Localization Of Abscisic Acid Research Articles

Влияние засоления на устьичную и гидравлическую проводимость, а также на уровень аквапоринов в клетках листьев растений ячменя, различающихся по солеустойчивости

We studied participation of aquaporins in the regulation of leaf hydraulic conductivity and relationship of hydraulic conductivity with accumulation of ABA and stomatal closure during salt stress. Using the method of immunohistochemical localization we showed that salinity led to greater decline in the level of aquaporins in the region of the vascular leaf bundles of the more salt-tolerant Prairia cultivar, accompanied by a noticeable decrease in hydraulic conductivity of the leaf. In the less salt-tolerant plants of the Mikhailovsky cultivar, significant changes in the level of aquaporins under the influence of salt stress were not found. The degree of decrease in the hydraulic conductivity of the leaf in plants of two cultivars under the influence of salt stress correlated with a decrease in transpiration. Immunohistochemical localization of abscisic acid (ABA) in leaf cells showed that during salt stress this hormone accumulated in leaf mesophyll cells and stomata. The uptake of exogenous hormone from the nutrient solution and its entry into the leaf through the vascular bundles was accompanied by an increase in staining for aquaporins and the hydraulic conductivity of the leaves, which is characteristic of the ABA action. Differences in the localization of exogenous and endogenous hormones were obviously the cause of the opposite directions of changes in hydraulic conductivity: its increase under the influence of an exogenous ABA and a decrease - under the influence of salt stress. ABA concentration assessment in xylem showed the absence of its increase during salt stress, which explains the absence changes of staining for this hormone in the region of the leaf vascular bundles and indicates that accumulation of ABA in a short-term salt stress is not the result of its delivery from the roots, but the result of its synthesis in the shoot itself.

Влияние 24-эпибрассинолида на локализацию АБК, АЗП и дегидринов в корнях растений пшеницы при обезвоживании

We studied the immunohistochemical localization of abscisic acid (ABA), wheat germ agglutinin (WGA) and dehydrins in the roots of wheat seedlings (Triticum aestivum L.) during 24-epibrassinolide-pretreatment (EB-pretreatment) and PEG-induced dehydration. It was found coimmunolocalization of ABA, WGA and dehydrins in the cells of central cylinder of basal part untreated and EB-pretreated roots of wheat seedlings under normal conditions and under osmotic stress. Such mutual localization ABA and protective proteins, WGA and dehydrins, indicates the possible effect of their distribution in the tissues of EB-pretreated wheat roots during dehydration on the apoplastic barrier functioning, which apparently contributes to decrease the water loss under dehydration. Perhaps, the significant localization of ABA and wheat lectin in the metaxylem region enhances EB-induced transport of ABA and WGA from roots to shoots under stress. It can be assumed that brassinosteroids can serve as intermediates in the realization of the protective effect of WGA and wheat dehydrins during water deficit.

Development of sugar beet leaves: contents of hormones, localization of abscisic acid, and the level of products of photosynthesis

ABSTRACTThe level of hormones in the tissues of sugar beet leaves of different age in parallel with their growth and metabolic activity was assayed; the latter was analyzed, measuring the contents of sugars and N-containing compounds, and the activities of Rubisco and proteases. The highest auxin and ABA concentration was detected in the actively growing upper leaf, while high level of cytokinins was maintained in the middle and upper leaves characterized by intensive photosynthesis. Leaf senescence being manifested in decline of chlorophyll content, decrease of photosynthesis and activation of proteolysis was accompanied by a decline in concentration of cytokinins. Glucose level gradually increased from upper (younger) to a lower (elder) leaves; this was accompanied with the signs of senescence on the background of decreased cytokinins level. Immuno-histochemical technique revealed increased level of abscisic acid in phloem parenchyma of the lowest leaf. The results suggest a possible involvement of auxins in maintaining leaf growth, an implication of decreased cytokinins level in the hypothesized induction of senescence by glucose, and a participation of abscisic acid in the active loading of metabolites into the phloem of senescing leaf.

Вплив гіпертермії на характер акумуляції та локалізацію абсцизової кислоти у сортів Glycine max (L.) Merr. з різною стійкістю до абіотичних стресорів

Вплив гіпертермії на характер акумуляції та локалізацію абсцизової кислоти у сортів Glycine max (L.) Merr. з різною стійкістю до абіотичних стресорів

Localization of Abscisic Acid in Grape Berry by Immunohistochemical Techniques.

In the grape berry, which accumulates abscisic acid (ABA) markedly during ripening, the localization of this hormone was investigated by instrumental analysis and immunohistochemistry using an indirect immunoperoxidase method. In the instrumental analysis the levels of ABA in the outer wall, inner wall and placenta from unripe berries were nearly the same, ranging between 50 to 80 ng/gfw. After veraison, ABA levels in these tissues increased and reached a peak at 11 weeks after full bloom. The lowest level of ABA was in the inner wall ; it was intermediate in the outer wall, and highest in the placenta. Mouse antiserum raised against free (+) cis, trans abscisic acid was used in the first immunostaining step. Although positive immunoreactivity was detected on the sections, there were no visible differences in the immunoreactivity of the outer wall, inner wall and placenta. Phloem in both the peripheral and the central vascular bundles revealed high immunoreactivity in the ripe, but not in the unripe grape berries. In the ripe grape berry, the immunoreactivity of xylem in the peripheral and central vascular bundles was considerably lower than that of the phloem. This result suggests that the transport of abscisic acid from the leaves via the phloem contributes to its increase in the grape berry during ripening.

Immunogold localization of free abscisic acid in tomato root cells

Ultrastructural localization of abscisic acid in tomato (Lycopersicon esculentum Mill. cv. Vedettos) seedling roots is determined with the indirect protein A–gold approach. Polyclonal antibodies recognizing specifically the free (+)cis, trans form of abscisic acid are used as the first step in the immunolocalization procedure. Evidence is presented that its distribution varies within the different tissues of the tomato root. In the root cap cells, free abscisic acid accumulates mainly in the apoplast, in the cytoplasmic vesicles, and in the amyloplasts, around starch grains. In columella and meristematic cells, it accumulates mainly at the junction area with root cap cells, in the wall, and in the mucigel layer outside the root. Abscisic acid accumulation in the wall, the middle lamella, and the mucigel layer of the root cap cells may play a role in the root response to environmental stimuli. The cytochemical labeling of polygalacturonic acids, as recognized by the Aplysia depilans gonad lectin complexed to colloidal gold, follows closely the immunolocalization of abscisic acid. The secretory process of the root mucilage and the translocation of abscisic acid may be related. The significance of the apparent relationship between abscisic acid accumulation and the secretion of polygalacturonic acids is not yet understood. A role for apoplastic abscisic acid in a root-to-shoot communication system is discussed. Key words: abscisic acid, root physiology, immunolocalization, tomato.

A pleiotropic mutation results in cross-resistance to auxin, abscisic acid and paclobutrazol

Mutant lines of Nicotiana plumbaginifolia resistant to the synthetic auxins 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA) were isolated as germinating seedlings on selective medium. In each case, resistance was conferred by a single recessive nuclear mutation at one of 3 loci designated iba1, iba2 and iba3. Labelling studies with 14C NAA suggest that resistance was not due to changes in the uptake or metabolism of NAA. Plants homozygous for the iba1 mutation exhibit a syndrome of atypical germination and growth suggestive of a defect in the biosynthesis, metabolism or localization of abscisic acid. Wild-type seeds treated with gibberellin exhibit the same syndrome, including resistance to NAA and IBA. On the basis of these observations, we propose that auxin toxicity in seeds may be mediated by a block in gibberellin biosynthesis.

Multiple regression analysis of the relationships between tobacco mosaic virus multiplication, the severity of mosaic symptoms, and the growth of tobacco and tomato

This paper deals with quantitative aspects of the control of growth of virus-infected plants. Tobacco and tomato plants were inoculated with a total of 26 different strains of tobacco mosaic virus. These multiplied to varying extents, and caused mosaic symptoms of varying severity. Virus multiplication, plant growth and severity of mosaic symptoms were measured. Multiple regression analysis showed that variation in virus multiplication and symptom severity could account for most of the variation in growth which occurred as a result ofinfection. In tomato, variation in symptom severity was the dominant factor, and variation in virus multiplication could account for negligible amounts of variation in growth. In tobacco, variation in symptom severity and in virus multiplication could account for approximately equal amounts of variation in growth. The implied importance of amount of virus multiplication in control of growth of infected tobacco, but not of tomato, might reflect the finding that the virus multiplied to higher concentrations overall in tobacco than in tomato. Possible mechanisms linking mosaic symptom severity and inhibition of growth are discussed: it is suggested that in tobacco, but not tomato, alterations in the metabolism and localization of abscisic acid may be important.

The Compartmentation of Abscisic Acid and β-d-Glucopyranosyl Abscisate in Mesophyll Cells

beta-d-Glucopyranosyl abscisate (ABA-GE) is synthesized in Xanthium strumarium L. leaves during water stress. Following recovery from stress, the amount of ABA-GE does not decline. These observations led to the hypothesis that ABA-GE is sequestered in the vacuole where it is metabolically inert. The localization of abscisic acid (ABA) and ABA-GE was investigated by a dimethyl sulfoxide (DMSO) compartmentation method and by direct isolation of vacuoles.With the DMSO compartmentation method it was shown that in Xanthium mesophyll cells ABA was in a compartment not accessible to DMSO, presumably the chloroplast, whereas ABA-GE was in a compartment accessible to DMSO, presumably the vacuole. Neutral red, which accumulates in the vacuoles, showed a similar DMSO concentration dependence for its release from the cells as ABA-GE.Vacuoles isolated from Vicia faba L. leaf protoplasts contained 22% of the total ABA and 91% of the ABA-GE. Some of the ABA in the vacuole preparations was probably due to cytoplasmic contamination. These findings indicate that ABA-GE is sequestered in the vacuoles of mesophyll cells where the conjugated form of ABA is removed from the active ABA pool.