VALLADARES RUIZ , Ana

En este trabajo se abordó, por un lado, el estudio del sistema de asimilacion de urea en cianobacterias, y, por otro, la estructura de los promotores funcionales en heterocistos de Anabaena sp. PCC 7120. En el contexto del sistema de metabolizacion de la urea, se ha identificado y caracterizado un sistema de transporte de urea de alta...

In Anabaena sp. strain PCC 7120, differentiation of heterocysts takes place in response to the external cue of combined nitrogen deprivation, allowing the organism to fix atmospheric nitrogen in oxic environments. NtcA, a global transcriptional regulator of cyanobacteria, is required for activation of the expression of multiple genes involved...

Many filamentous cyanobacteria respond to the external cue of nitrogen scarcity by the differentiation of heterocysts, cells specialized in the fixation of atmospheric nitrogen in oxic environments. Heterocysts follow a spatial pattern along the filament of two heterocysts separated by ca. 10–15 vegetative cells performing oxygenic...

The Anabaena organismic unit is a filament of communicating cells. Under conditions of nitrogen scarcity, some cells along the filament differentiate into heterocysts, which are specialized in the fixation of atmospheric N2 and provide the vegetative cells with N2 fixation products. At a certain stage, the differentiation process becomes...

Expression of the glnA gene encoding glutamine synthetase, a key enzyme in nitrogen metabolism, is subject to a variety of regulatory mechanisms in different organisms. In the filamentous, N2-fixing cyanobacteritim Anabaena sp. strain PCC 7120, glnA is expressed from multiple promoters that generate several transcripts whose abundance is...

Heterocyst differentiation in the cyanobacterium Anabaena sp. strain PCC 7120 depends on both the global nitrogen regulator NtcA and the cell differentiation regulatory protein HetR, and induction of hetR upon nitrogen step-down depends on NtcA. The use of two out of the four transcription start points (tsps) described for the hetR gene (those...

Heterocyst development was analyzed in mutants of the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 bearing inactivated cox2 and/or cox3 genes, encoding heterocyst-specific terminal respiratory oxidases. At the morphological level, the cox2 cox3 double mutant (strain CSAV141) was impaired in membrane reorganization involving...

Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that fixes N2 in specialized cells called heterocysts, which differentiate from vegetative cells in a process that requires the nitrogen control transcription factor NtcA. 2-Oxoglutarate-stimulated binding of purified NtcA to wild-type and modified versions of the ntcA gene promoter...

The organismic unit of heterocyst-forming cyanobacteria is a filament of communicating cells connected by septal junctions, proteinaceous structures bridging the cytoplasms of contiguous cells. This distinct bacterial organization is preserved during cell division. In Anabaena, deletion of the zipN gene could not be segregated. We generated...

The PipX factor is a regulatory protein that seems to occur only in cyanobacteria. In the filamentous, heterocyst-forming Anabaena sp. strain PCC 7120, open reading frame (ORF) asr0485, identified as the pipX gene, is expressed mainly under conditions of combined-nitrogen deprivation dependent on the global N regulator NtcA and the...

All known cyanobacteria contain Cyt c6, a small soluble electron carrier protein whose main function is to transfer electrons from the Cyt b6 f complex to PSI, although it is also involved in respiration. We have previously described a second isoform of this protein, the Cyt c6-like, whose function remains unknown. Here we describe a third...

Filamentous cyanobacteria grow by intercalary cell division, which should involve distinct steps compared to those producing separate daughter cells. The N-terminal region of FtsZ is highly conserved in the clade of filamentous cyanobacteria capable of cell differentiation. A derivative of the model strain Anabaena sp. PCC 7120 expressing only...