These results support the notion that microtubules were involved in the deccication tolerance mechanism in Atrichum undulatum.