A cyanobacterial AbrB‐like protein affects the apparent photosynthetic affinity for CO₂ by modulating low‐CO₂‐induced gene expression

Abstract

In Synechocystis sp. strain PCC 6803, over 450 genes are upregulated following transfer of the cells from a high (1-5% CO(2) in air, HC) to a low level of CO(2) (as in air or lower, LC). This includes sbtA, ndhF3 and cmpA involved in inorganic carbon (Ci) uptake. Earlier studies implicated NdhR in the regulation of LC-induced genes but there are indications that additional components are involved. Following extraction of proteins from cells grown under HC and (NH4)(2)SO(4) fractionation, we have identified LexA and two AbrB-like proteins, Sll0359 and Sll0822, which bind to a fragment of the sbtA promoter. Using extracts prepared from LC-grown cells, Sll0822 did not bind to the sbtA promoter despite its presence in the cells, suggesting that it may serve as a repressor of LC-induced genes. This is supported by the fact that sbtA, ndhF3 and cmpA normally expressed only under LC in the wild-type are transcribed under both HC and LC in a Deltasll0822 mutant. When grown under HC this mutant exhibits an elevated apparent photosynthetic affinity to Ci, typically observed in the wild-type only under LC. Clearly, expression of genes essential for Ci uptake was sufficient to raise the apparent photosynthetic affinity for external Ci.

Metabolic and Transcriptomic Phenotyping of Inorganic Carbon Acclimation in the Cyanobacterium Synechococcus elongatus PCC 7942

“…At least three transcriptional factors, CmpR, NdhR, and AbrB-like proteins, were found to be involved in the up-regulation of functionally defined gene groups (e.g. C i transporters, NDH1 complexes, and photosynthetic complexes; Omata et al, 2001;Wang et al, 2004;Lieman-Hurwitz et al, 2009). Moreover, the affinity of the transcription factor CmpR for the cmp promoter was stimulated by the binding of 2-phosphoglycolate (2PG; Nishimura et al, 2008), the first metabolite of the photorespiratory 2PG metabolism (Eisenhut et al, 2008b).…”

Deletion of the Transcriptional Regulator cyAbrB2 Deregulates Primary Carbon Metabolism in Synechocystis sp. PCC 6803

“…We have reported previously that the expression levels of Ci-uptake-related genes such as ndhF3 and sbtA (Lieman-Hurwitz et al, 2009;Yamauchi et al, 2011) and photosynthetic affinity to external Ci (LiemanHurwitz et al, 2009) are lower in the mutant under ambient CO 2 conditions. Nevertheless, the photosynthetic activity of the photoautotrophically grown mutant was comparable to that of the wild type (Fig.…”

“…The DcyabrB2 mutant exhibits the elevated apparent photosynthetic affinity for Ci that is typical in wild-type cells, but only under low CO 2 conditions. Binding of cyAbrB2 to the upstream region of sbtA, which encodes a Na + /HCO 3 -symporter, has been demonstrated (Lieman-Hurwitz et al, 2009). (5) The expression levels of genes encoding cell division-related proteins such as FtsZ and FtsW are lower in the DcyabrB2 mutant.…”

CalA, a cyAbrB protein, binds to the upstream region of ftsZ and is down-regulated in heterocysts in Anabaena sp. PCC 7120

“…The two cyAbrBs in Synechocystis sp. PCC 6803 (referred to as Synechocysits 6803 hereafter) have been shown to bind to the promoter regions of the hox operon encoding the bidirectional NiFe hydrogenase (Oliveira and Lindblad 2008), nitrogen-regulated genes (Ishii and Hihara 2008), low CO 2 -responsive genes (Lieman-Hurwitz et al 2009) and to affect their expression. One of the two cyAbrBs in Anabaena 7120, Alr0946 (CalA), has been shown to bind to the upstream regions of hypC, a gene encoding a hydrogenase assembly chaperone, alr0946-alr0947 and to repress their transcription (Agervald et al 2010).…”