In C4 photosynthesis, pyruvate orthophosphate dikinase （PPDK） catalyzes the regeneration of phospho- enolpyruvate in the carbon shuttle pathway. Although the biochemical function of PPDK in maize is well characteriz...In C4 photosynthesis, pyruvate orthophosphate dikinase （PPDK） catalyzes the regeneration of phospho- enolpyruvate in the carbon shuttle pathway. Although the biochemical function of PPDK in maize is well characterized, a genetic analysis of PPDK has not been reported. In this study, we use the maize transposable elements Nlutator and Ds to generate multiple mutant alleles of PPDK. Loss-of- function mutants are seedling lethal, even when plants were grown under 2% CO2, and they show very low capacity for CO2 assimilation, indicating C4 photosynthesis is essential in maize. Using RNA-seq and GC-MS technologies, we exam- ined the transcriptional and metabolic responses to a deficiency in PPDK activity. These results indicate loss of PPDK results in downregulation of gene expression ofenzymes of the C4 cycle, the Calvin cycle, and components of photochemistry. Furthermore, the loss of PPDK did not change Kranz anatomy, indicating that this metabolic defect in the C4 cycle did not impinge on the morphological differentiation of C4 characters. However, sugar metabolism and nitrogen utilization were altered in the mutants. An interaction between light intensity and genotype was also detected from transcriptome profiling, suggesting altered transcriptional and metabolic responses to environmental and endogenous signals in the PPDK mutants.展开更多
基金supported by the NSFC (31271393)National Key Research and Developmen Program of China (2016YFD0101003)+2 种基金Taishan Program to P. LiNSF (EF-1105249 IOS-092270, IOS-1127017) to TP. Brutnell
文摘In C4 photosynthesis, pyruvate orthophosphate dikinase （PPDK） catalyzes the regeneration of phospho- enolpyruvate in the carbon shuttle pathway. Although the biochemical function of PPDK in maize is well characterized, a genetic analysis of PPDK has not been reported. In this study, we use the maize transposable elements Nlutator and Ds to generate multiple mutant alleles of PPDK. Loss-of- function mutants are seedling lethal, even when plants were grown under 2% CO2, and they show very low capacity for CO2 assimilation, indicating C4 photosynthesis is essential in maize. Using RNA-seq and GC-MS technologies, we exam- ined the transcriptional and metabolic responses to a deficiency in PPDK activity. These results indicate loss of PPDK results in downregulation of gene expression ofenzymes of the C4 cycle, the Calvin cycle, and components of photochemistry. Furthermore, the loss of PPDK did not change Kranz anatomy, indicating that this metabolic defect in the C4 cycle did not impinge on the morphological differentiation of C4 characters. However, sugar metabolism and nitrogen utilization were altered in the mutants. An interaction between light intensity and genotype was also detected from transcriptome profiling, suggesting altered transcriptional and metabolic responses to environmental and endogenous signals in the PPDK mutants.
