Study On The Signal Transduction During The Process Of Negative Phototropism Of Rice Root

The process of negative phototropism of rice root invoved a series of signal transduction. In order to properly study the process, three main rice (Orysa sativa L.) varieties"QiMiaoXiang","YangDao 6"."Ribenqing"(Japonica) were chosen. The negative phototropic movement of rice root under unilateral light was tracked using a self-made device; the sensor of negative phototropism of rice root and its light-receptor were determined by root cap stripping, changing light quality, and SDS-PAGE for soluble protein of root cap. Fianlly, studies of roles played by Auxin and ROS in negetive phototropism of rice root were done. The results obtained from all the experiments were listed below :1. All the seminal roots, adventitious roots and their branched roots bent away from light when unilateral light was given to water cultured rice root, the negative phototropic curvature varied between differe rice varieties.2. According to our experiments, the root cap was light sensor and the 120KD protein of the cap could be blue-light receptor, phototropin, as the photoreceptor responging to blue/UV light,but not to red light.3. The negative phototropic bending of the rice root under unilateral light was mainly due to the larger extent of root-tip cells of the irradiated side than that of the shade side.? ?4. Endogenous auxin of shade side is greatly more than that of the other side after adentitious root exposed to unilareral light for 1.5h. 0.01μmol·L-1 exogenous IAA could mostly increase the curvature of rice root cultivated in the IAA solution, the growth of root would be inhibited if the IAA was above the optimal concentration; TIBA(IAA transportation inhibitor) could decrease the curvature at low concentration about 0.1mg·L-1; the air clutivated rice root would bend to the agar containing IAA under dark. The CPT1 gene was overexpessed in the root tip exposed to unilateral light.5. Endogenous ROS of the root elongation zone will be asymmetric concentration after adentitious root exposed to unilareral light for 1.5h; 0.01μmol·L-1 exogenous H2O2 could mostly increase the curvature of rice root cultivated in the H2O2 solution; Not only the negative curvature, but also the growth of water cultivated root would be promoted by applied 0.1mg·L-1 Asc or GSH solution. Agar containing H2O2 would also induce negative bent growth of air cultivated rice root under dark.6. The gowth of rice root would be severely inhibited under unilateral light, and the activity of CAT was severely decreased, but unilateral liht also slightly increase the activity of SOD, more importantly, significantly increased the activity of POD, great change also had taken place in the isoenzyme spectrum of POD.