New insights into other importantPublisher: NPG; Journal: Nature: Nature; Article Type: Biology letter DOI: 10.1038/nature06269Page 2 of 33 symbiotic functions including H 2 metabolism, CO 2 -reductive acetogenesis and N 2 fixation are also provided by this first system-wide gene analysis of a microbial community specialized towards plant lignocellulose degradation. Our results underscore how complex even a 1-μl environment can be.All known termite species form obligate, nutritional mutualisms with diverse gut microbial species found nowhere else in nature 3 . Despite nearly a century of study, however, science still has only a meagre understanding of the exact roles of the host and symbiotic microbiota in the complex processes of lignocellulose degradation and conversion. Especially conspicuous is our poor understanding of the hindgut communities of wood-feeding 'higher'termites, the most species-rich and abundant of all termite lineages 4 . Higher termites do not contain hindgut flagellate protozoa, which have long been known to be sources of cellulases and hemicellulases in the 'lower' termites. The host tissue of all wood-feeding termites is known to be the source of one cellulase, a single-domain glycohydrolase family 9 enzyme that is secreted and active in the anterior compartments of the gut tract 5 . Only in recent years has research provided support for a role of termite gut bacteria in the production of relevant hydrolytic enzymes. That evidence includes the observed tight attachment of bacteria to wood particles, the antibacterial sensitivity of particle-bound cellulase activity 2 , and the discovery of a gene encoding a novel endoxylanase (glycohydrolase family 11) from bacterial DNA harvested from the gut tract of a Nasutitermes species 6 . Here, in an effort to learn about gene-centred details relevant to the diverse roles of bacterial symbionts in these successful wood-degrading insects,we initiated a metagenomic analysis of a wood-feeding 'higher' termite hindgut community, performed a proteomic analysis with clarified gut fluid from the same sample, and examined a set of candidate enzymes identified during the course of the study for demonstrable cellulase activity.A nest of an arboreal species closely related to Nasutitermes ephratae and N. corniger ( Supplementary Fig. 1) was collected near Guápiles, Costa Rica. From worker specimens, luminal contents were sampled specifically from the largest hindgut compartment, the microbedense, microlitre-sized region alternatively known as the paunch or the third proctodeal segment (P3; Fig. 1a). In the interest of interpretive clarity, we specifically excluded sampling from and analysis of the microbiota attached to the P3 epithelium and the other distinct microbial communities associated with the other hindgut compartments.Publisher: NPG; Journal: Nature: Nature; Article Type: Biology letter DOI: 10.1038/nature06269Page 3 of 33Total community DNA from pooled P3 luminal contents was purified, cloned and sequenced. About 71 million base pairs of Sang...

Odorants are transmitted by small hydrophobic molecules that cross the aqueous sensillar lymph surrounding the dendrites of the olfactory neurons to stimulate the olfactory receptors. In insects, the transport of pheromones, which are a special class of odorants, is mediated by pheromone-binding proteins (PBPs), which occur at high concentrations in the sensillar lymph. The PBP from the silk moth Bombyx mori (BmPBP) undergoes a pH-dependent conformational transition between the forms BmPBP A present at pH 4.5 and BmPBP B present at pH 6.5. Here, we describe the NMR structure of BmPBP A , which consists of a tightly packed arrangement of seven ␣-helices linked by well defined peptide segments and knitted together by three disulfide bridges. A scaffold of four ␣-helices that forms the ligand binding site in the crystal structure of a BmPBP-pheromone complex is preserved in BmPBP A . The C-terminal dodecapeptide segment, which is in an extended conformation and located on the protein surface in the pheromone complex, forms a regular helix, ␣7, which is located in the pheromone-binding site in the core of the unliganded BmPBP A . Because investigations by others indicate that the pH value near the membrane surface is reduced with respect to the bulk sensillar lymph, the pH-dependent conformational transition of BmPBP suggests a novel physiological mechanism of intramolecular regulation of protein function, with the formation of ␣7 triggering the release of the pheromone from BmPBP to the membrane-standing receptor. Male moths have an exquisitely sensitive olfactory system capable of detecting over great distances single molecules of pheromones emitted by the female, and they are capable of distinguishing highly selectively between closely similar compounds or isomers (1). These capabilities of male moths are because of olfactory sensory organs that consist of large branched antennae and can readily be isolated for biochemical characterization or electrophysiological recordings (2). The surface of the antennae is covered with hairlike protrusions composed of cuticle, which form a sheath (sensillum) surrounding one or several dendrite endings from olfactory neurons. The dendrites in each sensillum are bathed in a special fluid, the sensillum lymph. Odorant molecules gain access to the dendritic membrane through pores penetrating the sensillum wall and then crossing the sensillar lymph to interact with G proteincoupled olfactory receptors, which form a large eukaryotic protein family. Upon interaction with the olfactory receptors, a cascade of events leads to a change of the membrane potential (3), resulting in opening of ion channels and depolarization.Common odorants are hydrophobic molecules that are poorly soluble in aqueous media, such as the sensillar lymph. Odorants overcome this barrier by binding to odorant-binding proteins (OBPs). OBPs are present at high concentrations in the lymph (up to 10 mM), bind the odorant, and transport it from the sensillum pore wall to the receptor at the dendritic membrane. It is ...

Receiver domains are the dominant molecular switches in bacterial signalling. Although several structures of non-phosphorylated receiver domains have been reported, a detailed structural understanding of the activation arising from phosphorylation has been impeded by the very short half-lives of the aspartylphosphate linkages. Here we present the first structure of a receiver domain in its active state, the phosphorylated receiver domain of the bacterial enhancer-binding protein NtrC (nitrogen regulatory protein C). Nuclear magnetic resonance spectra were taken during steady-state autophosphorylation/dephosphorylation, and three-dimensional spectra from multiple samples were combined. Phosphorylation induces a large conformational change involving a displacement of beta-strands 4 and 5 and alpha-helices 3 and 4 away from the active site, a register shift and an axial rotation in helix 4. This creates an exposed hydrophobic surface that is likely to transmit the signal to the transcriptional activation domain.

We used a systematic approach to build a network of genes associated with developmental and stress responses in rice by identifying interaction domains for 200 proteins from stressed and developing tissues, by measuring the associated gene expression changes in different tissues exposed to a variety of environmental, biological, and chemical stress treatments, and by localizing the cognate genes to regions of stress-tolerance trait genetic loci. The integrated data set suggests that similar genes respond to environmental cues and stresses, and some may also regulate development. We demonstrate that the data can be used to correctly predict gene function in monocots and dicots. As a result, we have identified five genes that contribute to disease resistance in Arabidopsis.