Biology subjects

Vallebueno-Estrada, M.

Publications and source records attributed to Vallebueno-Estrada, M..

8 recordsLinked to original sources

bioRxiv2026

BABYBOOM-like expression in the cowpea egg and central cellenables parthenogenesis, endosperm development, and viable haploid seed formation

Introductory Paragraph (Nature Plants format)Parthenogenesis or fertilization-independent embryogenesis occurs at low frequency in sexual plants. Expression of BABYBOOM-like (BBML) and PARTHENOGENESIS (PAR) genes in the egg cell of several diploid dicot crops induce parthenogenesis at varying frequency; however, recovery of viable haploid seeds has rarely been reported, perhaps due to a lack of viable endosperm formation. In the legume cowpea (Vigna unguiculata L. Walp), ectopic egg cell expression of the endogenous BBML homolog (VuBBML1) and PAR from Taraxacum officinale induces parthenogenesis; however, seeds abort as endosperm formation is blocked following self-pollination. Expression of VuBBML1 in both the egg cell and central cell, together with central cell fertilization following self-pollination, results in viable seeds that germinate and give rise to haploid plants. VuBBML1 has a functional role in the formation of cowpea embryo and endosperm seed compartments. This finding opens possibilities for establishing double haploid production during homozygous parental breeding, and asexual seed induction for fixing hybrid vigor in cowpea.

plant biology↗

bioRxiv2025

The influence of heavy metal stress on the evolutionary transition of teosinte to maize

Maize originated from teosinte parviglumis following a subspeciation event occurred in volcanic regions of Mesoamerica. The elucidation of the phenotypic changes that gave rise to maize have focused on the direct consequences of domestication, with no insights on how environmental factors could have influenced specific gene function and human selection. The genome of the Palomero toluqueno landrace suggested heavy metal (HM) effects on maize domestication (Vielle-Calzada et al., 2009). To test the hypothesis that HM stress influenced the evolutionary transition of teosinte to maize, we exposed both subspecies to sublethal concentrations of copper and cadmium. We also assessed the genetic diversity of three HM response genes mapping to chromosome 5 (chr.5) and previously shown to be affected by domestication: ZmHMA1, ZmHMA7 - encoding for heavy metal ATPases of the P1b family-, and ZmSKUs5, encoding for a multicopper oxidase. ZmHMA1 and ZmSKUs5 are within a genomic region containing hundreds of genes linked to QTLs with pleiotropic effects on domestication. The genomic analysis of chr.5 shows that the three genes were under strong positive selection as compared to previously identified domestication genes. Large-scale transcriptomic comparisons indicate that many other loci containing HM response genes were also positively selected across the maize genome. Exposure of teosinte parviglumis to HM stress results in a plant architecture reminiscent of extant maize, and upregulation of Teosinte branched1 (Tb1) in the meristem. ZmHMA1 and ZmHMA7 are expressed throughout development and respond to HM stress in both subspecies. ZmHMA1 is mainly involved in restricting plant height and optimizing the number of female inflorescences and seminal roots. Paleoenvironmental studies reveal a temporal and geographical convergence between volcanic eruptions and maize emergence during the early Holocene, at periods of climatic instability. Overall, these results suggest that abiotic stress influenced the evolutionary transition that gave rise to extant maize through the activity of heavy metal response genes and their phenotypic effects, as a possible consequence of volcanic activity.

plant biology↗

bioRxiv2024

In silico analysis of the evolution of root phenotypes during maize domestication in Neolithic soils of Tehuacan

Roots are essential for plant adaptation to changing environments, yet the role of roots in crop domestication remains unclear. This study examines the evolution of root phenotypes from teosinte to maize, a transition resulting in reduced nodal root number (NRN), multiseriate cortical sclerenchyma (MCS), and increased seminal root number (SRN). We reconstructed the root phenotypes of maize and teosinte, as well as the environments of the Tehuacan Valley over the last 18,000 years using a combination of ancient DNA, paleobotany, and functional-structural modeling. Our models reveal that increasing Holocene atmospheric CO2 concentrations favored the appearance of reduced NRN and MCS between 12000 to 8000 years before present (yBP), promoting deeper root systems. The advent of irrigation by 6000 yBP switched nitrogen distribution from topsoil to subsoil domains, a change which increased the utility of reduced NRN and MCS. Comparison of allelic frequencies among ancient samples ranging from 5500 to 500 yBP suggest that increased SRN may have appeared around 3500 yBP, coinciding with a period of increased human population, agricultural intensification, and soil degradation. Our results suggest that root phenotypes that enhance plant performance under nitrogen stress were important for maize adaptation to changing agricultural practices in the Tehuacan Valley. ClassificationPhysiology & Development

plant biology↗

bioRxiv2024

Exploring yield stability and the fitness landscape of maize landrace root phenotypes in silico

Integrated root phenotypes contribute to environmental adaptation and yield stability. We used the functional-structural plant/soil model OpenSimRoot_v2 to reconstruct the root phenotypes and environments of eight maize landraces to understand the phenotypic and environmental factors associated with broad adaptation. We found that accessions from low phosphorus regions have root phenotypes with shallow growth angles and greater nodal root numbers, allowing them to adapt to their native environments by improved topsoil foraging. We used machine learning algorithms to detect the most important phenotypes responsible for adaptation to multiple environments. The most important phene states responsible for stability across environments are large cortical cell size and reduced diameter of roots in nodes 5 and 6. When we dissected the components of root diameter, we observed that large cortical cell size improved growth by 28%, 23 % and 114%, while reduced cortical cell file number alone improved shoot growth by 137%, 66% and 216%, under drought, nitrogen and phosphorus stress, respectively. Functional-structural analysis of 96 maize landraces from the Americas, previously phenotyped in mesocosms in the greenhouse, suggested that parsimonious anatomical phenotypes, which reduce the metabolic cost of soil exploration, are the main phenotypes associated with adaptation to multiple environments, while root architectural traits were related to adaptation to specific environments. Our results indicate that integrated phenotypes with root anatomical phenes that reduce the metabolic cost of soil exploration will increase tolerance to stress across multiple environments and therefore improve yield stability, regardless of their root architecture.

plant biology↗

bioRxiv2023

Unified Multi-caller Ensemble (UME) generates an unbiased maize haplotype map for variable coverage whole genome data

We present a novel diversity-focused haplotype map (HapMap) that characterizes over 64.5 million maize (Zea mays ssp. mays) single nucleotide polymorphisms (SNPs) genotyped across 818 individuals from diverse backgrounds. This HapMap aims to balance the variation obtained from domesticated landraces and inbred lines, outgroup Zea spp. and more distant Tripsacum spp. in order to minimize ascertainment bias for diversity studies. Included individuals derive from public data from various experimental setups and coverages, which is challenging for standard SNP callers to accommodate. We provide evidence of coverage biases associated with standard callers that influence resulting variation and introduce a novel approach called Unified Multi-Caller Ensemble (UME), which enhances variant calling accuracy in low-coverage and mixed-coverage genomic datasets. UME corrects for coverage bias resulting from inter-sample coverage heterogeneity by leveraging evidence from variant callers with orthogonal strategies, re-calibrating the error probabilities across callers to minimize the impact of error biases inherent to a given caller. It outperforms individual strategies and excels in de novo variant calling, taking advantage of instances of higher depth reads, even in low coverage individuals, while preserving biologically informative variant relationships across coverage levels. An important feature of UME is the independence from population allele frequencies in the discovery panel, thus avoiding ascertainment bias resulting from unbalanced input genetic diversity. Discovered variants are unbiased because no population filtering is used, and the full diversity of SNPs is retained in the final variant call set to maximize the utility of the dataset for production calling newly sequenced samples. We present a strategy for filtering the recalibrated error profiles that relies on maximizing demographic signals to retain genetic relationships within the population while reducing sequencing error. After the variant discovery phase, we employ the UME production stage, which enriches genotype calling across all coverage levels, benefiting low-coverage samples. Error introduced in this process is removed through subsequent filtering. Using this approach, we generated a coverage bias-controlled maize HapMap database, providing a comprehensive representation of maize accessions and emphasizing landrace diversity. This diverse panel of domesticated maize and outgroups from across the Americas enables accurate genotyping in low-coverage samples while offering crucial context for interpreting diversity, particularly for natural diversity and paleogenomic analyses.

bioinformatics↗

bioRxiv2023

Two teosintes made modern maize

Despite its global importance as a crop with broad economic, dietary, and cultural importance, the origins of maize and its closest wild relatives remained the topic of vigorous debate for nearly a century. Molecular analyses ultimately concluded that maize was domesticated once from a common ancestor with its closest extant relative, the lowland wild grass Zea mays ssp. parviglumis. But neither the current genetic model nor earlier models based on archaeological data account for the totality of available data, and recent work has highlighted the potential contribution of a second wild relative, the highland Zea mays ssp. mexicana. Here we present a detailed population genetic analysis of the contributions of both wild taxa to modern maize diversity using the largest sample of traditional maize varieties sequenced to date. We show that all modern maize can trace its origin to an ancient admixture event between domesticated ancient maize and Zea mays ssp. mexicana in the highlands of Mexico ca 5300 cal BP, some 4,000 years after domestication began. We show that variation in admixture is a key component of modern maize genetic and phenotypic diversity, both at the level of individual loci and as a factor driving a substantial component of additive genetic variation across a number of agronomic traits. Our results clarify the long-debated origin of modern maize, highlight the potential contributions of crop wild relatives to agronomic improvement, and raise new questions about the anthropogenic mechanisms underlying multiple waves of dispersal throughout the Americas. One-Sentence SummaryOur results clarify the long-debated origin of modern maize and highlight the contributions of crop wild relatives to the agronomic improvement of modern varieties.

evolutionary biology↗

bioRxiv2022

Domestication and lowland adaptation of coastal preceramic maize from Paredones, Peru

Archaeological cobs from Paredones and Huaca Prieta (Peru) are phenotypically indistinguishable from modern maize. This contrasts with the earliest Mexican macro-specimens from Guila Naquitz and San Marcos, which are phenotypically intermediate even though they date more recently in time. These observations suggest at least two alternative scenarios, one in which maize was domesticated earlier than previously thought in the lowland Mesoamerica, followed by rapid lowland dispersal to Peru, and another in which maize was independently domesticated in South America and subsequently lost, as current evidence supports a single origin for all modern maize. To gain insights into the origins of ancient Peruvian maize, we sequenced DNA from three Paredones specimens dating 6775 to 5000 calibrated years before present (BP) and conducted comparative analyses with two teosinte subspecies (Zea mays ssp. mexicana and parviglumis) and extant maize, including highland and lowland landraces from Mesoamerica and South America. We show that Paredones maize originated from the same domestication event as Mexican maize and was domesticated by 6775 BP, implying rapid dispersal followed by improvement. Paredones maize show minimal levels of gene flow from mexicana, smaller than those observed in teosinte parviglumis. It also harbors significantly fewer alleles previously found to be adaptive to highlands, but not of alleles adaptive to lowlands, supporting a lowland migration route. Our overall results imply that Paredones maize originated in Mesoamerica, arrived in Peru without mexicana introgression through a rapid lowland migration route, and underwent improvements in both Mesoamerica and South America. Significance StatementThe coastal Peruvian preceramic sites of Paredones and Huaca Prieta provide the earliest known maize macro-remains. Found more than 3,800 km away from the maize center of origin and presenting a phenotypically modern cob constitution relative to their antiquity, these specimens represent a paradox for understanding maize evolution and dispersal. We show that Paredones maize originated in Mesoamerica, like all known maize, and arrived in South America without introgression from the teosinte mexicana. Since modern maize has substantial contributions from mexicana, it raises the question of when mexicana introgression spread to South America. Paredones maize preferentially shares adaptive allelic diversity with lowland Mesoamerican samples, suggesting a migration route probably associated with a coastal corridor previously identified with archeological findings.

plant biology↗

bioRxiv2022

Multi-GBS: A massively multiplexed GBS-based protocol optimized for large, repetitive conifer genomes

Reduced representation library approaches are still a valuable tool for breeding and population and ecological genomics, even with impressive increases in sequencing capacity in recent years. Unfortunately, current approaches only allow for multiplexing up to 384 samples. To take advantage of increased sequencing capacity, we present Multi-GBS, a massively multiplexable extension to Genotyping-by-Sequencing that is also optimized for large conifer genomes. In Norway Spruce, a highly repetitive 20Gbp diploid genome with high population genetic variation, we call over a million variants in 32 genotypes from three populations, two natural forest in the Alps and Bohemian Alps, and a managed population from southeastern Austria using the existing TASSEL GBSv2 pipeline. Metric MDS analysis of replicated genotypes shows that technical bias in resulting genotype calling is minimal and that populations cluster in biologically meaningful ways.

genomics↗