Transgenic Perturbation of the Decarboxylation Phase of Crassulacean Acid Metabolism Alters Physiology and Metabolism But Has Only a Small Effect on Growth

摘要: Mitochondrial NAD-malic enzyme (ME) and/or cytosolic/plastidic NADP-ME combined with the pyruvate orthophosphate dikinase (PPDK) catalyze two key steps during light-period malate decarboxylation that underpin secondary CO2 fixation in some Crassulacean acid metabolism (CAM) species. We report generation and phenotypic characterization of transgenic RNA interference lines obligate CAM species Kalanchoe fedtschenkoi reduced activities NAD-ME or PPDK. Transgenic line rNAD-ME1 had 8%, rPPDK1 5% wild-type level activity, showed dramatic changes light/dark cycle fixation. In well-watered conditions, these fixed all their light; they thus performed C3 photosynthesis. The alternative decarboxylase, NADP-ME, did not appear to compensate for reduction NAD-ME, suggesting was decarboxylase CAM. activity other enzymes as a consequence knocking out either PPDK particularly phosphoenolpyruvate carboxylase (PPC) rNAD-ME1. Furthermore, circadian clock-controlled phosphorylation PPC dark both lines, especially This rhythms phosphorylation, kinase transcript levels classic rhythm were lost, dampened toward arrhythmia, under constant light temperature conditions. Surprisingly, oscillations abundance core clock genes also became arrhythmic line, perturbing K. feeds back perturb central clock.