Biology subjects

Theron, A.

Publications and source records attributed to Theron, A..

5 recordsLinked to original sources

bioRxiv2024

Transposable element accumulation drives genome size increase in Hylesia metabus (Lepidoptera: Saturniidae), an urticating moth species from South America

We present the first nuclear genome assembly and a complete mitogenome for Hylesia metabus (Arthropoda; Insecta; Lepidoptera; Saturniidae). The assembled nuclear genome sequence is 1,271 Mb long, which is among the 10 largest lepidopteran genome assemblies published to date. It is scaffolded in 31 pseudo chromosomes, has a BUSCO score of 99.5%, and has a highly conserved synteny compared to phylogenetically close species. Repetitive elements make up 67% of the nuclear genome and are mainly located in intergenic regions, among which LINEs were predominant, with CR1-Zenon being the most abundant. Phylogenetic and comparative analyses of H. metabus assembly and 17 additional Saturniidae and Sphingidae assemblies suggested that an accumulation of repetitive elements likely led to the increased size of H. metabus genome. Gene annotation using Helixer identified 26,122 transcripts. The Z scaffold was identified using both a synteny analysis and variations of coverage for two resequenced male and female H. metabus. The H. metabus nuclear genome and mitogenome assemblies can be found and browsed on the BIPAA website and constitute useful resources for future population and comparative genomics studies.

genomics↗

bioRxiv2023

The diallelic self-incompatibility system in Oleaceae is controlled by a hemizygous genomic region expressing a gibberellin pathway gene

Sexual reproduction in flowering plants is commonly controlled by self-incompatibility (SI) systems that are either homomorphic (and typically governed by large numbers of distinct allelic specificities), or heteromorphic (and then typically governed by only two allelic specificities). The SI system of the Oleaceae family is a striking exception to this rule and represents an evolutionary conundrum, with the long-term maintenance of only two allelic specificities, but often in the complete absence of morphological differentiation between them. To elucidate the genomic architecture and molecular bases of this highly unusual SI system, we obtained chromosome-scale genome assemblies of Phillyrea angustifolia individuals belonging to the two SI specificities and connected them to a genetic map. Comparison of the S-locus region revealed a segregating 543-kb indel specific to one of the two specificities, suggesting a hemizygous genetic architecture. Only one of the predicted genes in this indel is conserved with the olive tree Olea europaea, where we also confirmed the existence of a segregating hemizygous indel. We demonstrated full association between presence/absence of this gene and the SI groups phenotypically assessed across six distantly related Oleaceae species. This gene is predicted to be involved in catabolism of the Gibberellic Acid (GA) hormone, and experimental manipulation of GA levels in developing buds modified the male and female SI responses in an S-allele-specific manner. Thus, our results provide a unique example of a reproductive system where a single conserved gibberellin-related gene in a 500-700kb hemizygous indel underlies the long-term maintenance of two groups of reproductive compatibility.

evolutionary biology↗

bioRxiv2023

The Marchantia pangenome reveals ancient mechanisms of plant adaptation to the environment

Plant adaptation to a terrestrial life 450 million years ago played a major role in the evolution of life on Earth. This shift from an aquatic environment has been mostly studied by focusing on flowering plants. Here, we gathered a collection of 133 accessions of the non-vascular plants Marchantia polymorpha and studied its intraspecific diversity using selection signature analyses, genome-environment association study and a gene-centered pangenome. We identified adaptive features shared with flowering plants, such as peroxidases or nucleotide-binding and leucine-rich repeat (NLR), which likely played a role in the adaptation of the first land plants to the terrestrial habitat. The M. polymorpha pangenome also harbored lineage-specific accessory genes absent from seed plants. We conclude that different land plants lineages still share many elements from the genetic toolkit evolved by their most recent common ancestor to adapt to the terrestrial habitat, refined by lineage specific polymorphisms and gene family evolutions.

plant biology↗

bioRxiv2020

Multistage and transmission-blocking targeted antimalarials discovered from the open-source MMV Pandemic Response Box

New chemical matter is needed to target the divergent biology associated with the different life cycle stages of Plasmodium. Here, we report the parallel screening of the Medicines for Malaria Venture Pandemic Response Box to identify multistage-active and stage-specific compounds against various life cycle stages of Plasmodium parasites (asexual parasites, stage IV/V gametocytes, gametes, oocysts and liver stages) and for endectocidal activity. Hits displayed unique chemotypes and included two multistage-active compounds, 16 asexual-targeted, six with prophylactic potential and ten gametocyte-targeted compounds. Notably, four structurally diverse gametocyte-targeted compounds with potent transmission-blocking activity were identified: the JmjC inhibitor ML324, two azole antifungals including eberconazole, and the antitubercular clinical candidate SQ109. Besides ML324, none of these have previously attributed antiplasmodial activity, emphasizing the success of de novo parallel screening against different Plasmodium stages to deliver leads with novel modes-of-action. Importantly, the discovery of such transmission-blocking targeted compounds covers a previously unexplored base for delivery of compounds required for malaria elimination strategies.

microbiology↗

bioRxiv2019

Piezo1 is required for outflow tract and aortic valve development.

Aims-During embryogenesis, the onset of circulatory blood flow generates a variety of hemodynamic forces which reciprocally induce changes in cardiovascular development and performance. It has been known for some time that these forces can be detected by as yet unknown mechanosensory systems which in turn promote cardiogenic events such as outflow tract and aortic valve development. PIEZO1 is a mechanosensitive ion channel present in endothelial cells where it serves to detect hemodynamic forces making it an ideal candidate to play a role during cardiac development. We sought to determine whether PIEZO1 is required for outflow tract and aortic valve development. Methods and results-By analysing heart development in zebrafish we have determined that piezo1 is expressed in the developing outflow tract where it serves to detect hemodynamic forces. In particular, we have found that mechanical forces generated during the cardiac cycle activate Piezo1 which triggers nitric oxide to be released in the outflow tract. Consequently, disrupting Piezo1 signalling leads to defective outflow tract and aortic valve development and indicates this gene may be involved in the etiology of congenital heart diseases. Based on these findings, we analysed genomic data generated from a cohort of bicuspid aortic valve patients and identified 3 probands who each harboured a novel variant in PIEZO1. Subsequent in vitro and in vivo assays indicates that these variants behave as dominant negatives leading to an inhibition of normal PIEZO1 mechanosensory activity and defective aortic valve development. Conclusion-These data indicate that the mechanosensitive ion channel piezo1 is required for OFT and aortic valve development and, furthermore, dominant negative variants of PIEZO1 appear to be associated with BAV in humans.

developmental biology↗