Diversity of N2-fixing cyanobacteria from Andalusian paddy fields and analysis of their potential as bioinoculants

The marshes of the Guadalquivir River contain the largest area of rice cultivation in Spain, where more than 40,000 ha are used every year for rice production. These wetland areas provide a perfect place for rice cultivation, and represent a unique aquaticterrestrial habitat that hold more wintering waterfowl than any other European wetland. Paddies require large amounts nitrogen and phosphorus for their growth, development and production. Though, flooded conditions used for rice cultivation drastically diminish efficiency inorganic nitrogen fertilizers, being only 30–40% used by the plant, and in some cases even less. Large amounts of nitrogen fertilizers are dissolved in the surface water and lost, causing environmental pollution and health problems due to losses through N2O and NO volatilization, denitrification, and leaching (Ishii et al., 2011)

Overexpression of SepJ alters septal morphology and heterocyst pattern regulated by diffusible signals in Anabaena

Filamentous, N2 -fixing, heterocyst-forming cyanobacteria grow as chains of cells that are connected by septal junctions. In the model organism Anabaena sp. strain PCC 7120, the septal protein SepJ is required for filament integrity, normal intercellular molecular exchange, heterocyst differentiation, and diazotrophic growth. An Anabaena strain overexpressing SepJ made wider septa between vegetative cells than the wild type, which correlated with a more spread location of SepJ in the septa as observed with a SepJ-GFP fusion, and contained an increased number of nanopores, the septal peptidoglycan perforations that likely accommodate septal junctions. The septa between heterocysts and vegetative cells, which are narrow in wild-type Anabaena, were notably enlarged in the SepJ-overexpressing mutant. Intercellular molecular exchange tested with fluorescent tracers was increased for the SepJ-overexpressing strain specifically in the case of calcein transfer between vegetative cells and heterocysts. These results support an association between calcein transfer, SepJ-related septal junctions, and septal peptidoglycan nanopores. Under nitrogen deprivation, the SepJ-overexpressing strain produced an increased number of contiguous heterocysts but a decreased percentage of total heterocysts. These effects were lost or altered in patS and hetN mutant backgrounds, supporting a role of SepJ in the intercellular transfer of regulatory signals for heterocyst differentiationEspaña, Plan nacional de Investigación BFU2014-56757-

Challenging the term symbiosis in plant-microbe associations to create an understanding across sciences

Scientific progress relies on clear and consistent definitions for effective communication and collaboration. The term "symbiosis" in the context of plant-microbe associations suffers from diverse interpretations, leading to ambiguity in classification of these associations. This review elaborates on the issue, proposing an inclusive definition as well as a keyword

Un crecimiento tempranamente quebrado: el producto agrario en Andalucía occidental en la Edad Moderna

En este artículo se presenta una estimación del crecimiento agrario de Andalucía occidental en la Edad Moderna, y se describen sus tendencias y los cambios en la composición del producto. Las "Rentas de las Mitras" y los registros decimales del Cabildo de la Catedral de Sevilla han constituído las fuentes básicas. Se ha utilizado la vía del producto para la estimación del crecimiento agrario. Las principales conclusiones son: 1) entre finales de los siglos XVI y XVIII el crecimiento agrario en Andalucía occidental fue bastante modesto; 2) esta región registró una depresión agraria de apreciable intensidad entre 1580 y 1685, debido principalmente al hundimiento de la producción de vino y aceite; y 3) tras un balance económico bastante favorable en el siglo XVI, sobre todo hasta 1580, Andalucía occidental desperdició en las dos centurias siguientes una parte considerable de su potencial de crecimiento agrario

Transcriptional regulation of genes involved in the symbiosis between Nostoc and Oryza

Motivation: Cyanobacteria of the genus Nostoc are capable of establishing symbiosis relationships with many different types of plants. In these mutualistic relationships the cyanobacterium provides the plant with fixed nitrogen, while the plant provides the cyanobacterium with protection from hostile environments and carbon compounds as energy for N2 fixation. It has recently been described that Nostoc punctiforme performs a stable symbiosis with Oryza sativa (Álvarez et al., 2020). In order to know the molecular mechanisms involved in the recognition between the plant and the cyanobacterium, a proteomic study was carried out in the early stages of co-culture of both organisms. In this study, proteins with homology to the Nod factors of Rhizobium sp. were identified in Nostoc, which could be related to signaling in the plant. The aim of this work is to study the regulation of the expression of the genes encoding these Nod proteins by means of RT-qPCR. Methods: The expression of Nostoc punctiforme Nod genes was studied in response to the presence of the plant at 1, 2, 3, 5 and 7 days of co-culture. On the one hand, a Nostoc punctiforme culture grown at 25°C in Roux flasks with 1% CO2, continuous illumination and at 30°C was prepared. On the other hand, Oryza sativa seedlings were obtained germination of seeds under axenic conditions. At one week of growth, the seedlings were transplanted into flasks with hydroponic medium. Co-culture was performed by adding a fixed amount of Nostoc to the Oryza culture medium, and incubating the mixture in thermostated chambers at 25°C, 12h light/dark cycles and 75% relative humidity. RNA was extracted from Nostoc samples that had been in contact with the plant. As a control, Nostoc incubated without the plant was used. After RNA retrotranscription, the resulting cDNA was used to evaluate the expression of the genes of interest. Results: It was observed that the expression of certain Nod genes is activated in the presence of Oryza, although there are other Nod genes whose expression remains unchanged in response to inoculation with the plant

Crop improvement through microbial biofertilisers and molecular markers of salt stress

The exponential growth of the population, the trend towards organic food consumption and the increasingly restrictive regulations imposed by the European Union are forcing the agricultural sector to evolve towards more sustainable practices that are less harmful to the environment. In addition to these challenges, farmers need to cope with other biotic and abiotic factors affecting plant productivity, such as drought, diseases and pests. To that end, biotechnological approaches to obtain food in a sustainable way are being explored. The lower Guadalquivir region, at the South of Spain, contains the largest area devoted to intensive agriculture practices in Andalusia. This region faces two main problems, which are high salinity in irrigation water and N contamination by synthetic fertilizers (Paredes et al., 2020). In this work we provide two different biotechnological approaches to address these problems: 1) We have characterized salt resistance in nine rice varieties that are being cultivated in the Guadalquivir paddies. This analysis has been complemented through morphological, physiological and biochemical approaches, using analytical methods such as HPLC and mass chromatography, among others. We have identified metabolites that are overproduced in salt stress conditions and might be used for the early detection of salt stress in the plant. A comparative analysis of the different rice varieties analysed provided valued information about the different tolerance to salt. 2) In order to reduce the use of synthetic nitrogen fertilizers, we tested three bioinoculants that had been previously isolated from cotton soils. First, we characterized them biochemically for the PGPR activities, comprising N2 fixation and production of plant phytohormones. Effectiveness of these bioinoculants was assayed in microcosms experiments. We found a significant plant growth stimulation in two of the three bioinoculants evaluated

Genetic variations in Spanish isolates of Phaeomoniella chlamydospora, the causal etiological agent of Petri disease of grapevine

Petri disease is currently considered as one of the most important mycoses of grapevine wood in terms of its incidence and extent, causing young grapevine decay in numerous vine-producing areas worldwide. One of its causal agents is the ascomycete Phaeomoniella chlamydospora (W. Gams, Crous, M. J. Wingfield & Mugnai) Crous & W. Gams. Recently, several studies focusing on the genetic and variability of this species have reported that its genetic variability is low. However, studies on the intraspecific characterisation of P. chlamydospora by other than molecular means are scarce. In this study, 57 Spanish isolates of P. chlamydospora were characterised by integrating data from morphological, pathogenic, cytological and ecological techniques. It was found that there was a relationship between the high polymorphism in these isolates (melanised, intermediate and albino cultures), and a number of groups, distinguished by their nuclear number, pathogenicity or survival in soil. The non-melanised phenotypes were associated with less virulent strains, generally possessing mono- or binucleate hyphae with low survival in soils, whilst melanised, multinucleate isolates were more virulent and survived up to 12 months in grapevine soils under laboratory conditions. Using these other criteria to distinguish forms of this pathogen, should make it easier to detect hypovirulent or non-pathogenic isolates and to advance our understanding of the biology of the fungus, especially its modes of dispersal or its ecological range in the field. The adoption of these criteria should also make it easier to characterise intraspecific variations in those cases where the genetic methods do not reflect them, as with P. chlamydospora

Impaired cell-cell communication in the multicellular cyanobacterium Anabaena affects carbon uptake, photosynthesis, and the cell wall

Cell-cell communication is an essential attribute of multicellular organisms. The effects of perturbed communication were studied in septal protein mutants of the heterocyst-forming filamentous cyanobacterium Anabaena sp. PCC 7120 model organism. Strains bearing sepJ and sepJ/fraC/fraD deletions showed differences in growth, pigment absorption spectra, and spatial patterns of expression of the hetR gene encoding a heterocyst differentiation master regulator. Global changes in gene expression resulting from deletion of those genes were mapped by RNA sequencing analysis of wild-type and mutant strains, both under nitrogen-replete and nitrogen-poor conditions. The effects of sepJ and fraC/fraD deletions were non-additive, and perturbed cell-cell communication led to significant changes in global gene expression. Most significant effects, related to carbon metabolism, included increased expression of genes encoding carbon uptake systems and components of the photosynthetic apparatus, as well as decreased expression of genes encoding cell wall components related to heterocyst differentiation and to polysaccharide export.Peer reviewe

Specific mutations in the permease domain of septal protein SepJ differentially affect functions related to multicellularity in the filamentous cyanobacterium Anabaena

Filamentous, heterocyst-forming cyanobacteria are multicellular organisms in which growth requires the activity of two interdependent cell types that exchange nutrients and regulators. Vegetative cells provide heterocysts with reduced carbon, and heterocysts provide vegetative cells with fixed nitrogen. Additionally, heterocyst differentiation from vegetative cells is regulated by inhibitors of differentiation produced by prospective heterocysts and heterocysts. Proteinaceous structures known as septal junctions join the cells in the filament. The SepJ protein is involved in formation of septal junctions in the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. SepJ bears extra-membrane and membrane (permease) domains and is located at the cell poles in the intercellular septa of the filament. Here we created Anabaena mutants that produce SepJ proteins altered in the permease domain. Some of these mutant SepJ proteins did not provide functions needed for Anabaena to form long filaments and (in some cases) differentiate heterocysts, identifying amino acids and amino acid stretches that are important for the structure or function of the protein. Some other mutant SepJ proteins fulfilled filamentation and heterocyst differentiation functions but failed to provide normal communication function assessed via the intercellular transfer of the fluorescent marker calcein. These mutant SepJ proteins bore mutations in amino acids located at the cytoplasmic face of the permease, which could affect access of the fluorescent marker to the septal junctions. Overall, the data are consistent with the idea that SepJ carries out multiple roles in the multicellular function of the Anabaena filament

NRT2.4 and NRT2.5 Are Two Half-Size Transporters from the Chlamydomonas NRT2 Family

The NRT2 transporters mediate High Affinity Nitrate/NitriteTransport (HAN/NiT), which are essential for nitrogen acquisition from these inorganic forms. The NRT2 proteins are encoded by a multigene family in plants, and contain 12 transmembrane-spanning domains. Chlamydomonas reinhardtii has six NRT2, two of which (NRT2.5 and NRT2.4) are located in Chromosome III, in tandem head to tail. cDNAs for these genes were isolated and their sequence revealed that they correspond to half-size NRT2 transporters each containing six transmembrane domains. NRT2.5 has long N- and C- termini sequences without known homology. NRT2.4 also contains long termini sequences but smaller than NRT2.5. Expression of both studied genes occurred at a very low level, slightly in darkness, and was not modified by the N or C source. Silencing of NRT2.4 by specific artificial miRNA resulted in the inhibition of nitrite transport in the absence of other HANNiT (NRT2.1/NAR2) in the cell genetic background. Nitrite transport activity in the Hansenula polymorpha Dynt::URA3 Leu2 mutant was restored by expressing CrNRT2.4. These results indicate that half-size NRT2 transporters are present in photosynthetic organisms and that NRT2.4 is a HANiT