The Integrity of the Cell Wall and Its Remodeling during Heterocyst Differentiation Are Regulated by Phylogenetically Conserved Small RNA Yfr1 in Nostoc sp. Strain PCC 7120

Yfr1 is a strictly conserved small RNA in cyanobacteria. A bioinformatic prediction to identify possible interactions of Yfr1 with mRNAs was carried out by using the sequences of Yfr1 from several heterocyst-forming strains, including Nostoc sp. strain PCC 7120. The results of the prediction were enriched in genes encoding outer membrane proteins and enzymes related to peptidoglycan biosynthesis and turnover. Heterologous expression assays with Escherichia coli demonstrated direct interactions of Yfr1 with mRNAs of 11 of the candidate genes. The expression of 10 of them (alr2458, alr4550, murC, all4829, all2158, mraY, alr2269, alr0834, conR, patN) was repressed by interaction with Yfr1, whereas the expression of amiC2, encoding an amidase, was increased. The interactions between Yfr1 and the 11 mRNAs were confirmed by site-directed mutagenesis of Yfr1. Furthermore, a Nostoc strain with reduced levels of Yfr1 had larger amounts of mraY and murC mRNAs, supporting a role for Yfr1 in the regulation of those genes. Nostoc strains with either reduced or increased expression of Yfr1 showed anomalies in cell wall completion and were more sensitive to vancomycin than the wild-type strain. Furthermore, growth in the absence of combined nitrogen, which involves the differentiation of heterocysts, was compromised in the strain overexpressing Yfr1, and filaments were broken at the connections between vegetative cells and heterocysts. These results indicate that Yfr1 is an important regulator of cell wall homeostasis and correct cell wall remodeling during heterocyst differentiation.IMPORTANCE Bacterial small RNAs (sRNAs) are important players affecting the regulation of essentially every aspect of bacterial physiology. The cell wall is a highly dynamic structure that protects bacteria from their fluctuating environment. Cell envelope remodeling is particularly critical for bacteria that undergo differentiation processes, such as spore formation or differentiation of heterocysts. Heterocyst development involves the deposition of additional layers of glycolipids and polysaccharides outside the outer membrane. Here, we show that a cyanobacterial phylogenetically conserved small regulatory RNA, Yfr1, coordinates the expression of proteins involved in cell wall-related processes, including peptidoglycan metabolism and transport of different molecules, as well as expression of several proteins involved in heterocyst differentiation.España Ministerio de Educación, Cultura y Deporte (FPU014/05123 and EST16-00088)España Ministerio de Economía y Competitividad BFU2013-48282-C2-1España Agencia Estatal de Investigación (AEI), Ministerio de Economía, Industria y Competitividad, both cofinanced by the Fondo Europeo de Desarrollo Regional (FEDER) BFU2016-74943-C2-1-

A combinatorial strategy of alternative promoter use during differentiation of a heterocystous cyanobacterium

Heterocystous cyanobacteria such as Nostoc sp. are filamentous photosynthetic organisms that, in response to nitrogen deficiency, undergo a differentiation process transforming certain, semi-regularly spaced cells into heterocysts, devoted to nitrogen fixation. During transition to a nitrogen-fixing regime, growth of most vegetative cells in the filament is temporarily arrested due to nutritional deprivation, but developing heterocysts require intense transcriptional activity. Therefore, the coexistence of arrested vegetative cells and actively developing prospective heterocysts relies on the simultaneous operation of somewhat opposite transcriptional programs. We have identified genes with multiple nitrogen-responsive transcriptional starts appearing in seemingly paradoxical combinations. For instance, sigA, encoding the RNA polymerase housekeeping sigma factor, is transcribed from one major nitrogen stress-repressed promoter and from a second, nitrogen stress-induced promoter. Here, we show that both promoters are expressed with complementary temporal dynamics. Using a gfp reporter we also show that transcription from the inducible promoter takes place exclusively in differentiating heterocysts and is already detected before any morphological or fluorescence signature of differentiation is observed. Tandem promoters with opposite dynamics could operate a compensatory mechanism in which repression of transcription from the major promoter operative in vegetative cells is offset by transcription from a new promoter only in developing heterocyst.Ministerio de Economía y Competitividad BFU2013-48282-C2-1Agencia Estatal de Investigación (AEI) BFU2016-74943-C2-1-PMinisterio de Educación, Cultura y Deportes FPU014/0512

Los cánones 1 y 59 del Concilio de Elvira. A propósito de un artículo de J. Vilella Masana

J. Vilella Masana, "Cánones pseudoiliberritanos y Código Teodosiano: la prohibición de los sacrificios paganos", Polis 17, 2005, 97-133.En controversia con el artículo publicado en esta misma revista por J. Vilella, se afirma en el presente trabajo que los cánones 1 y 59 del concilio de Elvira no se refieren al mismo pecado. A continuación se exponen algunas ideas sobre los conceptos de communio, excomunión y penitencia, no suficientemente claros en el artículo citado; y se defiende que ambos cánones se sitúan por sus prescripciones, en una primera época de máximas exigencias para la concesión de la communio y en un ambiente todavía muy lejano del Imperio cristiano y cuando el paganismo todavía no estaba reprimido.As an answer to the article Publisher by Prof. J. Vilella in this Review, it is held in this paper that the 1st and 59th canons of the council of Elvira do not refer to the same specific sin. Besides, some ideas are put forth about the concepts of communion, excommunio and paetitentia, not clear enough in the mentioned article. It is argued also that both canons, on account of its precriptions, are to be situated in an opening epoch of greatest demands for the grating of the communio, and it the atmosphere of a still far away Christian Empire, when paganism was not yet repressed

LA VILLA ROMANA DE BRUÑEL, EN QUESADA (JAÉN)

Si hoy podemos tener alguna noticia de este importante yacimiento romano, lo debemos en primer lugar a la desinteresada intervención de una serie de personas, a las que es un grato deber de justicia rendir antes que nada el testimonio de nuestro reconocimiento. Me refiero a D. Emilio Moreno Páez y D. Mario Ramos, vecinos de Cazorla y colaboradores del Instituto de Estudios Giennenses, que fueron quienes se apresuraron a dar noticia de los primeros hallazgos casuales. A ellos hay que añadir los nombres de D. Ramón Espantaleón Malina y D. Rafael del Nido. A su pronta intervención hay que atribuir la salvación del monumento y su primer conocimiento oficial. D. Rafael del Nido supo apreciar desde el primer momento la importancia del yacimiento y a su estudio se dedicó con entusiasmo y constancia. El propietario del terreno, D. Bernardo Rodríguez Aguilera, dio toda clase de facilidades para emprender los trabajos de excavación y soportó las molestias y perjuicios que fueron produciéndole éstos, al prolongarse más de lo esperado en un primer momento, dada la extensión insospechada de las ruinas conservadas en su cortijo, hasta el momento en que el Estado lo adquirió para conservar definitivamente el monumento.El 12 de julio de 1 965 daban comienzo las excavaciones arqueológicas de la villaromana situada en el cortijo "Plaza de Armas", en un cerro de 640 m. sobre el nivel del mar y 40 m. sobre el arroyo de Bruñel, en el término municipal de Quesada, provincia de Jaén

EL FORO DE LA GRANADA ROMANA. PLANOS, PLANTAS, ALZADOS Y DIBUJOS

In the middle of the eighteenth century Juan de Flores undertook a series of excavations in the district of Albaicín. He found the paved square of the forum of Roman Granada (Florentia Iliberritana), inscriptions, as well certain architectonic elements of neighbouring buildings. In parallel, he set about making various forgeries, especially through inscriptions, using for this different alphabets that only a few could decipher. He was arrested, tried and condemned, the falsifications destroyed and the remains he had found were covered up. These event shelped to promote the controversy that had been raised for more than a century about where the ancient Iberian-Roman city Iberian Iliberri (Ilíberis or Elvira) was located, whether inSierra Elvira or the Albaicin. The analysis of the elevations and plans made by Flores, which disappeared not long ago, presented in this article, together with others that were developed a posteriori, enable us to locate and confirm the authenticity, which now cannot be doubted, of Flores’ main finding: the forum of Municipium Florentinum Iliberritanum.A mediados del siglo XVIII Juan de Flores llevó a cabo una serie de excavaciones en el barrio del Albaicín. Localizó el enlosado de la plaza del foro de la Granada romana (Florentia Iliberritana), inscripciones, así como algunos elementos arquitectónicos de los edificios colindantes a la misma. Paralelamente se dedicó a crear falsificaciones, especialmente amodo de inscripciones, utilizando para ello diferentes alfabetos que sólo unos pocos podían descifrar. Fue detenido, juzgado y condenado por ello, destruyéndose lo falsificado y cubriéndose los restos que había localizado. Estos hechos ayudaron a fomentar la controversia que desde hacía ya más de un siglo se había suscitado en torno a donde estuvo ubicada la antigua ciudad ibero-romana de Iliberri (Ilíberis o Elvira), si en Sierra Elvira o en el Albaicín. El análisis de los planos alzados y planos que realizó Flores, desaparecidos hasta no hace mucho, presente en este artículo, junto a otros que se elaboraron a posteriori, permite situar y conocer la autenticidad, ya imposible de poner en duda, del principal hallazgo de Flores: el foro del Municipium Florentinum Iliberritanum

D. Juan de Flores y el «Carmen de la muralla» en el Albaicín

Con la ayuda de unos dibujos de 1754 y 1779 ha sido posible situar con precisión las zonas de la Alcazaba Cadima (Albaicín, Granada), en las que D. Juan de Flores y Oddouz realizó sus famosas excavaciones entre los años 1754 y 1763. La localización es importante, porque en dichas excavaciones Flores descubrió auténticos restos arqueológicos de gran interés para el conocimiento de la Granada romana.With the help of some drawings from 1754 and 1779, it has been possible to precisely locate the zones of the Alcazaba Cadima (Albaicín, Granada), in which Juan de Flores y Oddouz conducted his renowned excavations between 1754 and 1763. The localisation of these sites is significant because it is here that Flores discovered authentic archaeological remains of great interest for our understanding of Roman Granada

Identification of conserved and potentially regulatory small RNAs in heterocystous cyanobacteria

Small RNAs (sRNAs) are a growing class of non-protein-coding transcripts that participate in the regulation of virtually every aspect of bacterial physiology. Heterocystous cyanobacteria are a group of photosynthetic organisms that exhibit multicellular behavior and developmental alternatives involving specific transcriptomes exclusive of a given physiological condition or even a cell type. In the context of our ongoing effort to understand developmental decisions in these organisms we have undertaken an approach to the global identification of sRNAs. Using differential RNA-Seq we have previously identified transcriptional start sites for the model heterocystous cyanobacterium Nostoc sp. PCC 7120. Here we combine this dataset with a prediction of Rho-independent transcriptional terminators and an analysis of phylogenetic conservation of potential sRNAs among 89 available cyanobacterial genomes. In contrast to predictive genome-wide approaches, the use of an experimental dataset comprising all active transcriptional start sites (differential RNA-Seq) facilitates the identification of bona fide sRNAs. The output of our approach is a dataset of predicted potential sRNAs in Nostoc sp. PCC 7120, with different degrees of phylogenetic conservation across the 89 cyanobacterial genomes analyzed. Previously described sRNAs appear among the predicted sRNAs, demonstrating the performance of the algorithm. In addition, new predicted sRNAs are now identified that can be involved in regulation of different aspects of cyanobacterial physiology, including adaptation to nitrogen stress, the condition that triggers differentiation of heterocysts (specialized nitrogen-fixing cells). Transcription of several predicted sRNAs that appear exclusively in the genomes of heterocystous cyanobacteria is experimentally verified by Northern blot. Cell-specific transcription of one of these sRNAs, NsiR8 (nitrogen stress-induced RNA 8), in developing heterocysts is also demonstrate