Nitrogen Induction of Sugar Catabolic Gene Expression in Synechocystis sp. PCC 6803

Abstract

Nitrogen starvation requires cells to change their transcriptome in order to cope with this essential nutrient limitation. Here, using microarray analysis, we investigated changes in transcript profiles following nitrogen depletion in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Results revealed that genes for sugar catabolic pathways including glycolysis, oxidative pentose phosphate (OPP) pathway, and glycogen catabolism were induced by nitrogen depletion, and activities of glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD), two key enzymes of the OPP pathway, were demonstrated to increase under this condition. We recently showed that a group 2 sigma factor SigE, which is under the control of the global nitrogen regulator NtcA, positively regulated these sugar catabolic pathways. However, increases of transcript levels of these sugar catabolic genes under nitrogen starvation were still observed even in a sigE-deficient mutant, indicating the involvement of other regulatory element(s) in addition to SigE. Since these nitrogen activations were abolished in an ntcA mutant, and since these genes were not directly included in the NtcA regulon, we suggested that sugar catabolic genes were induced by nitrogen depletion under complex and redundant regulations including SigE and other unknown factor(s) under the control of NtcA.

Redox control of copper homeostasis in cyanobacteria

“…9 Later it was also shown to be induced under other conditions that alter the electron transport rate around PSI, such as sulfur and nitrogen starvation or low oxygen. [10][11][12] We have shown that copper is strictly required for these inductions, suggesting that these are indirect effects of reduction of photosynthetic electron transport. Plastocyanin, which is the main copper containing protein in Synechocystis, it is also the major difference between photosynthetic electron transport chains in copper replete and copper free medium.…”

Small Cab-like Proteins Retard Degradation of Photosystem II-associated Chlorophyll in Synechocystis sp. PCC 6803

“…However, cyanobacteria contain single-helix proteins of the Cab family, named SCPs (small Cab-like proteins) or Hli (high light-induced proteins) (6). We will use the SCP designation here, as the corresponding genes are induced not only at high light intensity (7)(8)(9)(10), but also in other stress conditions, such as at low temperature (11), low pH (12), nitrogen and sulfur starvation (8,13), salt and hyperosmotic stresses (11, 14 -16), presence of hydrogen peroxide (17), or inhibitors of photosynthetic electron transport (18).…”

“…Earlier we have shown that synthesis and degradation rates of porphyrins can be measured in Synechocystis cells in situ by analyzing 15 N or 13 C isotope incorporation into pigments (27,28). In this study, stable isotope labeling has been used to perform a systematic survey of mutants lacking single or multiple SCPs with respect to their ability to synthesize, degrade, and reuse chlorophyll under different growth conditions in the light.…”

NrrA, a Nitrogen-regulated Response Regulator Protein, Controls Glycogen Catabolism in the Nitrogen-fixing Cyanobacterium Anabaena sp. Strain PCC 7120

“…PCC 6803 (Fig. 3B), which is up-regulated by nitrogen deprivation (26). The NrrA binding region of the hetR promoter has been determined by DNase I footprinting assays (14), and a similar sequence (AATGTCA) was found within the region (Fig.…”

“…In Synechocystis PCC 6803, rre37, an ortholog of nrrA, and sigE are involved in regulation of sugar catabolism (26,27). Rre37 and SigE independently regulate sugar catabolism under the control of NtcA in contrast to Anabaena PCC 7120, and transcriptional regulation of sigE is exclusively dependent on NtcA (30).…”