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Mycorrhizal symbioses—the union of roots and soil fungi—are universal in terrestrial ecosystems and may have been fundamental to land colonization by plants1,2. Boreal, temperate and montane forests all depend on ectomycorrhizae1. Identification of the primary factors that regulate symbiotic development and metabolic activity will therefore open the door to understanding the role of ectomycorrhizae in plant development and physiology, allowing the full ecological significance of this symbiosis to be explored. Here we report the genome sequence of the ectomycorrhizal basidiomycete Laccaria bicolor (Fig. 1) and highlight gene sets involved in rhizosphere colonization and symbiosis. This 65-megabase genome assembly contains 20,000 predicted protein-encoding genes and a very large number of transposons and repeated sequences. We detected unexpected genomic features, most notably a battery of effector-type small secreted proteins (SSPs) with unknown function, several of which are only expressed in symbiotic tissues. The most highly expressed SSP accumulates in the proliferating hyphae colonizing the host root. The ectomycorrhizae-specific SSPs probably have a decisive role in the establishment of the symbiosis. The unexpected observation that the genome of L. bicolor lacks carbohydrate-active enzymes involved in degradation of plant cell walls, but maintains the ability to degrade non-plant cell wall polysaccharides, reveals the dual saprotrophic and biotrophic lifestyle of the mycorrhizal fungus that enables it to grow within both soil and living plant roots. The predicted gene inventory of the L. bicolor genome, therefore, points to previously unknown mechanisms of symbiosis operating in biotrophic mycorrhizal fungi. The availability of this genome provides an unparalleled opportunity to develop a deeper understanding of the processes by which symbionts interact with plants within their ecosystem to perform vital functions in the carbon and nitrogen cycles that are fundamental to sustainable plant productivity.

Collections of nonredundant, full-length complementary DNA (cDNA) clones for each of the model organisms and humans will be important resources for studies of gene structure and function. We describe a general strategy for producing such collections and its implementation, which so far has generated a set of cDNAs corresponding to over 40% of the genes in the fruit fly Drosophila melanogaster.

A comparative analysis of the genomes of Drosophila melanogaster, Caenorhabditis elegans, and Saccharomyces cerevisiae-and the proteins they are predicted to encode-was undertaken in the context of cellular, developmental, and evolutionary processes. The nonredundant protein sets of flies and worms are similar in size and are only twice that of yeast, but different gene families are expanded in each genome, and the multidomain proteins and signaling pathways of the fly and worm are far more complex than those of yeast. The fly has orthologs to 177 of the 289 human disease genes examined and provides the foundation for rapid analysis of some of the basic processes involved in human disease.

The thermal phenotype of an organism (heat and cold tolerance, thermal range, and thermal plasticity) is an essential feature of how the organism performs across thermal environments and in response to thermal stress. Porcelain crabs are of interest in addressing questions of thermal phenotype because of their high species diversity and the large variation in thermal phenotype among species, as well as the biogeographic patterning of these crabs along environmental stress gradients. We are studying the cellular bases of thermal phenotype and physiological responses to environmental stress using a functional genomics cDNA microarray approach. To do this, we have isolated total RNA from a range of tissues from 1 species of porcelain crab (Petrolisthes cinctipes) exposed to a suite of thermal conditions, and have used this RNA to construct a 13 824-clone EST library. Here, we describe construction, EST sequencing, assembly and clustering, and results of BLASTx homology search for our initial 13 824-clone library. From 12 060 usable ESTs, 6717 consensus sequences were identified, and roughly 50% of these have homology to known proteins. At present, an additional 50 000–75 000-clone library of P. cinctipes ESTs is being generated, with the aim of developing a library with near-complete coverage of the transcriptome. The libraries and sequence information that will be generated as a result of this project should be of value for crustacean biologists working across a broad range of scientific disciplines (for example, physiology, developmental biology, biological rhythms, ecology, fisheries biology), as well as in studies of molecular evolution and phylogeography.