The Role Of WRKY Transcription Factors In EATP-Regulated Root Growth Of Arabidopsis Thaliana

Root is a vital organ for plant fixation, nutrient absorption and transport, it is alsoan important resource of plant growth and development regulatoary subatances. Theroot is responding to various physical and chemical factors in the environment byadjusting its growth and development pattern continuously. Extracellular ATP (eATP)play a key role in root growth and development. WRKY transcription factors are alsoinvolved in plant growth, development and stress tolerance. Here, the role of WRKYfactors in eATP-regulated root growth and the possible signaling pathway wereinvestigated.Firstly, by using Arabidopsis (Col-0) as material and DNA microarry andreal-time PCR analysis as methods, eATP was found to promote expression of severalWRKY transcription factors. ATP was also found to inhibit gene expression ofexpansins and polygalacturonases, both of which are important regulators in cell wallmanufacturing and plant cell elongation. By using lost-of-function mutant of NADPHoxidase (rhd-2) and NO synthase (Atnos1), it was revealed that reactive oxygenspecies (ROS) may be involved in eATP-regulated WRKY expression, however, ROSwas not involved in eATP-inhibited gene expression of expansins andpolygalacturonases. NO was not involved in any eATP regulated gene expression.By using wild-type and WRKY gene null mutants as material, the role of WRKYin eATP regulated root growth was investigated. The results showed that, both in lightand dark, root growth of wild-type and mutants seedlings were significantly inhibitedby eATP. The responses of wild-type and mutants to eATP inhibition were notsignificantly different. In another experiment, the role of WRKY in eATP inhibitedgravitropic growth of young root was investigated. Preliminary result showed thateATP inhibited root gravitropism both in wild type and WRKY mutants.These results indicated that eATP inhibited expansins and polygalacturonasegenes expression may not result from eATP-induced WRKY expression. WRKY factors are also unlikely participated eATP-regulated root growth, development andgravitropism.