Controlling for genetic identity of varieties, pollen contamination and stigma receptivity is essential to characterize the self-incompatibility system of Olea europaea L.

open7siBervillé et al. express concern about the existence of the diallelic self-incompatibility (DSI) system in Olea europaea, mainly because our model does not account for results from previous studies from their group that claimed to have documented asymmetry of the incompatibility response in reciprocal crosses. In this answer to their comment, we present original results based on reciprocal stigma tests that contradict conclusions from these studies. We show that, in our hands, not a single case of asymmetry was confirmed, endorsing that symmetry of incompatibility reactions seems to be the rule in Olive. We discuss three important aspects that were not taken into account in the studies cited in their comments and that can explain the discrepancy: (i) the vast uncertainty around the actual genetic identity of vernacular varieties, (ii) the risk of massive contamination associated with the pollination protocols that they used and (iii) the importance of checking for stigma receptivity in controlled crosses. These studies were thus poorly genetically controlled, and we stand by our original conclusion that Olive tree exhibits DSI.openSaumitou-Laprade, Pierre; Vernet, Philippe; Vekemans, Xavier; Castric, Vincent; Barcaccia, Gianni; Khadari, Bouchaib; Baldoni, LucianaSaumitou-Laprade, Pierre; Vernet, Philippe; Vekemans, Xavier; Castric, Vincent; Barcaccia, Gianni; Khadari, Bouchaib; Baldoni, Lucian

A Paradigm Shift, or a Paradigm Adjustment? The Evolution of the Oleaceae Mating System as a Small-Scale Kuhnian Case Study

Kuhn (1962) proposed an evolutionary model to explain how scientific knowledge is built, based on the concept of paradigm. Even though Kuhn’s model is general, it has been applied to only a few topics in evolutionary biology, almost exclusively to broad-based paradigms. We analyze here, through the lens of Kuhn’s theory, a small-scale paradigm change that occurred with the resolution of the controversy about the mating system of a Mediterranean shrub Phillyrea angustifolia (Oleaceae). We first summarize the different steps of the paradigm change and replace them in the more general context of sex ratio theory. Second, we show how the different steps of the paradigm change can be interpreted by Kuhnian concepts and tools. Finally, we discuss the actual and future status of the new paradigm

Zinc distribution and speciation in Arabidopsis halleri x Arabidopsis lyrata progenies presenting various zinc accumulation capacities

The definitive version is available at http://www.blackwell-synergy.com/loi/nphInternational audienceThe purpose of this study was to investigate the relationship between the chemical form and localization of zinc (Zn) in plant leaves and their Zn accumulation capacity. * An interspecific cross between Arabidopsis halleri sp. halleri and Arabidopsis lyrata sp. petrea segregating for Zn accumulation was used. Zinc (Zn) speciation and Zn distribution in the leaves of the parent plants and of selected F1 and F2 progenies were investigated by spectroscopic and microscopic techniques and chemical analyses. * A correlation was observed between the proportion of Zn being in octahedral coordination complexed to organic acids and free in solution (Zn-OAs + Znaq) and Zn content in the leaves. This pool varied between 40% and 80% of total leaf Zn depending on the plant studied. Elemental mapping of the leaves revealed different Zn partitioning between the veins and the leaf tissue. The vein : tissue fluorescence ratio was negatively correlated with Zn accumulation. * The higher proportion of Zn-OAs + Znaq and the depletion of the veins in the stronger accumulators are attributed to a higher xylem unloading and vacuolar sequestration in the leaf cells. Elemental distributions in the trichomes were also investigated, and results support the role of carboxyl and ⁄ or hydroxyl groups as major Zn ligands in these cells

The Five AhMTP1 Zinc Transporters Undergo Different Evolutionary Fates towards Adaptive Evolution to Zinc Tolerance in Arabidopsis halleri

Gene duplication is a major mechanism facilitating adaptation to changing environments. From recent genomic analyses, the acquisition of zinc hypertolerance and hyperaccumulation characters discriminating Arabidopsis halleri from its zinc sensitive/non-accumulator closest relatives Arabidopsis lyrata and Arabidopsis thaliana was proposed to rely on duplication of genes controlling zinc transport or zinc tolerance. Metal Tolerance Protein 1 (MTP1) is one of these genes. It encodes a Zn2+/H+ antiporter involved in cytoplasmic zinc detoxification and thus in zinc tolerance. MTP1 was proposed to be triplicated in A. halleri, while it is present in single copy in A. thaliana and A. lyrata. Two of the three AhMTP1 paralogues were shown to co-segregate with zinc tolerance in a BC1 progeny from a cross between A. halleri and A. lyrata. In this work, the MTP1 family was characterized at both the genomic and functional levels in A. halleri. Five MTP1 paralogues were found to be present in A. halleri, AhMTP1-A1, -A2, -B, -C, and -D. Interestingly, one of the two newly identified AhMTP1 paralogues was not fixed at least in one A. halleri population. All MTP1s were expressed, but transcript accumulation of the paralogues co-segregating with zinc tolerance in the A. halleri X A. lyrata BC1 progeny was markedly higher than that of the other paralogues. All MTP1s displayed the ability to functionally complement a Saccharomyces cerevisiæ zinc hypersensitive mutant. However, the paralogue showing the least complementation of the yeast mutant phenotype was one of the paralogues co-segregating with zinc tolerance. From our results, the hypothesis that pentaplication of MTP1 could be a major basis of the zinc tolerance character in A. halleri is strongly counter-balanced by the fact that members of the MTP1 family are likely to experience different evolutionary fates, some of which not concurring to increase zinc tolerance

Does Speciation between Arabidopsis halleri and Arabidopsis lyrata Coincide with Major Changes in a Molecular Target of Adaptation?

Ever since Darwin proposed natural selection as the driving force for the origin of species, the role of adaptive processes in speciation has remained controversial. In particular, a largely unsolved issue is whether key divergent ecological adaptations are associated with speciation events or evolve secondarily within sister species after the split. The plant Arabidopsis halleri is one of the few species able to colonize soils highly enriched in zinc and cadmium. Recent advances in the molecular genetics of adaptation show that the physiology of this derived ecological trait involves copy number expansions of the AhHMA4 gene, for which orthologs are found in single copy in the closely related A. lyrata and the outgroup A. thaliana. To gain insight into the speciation process, we ask whether adaptive molecular changes at this candidate gene were contemporary with important stages of the speciation process. We first inferred the scenario and timescale of speciation by comparing patterns of variation across the genomic backgrounds of A. halleri and A. lyrata. Then, we estimated the timing of the first duplication of AhHMA4 in A. halleri. Our analysis suggests that the historical split between the two species closely coincides with major changes in this molecular target of adaptation in the A. halleri lineage. These results clearly indicate that these changes evolved in A. halleri well before industrial activities fostered the spread of Zn- and Cd-polluted areas, and suggest that adaptive processes related to heavy-metal homeostasis played a major role in the speciation process

De la sterilite male a la gynodioecie chez Beta maritima L : aspects genetiques et moleculaires

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Origine et évolution de la tolérance au zinc chez Arabidopsis halleri (Brassicaceae) (approches phénotypiques et génétiques)

La tolérance aux métaux lourds est la capacité des espèces métallophytes à se développer sur des sols pollués par les métaux. L'étude de ce caractère adaptatif exceptionnel engage aujourd'hui des technologies lourdes nécessitant l'emploi de quelques espèces modèles. La proximité de l'espèce pseudometallophyte tolérante au Zn et Cd Arabidopsis halleri (Brassicaceae) avec le modèle de la biologie végétale Arabidopsis thaliana offre l'opportunité d'exploiter les outils moléculaires développés chez A. thaliana. A. halleri est donc à son tour proposée comme espèce modèle pour l'étude des mécanismes génétiques et moléculaires de la tolérance aux métaux lourds chez les végétaux supérieurs. Cependant les connaissances disponibles sur l'écologie et l'évolution de l'espèce sont limitées. Pour une meilleure compréhension de l'origine et l'évolution de la tolérance au Zn chez A. halleri, ce travail proposait deux approches. Tout d'abord, évaluer la distribution des capacités de tolérance dans les populations de l'espèce en intégrant des populations métallicoles (M) recensées dans trois régions polluées du nord de l'Europe, et des populations non métallicoles (NM) réparties dans l'aire de distribution de l'espèce. Ensuite, décrire, à l'aide des approches contemporaines de la génétique des populations, la structure génétique de l'espèce, à l'échelle de l'Europe, pour donner un contexte génétique neutre à l'étude de la dynamique évolutive du caractère. L'analyse phénotypique de 33 populations confirme une tolérance constitutive, i.e. présente dans toutes les populations. Cependant, un polymorphisme quantitatif intra- et inter-population a été observé. Une tendance générale vers plus de tolérance a été notée chez les populations M.L'analyse de la distribution géographique d'une généalogie d'haplotypes identifiés par PCR-RFLP révèle des origines multiples et mutuellement indépendantes des populations M géographiquement distantes. L'analyse combinée de la structure des haplotypes chloroplastiques et de six microsatellites nucléaires montre clairement deux ensembles génétiques isolés par les Alpes et aux histoires phylogéographiques distinctes. Dans le groupe génétique au Nord des Alpes, les populations M forment un groupe hétérogène et ne se différencient des populations NM qu'à travers la distance géographique. L'origine d'une tolérance constitutive ne peut pas être déterminée par une étude intraspécifique. Des hypothèses sont néanmoins émises. L'observation d'un polymorphisme quantitatif atteste d'un potentiel génétique pour l'évolution du caractère au sein de l'espèce. La tolérance supérieure des populations M confirment une adaptation de ces populations aux sols pollués, en dépit de la tolérance constitutive. Les origines indépendantes des populations M géographiquement distantes interrogent la nature des mécanismes localement sélectionnées. Enfin, la similitude des génomes nucléaires aux locus neutres entre populations M et NM géographiquement proches posent la question des mécanismes microévolutifs du maintien des différences adaptatives et présente un contexte favorable à des approches de scan génomique.LILLE1-BU (590092102) / SudocSudocFranceF

Genetic characterisation of the MTP1 zinc transporter family in Arabidopsis halleri reveals a large functional and genetic diversity

International audienc