INBA   12521
INSTITUTO DE INVESTIGACIONES EN BIOCIENCIAS AGRICOLAS Y AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Sucrose hydrolysis regulation in the filamentous cyanobacteria Nostoc sp. PCC7120 under nitrogen deprivation.
Autor/es:
C.N. NISHI; H.G. PONTIS; G.L. SALERNO
Lugar:
San Miguel de Tucumán
Reunión:
Congreso; VII Congreso Argentino de Microbiología General; 2011
Institución organizadora:
Universidad Nacional de Tucumán
Resumen:
Sucrose (Suc), a key sugar in plant life, is also present in cyanobacteria, oxygen-evolving photosynthetic bacteria. They were shown to present proteins for Suc synthesis and degradation similar to plant´s enzymes. Particularly, the hydrolysis of Suc is performed by Alkaline/Neutral Invertases (A/N-Invs). Two A/N-Inv isoforms were biochemically and functionally characterized in Nostoc sp. PCC 7120, a filamentous nitrogen-fixing strain, and their encoding genes (invA and invB) were identified and functionally characterized. Whereas both genes are expressed simultaneously in vegetative cells, only invB is expressed in heterocysts during diazotrophic growth and mutants lacking of invB were not able to grow under this condition, concluding that Suc metabolism plays an important role in relation to nitrogen fixation. On the other hand, previous results showed that NtcA, a global nitrogen regulator that is present exclusively in cyanobacteria, may be also regulating the expression of other Suc metabolism genes. NtcA (encoded by ntcA) belongs to the Crp-FNR family of bacterial transcriptional regulators. The aim of this study was to investigate the role of NtcA in the regulation of Suc hydrolysis in the filaments of Nostoc sp. PCC 7120. Levels of soluble sugars and polysaccharides were analyzed after 24 h of combined-nitrogen step-down in an NtcA deficient mutant (CSE2, a derivative mutant strain from Nostoc sp. PCC 7120 that bears an inactivated version of the ntcA gene). Besides expression at the activity and transcript level of A/N-Invs were investigated, showing to be differentially expressed in the CSE2 mutant. Besides, the presence of putative NtcA-binding regions in the promoter region of invB suggested a possible physical interaction with the global regulator. Taken together, our results show that Suc hydrolysis through A/N-Invs is linked to nitrogen metabolism through the transcription factorNtcA.