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

Patterns d'expression des gènes régulateurs du cycle cellulaire et hormones endogènes en relation avec la capacité de dédifférenciation des tissus végétaux

PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocSudocFranceF

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

Auxin-Mediated Cell Cycle Activation during Early Lateral Root Initiation

Lateral root formation can be divided into two major phases: pericycle activation and meristem establishment. In Arabidopsis, the first lateral root initiation event is spatially and temporally asynchronous and involves a limited number of cells in the xylem pericycle. To study the molecular regulation during pericycle activation, we developed a lateral root–inducible system. Successive treatments with an auxin transport inhibitor and exogenous auxin were used to prevent the first formative divisions and then to activate the entire pericycle. Our morphological and molecular data show that, in this inducible system, xylem pericycle activation was synchronized and enhanced to cover the entire length of the root. The results also indicate that the inducible system can be considered a novel in planta system for the study of synchronized cell cycle reactivation. In addition, the expression patterns of Kip-Related Protein2 (KRP2) in the pericycle and its ectopic expression data revealed that the cyclin-dependent kinase inhibitor plays a significant role in the regulation of lateral root initiation. KRP2 appears to regulate early lateral root initiation by blocking the G1-to-S transition and to be regulated transcriptionally by auxin

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

International audienc

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

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

Microsome-associated proteome modifications of Arabidopsis

Growing plants in space for using them in bioregenerative life support systems during long-term human spaceflights needs improvement of our knowledge in how plants can adapt to space growth conditions. In a previous study performed on board the International Space Station (GENARA A experiment STS-132) we evaluate the global changes that microgravity can exert on the membrane proteome of Arabidopsis seedlings. Here we report additional data from this space experiment, taking advantage of the availability in the EMCS of a centrifuge to evaluate the effects of cues other than microgravity on the relative distribution of membrane proteins. Among the 1484 membrane proteins quantified, 227 proteins displayed no abundance differences between µ g and 1 g in space, while their abundances significantly differed between 1 g in space and 1 g on ground. A majority of these proteins (176) were over-represented in space samples and mainly belong to families corresponding to protein synthesis, degradation, transport, lipid metabolism, or ribosomal proteins. In the remaining set of 51 proteins that were under-represented in membranes, aquaporins and chloroplastic proteins are majority. These sets of proteins clearly appear as indicators of plant physiological processes affected in space by stressful factors others than microgravity