The Contrastive Study Of Mitoflash And Its Function In Two Thermogenic

Floral thermogenesis have been observed in several plant families.Different types of thermogenesis have been identified among different thermogenic plants.Numbers of evidences have proofed that mitochondrial energy metabolism played an important role in floral thermogenesis." mitochondrial superoxide flashes "were recently discovered as a "digital clock" to reflect mitochondrial activities,the frequency of mitochondrial superoxide flashes can reflect different physicalstates of cells.Therefore,in this study we firstly introduced the new concept of mitochondrial superoxide flashes in to the studiy of floral thermogenesis,to further study mitochondrial energy metabolism and mechanism of floral thermogenesis.In this study,we explored the function of mitochondrial ROS and superoxide flashes using flowers with two different thernogenic pattern:Magnolia denudata(pseudo-thermoregulatory)and Nelumbo nucifera(thermoregulatory).Firstly,the infrared imaging of Magnolia denudata(magnolia)and Nelumbo nucifera(lotus)were performed to determine the thermogenic tissues.Cell walls and epidermis cells of Magnolia denudata were scanned to explore the change of cell wall components and cell morphology during floral thermogenesis.Also,high viability mitochondria were isolated from pistil and petal of magnolia and lotus in both thermogenic and non-thermogenic stages.Mithocndria and ROS was labeled with fluorescent indicators to explore the mitochondria and the ROS fluorescence.Mitochondrial ROS and mitochondrial membrane potential was labeled with fluorescent indicator to study the frequency of superoxide flashes and fluctuation of mitochondrial membrane potential thermogenic and non-thermogenic stages.Besides,the changes of repiratory pathway and the activities of antioxidant enzyme in pistiles and petals of magnolia and lotus were study in both thermogenic and non-thermogenic stages to further explore the ROS signaling pathway.The main results of our study were as follows:(1)The infrared imaging of magnolia showed that the thermogenic tissue was pistil(stigma and receptacle)in both female and male stages.The infrared imaging of lotus showed that the thermogenic tissue was pistil(stigma and receptacle)from early florescense stage to blossom stage(stage 1-3).(2)The fluorescence of lignin and cellulose in cell walls of pistil of magnolia during female stage was significantly decreased compared with non-thermogenic stage.Similarly,more papillate cells and intercellular spaces were observed in female stage of magnolia,and the epidermal cells of pistil were round and turgid in female stage.(3)The location of ROS and mitochondria was in a good coincidence in both tissues of magnolia and lotus.The increase of mitochondrial ROS was also found in the pistils of both magnolia and lotus during thermogenic stages.(4)Higher frequency of superoxide flashes was found in the pistils of both magnolia and lotus during thermogenic stages.Moreover,higher frequency of superoxide flashes was found in the stage of large bud during the whole blossom of magnolia.(5)Higher frequency of fluctuation of mitochondrial membrane potential was found in the pistils of both magnolia and lotus during thermogenic stages.Moreover,higher frequency of fluctuation of mitochondrial membrane potential was found in the stage of large bud during the whole blossom of magnolia.(6)Significantly increased of oxygen consumption of mitochondrial AOX respiration pathway were observed in pistils of both magnolia and lotus during thermogenesis.Meanwhile,significantly increased of catalase(CAT)activity was found in pistils of both magnolia and lotus during thermogenesis,but significantly decreased of activities of other antioxidant enzymes were found in pistil.during thermogenic stages.In conlusion,our results showed that the increased of mitochondrial ROS,higher frequency of superoxide flashes together with higher frequency of fluctuation of mitochondrial membrane potential were found in pistil of both magnolia and lotus during thermogenic stages.And significantly increased of mitochondrial AOX respiration pathway together with the alternation of antioxidant enzymes in thermogenic stages showed that antioxidant enzymes were closely related to the ROS signaling pathway.Besides,the different changes of antioxidant enzymes activities in magnolia and lotus might attributed to the different thermogenic patterns.Our results showed that the increasing of ROS,higher frequency of superoxide flashes and fluctuation of mitochondrial membrane potential in thermogenic stages indicated that ROS together with superoxide flashes might act as the signaling molecule to regulate cellular antioxidant enzymes,energy dissipating pathway and AOX respiration pathway.Taken together,our study revealed the function of mitochondria superoxide flashes in floral thermogenesis via cell,energy metabolism and regulatory mechanism levels.