ИСТИНА

Roots must sense and respond to a variety of stimuli such as the direction of gravity, availability of nutrients and water and mechanical signals from objects they touch and integrate these to an appropriate growth response. We are interested in defining the regulatory processes that underlie this integration of stimuli and how this system translates to tropic growth control and development of root system architecture. We have found that both tropic and vertical root growth are associated with highly complex and dynamic oscillatory changes in surface pH and ROS centered over the proximal and distal elongation zones. Tropic growth is associated with a coalescence and stabilization of surface alkalinization and ROS production to the non-growing side of the root. Equivalent changes can be induced by mechanical stress of the same regions, suggesting a possible link between the mechanical forces inherent in growth and changes in wall properties that mediate local growth control. Auxin also elicits a rapid (within seconds) transient alkalinization over the surface of the root. This auxin-dependent dynamic change in surface pH is still observed in tir-1 and a range of auxin transport mutants such as the pins and aux-1, suggesting it does not simply reflect auxin transport phenomena and is not triggered by the TIR-1-dependent receptor system. Current work aims at defining the molecular mechanism behind auxin-dependent apoplastic alkalinization and ROS production and its relationship to dynamic growth control of the root as a whole.