Ammonia leakage can underpin nitrogen-sharing among soil microorganisms.

Soil microbial communities host a large number of microbial species that support important ecological functions such as biogeochemical cycling and plant nutrition. The extent and stability of these functions are affected by inter-species interactions among soil microorganisms, yet the different mechanisms underpinning microbial interactions in the soil are not fully understood. Here, we study the extent of nutrient-based interactions among two model, plant-supporting soil microorganisms, the fungi Serendipita indica, and the bacteria Bacillus subtilis.

Multiple candidate effectors from the oomycete pathogen Hyaloperonospora arabidopsidis suppress host plant immunity.

Oomycete pathogens cause diverse plant diseases. To successfully colonize their hosts, they deliver a suite of effector proteins that can attenuate plant defenses. In the oomycete downy mildews, effectors carry a signal peptide and an RxLR motif.

Molecular cloning of ATR5(Emoy2) from Hyaloperonospora arabidopsidis, an avirulence determinant that triggers RPP5-mediated defense in Arabidopsis.

RPP5 is the seminal example of a cytoplasmic NB-LRR receptor-like protein that confers downy mildew resistance in Arabidopsis thaliana. In this study, we describe the cloning and molecular characterization of the gene encoding ATR5(Emoy2), an avirulence protein from the downy mildew pathogen Hyaloperonospora arabidopsidis isolate Emoy2. ATR5(Emoy2) triggers defense response in host lines expressing the functional RPP5 allele from Landsberg erecta (Ler-0).

Signatures of adaptation to obligate biotrophy in the Hyaloperonospora arabidopsidis genome.

Many oomycete and fungal plant pathogens are obligate biotrophs, which extract nutrients only from living plant tissue and cannot grow apart from their hosts. Although these pathogens cause substantial crop losses, little is known about the molecular basis or evolution of obligate biotrophy. Here, we report the genome sequence of the oomycete Hyaloperonospora arabidopsidis (Hpa), an obligate biotroph and natural pathogen of Arabidopsis thaliana.

Hyaloperonospora Arabidopsidis as a pathogen model.

Hyaloperonospora arabidopsidis, a downy mildew pathogen of the model plant Arabidopsis, has been very useful in the understanding of the relationship between oomycetes and their host plants. This naturally coevolving pathosystem contains an amazing level of genetic diversity in host resistance and pathogen avirulence proteins. Oomycete effectors identified to date contain a targeting motif, RXLR, enabling effector entry into the host cell.