Studies on the regulation properties of CAM type photosynthesis in pineapple

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Although CAM type CO_2 exchange in pineapple was partially regulated by the phosphorylation of phosphoenolpyruvate (PEP) carboxylase in night as observing in Kalanchoe CAM, the contribution to the CAM expression was less than the Kalanchoe CAM. It was appeared that the driving force of the malate accumulation on the tonoplast, such as ATPase and PPase, and the tonplast ligidity contributed to the CAM regulation. In addition, phosphofructokinase (PFP) of pineapple was constructed by subunits of α and β, the result showed that α subunit concerned to the PFP regulation as similar to other plant species. External NADH oxidation in mitochondria of pineapple, a typical PEP carboxykinase (PCK)-CAM plant, was more connected with the cytochrome pathway and less with the alternative pathway. This capacity might be one of the fitting mechanisms of pineapple to produce a sufficient amount of ATP for cytosolic PCK in the daytime. That is, it was suggested that the connection of electron transfer chain to cytochrome oxydase or alternative oxydase is different between the CAM subtypes of PCK and malic enzyme (ME). In summery, pineapple CAM type photosynthesis has a different regulation mechanism to the authentic CAM regulation observed in Kalanchoe specied, although some similar properties also contributed to both CAM regulations of pineapple and Kalanchoe. In the next, cross-talks of different metabolism and organs, such as glycolysis and mitochondria are important topics in the CAM regulation.