Transcriptome and proteome analysis of nitrogen starvation responses in Synechocystis 6803 ΔglgC, a mutant incapable of glycogen storage

Journal Article · 17 November 2016 · Algal Research

DOI: https://doi.org/10.1016/j.algal.2016.11.003 · OSTI ID:1335210

Carrieri, Damian ^[1]; Lombardi, Thomas ^[2]; Paddock, Troy ^[1]; Cano, Melissa ^[3]; Goodney, Gabriel A. ^[2]; Nag, Ambarish ^[3]; Old, William ^[4]; Maness, Pin -Ching ^[3]; Seibert, Michael ^[3]; Ghirardi, Maria ^[3]; Yu, Jianping ^[3]

---

1. National Renewable Energy Lab. (NREL), Golden, CO (United States); Matrix Genetics, LLC, Seattle, WA (United States)
2. Washington and Jefferson College, Washington, PA (United States)
3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
4. Univ. of Colorado, Boulder, CO (United States)

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. Furthermore, 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.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: AC36-08GO28308; FWP ERWER0A; AC36-08-GO28308
• OSTI ID: 1335210
• Alternate ID(s): OSTI ID: 1396618
• Report Number(s): NREL/JA-2700-65975
• Journal Information: Algal Research, Vol. 21, Issue C; ISSN 2211-9264
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English