Role of NtcA, a cyanobacterial global nitrogen regulator, in the regulation of sucrose metabolism gene expression in Anabaena sp. PCC 7120

Abstract

In the heterocyst-forming cyanobacterium Anabaena sp. PCC 7120 (also known as Nostoc sp. PCC 7120), it has been shown that spsB and susA, the genes coding for proteins related to sucrose synthesis and cleavage, respectively, exhibit converse expression regarding the nitrogen source. In the nitrogen-fixing filament, spsB expression is mostly localized to the heterocysts and susA is only expressed in vegetative cells. The aim of this work was to investigate the participation of NtcA, a global nitrogen regulator that operates in cyanobacteria, in the regulation of sucrose metabolism genes in Anabaena sp. PCC 7120. The induction of spsB expression observed in the filaments upon combined-nitrogen depletion was abolished in an NtcA-deficient mutant. In vitro experiments showed that NtcA binds specifically but with different affinities to two sites in the spsB promoter region. When susA expression was analyzed after a combined-nitrogen starvation, the levels of mRNA, polypeptide and activity increased in the mutant in comparison with the wild-type strain. Also, NtcA interacted with one site in the promoter region of susA. We conclude that sucrose metabolism is coordinated at the transcriptional level with nitrogen metabolism, suggesting a global metabolism regulating role for NtcA.

A Comprehensively Curated Genome-Scale Two-Cell Model for the Heterocystous Cyanobacterium Anabaena sp. PCC 7120

“…In addition, the Suc metabolism of Anabaena sp. PCC 7120 was extended as compared to current database entries for this organism (Cumino et al, 2007;Marcozzi et al, 2009;Du et al, 2013). The reconstruction also includes a proposed pathway for the iron (III)-siderophore schizokinen based on the biosynthesis route of a similar siderophore, rhizobactin, from Sinorhizobium meliloti 1021 (Lynch et al, 2001;Nicolaisen et al, 2008;D.…”

Cyanobacterial Heterocysts

“…Heterocysts and vegetative cells are mutually interdependent. Because they lack photosystem II and carbon fixation, heterocysts are dependent on vegetative cells for a source of reductant and carbon, which is probably partially supplied as sucrose (Cumino et al 2007;Marcozzi et al 2009). In Anabaena PCC 7120, vegetative cells must also supply glutamate to heterocysts, which convert it to glutamine and other amino acids (Martin-Figueroa et al 2000).…”

“…5). The protein is conserved in all cyanobacteria and regulates a number of genes involved in carbon and nitrogen metabolism Marcozzi et al 2009). In Anabaena PCC 7120, NtcA is required for the expression of the genes in pathways for ammonium and nitrate assimilation, as well as heterocyst development (Wei et al 1993;Ramasubramanian et al 1994).…”

Nitrogen fixing cyanobacteria: their diversity, ecology and utilisation with special reference to rice cultivation

“…As such, they are dependent on vegetative cells for a source of carbon, which was probably partially supplied as sucrose (Cumino et al, 2007;Marcozzi et al, 2009) while vegetative cells obtain fixed nitrogen in the form of amino acids from the heterocysts (Meeks & Elhai, 2002). In certain species, vegetative cells also supply glutamate to heterocysts, which convert it to glutamine and other amino acids (Martin-Figueroa et al, 2000).…”