Fasano Jeremiah M, Massa Gioia D, Gilroy Simon
Biology Department, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Plant Growth Regul. 2002 Jun;21(2):71-88. doi: 10.1007/s003440010049. Epub 2002 May 23.
Touch and gravity are two of the many stimuli that plants must integrate to generate an appropriate growth response. Due to the mechanical nature of both of these signals, shared signal transduction elements could well form the basis of the cross-talk between these two sensory systems. However, touch stimulation must elicit signaling events across the plasma membrane whereas gravity sensing is thought to represent transformation of an internal force, amyloplast sedimentation, to signal transduction events. In addition, factors such as turgor pressure and presence of the cell wall may also place unique constraints on these plant mechanosensory systems. Even so, the candidate signal transduction elements in both plant touch and gravity sensing, changes in Ca2+, pH and membrane potential, do mirror the known ionic basis of signaling in animal mechanosensory cells. Distinct spatial and temporal signatures of Ca2+ ions may encode information about the different mechanosignaling stimuli. Signals such as Ca2+ waves or action potentials may also rapidly transfer information perceived in one cell throughout a tissue or organ leading to the systemic reactions characteristic of plant touch and gravity responses. Longer-term growth responses are likely sustained via changes in gene expression and asymmetries in compounds such as inositol-1,4,5-triphosphate (IP3) and calmodulin. Thus, it seems likely that plant mechanoperception involves both spatial and temporal encoding of information at all levels, from the cell to the whole plant. Defining this patterning will be a critical step towards understanding how plants integrate information from multiple mechanical stimuli to an appropriate growth response.
触摸和重力是植物为产生适当生长反应而必须整合的众多刺激因素中的两种。由于这两种信号都具有机械特性，共享的信号转导元件很可能构成这两种感觉系统之间相互作用的基础。然而，触摸刺激必须引发跨质膜的信号事件，而重力感知被认为是将一种内力（淀粉体沉降）转化为信号转导事件。此外，膨压和细胞壁的存在等因素也可能对这些植物机械感觉系统施加独特的限制。即便如此，植物触摸和重力感知中的候选信号转导元件，即Ca2+、pH和膜电位的变化，确实反映了动物机械感觉细胞中已知的信号离子基础。Ca2+离子独特的空间和时间特征可能编码有关不同机械信号刺激的信息。诸如Ca2+波或动作电位等信号也可能在整个组织或器官中迅速传递在一个细胞中感知到的信息，从而导致植物触摸和重力反应所特有的系统性反应。长期的生长反应可能通过基因表达的变化以及诸如肌醇-1,4,5-三磷酸（IP3）和钙调蛋白等化合物的不对称性得以维持。因此，植物机械感知似乎在从细胞到整个植物的所有层面都涉及信息的空间和时间编码。确定这种模式将是理解植物如何将来自多种机械刺激的信息整合为适当生长反应的关键一步。
