Biology subjects

Avelar-Rivas, J. A.

Publications and source records attributed to Avelar-Rivas, J. A..

7 recordsLinked to original sources

bioRxiv2026

Domestication and deep lineage divergence define two discrete trajectories in Kluyveromyces marxianus

Although genomics has greatly improved our ability to detect population structure and genetic divergence, it remains difficult to determine when diversity within a recognized species reflects continuous variation and when it marks the emergence of discrete evolutionary lineages. In yeasts, population-genomic studies often reveal overlapping signatures of environmental association, admixture, and domestication, making this distinction especially challenging. By analyzing 178 globally sampled genomes from Kluyveromyces marxianus, an emerging yeast of biotechnological interest, we show that diversity within this species resolves into two contrasting evolutionary trajectories that do not map onto broad geographic origin. Most industrial and clinical isolates belong to a lineage marked by gene loss, aneuploidy, and reduced fertility, consistent with genomic hallmarks of domestication. In contrast, isolates confined to traditional agave fermentations in Mexico and South Africa form a highly distinct lineage, separated from the other lineages by up to 4.8% genome-wide nucleotide divergence, widespread reciprocal monophyly, no detectable recent gene flow, and reduced mating compatibility despite co-occurrence with other lineages. Together, these results show that within a single yeast species, domestication-associated genome remodeling and deep lineage divergence can define distinct trajectories, with implications for strain selection in biotechnology.

evolutionary biology↗

bioRxiv2025

Ecological divergence of sympatric Saccharomyces species across wild and fermentative environments in the neotropics

The common yeast Saccharomyces cerevisiae is widely associated with anthropogenic habitats and dominates agave fermentations in Mexico, despite the absence of starter cultures in artisanal production. Yet, the origins and dispersal of the microorganisms involved in this fermentation system--including wild S. cerevisiae and its sister species S. paradoxus--remain poorly understood. Here, we analyzed the distribution of these two species across three regions in Mexico by collecting a total of 861 samples from 15 traditional distilleries and 25 nearby natural sites, including tree bark, insects, fermentation tanks, and distillery surfaces. Among 4,006 isolates identified by MALDI-TOF biotyping, S. cerevisiae and S. paradoxus were recovered at overall rates of 21% and 3.4%, respectively, with the former more frequently found in distilleries and the latter in natural habitats. Notably, Saccharomyces isolates were not exclusively associated with oak trees, as strains were also recovered from leguminous, pine, and Anacardiaceae trees, suggesting that the oak specialization observed in temperate regions may not hold in tropical environments. Genome sequencing of 100 Saccharomyces isolates and SNP-based analyses showed that S. cerevisiae strains clustered by geography, not by substrate, and were largely confined to two Mexican Agave clades, with minor representation from the North American Oak, Pacific West Coast, and Wine clades. Strains isolated from agave fermentations belonged to the same populations as those from plant substrates, with insects, especially Drosophilidae, likely mediating their dispersal. Meanwhile, S. paradoxus isolates grouped into the SpA (Eurasian) and SpB (North American) lineages, with three novel SpB subclades identified. Intriguingly, one of these, the SpB_MxAgave population, was exclusively associated with agave fermentations, providing the first evidence of a persistent association of S. paradoxus with an anthropogenic habitat. Our study sheds light on the ecological dynamics and diversity of S. cerevisiae and S. paradoxus populations in the neotropics.

microbiology↗

bioRxiv2024

Recurrent introgression and geographical stratification shape Saccharomyces cerevisiae in the Neotropics

HighlightsO_LIPhylogenetic analyses of S. cerevisiae isolates from agave fermentation reveal novel clades within the Neotropical cluster. C_LIO_LIThe Neotropical cluster shows geographical population structure. C_LIO_LIMultiple pulses of interspecific introgression are part of the evolutionary history of S. cerevisiae in the Neotropics C_LI From yeasts to humans, introgressive hybridization significantly influences the evolutionary history of living organisms by introducing new genetic diversity. Strains of Saccharomyces cerevisiae worldwide exhibit introgressions from the sister species S. paradoxus, despite the average sequence identity between these species being lower than 90%. While S. cerevisiae isolates from the Neotropics are known for their high levels of introgression, the evolutionary events leading to the unusually high prevalence of them remain unclear. Here, we sequenced 216 S. cerevisiae isolates living in open agave fermentation across Mexico, a habitat at the interface of natural and industrial environments. The genomes of these strains revealed considerable genetic diversity and population structure linked to geographic distribution, which had been overlooked due to undersampling of this megadiverse region. These strains, along with those from French Guiana, Ecuador, and Brazil, form a broader Neotropical phylogenetic cluster that is notably enriched in introgressed DNA. Surprisingly, the origins and conservation patterns of introgressions indicate multiple hybridization events, suggesting an unprecedented scenario of flexible species barriers in this region. Our findings underscore concurrent evolutionary processes--geographical stratification and multiple introgressions--that shape the genomes of a diverse lineage of S. cerevisiae. Neotropical yeasts thus provide a natural laboratory for exploring the mechanisms and adaptive significance of introgressive hybridization in eukaryotic genome evolution.

evolutionary biology↗

bioRxiv2023

Yeast diversity in open agave fermentations across Mexico

Yeasts are a diverse group of fungal microorganisms that are widely used to produce fermented foods and beverages. In Mexico, open fermentations are used to obtain spirits from agave plants. Despite the prevalence of this traditional practice throughout the country, yeasts have only been isolated and studied from a limited number of distilleries. To systematically describe the diversity of yeast species from open agave fermentations, here we generate the YMX.1.0 culture collection by isolating 4,524 strains from 68 sites in diverse climatic, geographical, and biological contexts. We used MALDI-TOF mass spectrometry for taxonomic classification and a subset of the strains was verified by ITS and D1/D2 sequencing. The most abundant species isolated from all producing regions were Saccharomyces cerevisiae, Pichia kudriavzevii, Pichia manshurica, and Kluyveromyces marxianus. Despite the great diversity of environmental conditions and production practices the composition of yeast communities remained largely homogeneous throughout locations and fermentation stages, even if less abundant but commonly occurring yeasts were considered. Furthermore, ITS and D1/D2 sequencing revealed two candidate new species of Saccharomycetales. To explore the intraspecific variation of the yeasts from agave fermentations, we conducted genome sequencing on four isolates of the non-conventional yeast Kazachstania humilis. The genomes of these four strains were considerably distinct from other genomes of the same species, suggesting that they belong to a different population. Our work contributes to the understanding and conservation of an open fermentation system of great cultural and economic importance, providing a valuable resource to study the biology and genetic diversity of microorganisms living at the interface of natural and human-associated environments. TAKE AWAYO_LIWe isolated and identified 4,524 yeast strains from open agave fermentations in Mexico. C_LIO_LIYeast communities remained largely homogeneous throughout diverse locations. C_LIO_LIKazachstania humilis genomes differed significantly from isolates in other regions of the world. C_LIO_LIWe report two candidate new species related to the Pichia clade. C_LI

microbiology↗

bioRxiv2022

Genomewide identification of subtelomeric silencing factors in budding yeast

Subtelomeric gene silencing is the negative transcriptional regulation of genes located close to telomeres. This phenomenon occurs in a variety of eukaryotes with salient physiological implications, such as cell adherence, virulence, immune-system escape, and aging. The process has been widely studied in the budding yeast Saccharomyces cerevisiae, where genes involved in this process have been identified mostly on a gene-by-gene basis. Here, we introduce a quantitative approach to study subtelomeric gene silencing, that couples the classical URA3 reporter with GFP monitoring, amenable to high-throughput flow cytometry analysis. This reporter was integrated into several subtelomeric loci in the genome, where it showed a gradual range of silencing effects. By crossing strains with this dual reporter at the COS12 and YFR057W subtelomeric query loci with gene-deletion mutants, we carried out a genome-wide, comprehensive screen for subtelomeric-silencing factors. The approach was replicable and allowed detection of expression changes caused by previously described silencing factors. We also identified new molecular players affecting this process, most of which are related to functions underlying chromatin conformation. This was the case of LGE1, a novel silencing factor herein reported, associated with histone ubiquitination. Our strategy can be readily combined with other reporters and gene perturbation collections, making it a versatile tool to study gene silencing at a genome-wide scale.

genetics↗

bioRxiv2019

A Competitive-Aging Method for Quantitative Genetic Analysis of the Chronological Lifespan of Saccharomyces cerevisiae

The chronological lifespan of budding yeast is a model of aging and age-related diseases. This paradigm has recently allowed genome-wide screening of genetic factors underlying post-mitotic viability in a simple unicellular system, which underscores its potential to provide a comprehensive view of the aging process. However, results from different large-scale studies show little overlap and typically lack quantitative resolution to derive interactions among different aging factors. We previously introduced a sensitive, parallelizable approach to measure the chronological-lifespan effects of gene deletions based on the competitive aging of fluorescence-labeled strains. Here, we present a thorough description of the method, including an improved multiple-regression model to estimate the association between death rates and fluorescent signals, which accounts for possible differences in growth rate and experimental batch effects. We illustrate the experimental procedure--from data acquisition to calculation of relative survivorship--for ten deletion strains with known lifespan phenotypes, which is achieved with high technical replicability. We apply our method to screen for gene-drug interactions in an array of yeast deletion strains, which reveals a functional link between protein glycosylation and lifespan extension by metformin. Competitive-aging screening coupled to multiple-regression modeling provides a powerful, straight-forward way to identify aging factors in yeast and their interactions with pharmacological interventions.

genetics↗

bioRxiv2017

Genome-Wide Mechanisms of Lifespan Extension by Dietary Restriction in Yeast

Dietary restriction is arguably the most promising non-pharmacological intervention to extend human life and health span. Yet, only few genetic regulators mediating the cellular response to dietary restriction are known, and the question remains which other transcription factors and regulatory pathways are involved. To gain a comprehensive view of how lifespan extension under dietary restriction is elicited, we screened the chronological lifespan of most gene deletions of Saccharomyces cerevisiae under two dietary regimens, restricted and non-restricted. We identified 472 mutants with enhanced or diminished extension of lifespan by dietary restriction. Functional analysis of such dietary-restriction genes revealed novel processes underlying longevity specifically by dietary restriction. Importantly, this set of genes allowed us to generate a prioritized catalogue of transcription factors orchestrating the dietary-restriction response, which underscored the relevance of cell-cycle arrest control as a key mechanism of chronological longevity in yeast. We show that the transcription factor Ste12 is needed for full lifespan extension and cell-cycle arrest in response to nutrient limitation; linking the pheromone/invasive growth pathway with cell survivorship. Strikingly, STE12 overexpression was sufficient to extend chronological lifespan under non-restricted conditions. Our global picture of the genetic players of longevity by dietary restriction highlights intricate regulatory cross-talks in aging cells.

genetics↗