Developmental expression of alcohol dehydrogenases in maize

Alcohol dehydrogenase (ADH) in Zea mays exists in five distinct electrophoretic forms (isozymes), ADH-1, ADH-2, ADH-3, ADH-4, and ADH-T. The mode of inheritance of ADH-1 and ADH-2 has been previously reported; preliminary data suggest that ADH-3 is controlled by a different locus than ADH-2; no genetic analysis has yet been made for ADH-4 and ADH-T. Analyses at different stages of ontogenesis and of different organs have shown that the ADH isozyme pattern fluctuates qualitatively and quantitatively during the course of development and differentiation of the maize plant. ADH-T is controlled spatially and temporally in a very strict manner, being present only in extracts from the pericarp of 19- to 40-day-old kernels. ADH-3 and ADH-4 are present in the scutella of mature kernels and during early sporophytic development. ADH-1 and ADH-2 are the most common isozymes in all tissues examined, but ADH-1 is not found in endosperm of mature kernels or during germination. None of the isozymes have been found to be associated with any particulate cellular component at any stage of development. These findings are discussed with respect to differential gene expression, physiology, and cellular metabolism.     

Characterization of Coturnix quail liver alcohol dehydrogenase enzymes

Livers from male or female Coturnix quail possess up to four electrophoretically distinct bands of alcohol dehydrogenase (ADH) activity. Three pyrazole-sensitive bands of enzymatic activity, designated ADH-1, ADH-2, and ADH-3, are cathodic at pH 8.2, and the fourth, ADH-An, is neutral to slightly anodic and insensitive to pyrazole. ADH-2 and ADH-3, and occasionally ADH-1, are present in livers from immature females. The predominant enzyme in immature male livers is ADH-3. At sexual maturity all three pyrazole-sensitive enzymes are present in livers from male birds, and livers from females possess predominantly ADH-3. ADH-2 and ADH-3, purified from female livers, are dimers of 80,000 daltons possessing 4 mol of Zn2+/mol of native protein. Both ADH-2 and ADH-3 were inhibited by 4-methylpyrazole with KI values of 430 and 335 nM, respectively. These values are similar to those of human class I isoenzymes. Neither enzyme oxidized methanol or ethylene glycol, which distinguished them from mammalian pyrazole-sensitive ADH isoenzymes. Both ADH-2 and ADH-3 showed specificity toward hydrophobic primary alcohols and were most active toward benzyl alcohol and n-octanol.     

Characterization of three isoenzymes of rat alcohol dehydrogenase. Tissue distribution and physical and enzymatic properties

Rat tissues contain three different isoenzymes of alcohol dehydrogenase (ADH) that we have named ADH-1, ADH-2 and ADH-3, ADH-1 is an anodic isoenzyme present in high amounts in the ocular tissues, stomach and lung. ADH-2 is also anodic and has been found in all the rat organs examined. ADH-3 is the group of cathodic ADH forms, mainly present in liver, that has been the subject of the majority of the previous studies on rat ADH. The three isoenzymes have been purified to homogeneity and characterized. All of them have similar physical characteristics: Mr 80,000, with two subunits of Mr 40,000; they contain four atoms of Zn per molecule, and prefer NAD+ as cofactor. Isoelectric points are, however, different: 5.1 for ADH-1, 5.95-6.3 for ADH-2 and 8.25-8.4 for ADH-3. ADH-3 exhibits a Km for ethanol of 1.4 mM, a broad substrate specificity and is strongly inhibited by pyrazole (Ki = 0.4 microM). ADH-2 shows substrate specificity toward long-chain alcohols and aldehydes, cannot be saturated by ethanol and is practically insensitive to pyrazole (Ki = 78.4 mM). ADH-1 has intermediate properties, with a Km for ethanol of 340 mM, a broad substrate specificity and Ki for pyrazole of 0.56 mM. Rat ADH-1, ADH-2 and ADH-3 exhibit many analogies with human ADH classes II, III and I respectively. The specific localization and kinetic properties of rat ADH isoenzymes suggest that ADH-1 and ADH-3 may act as metabolic barriers to external alcohols and aldehydes whereas ADH-2 may have a function in the metabolism of the endogenous long-chain alcohols and aldehydes.     

Two NAD-dependent alcohol dehydrogenases (E.C. 1.1.1.1) in callus cultures of wheat,rye and triticale

Summary Two NAD-dependent alcohol dehydrogenases ADH-1 and ADH-2, under independent genetic control of genes designated as Adh-1 and Adh-2 located on chromosomes 4A, 4B and 4D, have been reported in aestivum wheat (Hart 1980). Only ADH-1 is expressed in developing seeds, dry seeds, pollen and germinating seedlings. ADH-2 can be induced in seedling roots or shoots under conditions of partial anaerobiosis or by certain chemicals. Expression of ADH-1 and ADH-2 isoenzymes was investigated in undifferentiated calli from aestivum and durum wheats, rye, triticale and also in in vitro regenerated roots and leaves from aestivum cultures. Wheat callus cultures originating from seed, mature and immature embryos, mesocotyl and root, as well as cultures grown on media containing different supplements did not show any variation in the overall expression of ADH-1 or ADH-2, although differences in the band intensities were observed. The callus isoenzyme pattern was similar to that observed in roots under anaerobic conditions. Both ADH-1 and ADH-2 were expressed in in vitro regenerated roots but were absent in regenerated leaves. Expression of ADH-1 and ADH-2 in wheat calli seems to be related to the type of differentiation.     

Isolation and characterization of shrew (Suncus murinus) liver alcohol dehydrogenases

1. Starch gel electrophoresis of adult shrew (Suncus murinus) liver extracts revealed five forms of alcohol dehydrogenase (ADH 1-5) and four of them were purified. 2. ADH-4 and ADH-5 resemble human class I ADH in terms of electrophoretic mobility, substrate specificity and sensitivity to pyrazole inhibition. 3. ADH-2 does not belong to any of the three classes of human ADHs but rather with catalytic properties similar to those of the class B ADH found in guinea pig liver. 4. ADH-1 prefers secondary alcohol over primary alcohol substrates and between the enantiomers tested, the enzyme favors the S isomers.     

Deep analysis of N-cadherin/ADH-1 interaction: a computational survey

Due to the considerable role of N-cadherin in cancer metastasis, tumor growth, and progression, inhibition of this protein has been highly regarded in recent years. Although ADH-1 has been known as an appropriate inhibitor of N-cadherin in clinical trials, its chemical nature and binding mode with N-cadherin have not been precisely specified yet. Accordingly, in this study, quantum mechanics calculations were used to investigate the chemical nature of ADH-1. These calculations clarify the molecular properties of ADH-1 and determine its reactive sites. Based on the results, the oxygen atoms are suitable for electrophilic reactivity, while the hydrogen atoms that are connected to nitrogen atoms are the favorite sites for nucleophilic reactivity. The higher electronegativity of the oxygen atoms makes them the most reactive portions in this molecule. Molecular docking and molecular dynamics (MD) simulation have also been applied to specify the binding mode of ADH-1 with N-cadherin and determine the important residues of N-cadherin involving in the interaction with ADH-1. Moreover, the verified model by MD simulation has been studied to extract the free energy value and find driving forces. These calculations and molecular electrostatic potential map of ADH-1 indicated that hydrophobic and electrostatic interactions are almost equally involved in the implantation of ADH-1 in the N-cadherin binding site. The presented results not only enable a closer examination of N-cadherin in complex with ADH-1 molecule, but also are very beneficial in designing new inhibitors for N-cadherin and can help to save time and cost in this field.     

Dehydrogenase-dependent ethanol metabolism in deer mice (Peromyscus maniculatus) lacking cytosolic alcohol dehydrogenase. Reversibility and isotope effects in vivo and in subcellular fractions

Elimination of [2H]ethanol in vivo as studied by gas chromatography/mass spectrometry occurred at about half the rate in deer mice reported to lack alcohol dehydrogenase (ADH-) compared with ADH+ deer mice and exhibited kinetic isotope effects on Vmax and Km (D(V/K] of 2.2 +/- 0.1 and 3.2 +/- 0.8 in the two strains, respectively. To an equal extent in both strains, ethanol elimination was accompanied by an ethanol-acetaldehyde exchange with an intermolecular transfer of hydrogen atoms, indicating the occurrence of dehydrogenase activity. This exchange was also observed in perfused deer mouse livers. Based on calculations it was estimated that at least 50% of ethanol elimination in ADH- deer mice was caused by the action of dehydrogenase systems. NADPH-supported cytochrome P-450-dependent ethanol oxidation in liver microsomes from ADH+ and ADH- deer mice was not stereoselective and occurred with a D(V/K) of 3.6. The D(V/K) value of catalase-dependent oxidation was 1.8, whereas a kinetic isotope effect of cytosolic ADH in the ADH+ strain was 3.2. Mitochondria from both ADH+ and ADH- deer mice catalyzed NAD+-dependent ethanol oxidation and NADH-dependent acetaldehyde reduction. The kinetic isotope effects of NAD+-dependent ethanol oxidation in the mitochondrial fraction from ADH+ and ADH- deer mice were 2.0 +/- 0.1 and 2.3 +/- 0.3, respectively. The results indicate only a minor contribution by cytochrome P-450 to ethanol elimination, whereas the isotope effects are consistent with ethanol oxidation by the catalase-H2O2 system in ADH- deer mice in addition to the dehydrogenase systems.     

Alcohol Dehydrogenase in the Diploid Plant STEPHANOMERIA EXIGUA (Compositae): Gene Duplication, Mode of Inheritance and Linkage

Study of the biochemical genetics of alcohol dehydrogenase (ADH) in the annual plant Stephanomeria exigua (Compositae) revealed that the isozymes are specified by a small family of tightly linked structural genes. One set of ADH isozymes (ADH-1) was induced in roots by flooding, and was also expressed in thickened unflooded tap roots, stems, ovaries and seeds. As in other plants, the enzymes are dimeric and form homo- and heterodimers. An electrophoretic survey of ADH-1 phenotypes in two natural populations revealed seven different ADH-1 homodimers in various phenotypes having one to eight enzyme bands. Genetic analysis of segregations from crosses involving 59 plants showed that the ADH-1 isozymes are inherited as a single Mendelian unit, Adh1. Adh1 is polymorphic for forms that specify one, two, or three different ADH-1 subunits (which combine to form homo- and heterodimers), and are expressed co-dominantly in all genotypic combinations. Staining intensity of enzymes extracted from various homozygous and heterozygous plants indicated that the different subunit types specified by Adh1 are produced in approximately equal amounts. These observations suggest that Adh1 is a compound locus consisting of one to several tightly linked (0 recombinants among 579 testcross progeny), coordinately expressed structural genes. The genes in the two triplications also occur in various duplicate complexes and thus could have originated via unequal crossing over. The ADH-2 isozyme found in pollen and seeds is apparently specified by a different gene, Adh2. Adh1 and Adh2 are tightly linked (0 recombinants among 81 testcross progeny).     

Effects of O2 stress on tomato alcohol dehydrogenase activity: Description of a second ADH coding gene

Subjecting tomato seedlings to anaerobic conditions results in expression of a previously undescribed Adh gene, Adh-2. Induction profiles were similar for all tissues, including roots, hypocotyls, cotyledons, and true leaves. In sharp contrast to ADH-1, ADH-2 showed no induction under anaerobic stress. The only time ADH-2 activity was expressed (under noninduced conditions) was during the early stages of embryogenesis. By late embryogenesis, ADH-2 activity approached a zero level, concomitant with a sharp rise in ADH-1 activity, which is found in the cotyledons of quiescent embryo. Despite striking differences in the regulation of these two genes, their homology is demonstrated in the ability of their enzyme subunits to form presumed intergenic heterodimers, which are visible during the transient period of embryogenesis when the polypeptides encoded by both genes are expressed. A multiple point linkage test using isozymic marker genes places the Adh-2 locus on chromosome 6 near Aps-1, whereas Adh-1 resides on chromosome 4.     

Alcohol dehydrogenase (EC 1.1.1.1) isozymes as markers at 2,4-dichlorophenoxyacetic acid × kinetin combinations in callus cultures ofCereus peruvianus (Cactaceae)

Alcohol dehydrogenase (ADH; EC 1.1.1.1) isozymes were investigated in tissue ofCereus peruvianus cultured in different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin. Five ADH isozymes were detected in starch gel and showed different patterns in seeds, seedlings, calli cultured at 32 and 22°C, and plants regenerated from calli cultured in three 2,4-D and kinetin combinations. Four phenotypes formed by different combinations of ADH-2, ADH-3, ADH-4, and ADH-5 were detected in calli cultured at 32°C and in plants regenerated from calli. ADH-1 isozyme was detected only in calli subcultured for 1 or 2 weeks at 22°C and was indicated as a marker of stress conditions that affect the growth ofC. peruvianus callus tissues in culture. ADH phenotypes with either a higher or a lower number of isozymes were detected in different proportions in the callus tissues cultured in media containing different 2,4-D and kinetin ratios. ADH isozyme patterns were found to be sensitive markers at the highest kinetin concentration or at high kinetin/2,4-D ratios. The results indicate a high correlation between the ADH isozyme patterns and the capacity for regeneration. Thus, ADH isozymes are indicated as good biochemical markers and as a powerful tool for monitoring studies ofC. peruvianus callus cultures.This research was supported by the CNPq.     

Chromosomal location of alcohol dehydrogenase gene(s) in rye,using wheat-rye addition lines

Following disc electrophoresis on standard gels, rye seed extracts showed two bands (ADH-3 and 5) for alcohol dehydrogenase. The ADH-3 band was homologous to the ADH band observed in other diploid species of the Triticinae, and with the ADH-3 band of 4 × and 6 × wheat. It is proposed that the rye isoenzymes ADH-3 and 5 are governed respectively, by the genes Adh _R1 and Adh _R2. Using bread wheat (Holdfast) lines with disomic addition of individual rye (King II) chromosomes, we found that the ADH-5 band was associated with the addition of rye chromosome IV (after Riley), indicating thereby that Adh _R2 gene is located on this chromosome. The products of Adh _R1 and Adh _R2 do not form active heterodimers, among themselves, but do form active dimers with wheat ADH monomers. It is suggested that the use of chromosomal addition lines may provide a method for locating genes for those enzymes, where the rye and wheat isoenzymes are electrophoretically distinct.     

An intergenic alcohol dehydrogenase isozyme in sunflowers

The isozymes of alcohol dehydrogenase (ADH; E.C. 1.1.1.1) in wild and cultivated sunflower (Helianthus annuus) seeds can be resolved electrophoretically into 12 bands. The slowest- and probably the fastest-migrating sets of three are allozymic products of two genes, Adh ₁ and Adh ₂ , each having two alleles, F (for fast) and S (for slow). Evidence from dissociation-recombination experiments utilizing bands excised from starch gels indicates that an intermediately-migrating isozyme is a dimeric intergenic product consisting of ADH-1F and ADH-2S subunits. The hybrid isozyme was unstable in vitro in that its monomers spontaneously dissociated and recombined to produce ADH-1FF and ADH-2SS isozymes. The molecular weights of the hybrid as well as the parental isozymes were estimated at approximately 98,000.Supported by a Graduate School Research grant of the University of Kansas and by NSF grant GB-35853.     

Alcohol dehydrogenase polymorphism inDrosophila: Enzyme kinetics of product inhibition

Summary Because natural populations ofDrosophila melanogaster are polymorphic for different allozymes of alcohol dehydrogenase (ADH) and becauseD. melanogaster is more tolerant to the toxic effects of ethanol than its sibling speciesD. simulans, information regarding the sensitivities of the different forms of ADH to the products of ethanol degradation are of ecological importance. ADH-F, ADH-S, ADH-71k ofD. melanogaster and the ADH ofD. simulans were inhibited by NADH, but the inhibition was relieved by NAD⁺. The order of sensitivity of NADH was ADH-F<ADH-71k, ADH-S<ADH-simulans with ADH-F being about four times less sensitive than theD. melanogaster enzymes and 12 times less sensitive than theD. simulans enzyme. Acetaldehyde inhibited the ethanolto-acetaldehyde activity of the ADHs, but at low acetaldehyde concentrations ethanol and NAD⁺ reduced the inhibition. ADH-71k and ADH-F were more subject to the inhibitory action of acetaldehyde than ADH-S and ADH-simulans, with ADH-71k being seven times more sensitive than ADH-S. The pattern of product inhibition of ADH-71k suggests a rapid equilibrium random mechanism for ethanol oxidation. Thus, although the ADH variants only differ by a few amino acids, these differences exert a far larger impact on their intrinsic properties than previously thought. How differences in product inhibition may be of significance in the evolution of the ADHs is discussed.     

Identification of P-450ALC in microsomes from alcohol dehydrogenase-deficient deermice: contribution to ethanol elimination in vivo

Isozyme 3a of rabbit hepatic cytochrome P-450, also termed P-450ALC, was previously isolated and characterized and was shown to be induced 3- to 5-fold by exposure to ethanol. In the present study, antibody against rabbit P-450ALC was used to identify a homologous protein in alcohol dehydrogenase-negative (ADH-) and -positive (ADH+) deermice, Peromyscus maniculatus. The antibody reacts with a single protein having an apparent molecular weight of 52,000 on immunoblots of hepatic microsomes from untreated and ethanol-treated deermice from both strains. The level of the homologous protein was about 2-fold greater in microsomes from naive ADH- than from naive ADH+ animals. Ethanol treatment induced the protein about 3-fold in the ADH+ strain and about 4-fold in the ADH- strain. The antibody to rabbit P-450ALC inhibited the microsomal metabolism of ethanol and aniline. The homologous protein, termed deermouse P-450ALC, catalyzed from 70 to 80% of the oxidation of ethanol and about 90% of the hydroxylation of aniline by microsomes from both strains after ethanol treatment. The antibody-inhibited portion of the microsomal activities, which are attributable to the P-450ALC homolog, increased about 3-fold upon ethanol treatment in the ADH+ strain and about 4-fold in the ADH- strain, in excellent agreement with the results from immunoblots. The total microsomal P-450 content and the rate of ethanol oxidation were induced 1.4-fold and 2.2-fold, respectively, by ethanol in the ADH+ strain and 1.9-fold and 3.3-fold, respectively, in the ADH- strain. Thus, the total microsomal P-450 content and ethanol oxidation underestimate the induction of the P-450ALC homolog in both strains. A comparison of the rates of microsomal ethanol oxidation in vitro with rates of ethanol elimination in vivo indicates that deermouse P-450ALC could account optimally for 3 and 8% of total ethanol elimination in naive ADH+ and ADH- strains, respectively. After chronic ethanol treatment, P-450ALC could account maximally for 8% of the total ethanol elimination in the ADH+ strain and 22% in the ADH- strain. Further, cytochrome P-450ALC appears to be responsible for about one-half of the increase in the rate of ethanol elimination in vivo after chronic treatment with ethanol. These results indicate that the contribution of P-450ALC to ethanol oxidation in the deermouse is relatively small. Desferrioxamine had no effect on rates of ethanol uptake by perfused livers from ADH-negative deermice, indicating that ethanol oxidation by a hydroxyl radical-mediated mechanism was not involved in ethanol metabolism in this mutant.(ABSTRACT TRUNCATED AT 400 WORDS)     

The reduced stability of a plant alcohol dehydrogenase is due to the substitution of serine for a highly conserved phenylalanine residue

The zinc-binding long-chain alcohol dehydrogenases from plants and animals exhibit a considerable level of amino acid sequence conservation. While the functional importance of many of the conserved residues is known, the role of others has not yet been determined. We have identified a naturally occurring Adh-1 allele in the legume Phaseolus acutifolius with several unusual characteristics. Individuals homozygous for this allele, Adh-1CN, possess a single isozyme starch gel electrophoretic pattern suggestive of a null allele, and exhibit ADH enzyme activity levels ca. 60% lower than the standard wild-type Adh-1F line. Interestingly, analysis of Adh-1CN homozygotes on an alternative gel system indicates that Adh-1CN does encode a polypeptide capable of forming functional homo- and heterodimers. However, the levels of ADH activity displayed by these isozymes are far lower than those observed for the corresponding wild type ADH-1F isozymes. Dialysis experiments indicate that isozymes containing the ADH-1CN polypeptide are inactivated by slightly acidic conditions, which may explain the apparent null phenotype on starch gels. Elevated temperatures cause a similar loss of enzyme activity. The deduced amino acid sequences of ADH-1CN and ADH-1F were obtained from their corresponding cDNA clones, and the only significant difference detected between the two is a single amino acid replacement substitution. Residue 144 is occupied by phenylalanine in the ADH-1F polypeptide, whereas serine occupies this position in the ADH-1CN polypeptide. The proximity of residue 144 to the catalytic zinc in the substrate-binding pocket, coupled with the fact that it is integral to a defined hydrophobic core of the ADH polypeptide, may explain the observed disruptive effect that the serine substitution has on both the activity and stability of the ADH-1CN polypeptide. It also provides an explanation for the maintenance of phenylalanine or the structurally similar tyrosine at this residue in Zn-binding long-chain ADHs.     

Inhibition of alcohol dehydrogenase after 2-propanol exposure in different geographic races of Drosophila mojavensis: lack of evidence for selection at the Adh-2 locus

High frequencies of the fast allele of alcohol dehydrogenase-2 (Adh-2F) are found in populations of Drosophila mojavensis that inhabit the Baja California peninsula (race BII) whereas the slow allele (Adh-2S) predominates at most other localities within the species' geographic range. Race BII flies utilize necrotic tissue of pitaya agria cactus (Stenocereus gummosus) which contains high levels of 2-propanol, whereas flies from most other localities utilize different cactus hosts in which 2-propanol levels are low. To test if 2-propanol acts as a selective force on Adh-2 genotype, or whether some other yet undetermined genetic factor is responsible, mature males of D. mojavensis lines derived from the Grand Canyon (race A) and Santa Catalina Island (race C), each with individuals homozygous for Adh-2F and Adh-2S, were exposed to 2-propanol for 24 h and ADH-2 specific activity was then determined on each genotype. Flies from five other localities homozygous for either the fast or slow allele also were examined. Results for all reported races of D. mojavensis were obtained. 2-propanol exposure inhibited ADH-2 specific activity in both genotypes from all localities, but inhibition was significantly less in two populations of race BII flies homozygous for Adh-2F. When F/F and S/S genotypes in flies from the same locality were compared, both genotypes showed high 2-propanol inhibition that was not statistically different, indicating that the F/F genotype alone does not provide a benefit against the inhibitory effects of 2-propanol. ADH-1 activity in female ovaries was inhibited less by 2-propanol than ADH-2. These results do not support the hypothesis that 2-propanol acts as a selective factor favoring the Adh-2F allele.     

Activity variation in alcohol dehydrogenase paralogs is associated with adaptation to cactus host use in cactophilic Drosophila

Drosophila mojavensis and Drosophila arizonae are species of cactophilic flies that share a recent duplication of the alcohol dehydrogenase (Adh) locus. One paralog (Adh-2) is expressed in adult tissues and the other (Adh-1) in larvae and ovaries. Enzyme activity measurements of the ADH-2 amino acid polymorphism in D. mojavensis suggest that the Fast allozyme allele has a higher activity on 2-propanol than 1-propanol. The Fast allele was found at highest frequency in populations that utilize hosts with high proportions of 2-propanol, while the Slow allele is most frequent in populations that utilize hosts with high proportions of 1-propanol. This suggests that selection for ADH-2 allozyme alleles with higher activity on the most abundant alcohols is occurring in each D. mojavensis population. In the other paralog, ADH-1, significant differences between D. mojavensis and D. arizonae are associated with a previously shown pattern of adaptive protein evolution in D. mojavensis. Examination of protein sequences showed that a large number of amino acid fixations between the paralogs have occurred in catalytic residues. These changes are potentially responsible for the significant difference in substrate specificity between the paralogs. Both functional and sequence variation within and between paralogs suggests that Adh has played an important role in the adaptation of D. mojavensis and D. arizonae to their cactophilic life.     

The Drosophila alcohol dehydrogenase gene may have evolved independently of the functionally homologous medfly, olive fly, and flesh fly genes

cDNAs for alcohol dehydrogenase (ADH) isozymes were cloned and sequenced from two tephritid fruit flies, the medfly Ceratitis capitata and the olive fly Bactrocera oleae. Because of the high sequence divergence compared with the Drosophila sequences, the medfly cDNAs were cloned using sequence information from the purified proteins, and the olive fly cDNAs were cloned by functional complementation in yeast. The medfly peptide sequences are about 83% identical to each other, and the corresponding mRNAs have the tissue distribution shown by the corresponding isozymes, ADH-1 and ADH-2. The olive fly peptide sequence is more closely related to medfly ADH-2. The tephritid ADHs share less than 40% sequence identity with Drosophila ADH and ADH-related genes but are >57% identical to the ADH of the flesh fly Sarcophaga peregrina, a more distantly related species. To explain this unexpected finding, it is proposed that the ADH: genes of the family Drosophilidae may not be orthologous to the ADH: genes of the other two families, Tephritidae and Sarcophagidae.     

Cloning and sequence analysis of genes involved in erythromycin biosynthesis in Saccharopolyspora erythraea: sequence similarities between EryG and a family of S-adenosylmethionine-dependent methyltransferases.

Summary Treatment of tomato seeds with ethyl methanesulphonate (EMS) followed by allyl alcohol selection of M₂ seeds has led to the identification of one plant (B15-1) heterozygous for an alcohol dehydrogenase (Adh) null mutation. Genetic analysis and expression studies indicated that the mutation corresponded to the structural gene of the Adh-1 locus on chromosome 4. Homozygous Adh-1 null mutants lacked ADH-1 activity in both pollen and seeds. Using an antiserum directed against ADH from Arabidopsis thaliana, which crossreacts with ADH-1 and ADH-2 proteins from tomato, no ADH-1 protein was detected in seeds of the null mutant. Northern blot analysis showed that Adh-1 mRNA was synthesized at wild-type levels in immature seeds of the null mutant, but dropped to 25% in mature seeds. Expression of the Adh-2 gene on chromosome 6 was unaffected. The potential use of the Adh-1 null mutant in selecting rare transposon insertion mutations in a cross with mutable Adh-1 ⁺ tomato lines is discussed.