Transcriptome of Aphanomyces euteiches: New Oomycete Putative Pathogenicity Factors and Metabolic Pathways

Aphanomyces euteiches is an oomycete pathogen that causes seedling blight and root rot of legumes, such as alfalfa and pea. The genus Aphanomyces is phylogenically distinct from well-studied oomycetes such as Phytophthora sp., and contains species pathogenic on plants and aquatic animals. To provide the first foray into gene diversity of A. euteiches, two cDNA libraries were constructed using mRNA extracted from mycelium grown in an artificial liquid medium or in contact to plant roots. A unigene set of 7,977 sequences was obtained from 18,864 high-quality expressed sequenced tags (ESTs) and characterized for potential functions. Comparisons with oomycete proteomes revealed major differences between the gene content of A. euteiches and those of Phytophthora species, leading to the identification of biosynthetic pathways absent in Phytophthora, of new putative pathogenicity genes and of expansion of gene families encoding extracellular proteins, notably different classes of proteases. Among the genes specific of A. euteiches are members of a new family of extracellular proteins putatively involved in adhesion, containing up to four protein domains similar to fungal cellulose binding domains. Comparison of A. euteiches sequences with proteomes of fully sequenced eukaryotic pathogens, including fungi, apicomplexa and trypanosomatids, allowed the identification of A. euteiches genes with close orthologs in these microorganisms but absent in other oomycetes sequenced so far, notably transporters and non-ribosomal peptide synthetases, and suggests the presence of a defense mechanism against oxidative stress which was initially characterized in the pathogenic trypanosomatids

Large scale atmospheric contribution of trace elements registered in foliose lichens in remote French areas

The human activities affect atmospheric compartment by trace elements emissions. The evaluation of atmospheric deposition can be performed by means of bioaccumulator organisms. In this study, we investigated two lichen species (Xanthoria parietina and Parmelia sulcata) from five remote areas far from local sources of contamination in France. PCA and enrichment factor were used to set up the geochemical background of 16 trace elements (including metals and metalloids). Some elements known to be influenced by anthropogenic activities, merge into the geochemical background, like As. The enrichment factors showed a high enrichment for Sb, Cd, Zn, As, Cu, and Pb, and to a less extent Sn and Mn. Others elements were associated to lithogenic contribution, including particularly As. A significant gradient from the South to the North-East was observed, convergently to the increased concentration registered in soils