Transcriptome and Proteome Analysis of Nitrogen Starvation Responses in Synechocystis 6803 ..delta..glgC, a Mutant Incapable of Glycogen Storage

Jianping Yu, Ambarish Nag, Pin-Ching Maness, Michael Seibert, Damian Carrieri, Thomas Lombardi, Troy Paddock, Gabriel Goodney, William Old, Melissa Cano, Maria Ghirardi

Research output: Contribution to journalArticlepeer-review

21 Scopus Citations

Abstract

Molecular mechanisms that regulate carbon flux are poorly understood in algae. The ΔglgC mutant of the cyanobacterium Synechocystis sp. PCC 6803 is incapable of glycogen storage and displays an array of physiological responses under nitrogen starvation that are different from wild-type (WT). These include non-bleaching phenotype and the redirection of photosynthetically fixed carbon towards excreted organic acids (overflow metabolism) without biomass growth. To understand the role of gene/protein expression in these responses, we followed the time course of transcripts by genome-scale microarrays and proteins by shotgun proteomics in ΔglgC and WT cells upon nitrogen starvation. Compared to WT, the degradation of phycobilisome rod proteins was delayed and attenuated in the mutant, and the core proteins were less degraded; both contributed to the non-bleaching appearance despite the induction of nblA genes, suggesting the presence of a break in regulation of the phycobilisome degradation pathway downstream of nblA induction. The mutant displayed NtcA-mediated transcriptional response to nitrogen starvation, indicating that it is able to sense nitrogen status. Furthermore, some responses to nitrogen starvation appear to be stronger in the mutant, as shown by the increases in transcripts for the transcriptional regulator, rre37, which regulates central carbon metabolism. Accordingly, multiple proteins involved in photosynthesis, central carbon metabolism, and carbon storage and utilization showed lower abundance in the mutant. These results indicate that the transition in the central carbon metabolism from growth to overflow metabolism in ΔglgC does not require increases in expression of the overflow pathway enzymes; the transition and non-bleaching phenotype are likely regulated instead at the metabolite level.

Original languageAmerican English
Pages (from-to)64-75
Number of pages12
JournalAlgal Research
Volume21
DOIs
StatePublished - 1 Jan 2017

Bibliographical note

Publisher Copyright:
© 2016 Elsevier B.V.

NREL Publication Number

  • NREL/JA-2700-65975

Keywords

  • algae
  • cyanobacterium
  • glycogen storage
  • nitrogen starvation

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