Increased Resistance of Bt Aspens to Phratora vitellinae (Coleoptera) Leads to Increased Plant Growth under Experimental Conditions

One main aim with genetic modification (GM) of trees is to produce plants that are resistant to various types of pests. The effectiveness of GM-introduced toxins against specific pest species on trees has been shown in the laboratory. However, few attempts have been made to determine if the production of these toxins and reduced herbivory will translate into increased tree productivity. We established an experiment with two lines of potted aspens (Populus tremula×Populus tremuloides) which express Bt (Bacillus thuringiensis) toxins and the isogenic wildtype (Wt) in the lab. The goal was to explore how experimentally controlled levels of a targeted leaf beetle Phratora vitellinae (Coleoptera; Chrysomelidae) influenced leaf damage severity, leaf beetle performance and the growth of aspen. Four patterns emerged. Firstly, we found clear evidence that Bt toxins reduce leaf damage. The damage on the Bt lines was significantly lower than for the Wt line in high and low herbivory treatment, respectively. Secondly, Bt toxins had a significant negative effect on leaf beetle survival. Thirdly, the significant decrease in height of the Wt line with increasing herbivory and the relative increase in height of one of the Bt lines compared with the Wt line in the presence of herbivores suggest that this also might translate into increased biomass production of Bt trees. This realized benefit was context-dependent and is likely to be manifested only if herbivore pressure is sufficiently high. However, these herbivore induced patterns did not translate into significant affect on biomass, instead one Bt line overall produced less biomass than the Wt. Fourthly, compiled results suggest that the growth reduction in one Bt line as indicated here is likely due to events in the transformation process and that a hypothesized cost of producing Bt toxins is of subordinate significance

A thousand-genome panel retraces the global spread and adaptation of a major fungal crop pathogen

Human activity impacts the evolutionary trajectories of many species worldwide. Global trade of agricultural goods contributes to the dispersal of pathogens reshaping their genetic makeup and providing opportunities for virulence gains. Understanding how pathogens surmount control strategies and cope with new climates is crucial to predicting the future impact of crop pathogens. Here, we address this by assembling a global thousand-genome panel of Zymoseptoria tritici, a major fungal pathogen of wheat reported in all production areas worldwide. We identify the global invasion routes and ongoing genetic exchange of the pathogen among wheat-growing regions. We find that the global expansion was accompanied by increased activity of transposable elements and weakened genomic defenses. Finally, we find significant standing variation for adaptation to new climates encountered during the global spread. Our work shows how large population genomic panels enable deep insights into the evolutionary trajectory of a major crop pathogen

Regulation of aromatase gene expression in Leydig cells and germ cells

International audienceThe ability of the testis to convert irreversibly androgens into estrogens is related to the presence of a microsomal enzymatic complex named aromatase. Although somatic cells and germ cells (GC) have the capacity to produce estrogens the regulation of the CYP19 gene expression in adult rat testicular cells and specially in freshly purified Leydig cells, pachytene spermatocytes (PS) and round spermatids (RS) is not fully understood. In the present study we have analyzed the putative effects of steroid hormones, transforming growth factor beta (TGFbeta), cytokine (tumor necrosis factor alpha, TNFalpha) and dexamethasone (Dex) on CYP19 expression in these purified testicular cells from adult rat. In parallel the biological role of seminiferous tubules and Sertoli cells conditioned media on the expression of aromatase was studied. Using a highly specific quantitative competitive RT-PCR we established that testosterone (T) enhances CYP19 gene expression in Leydig cells and germ cells, and augments the estradiol outputs. The non-aromatizable androgen 5alpha-DHT induces the same effect as T on P450 aromatase (P450arom) gene expression but was inefficient on the estradiol output. In PS and RS an inhibitory effect on CYP19 gene transcription was observed with TGFbeta (1 ng/ml) alone or in combination with T. Conversely, the addition of TNFalpha (20 ng/ml) increases the P450arom transcription in PS although an inhibitory effect is observed in RS. Together with T, TNFalpha decreases the amount of P450arom mRNA in PS and RS. In PS we found that Dex regulates positively CYP19 expression and negatively in RS. Furthermore in PS a synergistic effect of Dex and TNFalpha on P450arom mRNA expression was observed whereas an additive one was recorded for RS. Therefore in germ cells TNFalpha likely enhances expression of aromatase through promoter PI.4 in PS, possibly via an AP1 site upstream the GAS element, while in RS TNFalpha requires glucocorticoids as a co-stimulator to increase CYP19 gene expression. Finally in presence of seminiferous tubules or Sertoli cell conditioned media, the amount of aromatase transcripts is increased in both Leydig cells and germ cells therefore suggesting that other locally produced modulators, yet unknown, but from Sertoli cell origin, are concerned in the regulation of the aromatase gene expression in rat testicular cells. In summary, using an in vitro model of mature rat Leydig cells, pachytene spermatocytes and round spermatids, we have shown that several factors direct the expression of the aromatase gene and it is obvious that not only promoter PII but also promoter PI.4 are concerned

Obesity-associated alterations of glucose metabolism are ameliorated after chronic stimulation of abdominal vagus nerve

Obesity-associated alterations of glucose metabolism are ameliorated after chronic stimulation of abdominal vagus nerv

Establishment of pangenome graphs for the analysis and monitoring of fungal plant pathogen populations

International audienceThe assembly of whole genomes by long-read sequencing has enabled the collection of resolved telomere-to-telomere (T2T) haplotypes, encouraging genome-wide approaches to study structural variations. Unlike comparative genomics approaches based on gene content or other types of annotation (transposable elements), the analysis of structural variants in genome-wide analysis is now commonly based on graph-oriented approaches. The pangenome graphs (PGG) are capable of storing the full genetic diversity of the genomes under study, achieving superior performance in read alignment, variant identification and genotyping for population studies. We propose to establish a pangenome graph for Zymoseptoria tritici with the available genomic sequences as well as 2 new assemblies of strains isolated on durum wheat (T. turgidum var. durum). Our goal is to evaluate the use of PGG instead of linear-reference genome for GWAS and GEA analyses and implement process to modify and improve the graph with upcoming new data. Establishing a shared reference PGG based on FAIR principles could be valuable to the community, such as the IPO323 reference genome. In addition, same analyses will be carried out with Pyricularia oryzae to validate the method and propose a common framework for other fungal species. We will present our first results on the establishment of graphs and the detections of variants compared to previous results obtained from single reference genome

Gene flow and gene flux shape evolutionary patterns of variation in Drosophila subobscura

Gene flow (defined as allele exchange between populations) and gene flux (defined as allele exchange during meiosis in heterokaryotypic females) are important factors decreasing genetic differentiation between populations and inversions. Many chromosomal inversions are under strong selection and their role in recombination reduction enhances the maintenance of their genetic distinctness. Here we analyze levels and patterns of nucleotide diversity, selection and demographic history, using 37 individuals of Drosophila subobscura from Mount Parnes (Greece) and Barcelona (Spain). Our sampling focused on two frequent O-chromosome arrangements that differ by two overlapping inversions (OST and O3+4), which are differentially adapted to the environment as observed by their opposing latitudinal clines in inversion frequencies. The six analyzed genes (Pif1A, Abi, Sqd, Yrt, Atpa and Fmr1) were selected for their location across the O-chromosome and their implication in thermal adaptation. Despite the extensive gene flux detected outside the inverted region, significant genetic differentiation between both arrangements was found inside it. However, high levels of gene flow were detected for all six genes when comparing the same arrangement among populations. These results suggest that the adaptive value of inversions is maintained, regardless of the lack of genetic differentiation within arrangements from different populations, and thus favors the Local Adaptation hypothesis over the Coadapted Genome hypothesis as the basis of the selection acting on inversions in these populations