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Regulation of Genes Involved in Heterocyst Differentiation in the Cyanobacterium Anabaena sp. Strain PCC 7120 by a Group 2 Sigma Factor SigC.

Ehira S, Miyazaki S - Life (Basel) (2015)

Bottom Line: We carried out DNA microarray analysis to identify genes regulated by SigC, SigE, and SigG.It was indicated that SigC regulated the expression of genes involved in heterocyst differentiation and functions.Moreover, genes regulated by SigC partially overlapped with those regulated by SigE, and deficiency of SigC was likely to be compensated by SigE.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan. ehira@tmu.ac.jp.

ABSTRACT
The filamentous cyanobacterium Anabaena sp. strain PCC 7120 differentiates specialized cells for nitrogen fixation called heterocysts upon limitation of combined nitrogen in the medium. During heterocyst differentiation, expression of approximately 500 genes is upregulated with spatiotemporal regulation. In the present study, we investigated the functions of sigma factors of RNA polymerase in the regulation of heterocyst differentiation. The transcript levels of sigC, sigE, and sigG were increased during heterocyst differentiation, while expression of sigJ was downregulated. We carried out DNA microarray analysis to identify genes regulated by SigC, SigE, and SigG. It was indicated that SigC regulated the expression of genes involved in heterocyst differentiation and functions. Moreover, genes regulated by SigC partially overlapped with those regulated by SigE, and deficiency of SigC was likely to be compensated by SigE.

No MeSH data available.


Related in: MedlinePlus

Heterocyst development after nitrogen deprivation in the sigC disruptant. Micrographs were taken before and 24 h after nitrogen deprivation. The polysaccharide layer of heterocysts was stained with Alcian blue.
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life-05-00587-f002: Heterocyst development after nitrogen deprivation in the sigC disruptant. Micrographs were taken before and 24 h after nitrogen deprivation. The polysaccharide layer of heterocysts was stained with Alcian blue.

Mentions: The transcript levels of 58 genes were lower in DRsigCS than in the WT strain (Table 2). Downregulated genes included genes encoding enzymes of the oxidative pentose phosphate (OPP) pathway (talB, talA, and fbp), those encoding terminal respiratory oxidases (coxB2, coxA2, and coxB3), and those involved in the synthesis of heterocyst envelope polysaccharide (HEP). Moreover, the transcript level of the ntcA gene was decreased by sigC disruption. The OPP pathway is required for nitrogen fixation in heterocysts [36], and genes involved in the OPP pathway are upregulated in heterocysts [32]. The coxBAC2 operon encodes an aa3-type cytochrome c oxidase, and the coxBAC3 operon encodes the alternative respiratory terminal oxidase [37]. Both operons are specifically expressed in heterocysts, and either oxidase is necessary for aerobic nitrogen fixation [37,38]. Synthesis of HEP depends on a cluster of genes, the HEP island (alr2825 to alr2841), and some genes, such as hepB and all4160, that are distant from the HEP island in the genome [5,13,39]. All genes in the HEP island (the relative ratio of the alr2840 transcript level in DRsigCS to that in the WT strain was −0.96 with a p value of 0.0015), hepB (the relative ratio was −0.96 with a p value of 0.0034), and all4160 were downregulated by sigC disruption (Table 2). It was indicated that SigC regulates genes involved in heterocyst differentiation and functions, which are highly expressed in heterocysts. In DRsigCS, heterocysts were observed after 24 h of nitrogen deprivation (Figure 2). However, the nitrogenase activity in DRsigCS at 24 h was reduced to about 30% of that in the WT strain (Table 3). The nitrogenase activity in DRsigCS increased to the level in the WT strain after 48 h of nitrogen deprivation (Table 3), indicating that sigC disruption did not block heterocyst differentiation, but delayed heterocyst development as previously reported [21,24].


Regulation of Genes Involved in Heterocyst Differentiation in the Cyanobacterium Anabaena sp. Strain PCC 7120 by a Group 2 Sigma Factor SigC.

Ehira S, Miyazaki S - Life (Basel) (2015)

Heterocyst development after nitrogen deprivation in the sigC disruptant. Micrographs were taken before and 24 h after nitrogen deprivation. The polysaccharide layer of heterocysts was stained with Alcian blue.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390870&req=5

life-05-00587-f002: Heterocyst development after nitrogen deprivation in the sigC disruptant. Micrographs were taken before and 24 h after nitrogen deprivation. The polysaccharide layer of heterocysts was stained with Alcian blue.
Mentions: The transcript levels of 58 genes were lower in DRsigCS than in the WT strain (Table 2). Downregulated genes included genes encoding enzymes of the oxidative pentose phosphate (OPP) pathway (talB, talA, and fbp), those encoding terminal respiratory oxidases (coxB2, coxA2, and coxB3), and those involved in the synthesis of heterocyst envelope polysaccharide (HEP). Moreover, the transcript level of the ntcA gene was decreased by sigC disruption. The OPP pathway is required for nitrogen fixation in heterocysts [36], and genes involved in the OPP pathway are upregulated in heterocysts [32]. The coxBAC2 operon encodes an aa3-type cytochrome c oxidase, and the coxBAC3 operon encodes the alternative respiratory terminal oxidase [37]. Both operons are specifically expressed in heterocysts, and either oxidase is necessary for aerobic nitrogen fixation [37,38]. Synthesis of HEP depends on a cluster of genes, the HEP island (alr2825 to alr2841), and some genes, such as hepB and all4160, that are distant from the HEP island in the genome [5,13,39]. All genes in the HEP island (the relative ratio of the alr2840 transcript level in DRsigCS to that in the WT strain was −0.96 with a p value of 0.0015), hepB (the relative ratio was −0.96 with a p value of 0.0034), and all4160 were downregulated by sigC disruption (Table 2). It was indicated that SigC regulates genes involved in heterocyst differentiation and functions, which are highly expressed in heterocysts. In DRsigCS, heterocysts were observed after 24 h of nitrogen deprivation (Figure 2). However, the nitrogenase activity in DRsigCS at 24 h was reduced to about 30% of that in the WT strain (Table 3). The nitrogenase activity in DRsigCS increased to the level in the WT strain after 48 h of nitrogen deprivation (Table 3), indicating that sigC disruption did not block heterocyst differentiation, but delayed heterocyst development as previously reported [21,24].

Bottom Line: We carried out DNA microarray analysis to identify genes regulated by SigC, SigE, and SigG.It was indicated that SigC regulated the expression of genes involved in heterocyst differentiation and functions.Moreover, genes regulated by SigC partially overlapped with those regulated by SigE, and deficiency of SigC was likely to be compensated by SigE.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan. ehira@tmu.ac.jp.

ABSTRACT
The filamentous cyanobacterium Anabaena sp. strain PCC 7120 differentiates specialized cells for nitrogen fixation called heterocysts upon limitation of combined nitrogen in the medium. During heterocyst differentiation, expression of approximately 500 genes is upregulated with spatiotemporal regulation. In the present study, we investigated the functions of sigma factors of RNA polymerase in the regulation of heterocyst differentiation. The transcript levels of sigC, sigE, and sigG were increased during heterocyst differentiation, while expression of sigJ was downregulated. We carried out DNA microarray analysis to identify genes regulated by SigC, SigE, and SigG. It was indicated that SigC regulated the expression of genes involved in heterocyst differentiation and functions. Moreover, genes regulated by SigC partially overlapped with those regulated by SigE, and deficiency of SigC was likely to be compensated by SigE.

No MeSH data available.


Related in: MedlinePlus