Study On The Physiological Function Of Extracellular ATP And The Regulation Of NO On Extracellular ATP Under The Change Of Phosphorus Supply

Extracellular ATP(eATP)is an important signaling molecule in plants,but its physiological function and its own level under the change of phosphorus supply are still unclear.In this study,tobacco suspension cells(Nicotiana tabacum L.cv.Bright Yellow-2)were used as material to study the effects of eATP on cells growth and metabolism before and after the ingestion of exogenous phosphate and regulation effects of nitric oxide(NO)on eATP levels at different levels of phosphate supply.The main findings are as follows:1.we compared the cell growth before and after the uptake of exogenous phosphorus.It was found that cell viability was higher,cell fresh weight was lower,hydrogen peroxide(H₂O₂)content was lower,and antioxidant enzyme activity was higher under the condition of phosphorus deficiency(-P,lack of phosphorus salts in the medium),compared with phosphorus-supplemented cells(+P:phosphorus salts in the medium).By adding exogenous ATP under different phosphorus supply conditions.it was found that the addition of exogenous ATP reduced the viability of-P cells,increased the fresh weight of-P cells,reduced the H₂O₂ content of-P cells,reduced the peroxidase(POD)and catalase(CAT)enzyme activity of-P cells,slightly(but not significant)reduced the superoxide dismutase(SOD)enzyme activity of-P cells.For+P cells,the addition of exogenous ATP increased cell viability and fresh weight,decreased H₂O₂ content,decreased POD activity,increased CAT activity,and slightly(but not significant)increased SOD activity.2.Under the low concentration of phosphate supply,the eATP content was lower.As the phosphate concentration gradually increased,the eATP content also increased,but the increase rate slowed down.Under different concentration of phosphate supply levels,the change trend of intracellular ATP(i ATP)and eATP content was similar,but there are some differences,indicating that under different concentrations of phosphate supply,the changes of eATP could be affected by i ATP and other factors unknow.NO is an important plant signal molecule in response to changes in phosphorus supply.Therefore,this paper investigated whether changes in eATP level under different phosphate supply levels are related to NO.The study found that as the level of phosphate supply increased,the NO content of cells continues to decrease.After treatment with nitroprusside(SNP,NO donor)and nitroso-L-arginine methyl ester(L-NAME,NO synthase inhibitor)on cells,it was found that under low-concentration phosphate supply conditions(0P,0.25P,here P represents the concentration of phosphate in the medium,1P=1.25 mmol·L^-1KH₂PO₄),NO increased the level of eATP and also increased the level of i ATP;under the normal phosphorus level(1P),NO increased eATP levels and also increased i ATP levels;under the high phosphorus level(2P),NO decreased eATP but increased i ATP levels.In conclusion,eATP can regulate cell viability,cell fresh weight and reactive oxygen metabolism,but the effect is related to the supply of phosphorus.And,eATP is regulated by NO under the supply of phosphate at different concentrations.The above studies are helpful to reveal the adaptive mechanism of plant cells to phosphorus supply changes,and are helpful to further understand the physiological functions of plant eATP.