Intercellular signalling in Vibrio harveyi: sequence and function of genes regulating expression of luminescence

Density-dependent expression of luminescence in Vibrio harveyi is regulated by the concentration of an extracellular signal molecule (autoinducer) in the culture medium. A recombinant clone that restored function to one class of spontaneous dim mutants was found to encode functions necessary for the synthesis of, and response to, a signal molecule. Sequence analysis of the region encoding these functions revealed three open reading frames, two (luxL and luxM) that are required for production of an autoinducer substance and a third (luxN) that is required for response to this signal substance. The LuxL and LuxM proteins are not similar in amino acid sequence to other proteins in the database, but the LuxN protein contains regions of sequence resembling both the histidine protein kinase and the response regulator domains of the family of two–component, signal transduction proteins. The phenotypes of mutants with luxL, luxM and luxN defects indicated that an additional signal–response system controlling density-dependent expression of luminescence remains to be identified.     

Replicated high-density genetic maps of two great tit populations reveal fine-scale genomic departures from sex-equal recombination rates

Linking variation in quantitative traits to variation in the genome is an important, but challenging task in the study of life-history evolution. Linkage maps provide a valuable tool for the unravelling of such trait−gene associations. Moreover, they give insight into recombination landscapes and between-species karyotype evolution. Here we used genotype data, generated from a 10k single-nucleotide polymorphism (SNP) chip, of over 2000 individuals to produce high-density linkage maps of the great tit (Parus major), a passerine bird that serves as a model species for ecological and evolutionary questions. We created independent maps from two distinct populations: a captive F2-cross from The Netherlands (NL) and a wild population from the United Kingdom (UK). The two maps contained 6554 SNPs in 32 linkage groups, spanning 2010 cM and 1917 cM for the NL and UK populations, respectively, and were similar in size and marker order. Subtle levels of heterochiasmy within and between chromosomes were remarkably consistent between the populations, suggesting that the local departures from sex-equal recombination rates have evolved. This key and surprising result would have been impossible to detect if only one population was mapped. A comparison with zebra finch Taeniopygia guttata, chicken Gallus gallus and the green anole lizard Anolis carolinensis genomes provided further insight into the evolution of avian karyotypes.     

Pelodera (syn. Rhabditis) strongyloides as a cause of dermatitis – a report of 11 dogs from Finland

Background  

Pelodera (Rhabditis) strongyloides is a small saprophytic nematode that lives in decaying organic matter. On rare occasions, it can invade the mammalian skin, causing a pruritic, erythematous, alopecic and crusting dermatitis on skin sites that come into contact with the ground. Diagnosis of the disease is based on case history (a dog living outdoors on damp straw bedding) with characteristic skin lesions and on the demonstration of typical larvae in skin scrapings or biopsy. Pelodera (rhabditic) dermatitis cases have been reported mainly from Central European countries and the United States.     

Bases and spaces: resources on the web for accessing the draft human genome - II - After publication of the draft

The volume of human genome sequence and the variety of web-based tools to access it continue to grow at an impressive rate, but a working knowledge of certain key resources can be sufficient to get the most from your genome. This article provides an update to Genome Biology 2000, 1(4):reviews2001.1-2001.5.