Biology subjects

Tibbs-Cortes, L. E.

Publications and source records attributed to Tibbs-Cortes, L. E..

7 recordsLinked to original sources

bioRxiv2026

Visualizing and integrating linear and graph pangenomes at the Maize Genetics and Genomics Database

Genome visualization has existed for as long as assembled genomes, with an array of tools and approaches to meet researchers' needs. The genome browser is one of these tools, and it has become a critical analytical resource for geneticists, genome biologists, and breeders. The evolution of genome browser capabilities is ongoing, and the USDA-ARS Maize Genetics and Genomics Database (MaizeGDB) has implemented JBrowse2, the most recent iteration of JBrowse. It includes multiple genome browser and alignment views, demonstrating pangenome visualization capability and permitting sophisticated functional characterization of maize loci. Described here also is MaizeGDB's new Pangenome Viewer, which integrates pangenome graph views with linear browser visualization to obtain an on-the-fly, interactive visual snapshot of structural variation across a pangenome at user-selected loci, with zoom capabilities and statistical and variant information for each subgraph. Finally, we demonstrate how different MaizeGDB pangenome pipelines complement one another to help guide accurate analyses. This functionality can lead to more precise characterization of loci that confer important agronomic traits, resulting in better outcomes for farmers and the public.

genomics↗

bioRxiv2025

MaizeGDB Phylostrata Tool: Exploring evolutionary origins of maize proteins

MotivationPhylostratigraphic analysis identifies the evolutionary origins and level of conservation of proteins, facilitating research in evolutionary biology and comparative genomics. ResultsWe developed the MaizeGDB Phylostrata Tool, a custom web application that enables users to explore the evolutionary origins of maize proteins. This tool features interactive visualizations and detailed gene pages incorporating subcellular localization, Gene Ontology (GO) terms, and other resources for homologs. Full-proteome downloads are available for 26 maize inbreds (B73 and the NAM founders). We also provide an updated version of the phylostratr R package that makes it more robust to taxonomic updates, as well as example scripts for phylostratigraphic analysis and webtool development for the use of researchers and curators of other species. Availability and ImplementationThe MaizeGDB Phylostrata Tool is freely available at phylostrata.maizegdb.org. Scripts used for the analysis and web tool are available at https://github.com/LTibbs/PhylostrataWebtool. Contactcarson.andorf@usda.gov

bioinformatics↗

bioRxiv2023

Streamline unsupervised machine learning to survey and graph indel-based haplotypes from pan-genomes

Identification and visualization of large insertion and deletion (indel) polymorphisms, which contribute significantly to natural phenotypic variation, are challenge from a pan-genome. Here, through streamlining two unsupervised machine learning algorithms, we developed a BRIDGEcereal webapp for surveying and graphing indel-based haplotypes for genes of interest from publicly accessible pangenomes. Over hundreds of assemblies from five major cereals were compiled. We demonstrated the potential of BRIDGEcereal in exploring natural variation with wheat candidate genes within QTLs and GWAS intervals. BRIDGEcereal is available from https://bridgecereal.scinet.usda.gov.

bioinformatics↗

bioRxiv2022

Fluorescence In Situ Hybridization Provides Evidence for the Presence of the Endosymbiotic Bacterial Genus Rickettsia in Tardigrades

Many ecdysozoans harbor endosymbiotic bacteria within their microbiota, and these endosymbionts can have a range of positive and negative effects on their hosts. Recent 16S rRNA gene amplicon sequencing studies have provided evidence for endosymbionts within the tardigrade microbiota. In a previous study amplicon study, we determined that sequences corresponding to the endosymbiotic genus Rickettsia were significantly more associated with tardigrades than with the substrate from which they were isolated. Here, we performed fluorescence in situ hybridization (FISH) using a Rickettsia-specific probe, RickB1, to determine if Rickettsia could be found in tardigrades. RickB1 and a probe targeting most bacteria, EUB338, colocalized within the tissues of tardigrades, indicating the presence of Rickettsia. We also performed FISH using RickB1 and a nonsense probe which allowed us to distinguish between false positives and true positives. This method revealed RickB1 signals in tardigrades that were not due to erroneous probe binding, providing further evidence that Rickettsia is present in tardigrades. Future research will be necessary to determine the effects, if any, of this endosymbiont on its tardigrade host.

microbiology↗

bioRxiv2022

Leveraging prior biological knowledge improves prediction of tocochromanols in maize grain

With an essential role in human health, tocochromanols are mostly obtained by consuming seed oils; however, the vitamin E content of the most abundant tocochromanols in maize grain is low. Several large-effect genes with cis-acting variants affecting mRNA expression are mostly responsible for tocochromanol variation in maize grain, with other relevant associated quantitative trait loci (QTL) yet to be fully resolved. Leveraging existing genomic and transcriptomic information for maize inbreds could improve prediction when selecting for higher vitamin E content. Here, we first evaluated a multikernel genomic best linear unbiased prediction (MK-GBLUP) approach for modeling known QTL in the prediction of nine tocochromanol grain phenotypes (12-21 QTL per trait) within and between two panels of 1,462 and 242 maize inbred lines. On average, MK-GBLUP models improved predictive abilities by 7.0 to 13.6% when compared to GBLUP. In a second approach with a subset of 545 lines from the larger panel, the highest average improvement in predictive ability relative to GBLUP was achieved with a multi-trait GBLUP model (15.4%) that had a tocochromanol phenotype and transcript abundances in developing grain for a few large-effect candidate causal genes (1-3 genes per trait) as multiple response variables. Taken together, our study illustrates the enhancement of prediction models when informed by existing biological knowledge pertaining to QTL and candidate causal genes. Core IdeasO_LIWith varying levels of vitamin E activity, tocochromanols found in maize grain are essential for human health C_LIO_LISelecting for higher vitamin E content in maize grain can be enhanced with genomic prediction C_LIO_LIPrediction models leveraging existing biological knowledge were evaluated in two panels of maize inbred lines C_LIO_LIMultikernel prediction models based on previously identified QTL improved predictive ability C_LIO_LIA multi-trait prediction model that had transcript abundances of a few large-effect causal genes performed the best C_LI

genetics↗

bioRxiv2022

Combining GWAS and TWAS to identify candidate causal genes for tocochromanol levels in maize grain

Tocochromanols (tocopherols and tocotrienols, collectively vitamin E) are lipid-soluble antioxidants important for both plant fitness and human health. The main dietary sources of vitamin E are seed oils that often accumulate high levels of tocopherol isoforms with lower vitamin E activity. The tocochromanol biosynthetic pathway is conserved across plant species but an integrated view of the genes and mechanisms underlying natural variation of tocochromanol levels in seed of most cereal crops remains limited. To address this issue, we utilized the high mapping resolution of the maize Ames panel of [~]1,500 inbred lines scored with 12.2 million single-nucleotide polymorphisms to generate metabolomic (mature grain tocochromanols) and transcriptomic (developing grain) data sets for genetic mapping. By combining results from genome- and transcriptome-wide association studies, we identified a total of 13 candidate causal gene loci, including five that had not been previously associated with maize grain tocochromanols: four biosynthetic genes (arodeH2 paralog, dxs1, vte5, and vte7) and a plastid S-adenosyl methionine transporter (samt1). Expression quantitative trait locus (eQTL) mapping of these 13 gene loci revealed that they are predominantly regulated by cis-eQTL. Through a joint statistical analysis, we implicated cis-acting variants as responsible for co-localized eQTL and GWAS association signals. Our multi-omics approach provided increased statistical power and mapping resolution to enable a detailed characterization of the genetic and regulatory architecture underlying tocochromanol accumulation in maize grain and provided insights for ongoing biofortification efforts to breed and/or engineer vitamin E and antioxidant levels in maize and other cereals.

genetics↗

bioRxiv2022

Tardigrade community microbiomes in North American orchards include putative endosymbionts and plant pathogens

The microbiome of tardigrades, a phylum of microscopic animals best known for their ability to survive extreme conditions, is poorly studied worldwide and completely unknown in North America. An improved understanding of tardigrade-associated bacteria is particularly important because tardigrades have been shown to act as vectors of the plant pathogen Xanthomonas campestris in the laboratory. However, the potential role of tardigrades as reservoirs and vectors of phytopathogens has not been investigated further. This study analyzed the microbiota of tardigrades from six apple orchards in central Iowa, USA, and is the first analysis of the microbiota of North American tardigrades. It is also the first ever study of the tardigrade microbiome in an agricultural setting. We utilized 16S rRNA gene amplicon sequencing to characterize the tardigrade community microbiome across four contrasts: location, substrate type (moss or lichen), collection year, and tardigrades versus their substrate. Alpha diversity of the tardigrade community microbiome differed significantly by location and year of collection but not by substrate type. Our work also corroborated earlier findings, demonstrating that tardigrades harbor a distinct microbiota from their environment. We also identified tardigrade-associated taxa that belong to genera known to contain phytopathogens (Pseudomonas, Ralstonia, and the Pantoea/Erwinia complex). Finally, we observed members of the genera Rickettsia and Wolbachia in the tardigrade microbiome; because these are obligate intracellular genera, we consider these taxa to be putative endosymbionts of tardigrades. These results suggest the presence of putative endosymbionts and phytopathogens in the microbiota of wild tardigrades in North America.

microbiology↗