Are modern pollen data representative of west African vegetation?

International audienc

The developing female genital tract: from genetics to epigenetics.

International audienceThe mammalian female reproductive tract develops from the Mullerian ducts which differentiate, in a cranial to caudal direction, into oviducts, uterine horns, cervix and the anterior vagina. The developmental processes taking place during this organogenesis are notably under the control of steroid hormones, such as members of the Wnt and Hox families, which regulate key developmental genes. At later stages, steroid hormones also participate in the development of the female genital tract. Chemical compounds homologous to steroids can thus act as agonists or antagonists in fetuses exposed to them. These so-called endocrine disruptors are nowadays found in increasing amounts in the environment and may therefore have a particular impact on such developing organs. Epidemiological studies have revealed that endocrine disruptors have had drastic effects on female health and fertility during the last decades. Furthermore, these adverse effects might be transmitted to subsequent generations through epigenetic modifications. Given the potential hazard of inherited epigenetic marks altering reproduction and/or human health, such molecular mechanisms must be urgently investigated. This review aims to summarize the cellular and molecular mechanisms involved in female genital tract development, to highlight key genes involved in this process and to present epigenetic mechanisms triggered by endocrine disruptors and their consequences in regard to female reproductive tract development

Analyzing theme penetration from specialized to non-specialized discourses with NLP: the case of the IPCC Special Report Global Warming of 1.5 ºC

Discourses as scientifically sharp and socially influential as the IPCC reports raise the question of their relationship with non-specialists discourses on climate change. IPCC reports are officially aimed at governments (IPCC, 2019), and their reception by the general public is certainly filtered by legacy media (O’Neill et al. 2015; Painter, 2014; Kunelius, 2017) and shaped through social media (Pearce et al., 2014; O’Neill et al., 2015). Social media discourses are known to be sometimes polarized and over-simplified, and one can expect such discourses to focus only on some of the IPCC reports topics. In this research, we use natural language processing (NLP) techniques as well as a qualitative analysis to identify the main concepts and topics in the Special Report Global Warming of 1.5ºC by the IPCC (2018) and track their presence and recycling in a sample of the general public discourses on social media. Our aim is to understand how topics covered in the last published IPCC report are represented in social media discourses, as a step towards a deeper understanding of the appropriation of specialized discourses on climate change (like IPCC documents) by the general public . The contribution of this communication is twofold. First, whereas other NLP-based investigation of climate discourse have mainly relied on Twitter data (O’Neill et al., 2015; Newman, 2017; Yagodin et al., 2018), our approach will make use of a different type of digital media data, namely Reddit. Reddit is a social platform where news and opinions are shared and debated. As such, it can be a valuable source of data on climate change discourses, and also provides new new perspectives to Twitter-based analyses. Second, previous studies have carried out rather limited topic analyses of Tweets, either manually classifying a small sample of Tweets into a few categories (Newman, 2017) or using the most frequent hashtags as topics (O’Neill et al., 2015). In this study, we have developed a system able to detect all concepts listed in the official glossary of the Special Report Global Warming of 1.5ºC (https://www.ipcc.ch/sr15/chapter/glossary/), which offer a much more representative outline of the topics occurring in IPCC reports than hashtags (which already reflects biases). The distribution of these concepts will first be compared across the whole IPCC 1.5 °C report, the 1.5 °C report’s “Summary for Policymakers”, and the subreddits threads related to climate issues. In a second step, we will automatically cluster these concepts into larger themes, based on the Doc2Vec similarity methods (Le et Mikolov, 2014) and compare their distribution on the three above corpora. Finally, a sample of threads will be manually analyzed in order to shed light on the results obtained by the automatic approach

Consecutive action of two BAHD acyltransferases promotes tetracoumaroyl spermine accumulation in chicory

International audienceFully substituted phenolamide accumulation in the pollen coat of Eudicotyledons is a conserved evolutionary chemical trait. Interestingly, spermidine derivatives are replaced by spermine derivatives as the main phenolamide accumulated in the Asteraceae family. Here, we show that the full substitution of spermine in chicory (Cichorium intybus) requires the successive action of two enzymes, i.e. CiSHT1 and CiSHT2 (spermidine hydroxycinnamoyl transferase-like protein 1 and 2), two members of the BAHD enzyme family. Deletion of these genes in chicory using CRISPR/Cas9 gene editing technology evidenced that CiSHT2 catalyzes the first N-acylation steps whereas CiSHT1 fulfills the substitution to give rise to tetracoumaroyl spermine. Additional experiments using Nicotiana benthamiana confirmed these findings. Expression of CiSHT2 alone promoted partially substituted spermine accumulation, and coexpression of CiSHT2 and CiSHT1 promoted synthesis and accumulation of the fully substituted spermine. Structural characterization of the main product of CiSHT2 using NMR revealed that CiSHT2 preferentially catalyzed N-acylation of secondary amines to form N5,N10-dicoumaroyl spermine, whereas CiSHT1 used this substrate to synthesize tetracoumaroyl spermine. We showed that spermine availability may be a key determinant towards preferential accumulation of spermine derivatives over spermidine derivatives in chicory. Our results reveal a subfunctionalization among the SHTs that was accompanied by a modification of free polyamine metabolism that has resulted in the accumulation of this new phenolamide in chicory and most probably in all Asteraceae. Finally, genetically engineered yeast (Saccharomyces cerevisiae) was shown to be a promising host platform to produce these compounds

Plant migration and plant communities at the time of the "Green Sahara"

Around 8500 cal years BP, at the time of the maximum of the African Humid Period, lakes and wetlands expanded in the present-day Sahara while large paleodrainages were formed or re-actived, in response to an orbitally-induced increase in monsoon rainfall. It has been suggested that the direct consequence of this increase in rainfall was the northward displacement of the Sahara/Sahel boundary, thought to have reached 23 degrees N in central and eastern Africa. Here, we show a more complex situation characterized by an increase in biodiversity as the desert accommodated more humid-adapted species from tropical forests and wooded grasslands: tropical plant species now found some 400 to 500 km to the south probably entered the desert as gallery-forest formations along rivers and lakes where they benefited from permanent fresh water. At the same time, Saharan trees and shrubs persisted, giving rise to a vegetation that has no analogue today. In this article, we present distribution maps of selected plant species to show both the amplitude of the vegetation change compared to the present and the composition of the past plant communities. We also estimate the migration rate of tropical plant taxa. to their northernmost position in the Sahara. This study is based on the use of several data sets: a data set of the modern plant distribution in northern Africa and a data set of modem and fossil pollen sites (from the African Pollen Database, http://fpd.mediasfrance.org/ and http://medias.obs-mip.fr/apd/). To cite this article: J. Watrin et al., C R. Geoscience 341 (2009). (C) 2009 Published by Elsevier Masson SAS on behalf of Academie des sciences