Injection Of Abscisic Acid Research Articles

Phytohormone abscisic acid boosts pentobarbital-induced sleep through activation of GABA-A, PPARβ and PPARγ receptor signaling.

Sleep disorders induce anxiety and forgetfulness and change habits. The chemical hypnotic drugs currently used have serious side effects and, therefore, people are drawn towards using natural compounds such as plant-based healing agents. Abscisic acid (ABA) is produced in a variety of mammalian tissues and it is involved in many neurophysiological functions. To investigate the possible effect of ABA on pentobarbital-induced sleep and its possible signaling through GABA-A and PPAR (γ and β) receptors, in male Wistar rats. The possible effect of ABA (5 and 10 µg/rat, intracerebroventricularly) on sleep onset latency time and duration was evaluated in a V-maze model of sleep. Pentobarbital sodium (40 mg/kg, intraperitoneally) was injected to induce sleep 30 min after administration of ABA. PPARβ (GSK0660, 80 nM/rat), PPARγ (GW9662, 3 nM/rat) or GABA-A receptor (bicuculline, 6 µg/rat) antagonists were given 15 min before ABA injection. Diazepam (2 mg/kg, intraperitoneally) was used as a positive control group. ABA at 5 µg significantly boosted the pentobarbital-induced subhypnotic effects and promoted induction of sleep onset in a manner comparable to diazepam treatment. Furthermore, pretreatment with bicuculline significantly abolished the ABA effects on sleep parameters, while the amplifying effects of ABA on the induction of sleep onset was not significantly affected by PPARβ or PPARγ antagonists. The sleep prolonging effect of ABA was significantly prevented by both PPAR antagonists. The data showed that ABA boosts pentobarbital-induced sleep and that GABA-A, PPARβ and PPARγ receptors are, at least in part, involved in ABA signaling.

Spinal protein kinase A and phosphorylated extracellular signal-regulated kinase signaling are involved in the antinociceptive effect of phytohormone abscisic acid in rats.

The phytohormone abscisic acid (ABA) as a signaling molecule exists in various types of organisms from early multicellular to animal cells and tissues. It has been demonstrated that ABA has an antinociceptive effect in rodents. The present study was designed to assess the possible role of PKA and phosphorylated ERK (p-ERK) on the antinociceptive effects of intrathecal (i.t.) ABA in male Wistar rats. The animals were cannulated intrathecally and divided into different experimental groups (n=6‒7): Control (no surgery), vehicle (received ABA vehicle), ABA-treated groups (received ABA in doses of 10 or 20 µg/rat), ABA plus H.89 (PKA inhibitor)-treated group which received the inhibitor 15 min prior to the ABA injection. Tail-flick and hot-plate tests were used as acute nociceptive stimulators to assess ABA analgesic effects. p-ERK was evaluated in the dorsal portion of the spinal cord using immunoblotting. Data showed that a microinjection of ABA (10 and 20 µg/rat, i.t.) significantly increased the nociceptive threshold in tail flick and hot plate tests. The application of PKA inhibitor (H.89, 100 nM/rat) significantly inhibited ABA-induced analgesic effects. Expression of p-ERK was significantly decreased in ABA-injected animals, which were not observed in the ABA+H.89-treated group. Overall, i.t. administration of ABA (10 µg/rat) induced analgesia and p-ERK down-expression likely by involving the PKA-dependent mechanism.

Phosphatidylinositol-3-kinase and protein kinase C are involved in the pro-cognitive and anti-anxiety effects of phytohormone abscisic acid in rats

The phytohormone abscisic acid (ABA) exists in animal tissues particularly in the brain. However, the neurophysiological effects of ABA have not yet been fully determined. Signaling molecules such as PKC and PI3K have been implicated in anxiety-like behavior as well as learning and memory processes. Recently, it has been demonstrated that PKC and PI3K signaling pathways participate in some biological effects of ABA. This study was designed to evaluate the effects of central injection of ABA on spatial learning and memory and anxiety-like behavior and determine its possible signaling mechanisms. Spatial learning and memory and anxiety-like behaviors were determined using Morris water maze (MWM) and plus maze tests, respectively. ABA alone or in accompanied with selective inhibitors of PKC (chelerythrine) and PI3K (LY2940029) was injected bilaterally into the cerebral lateral ventricles. The results indicated that ABA (10μg/rat) significantly improved rats’ performance in MWM which was blocked by PKC or PI3K inhibitors. In addition, ABA showed anti-anxiety effect in plus maze test, which was not observed in PKC or PI3K inhibitor-treated rats. Overall, the results indicated that ABA has positive effect on spatial learning and memory performance and elicits anti-anxiety effects which are performed, at least in part, through PI3K/PKC signaling pathway.

Influence of Abscisic Acid on the Biology and Hemocytes of the Model InsectGalleria mellonella(Lepidoptera: Pyralidae)

Concerns over the ecological impacts of insecticides have led researchers to look for environmentally friendly plant-derived pest control compounds such as plant growth regulators. Here we investigate whether the plant growth regulator abscisic acid (ABA) alters the life history traits and hemocytes of Galleria mellonella L. (Lepidoptera: Pyralidae) when injected into the hemocoel. The injection of ABA resulted in dose-dependent mortality of final-instar larvae, as well as an increase in the duration of the larval stage and adult emergence time, and decrease in pupation and adult emergence ratios. The mean adult longevity and fecundity of G. mellonella adults was lower at higher doses. Injection of different concentrations of ABA led to a remarkable decrease in the number of circulating hemocytes at all time intervals. Analyses of the differential hemocyte counts revealed that ABA altered the granulocyte and plasmatocyte ratio in a dose-dependent manner at different time intervals. The percentage of mitotic hemocytes also decreased at 10 and 50 mg/ml at 24 h post ABA injection. These findings demonstrate that ABA may interfere with development and the hemocytes of G. mellonella and could be a good candidate for pest control after detailed study of ingestion and contact effects in further studies.

Identification and transcript analysis of two glutamate decarboxylase genes, CsGAD1 and CsGAD2, reveal the strong relationship between CsGAD1 and citrate utilization in citrus fruit.

Glutamate decarboxylase (GAD, EC 4.1.1.15) has been suggested to be a key, regulatory point in the biosynthesis of γ-aminobutyrate (GABA) and in the utilization of citric acid through GABA shunt pathway. In this study we discovered two GAD genes, named as CsGAD1 and CsGAD2, in citrus genome database and then successfully cloned. Both CsGAD1 and CsGAD2 have a putative pyridoxal 5-phosphate binding domain in the middle region and a putative calmodulin-binding domain at the carboxyl terminus. Gene structure analysis showed that much difference exists in the size of exons and introns or in cis-regulatory elements in promoter region between the two GAD genes. Gene expression indicated that CsGAD1 transcript was predominantly expressed in flower and CsGAD2 transcript was predominantly expressed in fruit juice sacs; in the ripening fruit, CsGAD1 transcript level was at least 2-time higher than CsGAD2 transcript level. Moreover, CsGAD1 transcript level was increased significantly along with the increase of GAD activity and accompanied by a significant decrease of titratable acid (TA), suggesting that it is CsGAD1 rather than CsGAD2 plays a role in the citric acid utilization during fruit ripening. In addition, injection of abscisic acid and foliar spray of K2SO4 significantly increased the TA content of Satsuma mandarin, and significantly decreased GAD activity as well as CsGAD1 transcript, further suggesting the important role of CsGAD1 in the citrate utilization of citrus fruit.

Effects of humidity on short-term responses of stomatal conductance to an increase in carbon dioxide concentration

ABSTRACT The magnitude of the response of stomatal conductance toa change in the concentration of carbon dioxide external tothe leaf from 350 to 700 cm 3 m –3 was found to be extremelyvariable from day to day in the field in Glycine max,Hordeum vulgare and Triticum aestivum. It was found thatthe leaf-to-air water vapour pressure difference (LAVPD)during the midday measurements of the stomatal responseto carbon dioxide affected the magnitude of the response.On days when LAVPD was low, no significant change inconductance occurred with the increase in carbon dioxideconcentration. When LAVPD was higher, conductancedecreased by 24–52% with the increase in carbon dioxidewithin a few minutes. The sensitivity of conductance wasapproximately linearly related to LAVPD in wheat andbarley. Experiments with G. maxin the field indicatedthat, on days with low LAVPD, increasing the LAVPD justaround the measured portion of a leaflet made stomatalconductance responsive to increased carbon dioxide. Thisresult was also obtained under laboratory conditions withG. max , Helianthus annuus and Amaranthus retroflexus . InG. max, it was determined that leaves in which conduc-tance was not responsive to the increase in carbon dioxidecould be made responsive even at low LAVPD by the injec-tion of abscisic acid into their petioles. Because it is knownthat abscisic acid sensitizes stomata to carbon dioxide,these results are consistent with the idea that abscisic acidmay be involved in the response of stomatal conductanceto changes in LAVPD.Key-words: abscisic acid; carbon dioxide; humidity; stomatalconductance; vapour pressure deficit.

Effects of Abscisic Acid Injection on Sugar and Organic Acid Contents of Citrus Fruit.

The effect of exogenous abscisic acid (ABA) injections into citrus fruits in autumn on fruit drop, ABA catabolism, and sugar and organic acid contents were evaluated. Fruit drop increased after ABA injection proportional to the ABA concentration. Ninety-two percent of citrus fruits were retained 16 days after injection with 0.2 μmol ABA per fruit. Injection of 14C-ABA revealed that exogenously applied ABA was catabolized to a level of about 10% in the fruits within four days. Injection of ABA caused an increase in the glucose and fructose concentrations, but had no effect on the organic acid in the juice. ABA appears to play a role in increasing sugar content of fruit juice.

Evidence for an Extracellular Reception Site for Abscisic Acid in Commelina Guard Cells.

The phytohormone abscisic acid (ABA) triggers stomatal closing as a physiological response to drought stress. Several basic questions limit an understanding of the mechanism of ABA reception in guard cells. Whether primary ABA receptors are located on the extracellular side of the plasma membrane, within the intracellular space of guard cells, or both remains unknown. Furthermore, it is not clear whether ABA must be transported into guard cells to exert control over stomatal movements. In the present study, a combination of microinjection into guard cells and physiological assays of stomatal movements have been performed to determine primary sites of ABA reception in guard cells. Microinjection of ABA into guard cells of Commelina communis L. resulted in injected cytosolic concentrations of 50 to 200 [mu]M ABA and in additional experiments in lower concentrations of approximately 1 [mu]M ABA. Stomata with ABA-loaded guard cells (n > 180) showed opening similar to stomata with uninjected guard cells. The viability of guard cells following ABA injection was demonstrated by neutral red staining as well as monitoring of stomatal opening. Extracellular application of 10 [mu]M ABA inhibited stomatal opening by 98% at pH 6.15 and by 57% at pH 8.0. The pH dependence of extracellular ABA action may suggest a contribution of an intracellular ABA receptor to stomatal regulation. The findings presented here show that intracellular ABA alone does not suffice to inhibit stomatal opening under the imposed conditions. Furthermore, these data provide evidence that a reception site for ABA-mediated inhibition of stomatal opening is on the extracellular side of the plasma membrane of guard cells.

The directional control of sucrose and asparagine transport in lupin by abscisic acid

Injections of exogenous abscisic acid into the primary flowerhead of Lupinus luteus cv. Weiko III reduced the movement of 14C‐sucrose into the flowerhead from the uppermost leaves. Sucrose transported from below the lateral branches subtending the flowerhead, was diverted into the lateral branches by injection of the exogenous abscisic acid into the flowerhead. 14C‐sucrose was also diverted from a lateral branch injected with exogenous abscisic acid to all other parts of the plant, particularly the main stem and leaves, and the roots. Transport of 14C‐asparagine administered at the cotyledonary node was directed from the flowerhead into the subtending lateral branches by injection of abscisic acid into the flowerhead. Transport of both 14C‐sucrose and 14C‐asparagine into the flowerhead was reduced at least three fold at physiological levels of abscisic acid. No significant correlation was found between the amount of 14C‐asparagine entering a sink and the dry weight of the tissues of that sink. It is concluded that distribution of 14C‐sucrose and 14C‐asparagine between the flowerheads and lateral branches of L. luteus is actively and dynamically controlled and that abscisic acid levels play a significant part in that control. It is suggested that the relative levels of endogenous abscisic acid in plant organs could serve as an important factor in the directional control of assimilate transport in plants.

Seed-sprouting in tomato fruits

Although tomato juice possesses properties which are inhibitory to seed germination, sprouting of seeds has been observed frequently in ripe tomatoes of mechanical harvest cultivars ‘VF 145’ and ‘VF 13L’. Juice from these cultivars was less inhibitory to tomato seed germination, as determined by bioassays, than that of other cultivars. There was no difference in the inhibition between juice from the pulp and that from the locular gel. Soluble solids accounted for 44% of the inhibition, osmotic concentration 2%, and pH only 0.2%; and the remainder came from other constituents in the juice. Abscisic acid and 2 unidentified substances in the juice isolated by extraction and chromatography were shown to inhibit seed germination; the degree varied with maturity and cultivar. Injection of abscisic acid into the vascular tissue of the stem scar inhibited sprouting within the fruit. Gibberellic acid and kinetin gave variable results, depending upon harvest dates. Fruits from plants grown in low potassium nutrient culture solutions had increased sprouting of seeds. Presented at the XXth International Horticultural Congress, Sydney, Australia, August 1978, Abstract 1189