Spéciation chez les champignons et plus particulièrement chez le charbon des anthères Microbotryum violaceum

Les travaux récents sur la spéciation ont mis en évidence l'importance de l'écologie et de la sélection naturelle pour la formation et le maintien de nouvelles espèces. Les champignons pathogènes, et plus généralement les parasites, sont, de bons modèles pour l'étude de la spéciation notamment du fait de la diversité de leurs cycles de vie. Au cours de cette thèse, nous nous sommes intéressés à la spéciation au sein des champignons et plus particulièrement du champignon parasite Microboiryum violaceum. Une approche théorique nous a permis de mettre en évidence l'importance de la spécialisation en tant que barrière aux flux de gènes lors de la spéciation sympatrique de parasites possédant un cycle de vie avec reproduction dans l'hôte. Une étude bibliographique sur l'isolement reproducteur chez les champignons a permis de confirmer l'importance de la spécialisation en tant que barrière aux flux de gènes en sympatrie au sein des ascomycètes, qui se reproduisent principalement dans leur hôte. Cette même étude a mis en évidence au sein des basidiomycètes un déplacement des caractères reproducteurs lié aux choix du partenaire sexuel, soulignant l'importance de ce type d'isolement pour le maintien des espèces de basidiomycètes en sympatrie. Au sein de M. violaceum, des approches phylogénétiques et expérimentales ont révélé la coexistence de plusieurs espèces spécialisées sur des espèces hôtes différentes, ne présentant pas d'isolement reproducteur prézygotique lié à la reconnaissance des gamètes. Ces espèces présentent en revanche un isolement reproducteur postzygotique : la viabilité des hybrides diminue lorsque la distance génétique entre les espèces parentes augmente.Recent advances on speciation underline the importance of ecology and natural selection for the divergence and sympatric maintenance of incipient species. However, these results have mainly been obtained studying a few biological models. Pathogenic fungi, and more generally parasites, are good models to study speciation, in particular due to the diversity in their life cycles. During this thesis, we were interested in speciation in fungi and especially in the parasitic fungus Microbotryum violaceum, anther smut of Cayophyllaceae. A theoretical approach has underlined the importance of specialisation as a barrier to gene flow during sympatric speciation in parasites having a particular life cycle, with reproduction occurring within their host. A literature survey on reproductive isolation in fungi supported the importance of specialization as a barrier to gene flow within ascomycetes that mostly reproduce within their host. The same study showed a reproductive character displacement regarding assortative mating within basidiomycetes, emphasizing the importance of this kind of reproductive barrier for the sympatric maintenance of species in basidiomycetes, in contrast to ascomycetes. On the model M. violaceum, phylogenetic and experimental approaches revealed the coexistence of several cryptic species specialized on different host species, having no prezygotic reproductive isolation due to assortative mating. Postzygotic isolation however occurs among these species: hybrid inviability increases with parental genetic distance.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Protonated hexaphyrin–cyclodextrin hybrids: molecular recognition tuned by a kinetic-to-thermodynamic topological adaptation

International audienceProtonation study of [26/28]hexaphyrin-capped cyclodextrins revealed a temperature controlled conformational transition of the cap. The hexaphyrin undergoes a rectangular-to-triangular shape-shifting which strongly modifies the shape of the confined environment featured by the hybrids, and ultimately affects the encapsulation of the counterions. It provides an attractive access to innovative allosteric host-guest systems

Hexaphyrin-cyclodextrin hybrids: Getting larger, getting confused

International audienceThe diversity of hexaphyrin-cyclodextrin hybrids (HCD), previously formed from the covalent assembly of regular hexaphyrin and [Formula: see text]-cyclodextrin subunits, has been increased following two main directions: enlarging the confined space provided by the cyclodextrin and tuning the N-core of the hexaphyrin aiming at bimetallic complexes. The larger [Formula: see text]-cyclodextrin unit was selectively functionalized with aldehyde linkers on its primary rim which were further reacted with 2 eq. of pentafluorophenyl tripyrrane in acidic conditions, followed by DDQ oxidation. Doubly-linked HCD hybrids were obtained with structural variations in the hexaphyrin macrocycles depending on the MSA concentration (2 vs. 200 mM) producing either regular ([26] rectangular/[28] Möbius) or doubly N-confused dioxo ([26] rectangular) scaffolds. For the latter, two isomers were isolated featuring mirror transoid skeletons and long-side meso-linking patterns, giving rise to planar chirality at the origin of intense and opposite electronic circular dichroism (ECD) spectra. Zn(II) complexation was then investigated leading to two main findings. (i) The regular [28] Möbius HCD afforded a mixture of monometallic Möbius Zn(II) complexes in the presence of acac ligand. ECD spectroscopy indicated a chirality transfer from the [Formula: see text]-cyclodextrin favoring a [Formula: see text] Möbius twist, but opposite to that arising from the narrower [Formula: see text]-cyclodextrin congener ([Formula: see text] twist favored). (ii) Owing to N 3 O coordination boxes, dissymmetric bimetallic Zn(II) complexes were readily formed with the doubly N-confused dioxo HCDs through a positive cooperative process. Both metal centers bind a DMAP ligand in axial positions, which is of interest for th

Data from: Ecological and evolutionary dynamics of coexisting lineages during a long-term experiment with E. coli

Closely related organisms usually occupy similar ecological niches, leading to intense competition and even extinction. Such competition also can promote rapid phenotypic evolution and ecological divergence. This process may end with the stable occupation of distinct niches or, alternatively, may entail repeated bouts of evolution. Here we examine two Escherichia coli lineages, called L and S, that coexisted for more than 30,000 generations after diverging from a common ancestor. Both lineages underwent sustained phenotypic evolution based on global transcription and resource utilization profiles, with L seeming to encroach over time on the catabolic profile of S. Reciprocal invasion experiments with L and S clones from the same or different generations revealed evolutionary changes in their interaction, including an asymmetry that confirmed the encroachment by L on the niche of the S lineage. In general, L and S clones from the same generation showed negative frequency-dependent effects, consistent with stable coexistence. However, L clones could invade S clones from both earlier and later generations, whereas S clones could invade only L clones from earlier generations. In this system, the long-term coexistence of competing lineages evidently depended on successive rounds of evolution, rather than on initial divergence followed by a static equilibrium

Ecological and evolutionary dynamics of coexisting lineages during a long-term experiment with Escherichia coli.

International audienceClosely related organisms usually occupy similar ecological niches, leading to intense competition and even extinction. Such competition also can promote rapid phenotypic evolution and ecological divergence. This process may end with the stable occupation of distinct niches or, alternatively, may entail repeated bouts of evolution. Here we examine two Escherichia coli lineages, called L and S, that coexisted for more than 30,000 generations after diverging from a common ancestor. Both lineages underwent sustained phenotypic evolution based on global transcription and resource utilization profiles, with L seeming to encroach over time on the catabolic profile of S. Reciprocal invasion experiments with L and S clones from the same or different generations revealed evolutionary changes in their interaction, including an asymmetry that confirmed the encroachment by L on the niche of the S lineage. In general, L and S clones from the same generation showed negative frequency-dependent effects, consistent with stable coexistence. However, L clones could invade S clones from both earlier and later generations, whereas S clones could invade only L clones from earlier generations. In this system, the long-term coexistence of competing lineages evidently depended on successive rounds of evolution, rather than on initial divergence followed by a static equilibrium

Identification of allopatric clades in the cosmopolitan ophiuroid species complex Amphipholis squamata (Echinodermata). The end of a paradox?

Life history traits (absence of larval phase, small size and hermaphroditism) do not predispose Amphipholis squamata to dispersal, yet paradoxically it has a nearly cosmopolitan distribution. Recent phylogenetic analyses of 16S mitochondrial DNA (mt-DNA) sequences revealed that (1) Amphipholis squamata is a complex of diverging clades, each of them being found in the North Atlantic as well as in the South Pacific Ocean, and (2) genetic structure is low along the coasts of New Zealand, leading the authors to conclude that rafting may allow important gene flow in this taxon and possibly worldwide distribution of species. For the present study, we obtained 16S mt-DNA sequences from individuals of the Mediterranean Sea, which we analysed along with published data. We show that several sub-clades of previously identified clades display an allopatric distribution, either Atlantic versus Mediterranean, or Mediterranean and Atlantic versus New Zealand. Furthermore, none of the haplotypes (fro

Orchestrating Communications in a Three-Type Chirality Totem: Remote Control of the Chiroptical Response of a Mobius Aromatic System

International audienceAmong the various types of chirality (central, axial, helical, planar, etc.), that inherent to Möbius topology remains almost unexplored, partly due to the difficulty to access Möbius compounds. Over the past decade, [28]hexaphyrins have been revealed to be among the best candidates to build on Möbius aromaticity. Whereas their flexibility needs to be controlled to get / twist enantioselectivity, it could be of great interest to sustain dynamic chirality transfer. In this context, we report herein the first example of a Möbius aromatic ring capped by a cavity, consisting of a Möbius [28]hexaphyrin doubly linked to an α-cyclodextrin. This unique design affords a "totem" of three different chirality elements arising from the cyclodextrin (fix central chirality), the bridging pattern (dynamic planar chirality), and the hexaphyrin (dynamic topological chirality). Chirality transfers (as shown in the TOC graphic) are characterized by a stereospecific planar-to-topological communication (diastereomeric excess >95%; the highest asymmetric selectivity reported to date for a Möbius ring) combined to a stereoselective central-to-planar communication (up to 60% diastereomeric excess). Interestingly, the stereoselectivity is remotely controlled by coordination of an achiral effector to the hexaphyrin, increasing up to 5 times the chiroptical response of the Möbius aromatic π-system. These results highlight the advantageous use of dynamic chirality transfers to further incorporate Möbius chirality and aromaticity into all kinds of stimuli-responsive devices

Speciation in fungi

International audienc

Speciation in fungi

International audienc