The Physiological Role Of Plant Extracellular ATP In The Respiratory Chain Regulating Plant Cell Death And Photosynthesis

Plant mitochondrial electron transport chain as a main energy and central metabolism of the cell.Existing studies have found that the mitochondrial electron transport chain is involved in regulating cell death and photosynthesis.As a signal molecule,extracellular ATP has been shown to participate in a variety of physiological reaction processes in plants,and can stimulate intracellular Ca²⁺and other secondary signal molecules by binding to specific receptors on the cell membrane surface.However,there are few reports on whether extracellular ATP plays a certain biological function in the regulation of plant cell death and photosynthesis by the mitochondrial electron transport chain.Based on the above,this article uses tobacco suspension cells(Nicotiana tabacum L.CV.Bright Yellow-2)and Arabidopsis thaliana as research materials,and studies the physiological regulation function of extracellular ATP in the process of inhibiting plant cell death induced by respiratory chain inhibition and inhibiting photosynthesis.The main findings are as follows:(1)Antimycin A(AA)treatment could cause an increase in the death levels of tobacco suspension cells,and presented a concentration gradient-dependent effect.Further studies showed that AA could cause an increase in intracellular reactive oxygen species(ROS)levels.Exogenous application of ROS scavengers could effectively alleviate AA-induced cell death and the increase of cellular ROS levels,this result suggested that AA induced cell death is closely related to the increase of ROS production.AA treatment could also cause a significant decrease in extracellular ATP levels.Exogenous addition of an appropriate amount of exogenous ATP(20?mol·L^-1)could alleviate the decrease of extracellular ATP levels caused by AA.The addition of 20?mol·L^-1 exogenous ATP also significantly alleviated the AA-induced cell death and the increase of intracellular ROS(mainly distributed in mitochondria).This result indicated that extracellular ATP could alleviate the increase of cell death levels induced by AA by reducing the production of ROS in mitochondria.This study further explored the possible mechanism of extracellular ATP regulating AA-induced cell death and ROS production.Experiments showed that AA could reduce the intracellular Ca²⁺levels,and external addition of 20?mol·L^-1 ATP could alleviate the decrease of intracellular Ca²⁺levels caused by AA.Similar to the behavior of exogenous ATP,exogenous application of Ca²⁺could also alleviate AA-induced cell death and increased ROS levels.In addition,exogenous addition of EGTA(Ethylene glycol tetraacetic acid,Ca²⁺chelating agent)and La Cl₃(Lanthanum chloride,plasma membrane Ca²⁺channel inhibitor)could eliminate the alleviating effect of exogenous ATP on cell death caused by AA.Therefore,the regulation of extracellular ATP on AA-induced cell death and ROS rise depended on Ca²⁺signal.(2)Wild-type and extracellular ATP receptor mutant(dorn1)Arabidopsis were used as materials.It was found that AA caused the opening ratio of the above two kinds of Arabidopsis PS? reaction centers and the decrease of PS? photochemical operation efficiency.The results showed that AA could decrease the photochemical activity of the plant.Exogenous addition of 20?mol·L^-1 ATP could alleviate the decrease of photochemical activity of wild-type Arabidopsis caused by AA,but could not alleviate the decrease of photochemical activity in dorn1 Arabidopsis caused by AA.When salicylhydroxamic acid(SHAM)was used to inhibit the alternate respiratory pathway,the photochemical activity of wild-type Arabidopsis decreased significantly,but the photochemical activity of dorn1 Arabidopsis leaves did not change significantly.Exogenous addition of 20?mol·L^-1ATP only significantly alleviated the decrease of photochemical activity in wild-type Arabidopsis caused by SHAM,but still had no significant effect on the photochemical activity of dorn1 Arabidopsis.The above results indicated that the effect of respiratory chain inhibition on the photochemical reaction of Arabidopsis could be related to the extracellular ATP receptor protein DORN1,and that extracellular ATP could regulate the decrease in photochemical activity caused by the inhibition of the respiratory chain through DORN1.