Editor's Note: Science Scan is a roundup of recently published, biotechnology-relevant research.

Current research to sequence the genome of the silkworm (Bombyx mori) could help target insect pests while sparing harmless insects. Lepidoptera, a group of winged insects that includes butterflies and moths, cause more damage than any other agricultural pest in the world.

To further understand these insects, a team of Japanese lepidopterists and radiologists teamed with a pair of biologists at the University of Rhode Island in Kingston. They present findings in the Proceedings of the National Academy of Scientists (PNAS) paper released online Nov. 4, 2003. Its title: "The construction of an EST database for Bombyx mori and its application." (EST stands for "expressed sequence tags," for canvassing large numbers of genes.)

The silkworm, as a representative member of Lepidoptera, has long served as a model organism in basic laboratory experiments. To begin, the research team collected messenger RNA molecules (the instructions that genes send out) from a wide variety of tissues at all life stages to ensure a representative sample. They then translated that message back into DNA and pooled it into a series of libraries. Using this method, the co-authors estimate that they have identified sequences for about 55 percent of the silkworm's genes, with more on the way. They uploaded information to SilkBase, a searchable database that can be used to compare genome data.

To date, genome sequences have been completed for two insect species, the fruit fly (Drosophila melanogaster) and the malaria mosquito (Anopheles gambiae). "Lepidoptera," the PNAS paper points out, "include the most highly destructive agricultural pests; hundreds of species of caterpillars cause widespread economic damage on food and fiber crop plants, fruit trees, forests, and stored grains. They are also important indicators of ecosystem diversity and health, serving as both pollinators and prey. Lepidopteran genome information will make a strong impact on insect science and industries such as insecticide, pest control and silk production.

"SilkBase," the authors conclude, "could also be used to look for uniquely Lepidopteran-selective genes to target with designer insecticides."

In addition to text, the PNAS paper includes a visual panoply of the silkworm's life as it grows. It includes multicolored cocoons from inbred silkworm stocks. The colors originate in yellow, pink and green pigments found in mulberry leaves, which are the silkworm's main food source.

Other views show the first stage (instar) of silkworms eating their way out of their eggshells, and awaiting their first meal of mulberry leaves; then mature silkworms shortly before spinning their cocoons. Next a pair of mating silkmoths. After mating, the female lays her eggs, usually in a single night, and then has completed her life cycle.

Finally depicted is a silkworm mutant known as "Dragon horn" in China. The tumor-like growths near head and midsection result from excessive cell division in regions with varied distinctive surface patterns and pigmentation. They serve as markers for genetic studies.

Lancet Condemns U.S., European, Asian Refusal Of New Drug, Thus Risking Resistant Antibiotics

A "Leading Edge" editorial in The Lancet looks at drugs for acute self-limiting viral illnesses, in particular the common cold. One such drug, pleconaril, was recently refused a license in the USA. The editorial suggests that it may be better to treat a cold with an antiviral - even one of limited efficacy - than to prescribe a totally inappropriate antibiotic (as often happens) because that will reduce the selective pressure leading to the spread of potentially lethal antibiotic-resistant bacteria.

The Lancet commentary bears the title: "Treatment of drug-resistant pneumococcal pneumonia," and discusses the growing number of failures of antibiotic treatment for pneumococcal pneumonia, and ways to deal with the problem. The author of the review, Javiar Garau, observes: "In some areas of the USA, Europe and East Asia, a prevalence of macrolide antibiotics as high as 35 percent or more has been reported recently. From the clinical standpoint, a growing number of failures following the use of these agents has been described."

U.S. Virologists Gang Up To Second-Guess Bioterrorism Menace Leveled At Ebola Virus

"Ebola and Marburg, the filoviruses, are nonsegmented, negative-strand RNA viruses that cause severe hemorrhagic fever with high mortality rates in humans. Natural outbreaks, though still limited, have risen in recent years. There is growing concern that these viruses could be used as agents of bioterrorism. Therefore, filoviruses remain a serious threat to global public health."

That cautionary warning leads off a paper in the current PNAS, released online Dec. 1, 2003. Its title: "In vivo oligomerization and raft localization of Ebola virus protein, VP40, during vesicular budding."

Its senior author, Javad Aman, is at the National Cancer Institute in Frederick, Md., and the U.S. Army Medical Research Institute of Infectious Diseases, also in Frederick.

The paper's abstract begins, "The matrix protein, VP40, plays a critical role in Ebola virus assembly and budding, a process that utilizes specialized membrane domains known as lipid rafts. Previous studies with purified protein suggest a role for oligomerization of VP40 in this process. Here we demonstrate VP40 oligomers in lipid rafts of mammalian cells, virus-like particles, and in the authentic Ebola virus. By mutagenesis, we identify several critical C-terminal sequences that regulate oligomerization at the plasma membrane, association with detergent-resistant membranes, and vesicular release of VP40, directly linking these phenomena.

"Furthermore, we demonstrate the active recruitment of TSG101 into lipid rafts by VP40. We also report the successful application of the biarsenic fluorophore, FlAsH, combined with a tetracysteine tag for imaging of Ebola VP40 in live cells.

"These findings," the article ends, "greatly enhance our understanding of the molecular mechanisms of [Ebola virus] pathogenesis and suggest that the C-terminal 18 amino acids, as well as the prolines 283 and 286 of VP40, may prove to be important targets for developing therapeutics against Ebola infection."