A survey of expressed genes in Caenorhabditis elegans.

As an adjunct to the genomic sequencing of Caenorhabditis elegans, we have investigated a representative cDNA library of 1,517 clones. A single sequence read has been obtained from the 5' end of each clone, allowing its characterization with respect to the public databases, and the clones are being localized on the genome map. The result is the identification of about 1,200 of the estimated 15,000 genes of C. elegans. More than 30% of the inferred protein sequences have significant similarity to existing sequences in the databases, providing a route towards in vivo analysis of known genes in the nematode. These clones also provide material for assessing the accuracy of predicted exons and splicing patterns and will lead to a more accurate estimate of the total number of genes in the organism than has hitherto been available.     

The physical maps for sequencing human chromosomes 1, 6, 9, 10, 13, 20 and X

We constructed maps for eight chromosomes (1, 6, 9, 10, 13, 20, X and (previously) 22), representing one-third of the genome, by building landmark maps, isolating bacterial clones and assembling contigs. By this approach, we could establish the long-range organization of the maps early in the project, and all contig extension, gap closure and problem-solving was simplified by containment within local regions. The maps currently represent more than 94% of the euchromatic (gene-containing) regions of these chromosomes in 176 contigs, and contain 96% of the chromosome-specific markers in the human gene map. By measuring the remaining gaps, we can assess chromosome length and coverage in sequenced clones.     

The role of zinc in regulating tabtoxin production

Summary The phytotoxin, tabtoxinine--lactam, is produced by severalPseudomonas syringae pathovars if adequate Zn is available, otherwise its biologically inactive form, tabtoxin, is produced. The Zn is required for the action of a peptidase which cleaves tabtoxin, releasing the toxic -lactam.This research was supported in part by U.S.D.A. Competitive Research Grant No. 83-CRCR-1-1201.     

Bacterial phytotoxins: Mechanisms of action

Many species of phytopathogenic procaryotes produce toxins that appear to function in disease development. The affect the plant in different ways, the end result of which is the elicitation of chlorosis, necrosis, watersoaking, growth abnormalities or wilting. The most extensively studied toxins cause chlorosis. They specifically inhibit diverse enzymes, all critical to the plant cell. This inhibition results in a complex series of metabolic dysfunctions ultimately resulting in symptom expression. Substances causing growth abnormalities consist of known phytohormones and other compounds with plant hormone-like activities, but which have no structural relationship to the known hormones. The former act in the usual manner but, because of their elevated levels and imbalances, the host's regulatory mechanisms are overwhelmed and abnormal growth results (hyperplasia, shoot or root formation); the mechanisms of action of the latter group are unknown. High molecular weight, carbohydrate-containing substances, also acting in unknown ways, cause tissue watersoaking or wilting. Likewise, we know little about toxins causing necrosis except for syringomycin which affects ion transport across the plasmalemma.     

Hydrolysis of tabtoxins by plant and bacterial enzymes

Summary Tabtoxins, dipeptides that induce chlorosis in plants, are produced by several closely related phytopathogenicPseudomonas spp. Culture filtrates from these bacteria and extracts prepared from leaves of their hosts contain multiple enzymes that hydrolyze the peptide bond of the toxins.