Browsing by Author "Yoder, John H."

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    Abdominal segment reduction Development and evolution of a deeply fixed trait
    (Landes Biocience, 2012) Yoder, John H.; University of Alabama Tuscaloosa
    When a new student first begins to push flies, an immediate skill that must be learned is sorting the sexes. In Drosophila melanogaster several sexually dimorphic characters can be used to readily distinguish males from females including abdominal pigmentation, male sex combs and genital morphology. Another, often-overlooked, sexual dimorphism is adult abdominal segment number. Externally, adult Drosophila males possess one fewer abdominal segment than females; the terminal pregenital segment apparently either absent or fused with the next-most anterior segment. Beyond known roles for the homeotic protein Abdominal-B (Abd-B) and the sex-determining transcription factor Doublesex (Dsx) as key regulators of this trait, surprisingly little is known about either the morphogenetic processes or the downstream genetics responsible for patterning these events. We have explored both and found that rapid epithelial reorganization during pupation eliminates a nascent terminal male segment. We found this Abd-B-dependent process results from sex-and segment-specific regulation of diverse developmental targets including the wingless gene and surprisingly, dsx itself.(1,2) Here, I review our observations and discuss this trait as a model to explore both dynamics of epithelial morphogenesis as well as the evolution of developmental mechanisms.
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    Drosophila Pupal Abdomen Immunohistochemistry
    (MyJove Corporation, 2011) Wang, Wei; Yoder, John H.; University of Alabama Tuscaloosa
    The Drosophila pupal abdomen is an established model system for the study of epithelial morphogenesis and the development of sexually dimorphic morphologies(1-3). During pupation, which spans approximately 96 hours (at 25 degrees C), proliferating populations of imaginal cells replace the larval epidermis to generate the adult abdominal segments. These imaginal cells, born during embryogenesis, exist as lateral pairs of histoblast nests in each abdominal segment of the larvae. Four pairs of histoblast nests give rise to the adult dorsal cuticle (anterior and posterior dorsal nests), the ventral cuticle (ventral nests) and the spiracles associated with each segment (spiracle nests)(4). Upon puparation, these diploid cells (distinguishable by size from the larger polyploid larval epidermal cells-LECs) begin a stereotypical process of proliferation, migration and replacement of the LECs. Various molecular and genetic tools can be employed to investigate the contributions of genetic pathways involved in morphogenesis of the adult abdomen. Ultimate adult phenotypes are typically analyzed following dissection of adult abdominal cuticles. However, investigation of the underlying molecular processes requires immunohistochemical analyses of the pupal epithelium, which present unique challenges. Temporally dynamic morphogenesis and the interactions of two distinct epithelial populations (larval and imaginal) generate a fragile tissue prone to excessive cell loss during dissection and subsequent processing. We have developed methods of dissection, fixation, mounting and imaging of the Drosophila pupal abdominem epithelium for immunohistochemical studies that generate consistent high quality samples suitable for confocal or standard fluorescent microscopy.
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    Gain of cis-regulatory activities underlies novel domains of wingless gene expression in Drosophila
    (National Academy of the Sciences, 2015) Koshikawa, Shigeyuki; Giorgianni, Matt W.; Vaccaro, Kathy; Kassner, Victoria A.; Yoder, John H.; Werner, Thomas; Carroll, Sean B.; University of Wisconsin Madison; Howard Hughes Medical Institute; Kyoto University; University of Alabama Tuscaloosa; Michigan Technological University
    Changes in gene expression during animal development are largely responsible for the evolution of morphological diversity. However, the genetic and molecular mechanisms responsible for the origins of new gene-expression domains have been difficult to elucidate. Here, we sought to identify molecular events underlying the origins of three novel features of wingless (wg) gene expression that are associated with distinct pigmentation patterns in Drosophila guttifera. We compared the activity of cis-regulatory sequences (enhancers) across the wg locus in D. guttifera and Drosophila melanogaster and found strong functional conservation among the enhancers that control similar patterns of wg expression in larval imaginal discs that are essential for appendage development. For pupal tissues, however, we found three novel wg enhancer activities in D. guttifera associated with novel domains of wg expression, including two enhancers located surprisingly far away in an intron of the distant Wnt10 gene. Detailed analysis of one enhancer (the vein-tip enhancer) revealed that it overlapped with a region controlling wg expression in wing crossveins (crossvein enhancer) in D. guttifera and other species. Our results indicate that one novel domain of wg expression in D. guttifera wings evolved by co-opting pre-existing regulatory sequences governing gene activity in the developing wing. We suggest that the modification of existing enhancers is a common path to the evolution of new gene-expression domains and enhancers.
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    Homeotic functions of the Teashirt transcription factor during adult Drosophila development
    (Company of Biologists, 2013) Wang, Wei; Tindell, Neil; Yan, Shun; Yoder, John H.; University of Alabama Tuscaloosa
    During Drosophila development region-specific regulation of target genes by Hox proteins is modulated by genetic interactions with various cofactors and genetic collaborators. During embryogenesis one such modulator of Hox target specificity is the zinc-finger transcription factor Teashirt (Tsh) that is expressed in the developing trunk and cooperatively functions with trunk-specific Hox proteins to promote appropriate segment fate. This embryonic function of Tsh is characterized as homeotic since loss of embryonic Tsh activity leads to transformation of trunk segments toward head identity. In addition to this embryonic homeotic role, Tsh also performs vital Hox-independent functions through patterning numerous embryonic, larval and adult structures. Here we address whether the homeotic function of Tsh is maintained throughout development by investigating its contribution to patterning the adult abdomen. We show that Tsh is expressed throughout the developing abdomen and that this expression is dependent on the three Bithorax Hox proteins Ultrabithorax, Abdominal-A and Abdominal-B. Conditional reduction of Tsh activity during pupation reveals broad homeotic roles for this transcription factor throughout the adult abdomen. Additionally we show that, as during embryogenesis, the tsh paralog tiptop (tio) plays a partially redundant role in this homeotic activity. (C) 2012. Published by The Company of Biologists Ltd.
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    Utilizing the Shell-Less Aplacophorans to Uncover the Ancestral Molluscan Biomineralization Toolkit
    (University of Alabama Libraries, 2024) Yap-Chiongco, Meghan Kathleen; Kocot, Kevin M.
    Biomineralization is a dynamic biological process by which an organism produces solid, mineralized structures. This process is exemplified by members of the phylum Mollusca who form diverse mineralized structures including the characteristic molluscan shell. Mollusca is divided into two major clades--Conchifera (gastropods, bivalves, cephalopods, scaphopods, and monoplacophorans), and Aculifera, (chitons and aplacophorans). A molluscan mineralization "toolkit" containing both highly conserved genes and rapidly evolving genes with high levels of sequence novelty is supported from molecular studies of shelled conchiferans, however this remains largely unexplored within Aculifera. Aculiferan mineralized structures include the shell plates of chitons and calcareous spines and spicules (=sclerites) found in both chitons and aplacophorans. While the valves of chitons are thought to be non-homologous to the conchiferan shell, the relationship between sclerites and shells is unknown. First, I use a comparative genomic approach to study biomineralization genes through whole genome sequencing of two Solenogastres, Neomenia megatrapezata and Epimenia babai. Leveraging PacBio HiFi reads and Phase Genomics Hi-C, the highly contiguous genomes were used to analyze gene gain and loss across molluscan orthogroups. We observed some conservation in molluscan biomineralization genes with significant reduction in solenogaster lineages. Second, I use visualize expression of seven genes known to be involved in shell mineralization (SoxC, GATA2/3, Engrailed, Notch, BMP2/4, Goosecoid, and Pif) in the solenogaster Wirenia argentea using in situ hybridization. Expression of known regulatory genes in sclerite secreting tissues argue for deployment of a conserved mineralization toolkit present in at least the last common ancestor of Mollusca. Co-option of neuronal genes was also observed with expression of these genes in both the developing nervous system and sclerite-forming tissue. Additionally, I explore the diversity of the family Gymnomeniidae to aid in the establishment of W. argentea as a strong developmental model in aplacophoran research. DNA barcodes reveal the co-existence of cryptic species of the family Gymnomeniidae (including Wirenia), creating confusion in identification. Using an integrative taxonomic approach, I describe three new species of Wirenia (Wirenia bigali sp. nov., W. magdalenae sp. nov., and W. bruni sp. nov.) and improve understanding of the phylogeny and diversity of Gymnomeniidae.