Instituto de Bioquímica Vegetal y Fotosíntesis IBVF – CIC Cartuja

URI permanente para esta comunidadhttps://hdl.handle.net/11441/10948

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Antisense RNA Regulates Glutamine Synthetase in a Heterocyst-forming Cyanobacterium
(American Society of Plant Biologists, 2024) Álvarez Escribano, Isidro; Suárez Murillo, Belén; Brenes Álvarez, Manuel; Vioque Peña, Agustín; Muro Pastor, Alicia M.; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía
Glutamine synthetase (GS) is a key enzyme involved in nitrogen assimilation and the maintenance of C/N balance, and it is strictly regulated in all bacteria. In cyanobacteria, GS expression is controlled by nitrogen control A (NtcA) transcription factor, which operates global nitrogen regulation in these photosynthetic organisms. Furthermore, posttranslational regulation of GS is operated by protein–protein interaction with GS inactivating factors (IFs). In this study, we describe an additional regulatory mechanism involving an antisense RNA. In Nostoc sp. PCC 7120, the gifA gene (encoding GS inactivating factor IF7) is transcribed downstream of the GS (glnA) gene, from the opposite strand, and the gifA mRNA extends into the glnA coding sequence in antisense orientation. Therefore, the dual RNA transcript that encodes gifA constitutes two functional regions: a 5′ protein-coding region, encoding IF7, and a 3′ untranslated region that acts as an antisense to glnA. By increasing the levels of such antisense RNA either in cis or in trans, we demonstrate that the amount of GS activity can be modulated by the presence of the antisense RNA. The tail-to-tail disposition of the glnA and gifA genes observed in many cyanobacterial strains from the Nostocales clade suggests the prevalence of such antisense RNA-mediated regulation of GS in this group of cyanobacteria.
NsiR3, a nitrogen stress-inducible small RNA, regulates proline oxidase expression in the cyanobacterium Nostoc sp. PCC 7120
(Wiley-Blackwell, 2021) Álvarez Escribano, Isidro; Brenes Álvarez, Manuel; Olmedo Verd, Elvira de; Georg, Jens; Hess, Wolfgang R.; Vioque Peña, Agustín; Muro Pastor, Alicia María; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Agencia Estatal de Investigación. España BFU2016-74943-C2-1-P
NsiR3 (nitrogen stress-inducible RNA 3) is a small noncoding RNA strongly conserved in heterocyst-forming cyanobacteria. In Nostoc sp. PCC 7120, transcription of NsiR3 is induced by nitrogen starvation and depends on the global nitrogen regulator NtcA. A conserved NtcA-binding site is centered around position −42.5 with respect to the transcription start site of NsiR3 homologs, and NtcA binds in vitro to a DNA fragment containing this sequence. In the absence of combined nitrogen, NsiR3 expression is induced in all cells along the Nostoc filament but much more strongly in heterocysts, differentiated cells devoted to nitrogen fixation. Co-expression analysis of transcriptomic data obtained from microarrays hybridized with RNA obtained from Nostoc wild-type or mutant strains grown in the presence of ammonium or in the absence of combined nitrogen revealed that the expression profile of gene putA (proline oxidase) correlates negatively with that of NsiR3. Using a heterologous system in Escherichia coli, we show that NsiR3 binds to the 5′-UTR of putA mRNA, resulting in reduced expression of a reporter gene. Overexpression of NsiR3 in Nostoc resulted in strong reduction of putA mRNA accumulation, further supporting the negative regulation of putA by NsiR3. The higher expression of NsiR3 in heterocysts versus vegetative cells of the N2-fixing filament could contribute to the previously described absence of putA mRNA and of the catabolic pathway to produce glutamate from arginine via proline specifically in heterocysts. Post-transcriptional regulation by NsiR3 represents an indirect NtcA-operated regulatory mechanism of putA expression. Database: Microarray data are available in GEO database under accession numbers GSE120377 and GSE150191.
NsrR1, a Nitrogen stress-repressed sRNA, contributes to the regulation of nblA in Nostoc sp. PCC 7120
(Frontiers Media, 2018-09-24) Álvarez Escribano, Isidro; Vioque Peña, Agustín; Muro Pastor, Alicia María; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
Small regulatory RNAs (sRNAs) are currently considered as major post-transcriptional regulators of gene expression in bacteria. The interplay between sRNAs and transcription factors leads to complex regulatory networks in which both transcription factors and sRNAs may appear as nodes. In cyanobacteria, the responses to nitrogen availability are controlled at the transcriptional level by NtcA, a CRP/FNR family regulator. In this study, we describe an NtcA-regulated sRNA in the cyanobacterium Nostoc sp. PCC 7120, that we have named NsrR1 (nitrogen stress repressed RNA1). We show sequence specific binding of NtcA to the promoter of NsrR1. Prediction of possible mRNA targets regulated by NsrR1 allowed the identification of nblA, encoding a protein adaptor for phycobilisome degradation under several stress conditions, including nitrogen deficiency. We demonstrate specific interaction between NsrR1 and the 5′-UTR of the nblA mRNA, that leads to decreased expression of nblA. Because both NsrR1 and NblA are under transcriptional control of NtcA, this regulatory circuit constitutes a coherent feed-forward loop, involving a transcription factor and an sRNA.
The nitrogen stress-repressed srna nsrr1 regulates expression of all1871, a gene required for diazotrophic growth in nostoc sp. Pcc 7120
(Multidisciplinary Digital Publishing Institute (MDPI), 2020) Álvarez Escribano, Isidro; Brenes Álvarez, Manuel; Olmedo Verd, Elvira de; Vioque Peña, Agustín; Muro Pastor, Alicia María; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular
Small regulatory RNAs (sRNAs) are post-transcriptional regulators of bacterial gene expression. In cyanobacteria, the responses to nitrogen availability, that are mostly controlled at the transcriptional level by NtcA, involve also at least two small RNAs, namely NsiR4 (nitrogen stress-induced RNA 4) and NsrR1 (nitrogen stress-repressed RNA 1). Prediction of possible mRNA targets regulated by NsrR1 in Nostoc sp. PCC 7120 allowed, in addition to previously described nblA, the identification of all1871, a nitrogen-regulated gene encoding a protein of unknown function that we describe here as required for growth at the expense of atmospheric nitrogen (N2). We show that transcription of all1871 is induced upon nitrogen step-down independently of NtcA. All1871 accumulation is repressed by NsrR1 and its expression is stronger in heterocysts, specialized cells devoted to N2 fixation. We demonstrate specific interaction between NsrR1 and the 5′ untranslated region (UTR) of the all1871 mRNA, that leads to decreased expression of all1871. Because transcription of NsrR1 is partially repressed by NtcA, post-transcriptional regulation by NsrR1 would constitute an indirect way of NtcA-mediated regulation of all1871.

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Examinando Instituto de Bioquímica Vegetal y Fotosíntesis IBVF – CIC Cartuja por Autor "Álvarez Escribano, Isidro"