Metabolomic analysis reveals rewiring of Synechocystis sp. PCC 6803 primary metabolism by ntcA overexpression.

NtcA is a cAMP receptor protein-type transcription factor conserved among cyanobacteria and is essential for gene expression in response to nitrogen status. NtcA has been widely studied; however, no metabolomic analysis has been conducted using the ntcA mutant. Here, we generated a strain that overexpresses ntcA in Synechocystis sp. PCC 6803, named NOX10, and performed physiological, transcriptomic and metabolomic analyses. NOX10 grew faster than the wild-type strain under photoautotrophic conditions, but slower under light-activated heterotrophic conditions. Transcriptome analysis revealed that the expression of genes related to primary metabolism was altered by ntcA overexpression particularly under nitrogen-depleted conditions. Metabolomic analysis revealed that metabolite levels in sugar, purine/pyrimidine nucleotide, organic acid and amino acid metabolism were widely altered by ntcA overexpression. The protein levels of nitrogen-regulated transcriptional regulators were altered by ntcA overexpression during nitrogen starvation. These results demonstrate the alteration of primary metabolism by genetic engineering of NtcA, and they contribute to the current understanding of metabolic regulation of unicellular cyanobacteria.