The Signal Transduction Of Extracellular ATP Regulated Root Growth Of Arabidopsis Thaliana

Root is a critical organ in plant for absorption and regulation of growth and development.The signal transduction in root is one of important topics in plant physiological resesrch. Extracellular ATP (eATP) is an important extracellular messenger in plant,and played an important role in regulating plant growth and development. In this paper, the signal transduction mechanism of eATP regulated root growth was investigated in Arabidopsis thaliana.Wild-type (ws, col-0 ecotype), heterotrimeric G proteinα,β,γsubunit gene null mutants andαsubunit overexpression lines, NADPH oxidase gene null mutant rhd-2, and AtAPY1 gene null mutant (apy1) of Arabidopsis were used as materials, the role of eATP in plant root growth and development regulation was investigated.Results showed that added ATP inhibited main root growth in a close-dependent manner in wild-type. Root growth was promoted after adding apyrase into the medium,indicating that eATP may play a negative role in root growth regulation.The results of root cell morphological experiment by using laser confocal scanning microscopy showed that after eATP treatment, root cells in elongation zone and mature zone were shorter than that in control and cell layers were less than that in control. Length of root cells increased after apyrase treatment,while the layer number were not affected. Indicating that eATP inhibited the growth of root by inhibiting root cell elongation.The root of heterotrimeric G proteinα,βsubunit gene null mutants and Gαoverexpression lines responded to eATP treatment similarly to wild type.However, root of Gγsubunit was more sensitivie than wild type to eATP,stimulation indicating that Gα,βsubunit may be not involved in signal transduction of eATP inhibited root growth,whileγsubunit may be involved in it.The root length of NADPH oxidase gene null mutant was much longer than that in wild type after eATP treatment, indicating that NADPH oxidase catelyzed ROS synthesis may be involced in signal transduction of eATP.These results suggested that, eATP may act as a negative regulator in Arabidopsis root growth regulation, the inhibiting of Arabidopsis root growth may possibly result from suppression of cell division and elongation. Heterotrimeric G proteinα,βsubunit were unlikely involved in eATPsignal transduction,while Gγand ROS may be involved in this process.