Shevchenko G V, Kordyum E L
Institute of Botany, Cell Biology Department, Kiev, Ukraine.
Adv Space Res. 2005;35(2):289-95. doi: 10.1016/j.asr.2005.02.021.
Key role in cell gravisensing is attributed to the actin cytoskeleton which acts as a mediator in signaling reactions, including graviperception. Despite of increased attention to the actin cytoskeleton, major gaps in our understanding of its functioning in plant gravisensing still remain. To fill these gaps, we propose a novel approach focused on the investigation of actin involvement in the development of columella cells and cells in the transition zone of roots submitted to clinorotation. Both statocytes and cells in the transition zone represent the postmitotic cells which take origin in root meristems and are specified into graviperceptive (root cap) and gravireacting (transition zone) root tissues. The aim of the research was to investigate and compare the microfilament arrangements in root cap statocytes and peripheral root tissues (epidermis and cortex cells) in the transition zone and to find out how the actin cytoskeleton is involved in their specification under clinostat conditions. So far, our experiments have shown that under clinorotation the cytoplasmic microfilament network in the cortex cells in the transition zone is significantly enhanced. It is suggested that more abundant cytoplasmic microfilaments could strengthen the cortical actin cytoskeleton arranged parallel with the cortical microtubules, which are found to be partially disorganized in this area. Due to microtubule disorganization, the functioning of cellulose-synthesizing machinery and proper deposition of cell wall might be affected and could cause the alterations in the growth mode. But, in our case growth of the cells in the transition zone under clinorotation was rather stable. Due to our opinion, general stability of cell growth under clinorotation is promoted by mutual functional interrelation between actin and tubulin cytoskeletons. It is suggested that a strengthened cortical actin cytoskeleton restricts the cell growth instead of disorganized microtubules.
细胞重力感应的关键作用归因于肌动蛋白细胞骨架，它在包括重力感知在内的信号反应中起介导作用。尽管对肌动蛋白细胞骨架的关注有所增加，但我们对其在植物重力感应中功能的理解仍存在重大差距。为了填补这些差距，我们提出了一种新方法，重点研究肌动蛋白在柱状细胞发育以及经受回转的根过渡区细胞中的作用。平衡石细胞和过渡区细胞均为有丝分裂后细胞，起源于根分生组织，分别特化为重力感受性（根冠）和重力反应性（过渡区）根组织。本研究的目的是调查和比较根冠平衡石细胞和过渡区外周根组织（表皮和皮层细胞）中的微丝排列，并弄清楚在回转条件下肌动蛋白细胞骨架如何参与它们的特化过程。到目前为止，我们的实验表明，在回转条件下，过渡区皮层细胞中的细胞质微丝网络显著增强。有人认为，更丰富的细胞质微丝可以加强与皮层微管平行排列的皮层肌动蛋白细胞骨架，而在该区域发现皮层微管部分紊乱。由于微管紊乱，纤维素合成机制的功能和细胞壁的正常沉积可能会受到影响，并可能导致生长模式的改变。但是，在我们的研究中，回转条件下过渡区细胞的生长相当稳定。我们认为，回转条件下细胞生长的总体稳定性是由肌动蛋白和微管蛋白细胞骨架之间的相互功能关系促进的。有人认为，增强的皮层肌动蛋白细胞骨架会限制细胞生长，而不是紊乱的微管。
