Understanding genetic and phenotypic diversity in the speciation of Petunia : evolution of quantitative and qualitative traits

The diversity of flowering plants is connected with the recruitment of pollinators in the reproductive process. Some species of plants have specialised floral phenotypes that attract and reward one or few pollinators, and that allow efficient pollen exchange. The pollinator specificity of flowers can constitute a barrier to reproduction, by isolating plants pollinated by different animals. The group of traits (termed “pollination syndrome”) that defines which pollinator will transfer pollen efficiently can thus define species isolation. In this manuscript I focus on the genetic basis of the changes in pollination syndrome traits in the Petunia genus. P. axillaris and P. exserta have different pollinators, and their pollination syndrome traits differ in UV and visible colour, in scent production and in floral morphology. We investigated flower colour and morphology in individuals at two contact zones where the species live in sympatry and produce hybrid offspring. We used a genome-wide variant dataset to describe the population genetics of the individuals, and combined genotype information with phenotype data to estimate the genetic architecture of the traits and identify associated loci. The traits studied reveal different genetic architectures. Visible colour is associated with a polygenic basis, while UV colour with an oligogenic basis including less than 10 genes. Both the morphological traits (pistil and tube length) are predicted to have an oligogenic basis. We thus highlight that the classic association of discrete traits with a simple genetic basis, and continuous traits with a complex genetic basis is not always valid. The selection scan on these individuals identifies two broad regions experiencing positive selection. The regions do not include the speciation gene MYB-FL, responsible for the UV colour difference between the species. We suggest that this gene and the region associated with it are not under selection at the contact zones, maybe for a loss of importance of the trait in these populations. We then suggest that the regions positively selected may be the result of selection pressure acting on the morphology phenotypes, or may be due to incompatibilities developed during the divergence of the species. Scent production has changed several times during Petunia speciation. In particular, the shift from the bee pollination of P. inflata to the hawkmoth pollination of P. axillaris included an increase in the amount and number of volatiles produced. The biosynthesis of volatiles and the genetic changes that underlie scent production have been characterised in these species and have a simple genetic basis. On the other hand, the emission route of these volatiles has only been described in the research cultivar P. hybrida cv Mitchell. Scent production underwent important changes during Petunia evolution. We thus ask if these changes were accompanied by the adaptation of the scent emission system to sustain the new and increased production. We investigated the sequence conservation of the P. hybrida cv Mitchell transporter ABCG1 in the wild Petunia species, and we measured its expression in the strongly scented P. axillaris. P. axillaris and P. hybrida cv Mitchell share phenotypic similarities in their scent profiles as well as in other floral traits. P. hybrida cv Mitchell is derived from a series of crosses involving P. axillaris as a recurrent parent and a commercial variety descended from a species of the bee-pollinated short-tube clade (such as P. inflata). Consistently with its origin, the transcriptome of P. hybrida cv Mitchell is mostly constituted of P. axillaris transcript alleles. We thus hypothesised that the scent transporter ABCG1 function is conserved in P. axillaris. Unexpectedly we found that the sequence of the protein of P. hybrida is most similar to a species of the short-tube clade, suggesting that it was inherited from a modestly scented Petunia. Even more surprisingly, the ABCG1 transporter is not expressed in the scented P. axillaris. We thus identify other ABCG subfamily members that could effect scent emission in this wild Petunia by analysing their expression profiles. We suggest that another gene may be responsible for scent emission in P. axillaris, or alternatively that P. axillaris does not need a transporter to emit scent. While the scent biosynthetic pathway is generally conserved between P. hybrida cv Mitchell and P. axillaris, scent emission took a different route

Genetic architecture of a pollinator shift and its fate in secondary hybrid zones of two Petunia species.

BACKGROUND Theory suggests that the genetic architecture of traits under divergent natural selection influences how easily reproductive barriers evolve and are maintained between species. Divergently selected traits with a simple genetic architecture (few loci with major phenotypic effects) should facilitate the establishment and maintenance of reproductive isolation between species that are still connected by some gene flow. While empirical support for this idea appears to be mixed, most studies test the influence of trait architectures on reproductive isolation only indirectly. Petunia plant species are, in part, reproductively isolated by their different pollinators. To investigate the genetic causes and consequences of this ecological isolation, we deciphered the genetic architecture of three floral pollination syndrome traits in naturally occurring hybrids between the widespread Petunia axillaris and the highly endemic and endangered P. exserta. RESULTS Using population genetics, Bayesian linear mixed modelling and genome-wide association studies, we found that the three pollination syndrome traits vary in genetic architecture. Few genome regions explain a majority of the variation in flavonol content (defining UV floral colour) and strongly predict the trait value in hybrids irrespective of interspecific admixture in the rest of their genomes. In contrast, variation in pistil exsertion and anthocyanin content (defining visible floral colour) is controlled by many genome-wide loci. Opposite to flavonol content, the genome-wide proportion of admixture between the two species predicts trait values in their hybrids. Finally, the genome regions strongly associated with the traits do not show extreme divergence between individuals representing the two species, suggesting that divergent selection on these genome regions is relatively weak within their contact zones. CONCLUSIONS Among the traits analysed, those with a more complex genetic architecture are best maintained in association with the species upon their secondary contact. We propose that this maintained genotype-phenotype association is a coincidental consequence of the complex genetic architectures of these traits: some of their many underlying small-effect loci are likely to be coincidentally linked with the actual barrier loci keeping these species partially isolated upon secondary contact. Hence, the genetic architecture of a trait seems to matter for the outcome of hybridization not only then when the trait itself is under selection

Genetic architecture of a pollinator shift and its fate in secondary hybrid zones of two Petunia species

Background: Theory suggests that the genetic architecture of traits under divergent natural selection influences how easily reproductive barriers evolve and are maintained between species. Divergently selected traits with a simple genetic architecture (few loci with major phenotypic effects) should facilitate the establishment and maintenance of reproductive isolation between species that are still connected by some gene flow. While empirical support for this idea appears to be mixed, most studies test the influence of trait architectures on reproductive isolation only indirectly. Petunia plant species are, in part, reproductively isolated by their different pollinators. To investigate the genetic causes and consequences of this ecological isolation, we deciphered the genetic architecture of three floral pollination syndrome traits in naturally occurring hybrids between the widespread Petunia axillaris and the highly endemic and endangered P. exserta. Results Using population genetics, Bayesian linear mixed modelling and genome-wide association studies, we found that the three pollination syndrome traits vary in genetic architecture. Few genome regions explain a majority of the variation in flavonol content (defining UV floral colour) and strongly predict the trait value in hybrids irrespective of interspecific admixture in the rest of their genomes. In contrast, variation in pistil exsertion and anthocyanin content (defining visible floral colour) is controlled by many genome-wide loci. Opposite to flavonol content, the genome-wide proportion of admixture between the two species predicts trait values in their hybrids. Finally, the genome regions strongly associated with the traits do not show extreme divergence between individuals representing the two species, suggesting that divergent selection on these genome regions is relatively weak within their contact zones. Conclusions: Among the traits analysed, those with a more complex genetic architecture are best maintained in association with the species upon their secondary contact. We propose that this maintained genotype–phenotype association is a coincidental consequence of the complex genetic architectures of these traits: some of their many underlying small-effect loci are likely to be coincidentally linked with the actual barrier loci keeping these species partially isolated upon secondary contact. Hence, the genetic architecture of a trait seems to matter for the outcome of hybridization not only then when the trait itself is under selection

A single MYB transcription factor with multiple functions during flower development.

Members of the R2R3-MYB transcription factor subgroup 19 (SG19) have been extensively studied in multiple plant species using different silenced or mutated lines. Some studies have proposed a function in flower opening, others in floral organ development/maturation, or specialized metabolism production. While SG19 members are clearly key players during flower development and maturation, the resulting picture is complex, confusing our understanding in how SG19 genes function. To clarify the function of the SG19 transcription factors, we used a single system, Petunia axillaris, and targeted its two SG19 members (EOB1 and EOB2) by CRISPR-Cas9. Although EOB1 and EOB2 are highly similar, they display radically different mutant phenotypes. EOB1 has a specific role in scent emission while EOB2 has pleiotropic functions during flower development. The eob2 knockout mutants reveal that EOB2 is a repressor of flower bud senescence by inhibiting ethylene production. Moreover, partial loss-of-function mutants (transcriptional activation domain missing) show that EOB2 is also involved in both petal and pistil maturation through regulation of primary and secondary metabolism. Here, we provide new insights into the genetic regulation of flower maturation and senescence. It also emphasizes the function of EOB2 in the adaptation of plants to specific guilds of pollinators

Implementaion of Regional Burnt Area Algorithms for the GBA2000 initiative

Technical Report - Global Burnt Area 200

A global inventory of burned areas at 1km resolution for he year 2000 derived from spot vegetation data

Biomass burning constitutes a major contribution to global emissions of carbon dioxide, carbon monoxide, methane, greenhouse gases and aerosols. Furthermore, biomass burning has an impact on health, transport, the environment and land use. Vegetation fires are certainly not recent phenomena and the impacts are not always negative. However, evidence suggests that fires are becoming more frequent and there is a large increase in the number of fires being set by humans for a variety of reasons. Knowledge of the interactions and feedbacks between biomass burning, climate and carbon cycling is needed to help the prediction of climate change scenarios. To obtain this knowledge, the scientific community requires, in the first instance, information on the spatial and temporal distribution of biomass burning at the global scale. This paper presents an inventory of burned areas at monthly time periods for the year 2000 at a resolution of 1 kilometer (km) and is available to the scientific community at no cost. The burned area products have been derived from a single source of satellite-derived images, the SPOT VEGETATION S1 1 km product, using algorithms developed and calibrated at regional scales by a network of partners. In this paper, estimates of burned area, number of burn scars and average size of the burn scar are described for each month of the year 2000. The information is reported at the country level. This paper makes a significant contribution to understanding the effect of biomass burning on atmospheric chemistry and the storage and cycling of carbon by constraining one of the main parameters used in the calculation of gas emissions

Gestión del cumplimiento normativo (compliance) en fundaciones de la Argentina : dos posibles herramientas

Introducción: El vocablo “compliance” se ha comenzado a difundir en la Argentina en estos tiempos para denominar un proceso interno a las empresas u otras organizaciones que buscan prevenir la comisión de ilícitos o la realización de prácticas no éticas por parte de sus integrantes. Compliance es un vocablo del idioma ingles que el diccionario online Merriam-Webster define como: 1 a: the act or process of complying to a desire, demand, proposal, or regimen or to coercion b: conformity in fulfilling official requirements 2: a disposition to yield to others 3: the ability of an object to yield elastically when a force is applied: flexibility Teniendo en cuenta todos estos significados, podríamos decir que Compliance es la capacidad de una empresa u organización de aceptar la ley y diferentes regulaciones y normas y su disposición a cumplirlas. Sin embargo, compliance en las empresas no es nuevo. Las herramientas de compliance tienen su origen en la década del 80 en las Federal Sentences Guidelines de EEUU. Estas recomendaciones -a tener en cuenta por los jueces federales en las sentencias sobre la conducta de las empresas corporativas promueven que las empresas vean reducidas sus multas, si logran demostrar haber intentado prevenir que sus miembros cometan ilícitos. Esta forma de concebir prevenciones y sanciones se ha ido a extendiendo progresivamente y de distintos modos, a Europa y en nuestro país en los últimos tiempos..

Tight genetic linkage of genes causing hybrid necrosis and pollinator isolation between young species.

The mechanisms of reproductive isolation that cause phenotypic diversification and eventually speciation are a major topic of evolutionary research. Hybrid necrosis is a post-zygotic isolation mechanism in which cell death develops in the absence of pathogens. It is often due to the incompatibility between proteins from two parents. Here we describe a unique case of hybrid necrosis due to an incompatibility between loci on chromosomes 2 and 7 between two pollinator-isolated Petunia species. Typical immune responses as well as endoplasmic reticulum stress responses are induced in the necrotic line. The locus on chromosome 2 encodes ChiA1, a bifunctional GH18 chitinase/lysozyme. The enzymatic activity of ChiA1 is dispensable for the development of necrosis. We propose that the extremely high expression of ChiA1 involves a positive feedback loop between the loci on chromosomes 2 and 7. ChiA1 is tightly linked to major genes involved in the adaptation to different pollinators, a form of pre-zygotic isolation. This linkage of pre- and post-zygotic barriers strengthens reproductive isolation and probably contributes to rapid diversification and speciation

A Global Inventory of Burned Areas at 1 km Resolution for the Year 2000 Derived from SPOT VEGETATION Data

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra

Vegetation Burning in the Year 2000 - Global Burned Area Estimates from SPOT VEGETATION Data

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra