Massa Gioia D, Fasano Jeremiah M, Gilroy Simon
Biology Department, The Pennsylvania State University, University Park, PA, USA.
Gravit Space Biol Bull. 2003 Jun;16(2):71-82.
Plant roots are optimized to exploit resources from the soil and as each root explores this environment it will encounter a range of biotic and abiotic stimuli to which it must respond. Therefore, each root must possess a sensory array capable of monitoring and integrating these diverse stimuli to direct the appropriate growth response. Touch and gravity represent two of the biophysical stimuli that plants must integrate. As sensing both of these signals requires mechano-transduction of biophysical forces to biochemical signaling events, it is likely that they share signal transduction elements. These common signaling components may allow for cross-talk and so integration of thigmotropic and gravitropic responses. Indeed, signal transduction events in both plant touch and gravity sensing are thought to include Ca(2+)- and pH-dependent events. Additionally, it seems clear that the systems responsible for root touch and gravity response interact to generate an integrated growth response. Thus, primary and lateral roots of Arabidopsis respond to mechanical stimuli by eliciting tropic growth that is likely part of a growth strategy employed by the root to circumvent obstacles in the soil. Also, the mechano-signaling induced by encountering an obstacle apparently down-regulates the graviperception machinery to allow this kind of avoidance response. The challenge for future research will be to define how the cellular signaling events in the root cap facilitate this signal integration and growth regulation. In addition, whether other stimuli are likewise integrated with the graviresponse via signal transduction system cross-talk is an important question that remains to be answered.
植物根系经过优化，以便从土壤中获取资源。当每条根探索这种环境时，它会遇到一系列生物和非生物刺激，必须对这些刺激做出反应。因此，每条根都必须具备一种传感阵列，能够监测和整合这些不同的刺激，以引导适当的生长反应。触摸和重力是植物必须整合的两种生物物理刺激。由于感知这两种信号都需要将生物物理力机械转导为生化信号事件，它们很可能共享信号转导元件。这些共同的信号成分可能允许信号相互作用，从而整合向触性和向重力性反应。事实上，植物触摸和重力感知中的信号转导事件都被认为包括依赖于钙和pH的事件。此外，负责根触摸和重力反应的系统相互作用以产生综合的生长反应，这一点似乎很清楚。因此，拟南芥的主根和侧根通过引发向性生长对机械刺激做出反应，这可能是根在土壤中规避障碍物所采用的生长策略的一部分。而且，遇到障碍物引发的机械信号显然会下调重力感知机制，以实现这种规避反应。未来研究面临的挑战将是确定根冠中的细胞信号事件如何促进这种信号整合和生长调节。此外，其他刺激是否同样通过信号转导系统的相互作用与重力反应整合，这是一个有待回答的重要问题。
