Alcohol Dehydrogenase Activity Levels Research Articles

Pyramiding Submergence Tolerance and Three Bacterial Blight Resistance Genes in Popular Rice Variety Hasanta through Marker-Assisted Backcross Breeding

Flash flooding (FF) along with bacterial blight (BB) outbreak are very destructive for rice production in the rainfed shallow-lowland (RSL) ecosystem. The presence of dynamic Xoo races with varying levels of genetic diversity and virulence renders their management extremely challenging under RSL. In this context, the marker-assisted improvement of plant resistance/tolerance has been proven as one of the most promising strategies towards the development of sustainable cultivars. The present study demonstrates the marker-assisted introgression of the submergence tolerant (Sub1) and three bacterial blight resistant genes (Xa21 + xa13 + xa5) into the genetic background of Hasanta, a long duration popular rice variety in the eastern coastal region of India. The rice genotypes, Swarna Sub1 (carrying Sub1) and IRBB66 (carrying Xa21 + xa13 + Xa7 + xa5 + Xa4) had maximum genetic similarity (0.84 and 0.73, respectively) with Hasanta; recurrent parent (RP) was used as donor. The forward analysis of target genes in F1s, IC1F1s and backcross (BC) generations was performed by linked/genic markers (Sub1bc2; pTA248, xa13prom and RM122), whereas background recovery of RP in each BC and segregating generations was performed utilizing 108 hypervariable SSR markers. Intervened speed breeding (SB) strategy and intensive phenotyping could lead the development of near isogenic lines (NILs) as to the RP in all basic traits. The performance of the near isogenic lines (NILs, BC2F3 and BC2F4), HS 232-411-391-756-37, HS 232-411-391-809-8, HS 232-411-391-756-18, HS 110-224-197-10-36, HS 232-411-391-809-81, HS 110-224-197-10-41 and HS 232-411-391-809-63 establishes the utility of marker-assisted backcross-breeding (MAB) and SB in accelerated trait introgression. The introgressed lines carrying Sub1 + Xa21 + xa13 + xa5 showed 76% to 91% survival under 14 days of submergence and durable BB resistance (percent disease index-PDI of 2.68 ± 0.26 to 6.22 ± 1.08 and lesion length, LL of 1.29 ± 0.12 to 4.2 ± 0.64 cm). Physiological analysis revealed that improved NILs, carrying Sub1 gene conquered adaptive physiological modulations, had reduced the consumption of soluble sugar and the degradation of total chlorophyll contents (TCC), and an enhanced level of Alcohol Dehydrogenase activity (ADH) and proline accumulation in all submergence regimes. The pyramided lines attained complete product profile of RP, that will contribute to sustainable rice production under RSL, particularly in the coastal region that has substantial acreage under the variety Hasanta.

A survey of ethanol content in virgin olive oil

Ethanol is a substrate for the chemical synthesis of fatty acid ethyl esters (FAEE) during storage of virgin olive oil whose contents are officially regulated. Given the impact that the ethanol content might have on the olive oil commercialization, the level of this metabolite has been studied in an array of olive genotypes representing the diversity available in olive (Olea europaea L.). Substantial levels of ethanol have been found in the oils of all genotypes under study. Moreover, increasing levels of alcohol dehydrogenase activity have been found during olive fruit ripening in good correspondence with the accumulation of ethanol in advanced stages of fruit maturation. The results suggest that ethanol has a ubiquitous character in the fruits of Olea europaea and, therefore, in all the oils obtained from them. Besides, their concentration seems to depend on the cultivar, ripening stage and climatology, not discarding the influence of the growing conditions. Data suggest that the application of olive oil regulation for FAEE levels should consider the presence of basal levels of ethanol in the oils, which are quite high in many cultivars.

Survival Strategy in the Wetland SedgeCarex brevicuspis(Cyperaceae) in Response to Flood and Drought: Avoidance or Tolerance?

Survival strategies of plants to adapt to environmental stress include avoidance and tolerance. These strategies were investigated in the wetland sedge Carex brevicuspis (Cyperaceae) to determine the plasticity of its response to flood and drought. Individual plants were grown in PVC tubes and subjected to five water levels relative to soil surface: -40 cm, -20 cm, 0 cm, +20 cm, and +40 cm. After 60 days, plants were harvested and their biomass accumulation, number of leaves (a measure of growth), root and shoot elongation, aerenchyma formation (avoidance strategy), amount of malondialdehyde (MDA), amount of water-soluble carbohydrates (WSC), alcohol dehydrogenase (ADH) activity, amount of proline (tolerance strategy), and membrane permeability (a measure of degree of injury) were assessed. Relatively high amounts of MDA and proline and a high level of ADH activity, combined with relatively low aerenchyma area, short leaves, and low amount of WSC in the +20 cm and +40 cm treatments indicated that C. brevi...

Alcohol dehydrogenase activity in Lactococcus chungangensis: Application in cream cheese to moderate alcohol uptake

Many human gastrointestinal facultative anaerobic and aerobic bacteria possess alcohol dehydrogenase (ADH) activity and are therefore capable of oxidizing ethanol to acetaldehyde. However, the ADH activity of Lactococcus spp., except Lactococcus lactis ssp. lactis, has not been widely determined, though they play an important role as the starter for most cheesemaking technologies. Cheese is a functional food recognized as an aid to digestion. In the current study, the ADH activity of Lactococcus chungangensis CAU 28T and 11 reference strains from the genus Lactococcus was determined. Only 5 strains, 3 of dairy origin, L. lactis ssp. lactis KCTC 3769T, L. lactis ssp. cremoris KCCM 40699T, and Lactococcus raffinolactis DSM 20443T, and 2 of nondairy origin, Lactococcus fujiensis NJ317T and Lactococcus chungangensis CAU 28T KCTC 13185T, showed ADH activity and possessed the ADH gene. All these strains were capable of making cheese, but the highest level of ADH activity was found in L. chungangensis, with 45.9nmol/min per gram in tryptic soy broth and 65.8nmol/min per gram in cream cheese. The extent that consumption of cheese, following imbibing alcohol, reduced alcohol uptake was observed by following the level of alcohol in the serum of mice. The results show a potential novel benefit of cheese as a dairy functional food.

Adaptive strategies to tolerate prolonged flooding in seedlings of floodplain and upland populations of Himatanthus sucuuba, a Central Amazon tree

Long-term flooding imposes a strong selection pressure on plants for the development of protective mechanisms to alleviate the harmful effects of hypoxic and anoxic conditions. This is particularly critical in the Amazonian floodplains where plants withstand annual periods of flooding lasting 7 months and mean flooding amplitude reaching 10 m or more. Himatanthus sucuuba (Apocynaceae) is a tree that is found in the varzea (VZ) floodplains and non-flooded terra firme (TF) forests. It was examined whether individuals from these two contrasting habitats respond differently when subjected to extreme flooding conditions. TF and VZ seedlings were experimentally well-watered, waterlogged (roots and parts of the stems flooded), or submerged (whole plant flooded) during a 4-month period. Anaerobic respiration, evaluated by measuring alcohol dehydrogenase (ADH) activity, and root carbohydrate reserves were quantified, given that the availability of readily fermentable carbohydrates is essential to sustain an active fermentative metabolism. We also assessed changes in morphoanatomy, seedling survival, biomass accumulation and distribution. VZ seedlings had greater root concentrations of soluble sugars and starch, larger seedling mass and accumulated more biomass in roots and stems while TF seedlings allocated more towards stem and leaves. ADH activity was low in seedlings of both populations before exposure to flooding. Waterlogging induced an increase in ADH activity that reached a maximum value in 15 days. Thereafter activity decreased slowly, meanwhile a rapid formation of lenticels, adventitious roots and aerenchyma was observed. Submergence induced leaf shedding and the development of aerenchyma in the root cortex. While VZ seedlings maintained high levels of ADH activity throughout the whole 4-month period, ADH activity in TF seedlings peaked about 15 days after submersion followed by a continuous decrease and death of all the plants. Thus, VZ and TF seedlings differed considerably in terms of tolerating long-term exposure to flooding, especially under total submersion. These results suggest that the predictability and long-term duration of flooding in Central Amazon rivers can impose a selective pressure that is strong enough to result in large phenotypic differences between the two populations of H. sucuuba in the two habitat types.

Aerenchyma development and elevated alcohol dehydrogenase activity as alternative responses to hypoxic soils in the Piriqueta caroliniana complex

The ability of plants to make morphological or physiological adjustments in response to environmental cues allows them to survive and reproduce under a wide range of conditions. One stress that plants are often exposed to is soil oxygen depletion due to flooding. Plants can respond to hypoxic soils by producing oxygen-conducting aerenchymous tissue or through induction of enzymes in the ethanolic fermentation pathway. Here we use greenhouse experiments to examine flood responses in plants of the Piriqueta caroliniana (Turneraceae) complex, which occupy a range of moisture regimes. Morphotypes and hybrids in this complex exhibited contrasting responses to hypoxic conditions. Genotypes from flooded habitats developed aerenchyma and did not substantially elevate levels of alcohol dehydrogenase (ADH) activity, an enzyme associated with anaerobic respiration. Plants from drier sites, on the other hand, did not develop aerenchyma but had much higher levels of ADH activity. Plants with aerenchymous tissue had substantially higher rates of growth under sustained flooding. Results are consistent with the hypothesis that aerenchyma development is an effective strategy in habitats subject to persistent flooding, while elevating activity of enzymes for ethanolic fermentation is effective only under ephemeral flooding. The range of phenotypic responses observed illustrates contrasting adaptive strategies that can lead to habitat isolation and evolutionary divergence.

Characterisation of the ethanol‐induciblealcgene expression system for transgenic plants

Summary We describe a chemically induced gene control mechanism for plants based on the ALCR transcription factor and alcA promoter of Aspergillus nidulans , which we have called the alc system. Ethanol, the chemical inducer, is not toxic at levels required for induction, and can be applied to the plants by spraying, root drenching and addition to liquid growth media. The alc system is very sensitive to ethanol and the induction is rapid; 0.01% (1.7 mM) ethanol in liquid growth media initiates chloramphenicol acetyl transferase (CAT) reporter gene expression within 4 h, with maximal expression occurring after 4 days. In the complete absence of ethanol, there is no detectable expression of CAT, nor do we observe induction in plants subjected to wound, cold or drought stress, or following treatment with either salicylic acid or methyl jasmonate. However, extreme anoxia resulting in elevated levels of alcohol dehydrogenase activity in both roots and leaves gave substantial induction of CAT in leaves but not in roots. We believe that the alc system will have broad utility in the exogenous control of plant gene expression in pure science and that it also has considerable potential in agriculture.

Effect of growth substrates on formation of alcohol dehydrogenase in Acetobacter methanolicus and Acetobacter aceti

Two different strains of acetic acid bacteria, Acetobacter methanolicus and Acetobacter aceti, were grown on various carbon sources and their quinoprotein alcohol dehydrogenase (ADH) activities were measured. A. aceti was able to grow only on glycerol or glucose as a sole carbon source. The addition of another carbon source to a glycerol-containing medium promoted growth and increased the level of ADH activity. The results indicate that while ADH was constitutively produced under the growth conditions, an inactive form of ADH was formed besides the active form in cells grown in the medium containing glucose, acetic acid, or succinic acid. A. methanolicus was able to grow on a variety of carbon sources. ADH was formed in cells grown on glycerol or ethanol but not on methanol. ADH was also produced in cells grown on glucose or succinic acid, but the major part seemed to be the inactive form. The inactive form of ADH was thus shown to be produced under various growth conditions in both strains.

Insertion of the retroposable element, jockey, near the Adh gene of Drosophila melanogaster is associated with altered gene expression.

The alcohol dehydrogenase (Adh) gene of Drosophila melanogaster is well suited to be a gene expression reporter system. Adh produces a measurable phenotype at both the enzyme and mRNA levels. We recovered a spontaneous transposable element (TE) insertion mutation near the Adh gene. The insertion is a truncated retroposable element, jockey, inserted upstream of the adult Adh enhancer region. Comparisons between the Adhjockey allele and its direct wild-type ancestral allele were made in an isogenic background (i.e. identical cis and trans factors). Differences in Adhjockey expression compared with the wild-type can be attributed solely to the presence of the jockey element. This jockey insertion results in a decrease in adult mRNA transcript levels in the Adhjockey homozygous lines relative to the wild-type counterpart and accounts for a correlated decrease in alcohol dehydrogenase (ADH) enzyme activity. The larval ADH activity levels are not detectably different.

Alcohol dehydrogenase I of sake yeast Saccharomyces cerevisiae Kyokai no. 7

The sake yeast Saccharomyces cerevisiae Kyokai no. 7 (K-7) is capable of producing more than 20% (v/v) ethanol in culture. However, the activity of its alcohol dehydrogenase (ADH), which is a key enzyme in alcohol production, is less than that of the laboratory yeast S. cerevisiae X2180-1A. The ADH activities of brewery yeasts which were isolated and bred for the purpose of ethanol production were compared with those of laboratory yeasts. The ADH activities of a number of the brewery yeasts were found to be less than those determined for the laboratory yeasts. The level of ADH activity of each clone derived from a brewery yeast was also lower than that of each clone derived from laboratory yeasts when expressed in Escherichia coli cells. In the ADH1 gene of K-7, the region between the TATA ☐ and ATG start codon and the region of polyadenylation in this nucleotide sequence were consistent with previous data. The ratio of intracellular ADH activity of K-7 to that of X2180-1A was about 1 : 2. On the other hand, the ratio of ADH activity of the clones derived from K-7 and X2180-1A, expressed under the control of the same promoter and in the same host, was about 1 : 1.3. The amino acid sequence of K-7 ADH1 was compared with previous data. The Glu128 of K-7 ADH1 was unique among yeast ADH1s. Site-directed mutagenesis was carried out using ADH1 DNAs isolated from the sake yeast K-7 and the laboratory yeast X2180-1A, in order to determine amino acid alterations which affect activity. No single amino acid substitutions resulted in a change in the level of ADH activity. However, two double substitutions E128Q and E148Q or E128Q and V152I increased ADH activity to levels similar to that of X2180-1A Adh1. The substitutions of X2180-1A ADH1 to Q128E and Q148E or Q128E and I152V reduced ADH1 activity to the levels observed for K-7 Adh1.

The expression and anaerobic induction of alcohol dehydrogenase in cotton

The alcohol dehydrogenase (ADH) system in cotton is characterized, with an emphasis on the cultivated allotetraploid species Gossypium hirsutum cv. Siokra. A high level of ADH activity is present in seed of Siokra but quickly declines during germination. When exposed to anaerobic stress the level of ADH activity can be induced several fold in both roots and shoots of seedlings. Unlike maize and Arabidopsis, ADH activity can be anaerobically induced in mature green leaves. Three major ADH isozymes were resolved in Siokra, and it is proposed that two genes, Adh1 and Adh2, are coding for these three isozymes. The genes are differentially expressed. ADH1 is predominant in seed and aerobically grown roots, while ADH2 is prominent in roots only after anaerobic stress. Biochemical analysis demonstrated that the ADH enzyme has a native molecular weight of approximately 81 kD and a subunit molecular weight of approximately 42 kD, thus establishing that ADH in cotton is able to form and is active as dimers. Comparisons of ADH activity levels and isozyme patterns between Siokra and other allotetraploid cottons showed that the ADH system is highly conserved among these varieties. In contrast, the diploid species of cotton all had unique isozyme patterns.

ALCOHOL TOLERANCE, ADH ACTIVITY, AND ECOLOGICAL NICHE OF DROSOPHILA SPECIES.

In vitro alcohol dehydrogenase (ADH) activity was measured in adults of species belonging to Drosophila and to the related genus Zaprionus. Data were analyzed according to the known breeding sites and the level of ethanol tolerance of these species. Alcohol dehydrogenase activity was assayed with both ethanol (E) and isopropanol (I). Our results show a very broad range of activities among the 71 species investigated, the ratio of the highest value observed (D. melanogaster) to the lowest (D. pruinosa) being 65:1. A general positive correlation was found between the level of ADH activity and the capacity to detoxify ethanol. Nevertheless, many species show exceptions to this rule. Contrary to a logical expectation, adaptation to high alcoholic resources, which has been a recurrent evolutionary event, was not mediated by a more efficient use of ethanol, that is, an increase of the E/I ratio. This ratio seems to be quite variable according to the phylogeny and is especially low in the subgenus Sophophora as well as in Zaprionus. Alcohol tolerance clearly is related to the larval habitat of the species and shows that adaptation to alcoholic resources has been a major evolutionary challenge in drosophilids. This adaptation is not related to phylogeny, having occurred independently several times during the evolution of the group. Finally, it should be borne in mind that, besides metabolization and detoxification, other physiological processes such as nervous‐system tolerance or ethanol excretion may be involved in ethanol tolerance, and such functions also should be investigated. Environmental ethanol, which is certainly a major ecological parameter for many drosophilids, has selected a diversity of physiological adaptations, all related to the Adh locus, but presumably much more complicated than was previously believed.

The Response of Maize Seedlings of Different Ages to Hypoxic and Anoxic Stress (Changes in Induction of Adh1 mRNA, ADH Activity, and Survival of Anoxia).

Previously we showed that there is only a transient induction of alcohol dehydrogenase 1 (Adh1) transcripts and only a small induction of alcohol dehydrogenase (ADH) enzyme activity in root tips of maize (Zea mays L.) seedlings subjected to strict anaerobiosis without prior acclimation by exposure to low O2 (D.L. Andrews, B.G. Cobb, J.R. Johnson, M.C. Drew [1993] Plant Physiol 101: 403-414). Acclimation of root tips of seedlings by low O2 before anoxia appeared to be necessary for full induction of ADH. Here we have examined the effect of seedling age on changes in the protein content, induction of Adh1 transcripts, and ADH enzyme activity in 5-mm root tips, root axes, and shoots of maize (cv TX5855). Their ability to survive anoxia was also recorded. Some seedlings were sparged with 4% O2 for 6 or 18 h (a hypoxic pretreatment) followed by anoxia (sparged with N2) for up to 48 h. Other seedlings were not acclimated before anoxia. In general, younger seedlings had higher initial (aerobic) levels of total protein, Adh1 transcripts, and ADH activity than did seedlings that were 2 d older. For younger seedlings, anoxia alone induced Adh1 transcripts, which reached a peak within 6 to 12 h, whereas ADH activity increased throughout the 48-h treatment. For older seedlings, anoxia caused only a small, transient induction of Adh1 transcripts or ADH activity. For seedlings of either age, hypoxia induced Adh1 transcripts and ADH activity, both of which were increased further by subsequent anoxia in the younger seedlings but to a lesser extent in the older seedlings. Despite differences in ADH activity, roots of seedlings of either age showed a similar resistance to anoxia. Thus, acclimation of maize seedlings to survive anoxia does not appear to be related to induction of high levels of ADH activity.

Effects of thyroxine on the expression of alcohol dehydrogenase in rat liver and kidney

We studied the effect of thyroxine on alcohol dehydrogenase activity, immunoreactive protein levels and messenger RNA levels in the livers of thyroidectomized and sham-operated male rats. Effects on kidney alcohol dehydrogenase activity were also examined. Sham-operated rats injected with 100 micrograms thyroxine/kg/day, which induced hyperthyroidism, showed a 30% decrease in liver and a 40% decrease in kidney alcohol dehydrogenase activity compared with sham-operated rats injected with vehicle. Hypothyroid rats exhibited a 1.5-fold increase in alcohol dehydrogenase activity in liver and kidney compared with thyroidectomized rats injected with a replacement dose of 20 micrograms thyroxine/kg/day. We saw a twofold and a 2.5-fold higher level of alcohol dehydrogenase activity in liver and kidney, respectively, of hypothyroid rats compared with hyperthyroid rats. These effects were not accounted for by nutritional differences; daily food intake did not differ between groups. Immunoreactive protein levels as seen on Western blots varied in the same direction as enzyme activity. Northern-blot analysis showed higher levels of liver alcohol dehydrogenase messenger RNA in hypothyroid rats compared with euthyroid rats. These studies show that liver alcohol dehydrogenase activity and protein levels are modulated by thyroxine at pathophysiologically relevant levels and that this effect is not due to changes in food intake; kidney alcohol dehydrogenase activity is regulated in parallel. The change in alcohol dehydrogenase activity appears to be controlled in part by pretranslational mechanisms in hypothyroid animals and by posttranslational mechanisms in hyperthyroid animals.

Gender differences in ethanol oxidation and injury in the rat stomach

A significant fraction of orally consumed ethanol is metabolized by the alcohol dehydrogenase (ADH) enzyme present in the gastric mucosa. Human studies have shown that this “first pass metabolism” of ethanol correlates quite closely with gastric ADH activity which has been demonstrated to be greater in men than women. The present study was undertaken to determine if gender influences the magnitude of ethanol-induced injury in rat gastric mucosa and whether any differences can be linked to altered levels of ADH activity. Since prostaglandins (PGs) have been shown to markedly attenuate the severity of gastric injury induced by ethanol in the rat stomach, a further goal of this study was to determine whether the efficiency of PG's protective action was in any way influenced by gender. Accordingly, both male and female rats were pretreated subcutaneously with 16,16-dimethyl PGE 2 (10 μg/kg) or saline 30 minutes prior to administering an oral dose of 50% ethanol in saline or saline alone. They were then sacrificed 5 minutes later. In a portion of animals ( n = 6 per group), samples of mucosa from the glandular stomach were obtained and kinetic activity of ADH determined. In another portion of animals ( n = 6 per group), gastric tissue samples from the glandular mucosa were examined by light microscopy and the magnitude of mucosal injury quantified. Alcohol-treated females showed significantly ( p < 0.05) less superficial and more deep mucosal injury than male counterparts. Further, ADH kinetic activity in female rats was significantly less than that observed in male counterparts of similar weight (83% of males; p < 0.04). Despite these differences in ADH activity, and the magnitude of mucosal injury, the efficiency of protection by PG was equivalent in both sexes and involved primarily the deep epithelium. The results of this study indicate that ethanol damage to the gastric mucosa in female rats is more severe than that in corresponding males, and may be linked to the lower ADH kinetic activity present in female gastric mucosa. Despite these differences in ethanol oxidation and gastric injury, PG's protective action was equally efficatious in both sexes indicating that gender differences in ADH activity were of no importance in mediating this protection.

VARIATION IN ALCOHOL DEHYDROGENASE ACTIVITY AND FLOOD TOLERANCE IN WHITE CLOVER, TRIFOLIUM REPENS

Flooding results in induction of anaerobic metabolism in many higher plants. As an important component of anaerobic energy production, alcohol dehydrogenase (ADH) activity increases markedly in response to flooding in white clover, Trifolium repens. Significant inter-individual variation in flood-induced ADH activity exists in natural populations of T. repens. The genetic basis of this variation was analyzed by offspring-midparent regression of data from 75 greenhouse reared families; the estimated heritability of flood-induced ADH activity was 0.55 (±0.13). Genetic variation in flood-induced ADH activity has pronounced effects on physiological response and flood tolerance in this species. ADH activity is positively correlated with the rate of ethanol production, indicating that observed in vitro activity differences are manifested in in vivo physiological function. T. repens plants with higher ADH activities during flooding have greater flood tolerance (measured as growth rate when flooded/unflooded growth rate). Variation in ADH activity during flooding accounts for more than 79% of the variance in flood tolerance. On the basis of a limited field survey of populations occupying three sites differing in exposure to flooding conditions, individuals from site C, the most frequently flooded site, expressed significantly higher average ADH activity when flooded than individuals from site A, a site with no history of flooding. Since ADH activity levels are not correlated with electrophoretic mobility variation in T. repens, this work supports previous suggestions that regulatory variation in enzyme activity may play a central role in biochemical adaptations to environmental stress.

Genetic basis of the difference in alcohol dehydrogenase expression between Drosophila melanogaster and Drosophila simulans.

Drosophila melanogaster and its sibling species, Drosophila simulans, differ in expression of the enzyme alcohol dehydrogenase (ADH). Adult melanogaster flies that are homozygous for the Slow allozyme have approximately twice the level of ADH activity and crossreacting material as simulans adults. There is no corresponding difference in ADH mRNA, however, so this difference in ADH protein level is evidently due to a difference in the rate of translation of the two RNAs and/or to a difference in protein stability. Here we report an interspecific gene-transfer experiment, using P-element transformation, to determine whether this expression difference is due to genetic background differences between the species (trans-acting modifiers) or to cis-acting factors within the Adh gene. When the Adh genes from D. melanogaster and D. simulans are put into the same genetic background, there is no detectable difference in their level of expression. The level is relatively high in the melanogaster background and relatively low in the simulans background. Therefore, the interspecific difference in Adh expression is due entirely to trans-acting modifiers, in spite of the many sequence differences between the Adh genes of the two species, which include two amino acid substitutions.

Concurrent Synthesis and Degradation of Alcohol Dehydrogenase in Elicitor-Treated and Wounded Potato Tubers

The accumulation of alcohol dehydrogenase (ADH) in arachidonic acid-elicited potato (Solanum tuberosum L.) tuber discs was studied. In accordance with our previous report of the accumulation of Adh mRNA beginning 2 hours after elicitor treatment (DP Matton, CP Constabel, N Brisson [1990] Plant Mol Biol 14: 775-783), immunoprecipitation of ADH from in vivo labeled discs indicated that ADH synthesis occurred as early as 12 hours after treatment. However, levels of ADH activity and protein, as shown by enzyme assay and immunoblot, did not rise in parallel but decreased during the first 24 hours of treatment. After 24 hours, ADH activity and protein began to increase, reaching a several-fold increase at 96 hours after elicitation. Water-treated control discs showed a similar though delayed and less pronounced pattern. These results imply a turnover of ADH following elicitor treatment of potato tuber discs. As shown by nondenaturing gel electrophoresis, the synthesis and degradation involved the same ADH isozyme.

Gene regulation during anaerobiosis in soya roots

The proteins of soybean roots undergoing anaerobiosis can be grouped into three classes. Class 1 proteins are induced severalfold and at least 28 of these were identified by in vivo labeling. These proteins include the enzymes alcohol dehydrogenase (ADH), fructose aldolase, pyruvate decarboxylase, phosphoglucomutase, and lactate dehydrogenase. Class 2 proteins include such enzymes as glucose phosphate isomerase, sucrase, and malate dehydrogenase; their specific activity remains constant in aerobiosis or anaerobiosis. The third class of proteins includes those enzymes such as peroxidase whose activity decreases more than 90% after just 1 day in anaerobiosis. Immunoblotting coupled with two-dimensional chromatography of in vitro translated plant extracts demonstrated that ADH level during anaerobiosis is controlled by its mRNA concentration. Little or no mRNA for ADH was detected in aerobically grown roots. This suggests that the increased level of ADH activity is due to de novo synthesis of the mRNA rather than activation of a sequestered mRNA or superactivation of the protein.

Hypoxic Induction of Anoxia Tolerance in Root Tips of Zea mays

When root tips of fully aerobic, intact maize (Zea mays L.) seedlings are made anaerobic, viability normally is only 24 hours or less at 25 degrees C. We find that viability can be extended to at least 96 hours if seedlings are given a hypoxic pretreatment for 18 hours by sparging the solution with 4% O(2) in nitrogen (v/v) before anoxia. Fully aerobic root tips (sparged with 40% O(2)) had very low alcohol dehydrogenase (ADH) activity (per gram root fresh weight), and the level remained low under anoxia. In hypoxically pretreated roots, however, high levels of ADH activity were induced, and activity rose further during the initial 24 hours of anoxia, and then remained high at about 20 times that of controls in 40% O(2). ADH activity in roots in solution sparged with air (21% O(2)) was about three times that in 40% O(2). Improved viability of hypoxically pretreated root tips was associated with maintenance of a high energy metabolism (ATP concentration, total adenylates, and adenylate energy charge). Roots that were not pretreated lost 94% of the total adenylates and ATP at 24 hours of anoxia. The relation between induced ADH activity, energy metabolism, and improved anoxia-tolerance in acclimated maize root tips is discussed.