Biology subjects

Brown, F. D.

Publications and source records attributed to Brown, F. D..

3 recordsLinked to original sources

bioRxiv2024

First chromosome-level genome assembly of the colonial tunicate Botryllus schlosseri

Botryllus schlosseri (Tunicata) is a colonial chordate that has long been studied for its multiple developmental pathways and regenerative abilities and its genetically determined allorecognition system based on a polymorphic locus that controls chimerism and cell parasitism. We present the first chromosome-level genome assembly from an isogenic colony of B. schlosseri clade A1 using a mix of long and short reads scaf-folded using Hi-C. This haploid assembly spans 533 Mb, of which 96% are found in 16 chromosome-scale scaffolds. With a BUSCO completeness of 91.2%, this complete and contiguous B. schlosseri genome assembly provides a valuable genomic resource for the scientific community and lays the foundation for future investigations into the molecular mechanisms underlying coloniality, regeneration, histocompatibility, and the immune system in tunicates.

genomics↗

bioRxiv2022

Comparing dormancy in two distantly related tunicates reveals morphological, molecular, and ecological convergences and repeated co-option

Many asexually-propagating marine invertebrates can survive extreme environmental conditions by developing dormant structures, i.e., morphologically simplified bodies that retain the capacity to completely regenerate a functional adult when conditions return to normal. Here, we examine the environmental, morphological, and molecular characteristics of dormancy in two distantly related clonal tunicate species: Polyandrocarpa zorritensis and Clavelina lepadiformis. In both species, we report that the dormant structures are able to withstand harsher temperature and salinity conditions compared to the adult, and are the dominant forms these species employ to survive the colder winter months. By finely controlling the entry and exit of dormancy in laboratory-reared individuals, we were able to select and characterize the morphology of dormant structures associated with their transcriptome dynamics. In both species, we identified putative stem and nutritive cells in structures that resemble the earliest stages of asexual propagation. By characterizing gene expression during dormancy and regeneration into the adult body plan (i.e., germination), we observed that genes which control dormancy and environmental sensing in other metazoans, notably HIF- and insulin signaling genes, are also expressed in tunicate dormancy. Germination-related genes in these two species, such as the retinoic acid pathway, are also found in other unrelated clonal tunicates during asexual development. These results are suggestive of repeated exaptation of conserved eco-physiological and regeneration programs for the origin of novel dormancy-germination processes across distantly related animal taxa.

developmental biology↗

bioRxiv2019

Colonial ascidians strongly preyed upon, yet dominate the substrate in a subtropical fouling community

Higher diversity and dominance at lower latitudes has been suggested for colonial species. We verified the latitudinal pattern in species richness of ascidians, finding that higher colonial-to-solitary species ratios occur in the tropics and subtropics. At the latitudinal region with the highest ratio, in south-eastern Brazil, we confirmed that colonial species dominate the space on artificial plates in two independent studies of five fouling communities. We manipulated settlement plates to measure effects of predation and competition on growth and survivorship of colonial vs. solitary ascidians. Eight ascidian species were subjected to a predation treatment, i.e. caged vs. exposed to predators, and a competition treatment, i.e. leaving vs. removing competitors, to assess main and interactive effects. Predation had a greater effect on growth and survivorship of colonial compared to solitary species, whereas competition did not show consistent patterns between the two life histories. We hypothesize that colonial ascidians dominate at this subtropical site despite being highly preyed upon because they regrow when partially consumed and can adjust in shape and space to grow into refuges. We contend that these means of avoiding mortality from predation can have large influences on the diversification patterns of colonial species at low latitudes, where predation intensity is greater.

ecology↗