Abscisic Acid as Inhibitor of α-Amylase from Aspergillus and Bacillus subtilis

Abscisic acid (ABA) inhibited the activity of α-amylase from both Aspergillus and Bacillus subtilis in vitro if ABA and enzyme solutions were allowed to react with each other before adding to the starch solution. If the ABA solution was put to starch before adding the enzyme, no inhibition occurred. The inhibition increased with increasing time between mixing ABA and enzyme solutions and adding the mixture to starch. It was not the absolute amounts of enzyme and ABA which were of importance for the inhibition, but the concentrations of ABA and enzyme in the ABA + enzyme mixture. Within certain limits the inhibition was proportional to the concentration of ABA, so that it should be possible to use the inhibition in quantitative tests for inhibitors. Dialysis of a mixture of ABA and enzyme showed that ABA is bound to the enzyme. The enzyme was still inhibited after dialysis for 25 h. On the other hand, partitioning with diethylether from acid water solution could free the enzyme from all ABA. Supposedly ABA acts as an allosteric inhibitor. The results may offer the foundation for one possible way to explain why inhibitors in plants sometimes inhibit growth and sometimes do not. If inhibitor, enzyme and substrate are compartmentalized, the degree of reaction should depend upon the sequence in which the three components meet each other.     

Effect of indoleacetic acid,abscisic acid,root tips and coleoptile tips on growth and curvature of maize roots

The effect of externally applied indoleacetic acid (IAA) and abscisic acid (ABA) on the growth of roots of Zea mays L. was measured. Donor blocks of agar with IAA or ABA were placed laterally on the roots and root curvature was measured. When IAA was applied to vertical roots, a curvature directed toward the donor block was observed. This curvature corresponded to a growth inhibition at the side of the root where the donor was applied. When IAA was applied to horizontal roots from the upper side, normal geotropic downward bending was delayed or totally inhibited. The extent of retardation and the inhibition of curvature were found to depend on the concentration of IAA in the donor block. ABA neither induced curvature in vertical roots nor inhibited geotropic curvature in horizontal roots; thus the growth of roots was not inhibited by ABA. However, when, instead of donor blocks, root tips or coleoptile tips were placed onto vertical roots, a curvature of the roots was observed.Abbreviations ABA abscisic acid - IAA 3-indoleacetic acid     

Abscisic Acid Effects on Growth and Metabolism in the Roots ofLemna minor

The effects of abscisic acid (ABA) on individual plants of Lemna minor L. were studied. The effects on growth and metabolism of the roots were the most noticeable and the most desirable to measure. Two mg/1 of ABA inhibited the root growth rate by 60% and this was accompanied by a 60% deceleration in the rate of uridine incorporation. The uptake of uridine and leucine and the incorporation of leucine were not affected by ABA. The latent period of root growth inhibition was 1 hour, whereas the inhibition of ribonucleic acid (RNA) synthesis occurred 2 to 4 hours after application. The growth inhibition caused an accumulation of starch in the peripheral, differentiated cell layer of the cortex. Apparently, the growth inhibition by ABA was not entirely due to an inhibition of RNA synthesis, and other plausible mechanisms of growth inhibition are discussed.     

The effect of abscisic acid on the uptake of potassium and chloride into Avena coleoptile sections

Summary The effect of abscisic acid (ABA) on uptake of potassium (⁸⁶Bb⁺ or ⁴²K⁺) by Avena sativa L. coleoptile sections was investigated. ABA lowered the potassium uptake rate within 30 min after its application and inhibition reached a maximum (ca. 75%) after 2 h. The inhibition of K⁺ uptake increased with ABA concentration over a range of 0.03 to 10 g/ml ABA. At a higher K⁺ concentration (20 mM) the percentage inhibition decreased. The percentage inhibition of K⁺ uptake by ABA remained constant with external K⁺ varied from 0.04 to 1.0 mM. After a loading period in 20 mM K⁺ (⁸⁶Rb⁺), apparent efflux of potassium was only slightly increased by ABA. Experiments in which growth was greatly reduced by mannitol or by omission of indole-3-acetic acid from the medium indicated there was no simple quantitative correspondence between ABA inhibition of coleoptile elongation and ABA inhibition of K⁺ uptake. Chloride uptake was also inhibited by ABA but to a smaller degree than was K⁺ uptake. No specificity for counterions was observed for K⁺ uptake. Uptake of 3,0-methylglucose and proline were inhibited by ABA to a much smaller extent (14 and 11%) than that of K⁺, a result which suggests that ABA acts on specific ion uptake mechanisms.     

OsDi19‐4 acts downstream of OsCDPK14 to positively regulate ABA response in rice

The drought‐induced 19 protein family consists of several atypical Cys2/His2‐type zinc finger proteins in plants and plays an important role in abiotic stress. In this study, we found that overexpressing OsDi19‐4 in rice altered the expression of a series of abscisic acid (ABA)‐responsive genes, resulting in strong ABA‐hypersensitive phenotypes including ABA‐induced seed germination inhibition, early seedling growth inhibition and stomatal closure. On the contrary, OsDi19‐4 knockdown lines were less sensitive to ABA. Additionally, OsCDPK14 was identified to interact with OsDi19‐4 and be responsible for the phosphorylation of OsDi19‐4, and the phosphorylation of OsDi19‐4 was further enhanced after the treatment of ABA. Apart from these, OsDi19‐4 was shown to directly bind to the promoters of OsASPG1 and OsNAC18 genes, two ABA‐responsive genes, and regulate their expression. Transient expression assays confirmed the direct regulation role of OsDi19‐4, and the regulation was further enhanced by the increased phosphorylation of OsDi19‐4 after the treatment of ABA. Taken together, these data demonstrate that OsDi19‐4 acts downstream of OsCDPK14 to positively regulate ABA response by modulating the expression of ABA‐responsive genes in rice.     

Abscisic Acid Suppresses the Hypersensitive Necrosis of Potato Tubers and Reverses the Arachidonic Acid-Induced Inhibition of Plasma Membrane-Bound ATPase

Abscisic acid (ABA) fully suppressed the development of the hypersensitive necrosis of potato tuber slices to crude elicitor from Phytophthora infestans and arachidonic acid (AA) if supplied before or up to 6 to 8 h after elicitor treatments. Later application of ABA only reduced the necrotic response. Added to highly purified plasma membrane preparation from tuber tissue, ABA eliminated the AA-induced inhibition of the plasma membrane-bound (K⁺+ Na⁺+ Mg²⁺) ATPase. It is suggested that ABA counteracts AA in the membrane.     

Effect of Competition and Treatment with Inhibitor of Ethylene Perception on Growth and Hormone Content of Lettuce Plants

We elucidated the effect of increased planting density (single and grouped competing plants) on concentrations of auxin, abscisic acid, and cytokinins in normal lettuce plants and in those with ethylene perception inhibited by 1-methylcyclopropene (1-MCP). An attempt was made to relate the changes in hormone concentration induced by competition and inhibition of ethylene sensitivity to growth responses of lettuce planting. The results showed changes in concentrations of auxins, cytokinins, and ABA in the response of lettuce to crowding. Accumulation of ABA in shoots was likely to contribute to inhibition of transpiration of the plants grown in the presence of neighbors. This assumption was supported by the results of application of an inhibitor of ABA synthesis (fluridone and carotenoid biosynthesis herbicide) resulting in increased transpiration of grouped, but not single plants. Increased planting density led to the decline in root auxins paralleled by inhibition of root growth. This effect was likely to be due to decreased auxin transport to the roots from the shoots suggested by accumulation of auxins in the shoots and inhibition of root growth by application of the auxin transport inhibitor [N-(1-naphtyl)phtalamic acid (NPA)]. Importance of the changes in hormone concentrations was confirmed by data showing that disturbance of auxin and cytokinin distribution detected in MCP-treated plants was accompanied by corresponding modification of the growth response.

     

Chemical genetic identification of a lectin receptor kinase that transduces immune responses and interferes with abscisic acid signaling

Insight into how plants simultaneously cope with multiple stresses, for example, when challenged with biotic stress from pathogen infection and abiotic stress from drought, is important both for understanding evolutionary trade‐offs and optimizing crop responses to these stresses. Mechanisms by which initial plant immune signaling antagonizes abscisic acid (ABA) signal transduction require further investigation. Using a chemical genetics approach, the small molecule [5‐(3,4‐dichlorophenyl)furan‐2‐yl]‐piperidine‐1‐ylmethanethione (DFPM) has previously been identified due to its ability to suppress ABA signaling via plant immune signaling components. Here, we have used forward chemical genetics screening to identify DFPM‐insensitive loci by monitoring the activity of ABA‐inducible pRAB18::GFP in the presence of DFPM and ABA. The ability of DFPM to attenuate ABA signaling was reduced in rda mutants (resistant to DFPM inhibition of ABA signaling). One of the mutants, rda2, was mapped and is defective in a gene encoding a lectin receptor kinase. RDA2 functions in DFPM‐mediated inhibition of ABA‐mediated reporter expression. RDA2 is required for DFPM‐mediated activation of immune signaling, including phosphorylation of mitogen‐activated protein kinase (MAPK) 3 (MPK3) and MPK6, and induction of immunity marker genes. Our study identifies a previously uncharacterized receptor kinase gene that is important for DFPM‐mediated immune signaling and inhibition of ABA signaling. We demonstrate that the lectin receptor kinase RDA2 is essential for perceiving the DFPM signal and activating MAPKs, and that MKK4 and MKK5 are required for DFPM interference with ABA signal transduction.     

An Abscisic Acid-like Substance in Dry and Soaked Phaseolus vulgaris Seeds Determined by the Lemna Growth Bioassay

An acid inhibitor, probably abscisic acid (ABA) in low concentrations was found to be present in bean seeds. The evidence is based on data from paper electrophoresis, chromatography, UV absorption and growth inhibition in the Lemna bioassay, sensitive down to a concentration of 10^-11M ABA or 0.02–0.03 ng/flask. The inhibitor level as measured by this bioassay decreases considerably with increasing soaking time. Acid ether-soluble inhibitors could even be detected in the soaking water from the soaked seeds.     

Abscisic-acid-induced turion formation in Spirodela polyrrhiza L III. Specific changes in protein synthesis and translatable RNA during turion development

Abstract The developmental process leading to the formation of the abscisic acid (ABA) induced turion of Spirodela polyrrhiza was accompanied by a repression of nucleic acid and protein synthesis. DNA synthesis in the developing lurion (induced by 10⁻⁴mol m⁻³ ABA) was inhibited within 3h of ABA addition, followed by a repression of protein synthesis after 24 h, while RNA synthesis was not inhibited until 3 d. The inhibitory effect of ABA on protein synthesis was found to be selective and the synthesis of several novel proteins appeared to be induced. These effects were specific to ABA-sensitive tissue. The relationship between the changes in the protein and mRNA profiles during the development of the turion was investigated. The rapid general inhibition of protein synthesis at early stages of lurion formation could not be accounted for by the level of translatable mRNA, indicating an effect of ABA at the translational level. The specific alteration to the pattern of in vivo labelled proteins could have resulted, however, from control of the level of specific mRNAs for those particular proteins. Only after 3 d in ABA, when the developing primordium is committed to the turion developmental pathway, is there a total inhibition in the production of mRNA leading to the shutdown of all primary processes and the onset of the irreversible events leading to the dormant state.     

Modulation of carrier-mediated uptake of abscisic acid by methyl jasmonate in Phaseolus coccineus L

The effects of methyl jasmonate and jasmonic acid on uptake of abscisic acid (ABA) by suspension-cultured runner-bean cells and subapical runner-bean root segments have been investigated. Increasing concentrations of methyl jasmonate inhibit ABA uptake by the cultured cells with a K _i of 22±3 M. This is not due to cytoplasmic acidification or to effects on metabolism of ABA, and is not additive with inhibition of radioactive ABA uptake by nonradioactive ABA. Uptake of indol-3-yl acetic acid (IAA) is unaffected by methyl jasmonate. The maximum effect of nonradioactive ABA in inhibiting uptake of radioactive ABA, previously shown to reflect saturation of an ABA carrier, is generally greater than the effect of maximally inhibitory concentrations of methyl jasmonate. Similar results were obtained with root segments, but longer incubation times were necessary to observe inhibitory effects of methyl jasmonate. Demethylation of methyl jasmonate to jasmonic acid does not appear to be required since similar concentrations of jasmonic acid had no observable direct effect on ABA uptake other than that attributable to cytoplasmic acidification. Histidine reagents, a proton ionophore and acidic external pH all affect in parallel the inhibition by methyl jasmonate and nonradioactive ABA of uptake of radioactive ABA by the cultured cells. There is no effect of ABA or nonradioactive methyl jasmonate on uptake of radioactive methyl jasmonate by the cultured cells. It is proposed that methyl jasmonate interacts with the ABA carrier. Various models for this interaction are discussed.Abbreviations ABA abscisic acid - DMO 5,5-dimethyloxazolidine-2,4-dione - IAA indol-3-yl acetic acid     

Abscisic Acid in Prunus Trees: Isolation and the Effect on Growth of Excised Shoot Tissue

The abscisic acid content of the mature shoot tissue of vigorous Prunus avium, medium sized Prunus cerasus and dwarfing Prunus cerasus self (S) was estimated by spectropolarimetry and gas chromatography. There is no correlation between the levels of ABA found in the tissue and the dwarfing potential of the trees investigated. However, Prunus arium stem tissue shows the lowest sensitivity to ABA, whereas the explants of normal and dwarfing Prunus cerasus exhibit a stronger inhibition.     

Effects of Abscisic Acid on Phenolic Content and Lignin Biosynthesis in Tobacco Tissue Culture

A significant depression of callus growth resulted from low concentrations of abscisic acid (ABA) added to the medium recommended by Linsmaier and Skoog. Low concentrations also decreased the chlorogenic acid and lignin content of the callus, and generally decreased amounts of scopolin and scopoletin in the tissue. Gibberellic acid (GA₃) stimulated callus growth in a low concentration (0.1 mg/1) and inhibited growth at a high concentration (10.0 mg/1). Both levels of GA₃ increased scopoletin accumulation in tobacco callus. A high concentration of GA₃ increased the accumulation of scopolin and chlorogenic acids, whereas a low concentration decreased the amounts of these two phenolic compounds. In comparison with the control, lignin synthesis was stimulated by a low GA₃ concentration, but a high GA₃ concentration did not have a significant effect. Both low and high concentrations of GA₃ overcame ABA inhibition of growth and lignin synthesis, and partially reversed ABA inhibition of scopoletin production. However, GA₃ did not reverse the inhibitory effect of ABA on scopolin production. The low concentration of GA₃ overcame the inhibition of chlorogenic acid production resulting from a 0.01 mg/1 concentration of ABA, but this was the only reversal of chlorogenic acid inhibition resulting from addition of GA₃ to the medium.     

Synthesis and metabolism of abscisic acid in detached leaves of Phaseolus vulgaris L. after loss and recovery of turgor

Metabolism of abscisic acid (ABA) was studied after wilting and upon recovery from water stress in individual, detached leaves of Phaseolus vulgaris L. (red kidney bean). Loss of turgor was correlated with accumulation of ABA and its metabolites, resulting in a 10-fold increase in the level of phaseic acid (PA) and a doubling of the level of conjugated ABA. The level of conjugated ABA in turgid leaves was no higher than that of the free acid. These results indicate that accumulation of ABA in wilted leaves resulted from a stimulation of ABA synthesis, rather than from a release from a conjugated form or from inhibition of the metabolism of ABA. The rate of synthesis of ABA was at its maximum between 2.5 and 5 h after turgor was lost, and slackened there-after. In wilted leaves, the rate of conversion of ABA to PA climbed steadly until it matched the rate of synthesis, after about 7.5 h. Upon rehydration of sections from wilted leaves, the rate of synthesis of ABA dropped close to zero within about 3 h, while the rate of conversion to PA accelerated. Formation of PA was two to four times faster than in sections maintained in the wilted condition; it reached a rate sufficient to convert almost one-half of the ABA present in the tissue to PA within 1 h. In contrast, the alternate route of metabolism of ABA, synthesis of conjugated ABA, was not stimulated by rehydration. The role of turgor in the stimulation of the conversion of ABA to PA was investigated. When leaves that had been wilted for 5 h were rehydrated to different degrees, the amount of ABA which disappeared, or that of PA which accumulated during the next 3 h, did not depend linearly on the water potential of the rehydrated leaf. Rather, re-establishment of the slightest positive turgor was sufficient to result in maximum stimulation of conversion of ABA to PA.Abbreviations ABA abscisic acid - DPA dihydrophaseic acid - PA phaseic acid - _leaf leaf water potential - osmotic pressure     

Modalités de l'inhibition de la croissance et de la synthèse des acides nucléiques des plantules de blé par l'acide abscissique

The growth of wheat seedlings (Triticum sativum) is inhibited by abscisic acid (ABA). The inhibition increases with the concentration of ABA (from 10^-6M to 5 × 10^-5M) and is stronger in the case of coleoptiles and first leaves than in roots. In contrast, naphthaleneacetic acid (ANA), at 10^-5M, exerts its greatest inhibitory effect on the roots. The inhibitory effect of ABA on coleoptiles can be partially overcome by kinetin and to a much smaller degree by gibberellic acid. Neither of these two compounds, at 10^-5M, had any effect on the ABA-induced inhibition of root growth. The RNA and DNA contents per plant organ are considerably reduced after treatment of the seedlings with ABA, particularly in the coleoptiles and the first leaves. The incorporation of uracil-2-¹⁴C and uridine T (G) into RNA of treated seedlings is reduced in the case of coleoptiles and first leaves, but considerably enhanced in roots. The mechanism of the action of ABA is discussed in the light of these results.     

Time course of uptake of 14C-abscisic acid by Lemna gibba in relation to growth

The time course of growth of Lemna gibba L. in low concentrations of abscisic acid (ABA) and of uptake of ¹⁴C-labelled ABA into the plants was followed for up to 15 days. Fresh weight increase was arrested when the plants were transferred to ABA solutions. This inhibition was greatest during the first days after which a marked recovery took place. Dry matter production was only slightly affected by ABA. On a culture basis, the uptake of ABA was almost linear with time during the experimental period. The rate of uptake on a fresh weight basis was highest during the first two days but decreased rapidly from the third day. Most of the applied ¹⁴C remained in the culture solution throughout the experiments. Plants transferred to a solution without ABA retained most of their accumulated ¹⁴C. Possible explanations for the decrease in rate of ABA uptake and restoration of growth are discussed.     

Effects of cycloheximide on abscisic Acid biosynthesis and stomatal aperture in bean leaves

Cycloheximide was shown to block abscisic acid (ABA) biosynthesis in nonstressed as well as in stressed Phaseolus vulgaris leaves. Leaf wilting caused by cycloheximide resulted from increased stomatal opening as judged by a decreased stomatal diffusion resistance. The inhibition of ABA biosynthesis by cycloheximide was at least partially responsible for the increase in stomatal opening as suggested by the cooccurrence of inhibition of ABA biosynthesis and increased stomatal opening, and the partial reversal of stomatal opening in cycloheximide-treated leaves by exogenous ABA. Dark treatment failed to close stomatal in cycloheximide-treated leaves, suggesting that stomatal closure in response to darkness may normally be mediated by ABA.     

Levels of short-chain fatty acids and of abscisic acid in water-stressed and non-stressed leaves and their effects on stomata in epidermal strips and excised leaves

Straight-chain saturated fatty acids (C6-C11) and abscisic acid (ABA) accumulate in the leaves of Phaseolus vulgaris L. and Hordeum vulgare L. under water stress. ABA and certain of the fatty acids, particularly decanoic and undecanoic acid, can inhibit stomatal opening and cause stomatal closure in epidermal strips of Commelina communis L. depending on the incubating medium used. 10^-4 M (±)-ABA inhibits opening in media containing either high or relatively low concentrations of KCl but causes closure only in the latter medium. The fatty acids (at 10^-4 M) prevent opening in both media while significant closure of open stomata was caused only by undecanoic acid in both media and, additionally, by decanoic acid in the low-KCl medium. 10^-4 M formic acid also caused stomatal closure and prevented opening to significant extents in the low-KCl medium (it was not tested in the high-KCl medium). The efficacy of undecanoic acid in causing 50% inhibition of opening is about three orders of magnitude lower than that of ABA. At a concentration of 10^-3 M, nonanoic, decanoic and particularly undecanoic acid and all-trans-farnesol cause increased cell leakage in Beta vulgaris L. root tissue. Undecanoic acid (10^-4 M) also causes some loss of guard cell integrity in C. communis within 1.5 h of treatment. ABA (10^-4 M) reduces transpiration rates in barley and C. communis leaves when applied via the transpiration stream but decanoic and undecanoic acids did not have this effect. Transpiration was not affected when ABA or the fatty acids were applied to the leaf surfaces.Abbreviations ABA abscisic acid - RWC relative water content - SCFA short-chain fatty acids Deceased May 1977     

Abscisic acid inhibits germination of mature Arabidopsis seeds by limiting the availability of energy and nutrients

The addition of abscisic acid (ABA) to mature non-dormant seeds inhibits their germination. This effect of ABA might be related to its natural function as an endogenous inhibitor of precocious germination during seed formation. In this work, we studied how ABA affects the germination of mature seeds and the growth of nascent seedlings of Arabidopsisthaliana (L.) Heynh. Our findings were as follows: (i) inhibition by ABA was gradual, dose-dependent, and did not disappear after germination; (ii) inhibition of germination was relieved by the addition of metabolizable sugars or amino acids to the plating media; (iii) the effect of sugars and amino acids was cooperative, indicating that these two groups of metabolites relieve different deficiencies; (iv) ABA caused appreciable alterations in energy and nitrogen metabolism; and (v) ABA prevented the degradation of the seed storage proteins. In summary, ABA appears to inhibit seed germination by restricting the availability of energy and metabolites. This mechanism seems consistent with other known effects of ABA. Received: 3 February 1997 / Accepted: 10 March 1997     

Abscisic acid-induced growth inhibition of sweet potato (Ipomoea batatas L.) in vitro

The inhibitory effects of abscisic acid (ABA) on in vitro growth and development of axillary buds from nodal segments of sweet potato (Ipomoea batatas L.) was investigated. ABA at concentrations of 0.01, 0.1, 1.0 or 10.0 mg 1^-1 inhibited axillary bud and root development and subsequent plantlet growth. ABA at 10 mg 1^-1 completely inhibited axillary shoot development but did not affect the viability of cv. Jewel explants over a culture period of 365 days. Transfer of nodal segments cultured for 90, 180 or 365 days from basal medium containing 10 mg 1^-1 ABA to growth regulator-free media resulted in rapid and normal plantlet development. Gibberellic acid at 0.1, 1.0 or 10.0 mg 1^-1 in the presence of ABA at 0.1, 1.0 or 10.0 mg 1^-1 did not counteract the ABA-induced growth inhibition. Although ABA totally inhibited the growth of 6 sweet potato plant introductions at a concentration of 10.0 mg 1^-1, the efficacy of ABA as a suppressant of shoot growth varied with genotype.Abbreviations ABA abscisic acid - GA gibberellic acid - cDNA complementary DNA - PI plant introduction - SE standard error