Biology subjects

Fritsch, C.

Publications and source records attributed to Fritsch, C..

3 recordsLinked to original sources

bioRxiv2019

Identifying conversion efficiency as a key mechanism underlying food webs evolution: A step forward, or backward?

Body size or mass is generally seen as one of the main factors which structure food webs. A large number of evolutionary models have shown that indeed, the evolution of body size (or mass) can give rise to hierarchically organized trophic levels with complex between and within trophic interactions. However, because these models have often very different assumptions, sometimes arbitrary, it is difficult to evaluate what are the real key factors that determine food webs evolution, and whether these models results are robust or not. In this paper, we first review the different adaptive dynamics models, especially highlighting when their assumptions strongly differ. Second, we propose a general model which encompasses all previous models. We show that our model recovers all previous models results under identical assumptions. However, most importantly, we also show that, when relaxing some of their hypotheses, previous models give rise to degenerate food webs. Third, we show that the assumptions made regarding the form of biomass conversion efficiency are key for food webs evolution, a parameter which was neglected in previous models. We conclude by discussing the implication of biomass conversion efficiency, and by questioning the relevance of such models to study the evolution of food webs.

ecology↗

bioRxiv2019

Oriented basement membrane fibrils provide a memory for F-actin planar polarization via the Dystrophin-Dystroglycan complex during tissue elongation

How extracellular matrix participates to tissue morphogenesis is still an open question. In the Drosophila ovarian follicle, it has been proposed that after Fat2-dependent planar polarization of the follicle cell basal domain, oriented basement membrane (BM) fibrils and F-actin stress fibers constrain follicle growth, promoting its axial elongation. However, the relationship between BM fibrils and stress fibers and their respective impact on elongation are unclear. We found that Dystroglycan (Dg) and Dystrophin (Dys) are involved in BM fibril deposition. Moreover, they orient stress fibers, by acting locally and in parallel to Fat2. Nonetheless, Dg-Dys complex-mediated cell autonomous control of F-actin fibers orientation relies on the previous BM fibril deposition, indicating two distinct but interdependent functions. Thus, the Dg-Dys complex works as a critical organizer of the epithelial basal domain, regulating both F-actin and BM. Furthermore, BM fibrils act as a persistent cue for the orientation of stress fibers that are the main effector of elongation.

developmental biology↗

bioRxiv2019

Multilevel regulation of the glass locus during Drosophila eye development

Development of eye tissue is initiated by a conserved set of transcripton factors termed retinal determination network (RDN). In the fruit fly Drosophila melanogaster, the zinc-finger transcription factor Glass acts directly downstream of the RDN to control idendity of photoreceptor as well as non-photoreceptors cells. Tight control of spatial and temporal gene expression is a critical feature during development, cell-fate determination as well as maintainance of differentiated tissues. The molecular mechanisms that control expression of glass, however remain largely unknown. We here identify complex regulatory mechanisms controlling expression of the glass locus. All information to recapitulate glass expression are contained in a compact 5.2 kb cis-acting genomic element by combining different cell-type specific and general enhancers with repressor elements. Moreover, the immature RNA of the locus contains an alterantive small open reading frame (smORF) upstream of the actual glass translation start, resulting in a small peptide instead of the three possible glass protein isoforms. CRISPR/Cas9-based mutagenesis shows that the smORF is not required for the formation of functioning photoreceptors, but to attenuate effects of glass misexpression. Furthermore, editing the genome to generate glass loci eliminating either one or two isoforms shows that only one of the three proteins is critical for formation of functioning photoreceptors, while removing the two other isoforms did not cause defects in developmental or photoreceptor function. Our results show that eye development and function is surprisingly robust and appears buffered to targeted manipulations of critical features of the glass transcript, suggesting a strong selection pressure to allow the formation of a functioning eye.

developmental biology↗