The Effect Of Extracellular ATP On Growth And Development Of Etiolated Arabidopsis Seedlings And Its Signal Transduction Pathway

Extracellular ATP (eATP) is a new signal molecule in apoplast of plant cells. Here, to verify the physiological function of eATP in plant development and its possible signal transduction mechanism. The effect of ATP on growth of etiolated seedling, which were growing in dark, was investigated.Firstly, ATP was found to inhibit seedling growth and development markedly. Seedlings which were growing in medium containning ATP showed shorter, thicker, curved hypocytol and shorter roots, indicating that eATP inhibited elongation of hypercytol and root. ATP inhibited growth and development in a dose-dependent manner. Non-hydrolyzable ATP analog, ATPγS, affected seedling growth similarly. These results indicated that eATP regulated growth and development of etiolated seedling as a signal molecule.Then, to verify the role of auxin in eATP regulated growth and development, the effect of ATP on concentration and distribution of auxin in seedlings was detected with DR5-GUS transgenic material. Results showed that, ATP stimulation induced uneven auxin accumulation in hypercotyl cells. Data of cell length and width measurement showed that, heterogeneous growth rate of different hypercotyl cells is the main reason of curved growth.After that, to verify the possible signal transduction mechanism, the role of ROS and annexin in eATP-regulated seedling growth and development were investigated by using lost-of-function mutant of them. Seedlings of NADPH oxidase null mutants, kjk-2and rhd-2, are far less sensitive to eATP treatment, comparing to the sensitivity of wild-type, indicating that ROS may be involved in eATP-regulated seedling growth and development. While, mutant of annexin (Atann1) and its complemented srain (Atann1/ATANN1) responded to eATP similarly as wild-type, indicating that annexin is unlikely involved in eATP-regulated physiological process.Later on, to verify the role of ethylene in eATP-regulated seedlings growth, the effect of ethylene precursor, ACC, on growth and development of seedlings is detected. Results showed that, ACC regulated seedling growth in a style similar to ATP.Finally, to verify the role of ethylene signalling in eATP-regulated seedlings growth, null mutants of ethylene signalling components was used to investigate their response to ATP treatment. All mutants, including an ethylene receptor ETR1(etr1), a key component of the ethylene signalling EIN2(ein2), an ethylene response factor ERFy (erfy), respond to ATP treatment far less sensitively than their wild type. Indicating that ETR1、EIN2and ERFy may be possibly involved in ATP-regulated seedling growth and development.Based on above results, we suggest that eATP may induce the synthesis of ethylene (possibly by using ROS signal), and then ethylene bind and stimulate some signal transduction components (ETR1and EIN2), induced ERFy transcription factor generation, which will regulate function genes related to growth and development.