Human dopamine transporter gene (DAT1) maps to chromosome 5p15.3 and displays a VNTR.

The human dopamine transporter (DAT1) gene is localized to chromosome 5p15.3 by in situ hybridization and PCR amplification of rodent somatic cell hybrid DNA. Analysis of a 40-bp repeat in the 3' untranslated region of the message revealed variable numbers of the repeat ranging from 3 to 11 copies. These results will aid in the investigation of a role for this gene in genetic disorders of the dopaminergic system in humans.     

Metabolism of volatile chlorinated aliphatic hydrocarbons by Pseudomonas fluorescens.

A Pseudomonas fluorescens strain designated PFL12 was isolated from soil and water that were contaminated with various chloroaliphatic hydrocarbons. The isolate was able to metabolize 1,2-dichloroethane, 1,1,2-trichloroethane, 1,2-dichloropropane, 2,2-dichloropropane, and trichloroethylene.     

Puberty in pine voles, Microtus pinetorum, and the influence of chemosignals on female reproduction

We investigated the reproductive biology of an induced ovulator, the pine vole (Microtus pinetorum). Male puberty, measured as age at first impregnation, was found to occur as early as 44 days of age. Female puberty measured as age at first conception, was found to occur as early as 32 days of age, considerably earlier than previously reported. Females paired with stud males exhibited a doubling of uterine weight within 12 h, and vaginal sperm were present after 48 h. This indicates that although behavioral responses to males--including mating--require prolonged contact, physiological responses to males occur rapidly. Chemosignals from males slightly increased uterine and ovarian weights of females, but chemosignals from other females did not. Young females paired with stud males for 48 h in the presence of soiled bedding from the female's family had significantly smaller increases in ovarian and uterine weights than similar females paired on clean bedding. Suppression of reproduction in female offspring while they remain with the extended family unit is discussed as a life-history tactic and as a possible mechanism for inbreeding avoidance.     

Iron-Chelating Compounds Produced by Soil Pseudomonads: Correlation with Fungal Growth Inhibition

Strains of Pseudomonas putida, Pseudomonas sp., and Pseudomonas aeruginosa were examined for their ability to grow in the presence of the iron chelator, ethylenediamine-di-(o-hydroxyphenylacetic acid). In vitro fungal inhibition assays showed that the isolates varied in their ability to inhibit the growth of representative fungal plant pathogens. Fungal inhibition in vitro was superior to that of previously reported Pseudomonas sp. Studies with Fusarium oxysporum forma sp. lycopersici and a susceptible tomato cultivar demonstrated that Pseudomonas putida PPU3.1 was able to significantly reduce wilt disease.     

Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

Expression of a Lactococcus lactis Phage Resistance Mechanism by Streptococcus thermophilus

The 7.8-kb lactococcal plasmid pSRQ700 encodes the LlaII restriction/modification system which recognizes and cleaves the sequence 3(prm1)-GATC-5(prm1). When the plasmid pSRQ700 is introduced into a phage-sensitive Lactococcus lactis strain, strong phage resistance is conferred by the LlaII system. In this report, we show that pSRQ700 cannot replicate in Streptococcus thermophilus. However, if cloned into the vector pNZ123, the native LlaII system is expressed and strong phage resistance is conferred to various industrial S. thermophilus strains. Resistance against phages isolated from yogurt and mozzarella wheys was observed. To our knowledge, this is the first report of increased phage resistance in S. thermophilus.     

Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans

Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and D. simulans for two common allozyme forms, as well as for several other less common variants. Parallel latitudinal clines in the frequencies of the common EST6-F and EST6-S allozymes in these species have previously been interpreted in terms of a shared amino acid polymorphism that distinguishes the two variants and is subject to selection. Here we compare the sequences of four D. simulans Est-6 isolates and show that overall estimates of nucleotide heterozygosity in both coding and 5' flanking regions are more than threefold higher than those obtained previously for this gene in D. melanogaster. Nevertheless, the ratio of replacement to exon silent-site polymorphism in D. simulans is less than the ratio of replacement to silent divergence between D. simulans and D. melanogaster, which could be the result of increased efficiency of selection against replacement polymorphisms in D. simulans or to divergent selection between the two species. We also find that the amino acid polymorphisms separating EST6- F and EST6-S in D. simulans are not the same as those that separate these allozymes in D. melanogaster, implying that the shared clines do not reflect shared molecular targets for selection. All comparisons within and between the two species reveal a remarkable paucity of variation in a stretch of nearly 400 bp immediately 5' of the gene, indicative of strong selective constraint to retain essential aspects of Est-6 promoter function.