Datathons: fostering equitability in data reuse in ecology.

Approaches to rapidly collecting global biodiversity data are increasingly important, but biodiversity blind spots persist. We organized a three-day Datathon event to improve the openness of local biodiversity data and facilitate data reuse by local researchers. The first Datathon, organized among microbial ecologists in Uruguay and Argentina assembled the largest microbiome dataset in the region to date and formed collaborative consortia for microbiome data synthesis.

Phenotypic, genomic and in planta characterization of Bacillus sensu lato for their phosphorus biofertilization and plant growth promotion features in soybean.

Bacillus sensu lato were screened for their capacity to mineralize organic phosphorus (P) and promote plant growth, improving nitrogen (N) and P nutrition of soybean. Isolates were identified through Type Strain Genome Server (TYGS) and Average Nucleotide Identity (ANI). ILBB95, ILBB510 and ILBB592 were identified as Priestia megaterium, ILBB139 as Bacillus wiedmannii, ILBB44 as a member of a sister clade of B. pumilus, ILBB15 as Peribacillus butanolivorans and ILBB64 as Lysinibacillus sp. These strains were evaluated for their capacity to mineralize sodium phytate as organic P and solubilize inorganic P in liquid medium. These assays ranked ILBB15 and ILBB64 with the highest orthophosphate production from phytate. Rhizocompetence and plant growth promotion traits were evaluated in vitro and in silico. Finally, plant bioassays were conducted to assess the effect of the co-inoculation with rhizobial inoculants on nodulation, N and P nutrition. These bioassays showed that B. pumilus, ILBB44 and P. megaterium ILBB95 increased P-uptake in plants on the poor substrate of sand:vermiculite and also on a more fertile mix. Priestia megaterium ILBB592 increased nodulation and N content in plants on the sand:vermiculite:peat mixture. Peribacillus butanolivorans ILBB15 reduced plant growth and nutrition on both substrates. Genomes of ILBB95 and ILBB592 were characterized by genes related with plant growth and biofertilization, whereas ILBB15 was differentiated by genes related to bioremediation. Priestia megaterium ILBB592 is considered as nodule-enhancing rhizobacteria and together with ILBB95, can be envisaged as prospective PGPR with the capacity to exert positive effects on N and P nutrition of soybean plants.

Abundance and phylogenetic distribution of eight key enzymes of the phosphorus biogeochemical cycle in grassland soils.

Grassland biomes provide valuable ecosystem services, including nutrient cycling. Organic phosphorus (Po) represents more than half of the total P in soils. Soil microorganisms release organic P through enzymatic processes, with alkaline phosphatases, acid phosphatases and phytases being the key P enzymes involved in the cycling of organic P. This study analysed 74 soil metagenomes from 17 different grassland biomes worldwide to evaluate the distribution and abundance of eight key P enzymes (PhoD, PhoX, PhoA, Nsap-A, Nsap-B, Nsap-C, BPP and CPhy) and their relationship with environmental factors. Our analyses showed that alkaline phosphatase phoD was the dataset's most abundant P-enzyme encoding genes, with a wide phylogenetic distribution. Followed by the acid phosphatases Nsap-A and Nsap-C showed similar abundance but a different distribution in their respective phylogenetic trees. Multivariate analyses revealed that pH, Tmax , SOC and soil moisture were associated with the abundance and diversity of all genes studied. PhoD and phoX genes strongly correlated with SOC and clay, and the phoX gene was more common in soils with low to medium SOC and neutral pH. In particular, P-enzyme genes tended to respond in a positively correlated manner among them, suggesting a complex relationship of abundance and diversity among them.

Comparative genomics of plant pathogenic Diaporthe species and transcriptomics of Diaporthe caulivora during host infection reveal insights into pathogenic strategies of the genus.

BACKGROUND: Diaporthe caulivora is a fungal pathogen causing stem canker in soybean worldwide. The generation of genomic and transcriptomic information of this ascomycete, together with a comparative genomic approach with other pathogens of this genus, will contribute to get insights into the molecular basis of pathogenicity strategies used by D. caulivora and other Diaporthe species. RESULTS: In the present work, the nuclear genome of D. caulivora isolate (D57) was resolved, and a comprehensive annotation based on gene expression and genomic analysis is provided. Diaporthe caulivora D57 has an estimated size of 57,86 Mb and contains 18,385 predicted protein-coding genes, from which 1501 encode predicted secreted proteins. A large array of D. caulivora genes encoding secreted pathogenicity-related proteins was identified, including carbohydrate-active enzymes (CAZymes), necrosis-inducing proteins, oxidoreductases, proteases and effector candidates. Comparative genomics with other plant pathogenic Diaporthe species revealed a core secretome present in all Diaporthe species as well as Diaporthe-specific and D. caulivora-specific secreted proteins. Transcriptional profiling during early soybean infection stages showed differential expression of 2659 D. caulivora genes. Expression patterns of upregulated genes and gene ontology enrichment analysis revealed that host infection strategies depends on plant cell wall degradation and modification, detoxification of compounds, transporter activities and toxin production. Increased expression of effectors candidates suggests that D. caulivora pathogenicity also rely on plant defense evasion. A high proportion of the upregulated genes correspond to the core secretome and are represented in the pathogen-host interaction (PHI) database, which is consistent with their potential roles in pathogenic strategies of the genus Diaporthe. CONCLUSIONS: Our findings give novel and relevant insights into the molecular traits involved in pathogenicity of D. caulivora towards soybean plants. Some of these traits are in common with other Diaporthe pathogens with different host specificity, while others are species-specific. Our analyses also highlight the importance to have a deeper understanding of pathogenicity functions among Diaporthe pathogens and their interference with plant defense activation.

Reduced tillage, cover crops and organic amendments affect soil microbiota and improve soil health in Uruguayan vegetable farming systems.

Conventional tillage and mineral fertilization (CTMF) jeopardize soil health in conventional vegetable production systems. Using a field experiment established in Uruguay in 2012, we aimed to compare the soil restoration potential of organic fertilization (compost and poultry manure) combined with conventional tillage and cover crop incorporated into the soil (CTOF) or with reduced tillage and the use of cover crop as mulch (RTOF). In 2017, table beet was cultivated under CTMF, CTOF and RTOF, and yields, soil aggregate composition and nutrients, as well as soil and table beet rhizosphere microbiota (here: bacteria and archaea) were evaluated. Microbiota was studied by high-throughput sequencing of 16S rRNA gene fragments amplified from total community DNA. RTOF exhibited higher soil aggregation, soil organic C, nutrient availability and microbial alpha-diversity than CTMF, and became more similar to an adjacent natural undisturbed site. The soil microbiota was strongly shaped by the fertilization source which was conveyed to the rhizosphere and resulted in differentially abundant taxa. However, 229 amplicon sequencing variants were found to form the core table beet rhizosphere microbiota shared among managements. In conclusion, our study shows that after only 5 years of implementation, RTOF improves soil health under intensive vegetable farming systems.

Genetic architecture of photosynthesis energy partitioning as revealed by a genome-wide association approach.

The photosynthesis process is determined by the intensity level and spectral quality of the light; therefore, leaves need to adapt to a changing environment. The incident energy absorbed can exceed the sink capability of the photosystems, and, in this context, photoinhibition may occur in both photosystem II (PSII) and photosystem I (PSI). Quantum yield parameters analyses reveal how the energy is managed. These parameters are genotype-dependent, and this genotypic variability is a good opportunity to apply mapping association strategies to identify genomic regions associated with photosynthesis energy partitioning. An experimental and mathematical approach is proposed for the determination of an index which estimates the energy per photon flux for each spectral bandwidth (Δλ) of the light incident (QI index). Based on the QI, the spectral quality of the plant growth, environmental lighting, and the actinic light of PAM were quantitatively very similar which allowed an accurate phenotyping strategy of a rice population. A total of 143 genomic single regions associated with at least one trait of chlorophyll fluorescence were identified. Moreover, chromosome 5 gathers most of these regions indicating the importance of this chromosome in the genetic regulation of the photochemistry process. Through a GWAS strategy, 32 genes of rice genome associated with the main parameters of the photochemistry process of photosynthesis in rice were identified. Association between light-harvesting complexes and the potential quantum yield of PSII, as well as the relationship between coding regions for PSI-linked proteins in energy distribution during the photochemical process of photosynthesis is analyzed.

Soil structure, nutrient status and water holding capacity shape Uruguayan grassland prokaryotic communities.

Soil microbial communities play critical roles in maintaining natural ecosystems such as the Campos biome grasslands of southern South America. These grasslands are characterized by a high diversity of soils, low available phosphorus (P) and limited water holding capacity. This work aimed to describe prokaryotic communities associated with different soil types and to examine the relationship among these soil communities, the parent material and the soil nutrient status. Five Uruguayan soils with different parent material and nutrient status, under natural grasslands, were compared. The structure and diversity of prokaryotic communities were characterized by sequencing 16S rRNA gene amplicons. Proteobacteria, Actinobacteria, Firmicutes,Verrucomicrobia, Acidobacteria, Planctomycetes and Chloroflexi were the predominant phyla. Ordination based on several distance measures was able to discriminate clearly between communities associated with different soil types. Edge-PCA phylogeny-sensitive ordination and differential relative abundance analyses identified Archaea and the bacterial phyla Firmicutes, Acidobacteria, Actinobacteria and Verrucomicrobia as those with significant differences among soil types. Canonical analysis of principal coordinates identified porosity, clay content, available P, soil organic carbon and water holding capacity as the main variables contributing to determine the characteristic prokaryotic communities of each soil type.

Genome-Wide Association Study Using Historical Breeding Populations Discovers Genomic Regions Involved in High-Quality Rice.

Rice ( L.) is one of the most important staple food crops in the world; however, there has recently been a shift in consumer demand for higher grain quality. Therefore, understanding the genetic architecture of grain quality has become a key objective of rice breeding programs. Genome-wide association studies (GWAS) using large diversity panels have successfully identified genomic regions associated with complex traits in diverse crop species. Our main objective was to identify genomic regions associated with grain quality and to identify and characterize favorable haplotypes for selection. We used two locally adapted rice breeding populations and historical phenotypic data for three rice quality traits: yield after milling, percentage of head rice recovery, and percentage of chalky grain. We detected 22 putative quantitative trait loci (QTL) in the same genomic regions as starch synthesis, starch metabolism, and cell wall synthesis-related genes are found. Additionally, we found a genomic region on chromosome 6 in the population that was associated with all quality traits and we identified favorable haplotypes. Furthermore, this region is linked to the gene that codes for a starch branching enzyme I, which is implicated in starch granule formation. In , we also found two putative QTL linked to , , and . Our study provides an insight into the genetic basis of rice grain chalkiness, yield after milling, and head rice, identifying favorable haplotypes and molecular markers for selection in breeding programs.

Resistance to Multiple Temperate and Tropical Stem and Sheath Diseases of Rice.

Stem rot and aggregated sheath spot are the two major stem and sheath diseases affecting rice (Oryza sativa L.) in temperate areas. A third fungal disease, sheath blight, is a major disease in tropical areas. Resistance to these diseases is a key objective in rice breeding programs but phenotyping is challenged by the confounding effects of phenological and morphological traits such as flowering time (FT) and plant height (PH). This study sought to identify quantitative trait loci (QTL) for resistance to these three diseases after removing the confounding effects of FT and PH. Two populations of advanced breeding germplasm, one with 316 tropical japonica and the other with 325 indica genotypes, were evaluated in field and greenhouse trials for resistance to the diseases. Phenotypic means for field and greenhouse disease resistance, adjusted by FT and PH, were analyzed for associations with 29,000 single nucleotide polymorphisms (SNPs) in tropical japonica and 50,000 SNPs in indica. A total of 29 QTL were found for resistance that were not associated with FT or PH. Multilocus models with selected resistance-associated SNPs were fitted for each disease to estimate their effects on the other diseases. A QTL on chromosome 9 accounted for more than 15% of the phenotypic variance for the three diseases. When resistance-associated SNPs at this locus from both the tropical japonica and indica populations were incorporated into the model, resistance was improved for all three diseases with little impact on FT and PH.

A strategy to recover a high-quality, complete plastid sequence from low-coverage whole-genome sequencing.

PREMISE OF THE STUDY: We developed a bioinformatic strategy to recover and assemble a chloroplast genome using data derived from low-coverage 454 GS FLX/Roche whole-genome sequencing. METHODS: A comparative genomics approach was applied to obtain the complete chloroplast genome from a weedy biotype of rice from Uruguay. We also applied appropriate filters to discriminate reads representing novel DNA transfer events between the chloroplast and nuclear genomes. RESULTS: From a set of 295,159 reads (96 Mb data), we assembled the chloroplast genome into two contigs. This weedy rice was classified based on 23 polymorphic regions identified by comparison with reference chloroplast genomes. We detected recent and past events of genetic material transfer between the chloroplast and nuclear genomes and estimated their occurrence frequency. DISCUSSION: We obtained a high-quality complete chloroplast genome sequence from low-coverage sequencing data. Intergenome DNA transfer appears to be more frequent than previously thought.