An iTRAQ-Based Quantitative Analysis To Elaborate the Proteomic Response of Nostoc sp. PCC 7120 under N₂ Fixing Conditions

Abstract

Nostoc sp. PCC 7120 is an oxygen-evolving photoautotrophic N2 fixing filamentous cyanobacterium. Upon nitrogen starvation, a range of processes are initiated, such as differentiation of the heterocysts, specific cells where N2 fixation takes place. We have characterized and quantified the proteome of the Nostoc sp. PCC 7120 wild-type strain grown under N2 fixing and non-N2 fixing conditions. To assess global proteome changes in response to environmental changes, measurements were made using the quantitative proteomics tool, iTRAQ, on a whole cell digest. From this approach, a total of 486 different proteins was accurately identified across 2 biological replicate experiments, where 226 identifications contained 2 or more distinct peptides. Results of metabolic regulation will be discussed to demonstrate that proteomics represents an important tool for the development of heterocystous cyanobacteria for future biological H2 production.

FraH Is Required for Reorganization of Intracellular Membranes during Heterocyst Differentiation in Anabaena sp. Strain PCC 7120

“…This increase is impaired in ntcA and hetR mutants, which would be consistent with induction taking place largely in the cells that are differentiating into heterocysts. In a proteomic analysis of filaments grown with or without combined nitrogen, FraH was also found at 2-fold higher levels in the diazotrophic cultures (36). As observed in this work (Fig.…”

CalA, a Cyanobacterial AbrB Protein, Interacts with the Upstream Region of hypC and Acts as a Repressor of Its Transcription in the Cyanobacterium Nostoc sp. Strain PCC 7120

“…The band of approximately 2,100 nt is stronger for the cultures grown in an N 2 -fixing environment than for the cultures grown in the non-N 2 -fixing one. This is in accordance with two quantitative proteomic iTRAQ studies of Nostoc PCC 7120 and Nostoc punctiforme ATCC 29133, showing a relative higher level of CalA in N 2 -fixing filaments than in the non-N 2 -fixing filament (46) and an upregulation of 1.67 times of the FIG. 5.…”

“…CalA is annotated as a hypothetical protein, although it has been identified before in proteomic studies (46), consisting of 144 aa and with a predicted molecular mass of 16.06 kDa (see Fig. S1A in the supplemental material) (40).…”

“…strain PCC 7120, also known as Anabaena sp. strain PCC 7120 (Nostoc PCC 7120), was cultured in BG11 0 supplemented with 5 mM NH 4 Cl and 5 mM MOPS (morpholinepropanesulfonic acid; pH 7.8) or in BG11 0 (38), sparged with air, and grown at 25°C, with a continuous irradiance of 40 mol of photons m Ϫ2 s Ϫ1 (46). In the Northern blot experiments some of the cultures of Nostoc PCC 7120 were grown in darkness and sparged with argon 12 h before harvesting.…”

The anatomy of microbial cell state transitions in response to oxygen

“…To determine the extent to which the transcript level changes described above are dynamically reflected at the protein level, and in turn, at the phenotype level, whole-cell quantitative proteomics analysis was conducted using the mass spectrometrybased iTRAQ method (Ross et al 2004;Whitehead et al 2006;Stensjo et al 2007).…”