Checklist and distribution of the liverworts of the Andasibe (Périnet) region (Madagascar)

This updated checklist of Marchantiophyta (liverworts) of Andasibé (Périnet) region, Madagascar was compiled from the literature, from herbarium specimens and recent collections. A total of 222 species including 9 infraspecific taxa, from 62 genera are recorded. Five species: Cheilolejeunea ngongensis Malombe et Pócs, Cheilolejeunea unciloba (Lindenb.) Malombe, Heteroscyphus grandistipus (Steph.) Schiffn., Lejeunea angulifolia Mitt. and Kymatocalyx africanus Vána et Wigginton are newly reported for Madagascar. Detailed informations on species occurrences are provided as a basis for subsequent research on species distributions and conservation

Diversity and distribution of ferns and clubmosses in the eastern canyons of Isalo National Park, Madagascar

Background and aims – In contrast to the flowering plants, the pteridophyte flora of Madagascar is still understudied. While several studies have been published on the eastern and central parts of the island, there are currently few works dedicated to the pteridophytes of southwestern Madagascar. The aim of this work is to increase the knowledge of the pteridophyte flora of the Isalo massif in southwestern Madagascar. It presents a checklist of Isalo’s pteridophytes and an analysis of the diversity and distribution patterns of pteridophyte communities across ecological gradients in the eastern canyons of Isalo. Material and methods – Eighty plots were placed in six canyons. In each plot, pteridophyte species abundance was inventoried, as well as several ecological and geomorphological variables. A census in the field and observations on specimens in herbaria were carried to make a checklist of all the pteridophyte species known for Isalo. Statistical analysis was carried out to understand the pteridophyte diversity and distribution patterns in the Isalo’s canyons: (1) exploratory analysis (FAMD and HCPC) highlights the general patterns of ecological gradients, (2) a rarefaction curve was used to compare species diversity, and (3) co-inertia analysis investigated the relationship between ecological gradient and pteridophyte communities. Key results – In total, 60 species of ferns and lycophytes have been recorded in the massif, including ten endemic species to Madagascar and 11 species reported for the first time in the Isalo massif. Species diversity is especially high in the northern canyons (Anjofo, Andramanero, Antsifotra) in contrast to the middle (Maki and Rats) and southern (Namaza) canyons. Fern distribution patterns were correlated to a combination of environmental factors, highlighting species-specific ecological preferences

Diversity and taxonomy of the fern genus Vandenboschia Copel. (Hymenophyllaceae, Polypodiidae) in the Afro-Malagasy region and description of a new species

International audienceVandenboschia radicans (supposedly Neotropical and African), V. speciosa (supposedly European and Macaronesian) and V. gigantea (supposedly from western Indian Ocean) are morphologically close species and often confused in collections and in floras. Moreover, the status of African populations is still strongly debated. We undertook to combine morphological, morphometrics and molecular phylogenetic analyses, on these three species, by also including the Neotropical V. collariata, morphologically close to V. radicans, to try to discriminate putative geographical lineages and discuss their taxonomic status. Our results show that V. collariata is distinct from the other species, and that V. radicans, V. speciosa, V. gigantea and the African specimens remain morphologically and morphometrically indistinguishable. Nevertheless, the Neotropical specimens of V. radicans, V. speciosa and V. gigantea are each genetically strongly distinct and are thus clearly supported as distinct species. African specimens are all grouped into a distinct clade sister to V. gigantea and are distinguished by the presence of a well-developed wing on the stipe, lacking in V. gigantea. Taking into account this stipe feature as well as genetic differences, we describe here Vandenboschia confusa as a new species corresponding to the African populations. The origin of this species in the region is discussed, in addition to the complex taxonomy of European-Macaronesian V. speciosa

Pluripotency of Arabidopsis xylem pericycle underlies shoot regeneration from root and hypocotyl explants grown in vitro

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Disentangling the diversity and taxonomy of Hymenophyllaceae (Hymenophyllales, Polypodiidae) in the Mascarene archipelago, with ecological implications

International audienceWe here explore the diversity and ecology, and update the taxonomy of the fern family Hymenophyllaceae, which forms one of the most diverse and emblematic fern assemblages in rainforests of the Mascarene archipelago in western Indian Ocean. Since 1999, we extracted data from floras, literature, and field investigations conducted, and from an exhaustive examination of the collections at P, REU, and MAU. Our checklist recognizes 26 taxa involving 23 species, 2 local varieties and 1 new forma. We reconsider area of distribution in Mascarene Hymenophyllaceae and at least 3 species appear to be restricted to the archipelago. We discuss the updated taxonomy and discrimination of each taxon (including a new nomenclatural proposition for Hymenophyllum tenellum here renamed as H. fumarioides) and provide a dichotomous key. We present and discuss the ecology and elevational distribution of each species, in addition to the local endemicity. Finally, we emphasize the importance of threatened lowland rainforests and of wet ravines in semi-dry forests, which host a high level of diversity in the context of local conservation of habitats

Diarch Symmetry of the Vascular Bundle in Arabidopsis Root Encompasses the Pericycle and Is Reflected in Distich Lateral Root Initiation1[W]

The outer tissues of dicotyledonous plant roots (i.e. epidermis, cortex, and endodermis) are clearly organized in distinct concentric layers in contrast to the diarch to polyarch vascular tissues of the central stele. Up to now, the outermost layer of the stele, the pericycle, has always been regarded, in accordance with the outer tissue layers, as one uniform concentric layer. However, considering its lateral root-forming competence, the pericycle is composed of two different cell types, with one subset of cells being associated with the xylem, showing strong competence to initiate cell division, whereas another group of cells, associated with the phloem, appears to remain quiescent. Here, we established, using detailed microscopy and specific Arabidopsis thaliana reporter lines, the existence of two distinct pericycle cell types. Analysis of two enhancer trap reporter lines further suggests that the specification between these two subsets takes place early during development, in relation with the determination of the vascular tissues. A genetic screen resulted in the isolation of mutants perturbed in pericycle differentiation. Detailed phenotypical analyses of two of these mutants, combined with observations made in known vascular mutants, revealed an intimate correlation between vascular organization, pericycle fate, and lateral root initiation potency, and illustrated the independence of pericycle differentiation and lateral root initiation from protoxylem differentiation. Taken together, our data show that the pericycle is a heterogeneous cell layer with two groups of cells set up in the root meristem by the same genetic pathway controlling the diarch organization of the vasculature

Microgravity Induces Changes in Microsome-Associated Proteins of Arabidopsis Seedlings Grown on Board the International Space Station

International audienceThe ''GENARA A'' experiment was designed to monitor global changes in the proteome of membranes of Arabidopsis thaliana seedlings subjected to microgravity on board the International Space Station (ISS). For this purpose, 12-day-old seedlings were grown either in space, in the European Modular Cultivation System (EMCS) under microgravity or on a 1 g centrifuge, or on the ground. Proteins associated to membranes were selectively extracted from microsomes and identified and quantified through LC-MS-MS using a label-free method. Among the 1484 proteins identified and quantified in the 3 conditions mentioned above, 80 membrane-associated proteins were significantly more abundant in seedlings grown under microgravity in space than under 1 g (space and ground) and 69 were less abundant. Clustering of these proteins according to their predicted function indicates that proteins associated to auxin metabolism and trafficking were depleted in the microsomal fraction in mg space conditions, whereas proteins associated to stress responses, defence and metabolism were more abundant in mg than in 1 g indicating that microgravity is perceived by plants as a stressful environment. These results clearly indicate that a global membrane proteomics approach gives a snapshot of the cell status and its signaling activity in response to microgravity and highlight the major processes affected

Proteins specifically identified in one extraction fraction and common to the three gravity conditions (i.e. 1 g ground, 1 g space and µg space).

<p>Blue bars indicate the total number of proteins identified. Red bars show the number of proteins with at least one transmembrane segment and the green bars the number of proteins which are annotated as “membrane” in Gene Ontology (The number of proteins is indicated at the top of the bars).</p

Comparative distribution of under and over-represented proteins according to functional categories.

<p>Black bars = over-represented, Grey bars = under-represented.</p