News Notes

Raven Advances at AAAS The American Association for the Advancement of Science (AAAS) will ring in the millennium with a new president-elect: Peter Raven, director of the Missouri Botanical Garden and Engelmann professor of botany at Washington University in St. Louis. Raven succeeds Mary Good, who moves up to president at the end of Stephen J. Gould's term. Raven told The Scientist, "I'm very proud to have been elected. I'm impressed by the way AAAS has developed, and I want to do what I can to support its ongoing programs." He also looks forward to promoting four issues close to his heart: sustainable development, including conservation of biodiversity; a more international outlook; expanding the role of women and minorities in science; and evolution vs. creationism. -- Barry Palevitz BT Underground A team led by Guenther Stotzky of New York University's department of biology recently reported that roots of maize transformed with a Bacillus thuringiensis gene exude caterpillar-zapping Bt toxin (D. Saxena et al., "Insecticidal toxin in root exudates from Bt corn," Nature, 402:480, Dec. 2, 1999). The plants deposit toxic protein in liquid hydroponic medium or soil--both kill tobacco hornworm larvae. While binding of Bt toxin to soil particles isn't new, "this is the first time it's been shown that [toxin] comes from root exudate," says Stotzky. Stotzky's paper fueled concerns over genetically modified crops. Some were troubled by the team's claim that Bt corn encodes truncated, active toxin rather than the precursor form produced by bacteria, and by a press statement implying that previous studies hadn't addressed the problem of Bt in soil. It's also unclear how toxin exits the roots. While root cap cells of maize and other plants actively secrete glycoproteins and polysaccharides, commercial Bt genes don't include a secretion signal, so the protein probably remains in the cytoplasm until cells die after they're shed from the root. How soilborne toxin might kill caterpillars is also a mystery, since it's resistant to microbial degradation. --Barry Palevitz Minimalizing the Genome The Institute for Genomic Research (TIGR) has taken the first steps toward characterizing and developing an organism with a minimal genome, the smallest set of genes that confers survival and reproduction. With 517 genes, the microbial parasite Mycoplasma genitalium possesses the smallest known cellular genome. Using a pool of M. genitalium, TIGR scientists systematically knocked out nearly every gene, one gene per microbe, to discover which ones were essential (C.A. Hutchinson et al., "Global transposon mutagenesis and a minimal mycoplasma genome," Science, 286:2165-69, Dec. 10, 1999). But since each of the 300 genes found to be essential could have multiple functions (pleiotropism), investigators had no way of finding the degree of redundancy and whittling the genome down further. The next logical step: make a synthetic chromosome of just those genes to build a living cell from the ground up. At this point, though, the TIGR group decided to stop the experiment and seek ethical input. In an accompanying paper (M.K. Cho et al., "Ethical considerations in synthesizing a minimal genome," Science, 286:2086-87) the bioethics group didn't give the work a thumbs up or down, but flagged several genetic engineering related issues for consideration, including safety concerns, utility for pollution or radiation cleanup and the potential misuse of biological warfare. TIGR scientists haven't yet decided to move forward with the costly project, which, ethical issues aside, faces some major technical hurdles.--Eugene Russo

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