endemic to semi-dry forests in La Réunion

Unexpected populations of Hymenophyllaceae ferns were observed and collected at low to middle elevations as epilithic in wet ravines within the semi-dry forest in La Réunion Island. These populations would represent lowland ecotypes of the montane Crepidomanes inopinatum, which is usually restricted to humid rainforests at higher elevations. Because of this unexpected habitat and the dwarfed size of the specimens by comparison to typical populations, we thus describe a new variety for the island. Résumé Des populations inattendues de fougères Hymenophyllaceae ont été observées et collectées à basses et moyennes altitudes en épilithes dans des ravines humides au sein de la forêt semi-sèche à la Réunion. Ces populations représenteraient des écotypes de basses altitudes de l’espèce de montagne Crepidomanes inopinatum normalement restreinte aux forêts humides d’altitude. Compte-tenu de cet habitat inattendu et de la taille naine des individus comparativement à celle des populations types, nous proposons donc de décrire une nouvelle variété pour l’île. Filmy ferns (Hymenophyllaceae) are typical hygrophilous ferns that can only grow in the wettest places. The one-cell thick lamina and the absence of cuticle do not allow these plants to endure a long period of drought, even if many species are poikilohydric but only for a relative short period (see Dubuisson et al. 2013a). In the western Indian Ocea

The C-terminal domain of the MERS coronavirus M protein contains a trans -Golgi network localization signal

International audienceCoronavirus M proteins represent the major protein component of the viral envelope. They play an essential role during viral assembly by interacting with all the other structural proteins. Coronaviruses bud into the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC), but the mechanisms by which M proteins are transported from their site of synthesis, the ER, to the budding site remain poorly understood. Here, we investigated the intracellular trafficking of the Middle East respiratory syndrome coronavirus (MERS-CoV) M protein. Subcellular localization analyses revealed that the MERS-CoV M protein is retained intracellularly in the trans-Golgi network (TGN), and we identified two motifs in the distal part of the C-terminal domain as being important for this specific localization. We identified the first motif as a functional diacidic DxE ER export signal, since substituting Asp-211 and Glu-213 with alanine induced retention of the MERS-CoV M in the ER. The second motif, 199 KxGxYR 204 , was responsible for retaining the M protein in the TGN. Substitution of this motif resulted in MERS-CoV M leakage toward the plasma membrane. We further confirmed the role of 199 KxGxYR 204 as a TGN retention signal by using chimeras between MERS-CoV M and the M protein of infectious bronchitis virus (IBV). Our results indicated that the C-terminal domains of both proteins determine their specific localization, namely, TGN and ERGIC/cis-Golgi for MERS-M and IBV-M, respectively. Our findings indicate that MERS-CoV M protein localizes to the TGN because of the combined presence of an ER export signal and a TGN retention motif

Identification of Novel Functions for Hepatitis C Virus Envelope Glycoprotein E1 in Virus Entry and Assembly

International audienceHepatitis C virus (HCV) envelope glycoprotein complex is composed of E1 and E2 subunits. E2 is the receptor-binding protein as well as the major target of neutralizing antibodies, whereas the functions of E1 remain poorly defined. Here, we took advantage of the recently published structure of the N-terminal region of the E1 ectodomain to interrogate the functions of this glycoprotein by mutating residues within this 79-amino-acid region in the context of an infectious clone. The phenotypes of the mutants were characterized to determine the effects of the mutations on virus entry, replication, and assembly. Furthermore, biochemical approaches were also used to characterize the folding and assembly of E1E2 heterodimers. Thirteen out of 19 mutations led to viral attenuation or inactivation. Interestingly, two attenuated mutants, T213A and I262A, were less dependent on claudin-1 for cellular entry in Huh-7 cells. Instead, these viruses relied on claudin-6, indicating a shift in receptor dependence for these two mutants in the target cell line. An unexpected phenotype was also observed for mutant D263A which was no longer infectious but still showed a good level of core protein secretion. Furthermore, genomic RNA was absent from these noninfectious viral particles, indicating that the D263A mutation leads to the assembly and release of viral particles devoid of genomic RNA. Finally, a change in subcellular colocalization between HCV RNA and E1 was observed for the D263A mutant. This unique observation highlights for the first time cross talk between HCV glycoprotein E1 and the genomic RNA during HCV morphogenesis

NS2 Protein of Hepatitis C Virus Interacts with Structural and Non-Structural Proteins towards Virus Assembly

Growing experimental evidence indicates that, in addition to the physical virion components, the non-structural proteins of hepatitis C virus (HCV) are intimately involved in orchestrating morphogenesis. Since it is dispensable for HCV RNA replication, the non-structural viral protein NS2 is suggested to play a central role in HCV particle assembly. However, despite genetic evidences, we have almost no understanding about NS2 protein-protein interactions and their role in the production of infectious particles. Here, we used co-immunoprecipitation and/or fluorescence resonance energy transfer with fluorescence lifetime imaging microscopy analyses to study the interactions between NS2 and the viroporin p7 and the HCV glycoprotein E2. In addition, we used alanine scanning insertion mutagenesis as well as other mutations in the context of an infectious virus to investigate the functional role of NS2 in HCV assembly. Finally, the subcellular localization of NS2 and several mutants was analyzed by confocal microscopy. Our data demonstrate molecular interactions between NS2 and p7 and E2. Furthermore, we show that, in the context of an infectious virus, NS2 accumulates over time in endoplasmic reticulum-derived dotted structures and colocalizes with both the envelope glycoproteins and components of the replication complex in close proximity to the HCV core protein and lipid droplets, a location that has been shown to be essential for virus assembly. We show that NS2 transmembrane region is crucial for both E2 interaction and subcellular localization. Moreover, specific mutations in core, envelope proteins, p7 and NS5A reported to abolish viral assembly changed the subcellular localization of NS2 protein. Together, these observations indicate that NS2 protein attracts the envelope proteins at the assembly site and it crosstalks with non-structural proteins for virus assembly

Le genre Hymenophyllum Sm. (Hymenophyllaceae, Filicopsida) (systématique phylogénétique, évolution morphologique et histoire biogéographique)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Disentangling the diversity and taxonomy of Hymenophyllaceae (Hymenophyllales, Polypodiidae) in the Comoros

The inventory of biodiversity in the Comoros archipelago is still in progress. We propose here to contribute to this effort by assessing the diversity of the Hymenophyllaceae family, which forms one of the most diverse and emblematic fern communities in rainforests of the region. Data were extracted from floras, literature, recent collects and observations, and from an exhaustive investigation of the Paris herbarium collection. We also completed an online knowledge database including a computer-aided identification (CAI) tool by using the Xper platform. Our checklist recognizes 21 taxa involving 1 endemic and 7 species newly reported for the archipelago. The taxonomy and discrimination of each taxon is discussed and a dichotomous key is provided. We also defined 80 morphological characters and their corresponding states into the Xper database and CAI that could be easily enriched for neighbouring areas and additional taxa.</p

Diversité et évolution de la mégaphylle chez les Euphyllophytes : hypothèses phylogénétiques et le problème de la définition de l’organe foliaire

De récentes études paléobotaniques ont suggéré que la mégaphylle est apparue plusieurs fois au cours de l’évolution des plantes terrestres, ceci implique que le mot « mégaphylle » décrit des notions et des concepts très différents. Nous proposons donc une révision des connaissances portant sur les divers organes foliaires ainsi que leurs caractères associés observables chez les fossiles et les plantes actuelles. Les origines et l’évolution de ces organes sont inférées à partir d’une hypothèse phylogénétique issue de la littérature. Quatre organes foliaires et un axe latéral sont décrits en détails et se distinguent par la combinaison différentielle de quatre principaux caractères : la symétrie des organes latéraux, l’abdaxité ainsi que les processus d’aplanissement et de « palmure ». Les inférences phylogénétiques montrent que la mégaphylle dite « vraie » serait apparue au moins deux fois chez les Euphyllophytes et que les caractères impliqués dans sa définition n’évoluent pas de la même manière dans les deux cas. La définition même de la mégaphylle est discutée, nous proposons donc une terminologie claire et précise afin de lever les ambiguïtés du vocabulaire. De nouvelles analyses traitant de son évolution sont à entreprendre et nécessiteraient aussi bien l’usage de nouveaux descripteurs et définitions, que de nouvelles phylogénies.Recent paleobotanical studies suggest that megaphylls evolved several times in land plant evolution, implying that behind the single word “megaphyll” are hidden very different notions and concepts. We therefore review current knowledge about diverse foliar organs and related characters observed in fossil and living plants, using one phylogenetic hypothesis to infer their origins and evolution. Four foliar organs and one lateral axis are described in detail and differ by the different combination of four main characters: lateral organ symmetry, abdaxity, planation and webbing. Phylogenetic analyses show that the “true” megaphyll appeared at least twice in Euphyllophytes, and that the history of the four main characters is different in each case. The current definition of the megaphyll is questioned; we propose a clear and accurate terminology in order to remove ambiguities of the current vocabulary. Further analyses of megaphyll evolution need to consider new definitions and descriptors, as well as make use of improved phylogenetic hypotheses.</p

Systématique des dombeyoideae (Malvaceae, ex-"Sterculiaceae") des Mascareignes (approches morphologique et moléculaire)

La sous-famille des Dombeyoideae (Malvaceae, ex-Sterculiaceae ) présente dans l archipel des Mascareignes (îles de la Réunion, Maurice et Rodrigues) une diversité spécifique importante (4 genres, 23 espèces dont 22 sont endémiques) et des traits d histoire de vie originaux, telle la dioécie. Notre objectif a été d étudier les relations de parenté entre les taxons mascarins et les représentants africains, malgaches et asiatiques de cette sous-famille. Des caractères morphologiques et moléculaires ont été utilisés indépendamment et conjointement pour reconstruire des scénarios phylogénétiques. Les analyses montrent que les Dombeyoideae des Mascareignes sont polyphylétiques et regroupés au sein de quatre clades ayant chacun pour origine un unique évènement de dispersion/colonisation de Madagascar vers l archipel. L inférence de l évolution des systèmes de reproduction montre que la dioécie dériverait de l hermaphrodisme. Aux Mascareignes, la séparation des sexes se serait ainsi différenciée au moins trois fois de façon convergentePARIS-BIUSJ-Physique recherche (751052113) / SudocPARIS-Museum-Bib. Botanique (751052309) / SudocSudocFranceF

Ecological survey of the Lycophytes and Ferns of the Vohimana Reserve, Madagascar

Background and aims – The Malagasy Vohimana Reserve, is situated in an ecologically sensitive area subject to mining and the pressure from neighbouring communities. The aim of this study is to look at the structure of the plant community, to determine indicator species of undisturbed areas and areas affected by human activities, and to present a checklist of ferns and lycophytes of the reserve. Methods – The Vohimana Reserve was visited twice and an improved quadrat method of sampling was used; specimens were collected and identified at both TAN and P herbaria. Ecological data were statistically analysed using the Factorial Correspondence Analysis methods. Key results – One hundred and thirty two lycopod and fern taxa were identified, including four undescribed fern species. The plant community structure suggests a gradation from primary forest to disturbed zones. This can be explained by local ecological factors and topography, as well as the effect of human pressure on the plant community. The narrow altitudinal gradient (780–1,030 m) is not considered as a factor influencing species composition, as shown in analogous studies performed in larger parks or reserves elsewhere in Madagascar. Conclusion – Despite the human impact on the reserve, the fern and lycophyte diversity indices suggest that it should be classified as an area of significant diversity