Horizontal gene transfer facilitated the evolution of plant parasitic mechanisms in the oomycetes

Horizontal gene transfer (HGT) can radically alter the genomes of microorganisms, providing the capacity to adapt to new lifestyles, environments, and hosts. However, the extent of HGT between eukaryotes is unclear. Using whole-genome, gene-by-gene phylogenetic analysis we demonstrate an extensive pattern of cross-kingdom HGT between fungi and oomycetes. Comparative genomics, including the de novo genome sequence of Hyphochytrium catenoides, a free-living sister of the oomycetes, shows that these transfers largely converge within the radiation of oomycetes that colonize plant tissues. The repertoire of HGTs includes a large number of putatively secreted proteins; for example, 7.6% of the secreted proteome of the sudden oak death parasite Phytophthora ramorum has been acquired from fungi by HGT. Transfers include gene products with the capacity to break down plant cell walls and acquire sugars, nucleic acids, nitrogen, and phosphate sources from the environment. Predicted HGTs also include proteins implicated in resisting plant defense mechanisms and effector proteins for attacking plant cells. These data are consistent with the hypothesis that some oomycetes became successful plant parasites by multiple acquisitions of genes from fungi

The West African Monsoon Modeling and Evaluation project (WAMME) and its First Model Intercomparison Experiment

International audienceThis paper presents the scientific challenge in West African monsoon (WAM) simulation and discusses the West African Monsoon Modeling and Evaluation project (WAMME) initiative and its approaches to improve WAM simulations. Major scientific highlights from the first WAMME model comparison are the focus of the paper. Based on the first WAMME experiment, the WAMME models' performance is evaluated with precipitation being the major focus. The analyses indicate that the models with specified SST generally have reasonable simulations of the mean spatial distribution of WAM precipitation but largely fail to produce proper daily precipitation frequency distributions. WAMME multi-model ensembles, however, produce excellent WAM precipitation spatial distribution, intensity, and temporal evolution, better than Reanalysis. In addition, the WAMME is the first project consisting of the most state-of-the-art general circulation models (GCMs) and regional climate models (RCMs) to collectively investigate the WAM/external forcing feedbacks. Cases based on the first WAMME experiment are presented to demonstrate scientific challenges for further investigation of WAM, SST, land, and aerosol interactions. The analyses in this article provide a quantitative assessment on model uncertainty, identify main issues in WAM modeling, and provide a good starting point as benchmarks for future studies