NtcA, a cyanobacterial global regulator, is involved in the regulation of sucrose metabolism genes, contributing to the interconvection between carbon metabolism and nitrogen fixation in Anabaena sp. PCC 7120

C. MARCOZZI; A. CUMINO; G.L. SALERNO

ARCHIVES OF MICROBIOLOGY

Springer-Verlag

Lugar: Heidelberg; Año: 2009 vol. 191 p. 255 - 263

0302-8933

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-US; mso-fareast-language:ES;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> 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 an opposite 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 analysed 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.