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Biochemical Genetics (v.35, #3-4)

Isozyme Polymorphism of Esterases in the Genus Lanistes (Mollusca: Prosobranchiata) and Genetic Analysis of Populations by M. B. Abdelmordy; S. H. Sleem; T. A. Tantawi (pp. 77-89).

Esterases from the digestive gland of the snails Lanistes carinatusand Lanistes boltenicollected from four Egyptian governorates were extracted and analyzed using starch gel electrophoresis and five substrates. Twelve esterase bands were detected in both Lanistes species. The esterase bands were distributed in three main zones, which could be classified as acetylesterases, carboxylesterases, and cholinesterases. Depending on the substrate specificity, inhibition properties, and relative mobility of esterase bands, the three zones of esterase activity could be traced to eight genetic loci. Locality-specific loci were found. Inter- and intrapopulation variations are discussed. There is an absence of equilibria at all esterase loci in all populations studied, and a high proportion of genetic diversity in different esterase loci. The absence of interspecific variations proves that Lanistessnails in Egypt belong to one species.

Keywords: esterases; Lanistes ; electrophoresis; specificity; probable loci; population differentiation

Tyrosine Decarboxylase and Dopa Decarboxylase in Drosophila virilis Under Normal Conditions and Heat Stress: Genetic and Physiological Aspects by M. Jh. Sukhanova; L. V. Shumnaya; L. G. Grenback; N. E. Gruntenko; T. M. Khlebodarova; I. Yu. Rauschenbach (pp. 91-103).

The activity of tyrosine decarboxylase (TDC) and dopa decarboxylase (DDC) was studied in adults of two lines of Drosophila virilis,contrasting in their reaction to stress conditions. Differences were found in the activity of both enzymes between individuals of the examined lines. Genetic analysis of these differences was made. Each of the two enzymes was found to be controlled by a single gene or, possibly, by a block of closely linked genes. The gene responsible for TDC activity is located on one of the autosomes (excluding chromosome II). DDC activity in D. virilisis regulated by a gene located, apparently, on chromosome II. Adults of the line responding to stress by a stress reaction (r-line) were shown to react to a short-term heat stress (38°C, 60 min) by a decrease in TDC activity. TDC activity in flies of the line incapable of the stress reaction (nr-line) did not alter in such conditions. DDC activity of adults of both lines was found to be unchangeable under stress conditions.

Keywords: tyrosine decarboxylase; dopa decarboxylase; octopamine; dopamine; Drosophila virilis

Genetic Mapping of a Possible New Alcohol Dehydrogenase Sequence to Mouse Chromosome 3 at the Adh-1/Adh-3 Complex by Yao Wu Zheng; Michael R. Felder (pp. 105-117).

Southern blot analysis of mouse genomic DNA reveals two Eco RI fragments which faintly hybridize to mouse Adh-1 cDNA and are not part of the Adh-1 gene. These fragments were isolated from agarose gels, cloned, and characterized. Sequence analysis of the 2.1-kb Eco RI fragment suggests that it is likely a pseudogene since it does not contain a long open reading frame. However, the 2.0-kb Eco RI fragment contains a coding sequence with a long open reading frame which corresponds to exon 6 of the mouse Adh-1 gene. Comparison of the coding sequence with other known ADHs suggests that the sequence has diverged sufficiently from any currently known class of ADH to be a possible distinct class. Further confirmation awaits analysis of currently available genomic clones. Using these sequences as probe, restriction fragment length polymorphisms were identified for each sequence between C57Bl/6J and DBA/2J inbred mouse strains. The strain distribution pattern for these allelic differences was determined among the B × D recombinant inbred strains. This analysis revealed that the 2.1-kb Eco RI sequence is located on chromosome 3 but at a distance from the Adh-1/Adh-3 complex as previously reported. However, the new polymorphism identified in the 2.0-kb Eco RI fragment enabled this sequence to be mapped at the Adh-1/Adh-3 complex.

Keywords: alcohol dehydrogenase; recombinant inbred strains; mouse; DNA sequence; restriction fragment length polymorphisms

Isolation and Characterization of an Unamplified Esterase B3 Gene from Malathion-Resistant Culex tarsalis by Claus Tittiger; Virginia K. Walker (pp. 119-138).

A malathion-resistant strain of Culex tarsalis has a malathion carboxylesterase which rapidly hydrolyzes the insecticide. This is in contrast to organophosphate-resistant strains of C. quinquefasciatus and C. pipiens, which have elevated levels of general B esterases due to amplification of the corresponding genes, producing increased amounts of enzyme which appear to protect the insects by sequestering the insecticide. The contribution to resistance of the homologous esterase B3 (Estβ3) gene (estβ3) in C. tarsalis was investigated by cloning and characterizing sequences from resistant and susceptible strains. estβ3 is similar to estβ1, both structurally and in sequence. The first intron of estβ3,however, has a region of extensive repeats which may be responsible for the inefficient processing of the transcript. Southern blots indicate that the gene is single copy in both strains, and northern blots show that it is not greatly overexpressed in the resistant insects. estβ3 cDNAs from resistant and susceptible strains have 98% amino acid identity. It appears that, in contrast to other studies, estβ3 does not play a significant role in insecticide resistance in our strains of C. tarsalis, and the molecular responses of pest insects to organophosphates may be more diverse than has been suggested.

Keywords: insecticide resistance; mosquitoes; esterase; cDNA

A Mutant of Arabidopsis thaliana lpar;L.) Heynh. with Modified Control of Aspartate Kinase by Threonine by Betty Heremans; Michel Jacobs (pp. 139-153).

Mutagenesis and subsequent selection of Arabidopsis thaliana plantlets on a growth inhibitory concentration of lysine has led to the isolation of lysine-resistant mutants. The ability to grow on 2 m M lysine has been used to isolate mutants that may contain an aspartate kinase with altered regulatory-feedback properties. One of these mutants (RL 4) was characterized by a relative enhancement of soluble lysine. The recessive monogenic nuclear transmission of the resistance trait was established. It was associated with an aspartate kinase less sensitive to feedback inhibition by threonine. Two mutants (RLT 40 and RL 4) in Arabidopsis, characterized by an altered regulation of aspartate kinase, were crossed to assess the effects of the simultaneous presence of these different aspartate kinase forms. A double mutant (RLT40 × RL4) was isolated and characterized by two feedback-desensitized isozymes of aspartate kinase to, respectively, lysine and threonine but no threonine and/or lysine overproduction was observed. Genetical analysis of this unique double aspartate kinase mutant indicated that both mutations were located on chromosome 2, but their loci (ak1and ak2) were found to be unlinked.

Keywords: Arabidopsis thaliana (L.) Heynh.; aspartate kinase (AK); double AK mutant; lysine accumulation

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Biochemical Genetics (v.35, #3-4)

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Biochemical Genetics (v.35, #3-4)