Effect Of ABA Research Articles

Effects of exogenous GA, IAA, ABA and ethylene on pear (Pyrus pyrifolia) fruit during different development stages

Effects of exogenous GA, IAA, ABA and ethylene on pear (Pyrus pyrifolia) fruit during different development stages

Drought Protective Effects of Exogenous ABA and Kinetin on Lettuce: Sugar Content, Antioxidant Enzyme Activity, and Productivity.

Drought is an environmental stressor that significantly impacts plant growth and development. Comprehending the complexity of drought stress and water utilization in the context of plant growth and development holds significant importance for sustainable agriculture. The aim of this study was to evaluate the effect of exogenously applied phytohormones on lettuce (Lactuca sativa L.) sugar content profiles and antioxidant enzyme activity and productivity. Lettuce plants were grown under normal and drought conditions in a growth chamber with a photoperiod of 14/10 h (day/night). Kinetin and abscisic acid were applied separately and in combinations when the second leaf was fully expanded. The results showed that sugar accumulation and productivity of the pretreated plants under drought were significantly higher than the controls. The perspective offered by this work showed that growth-related and stress-related phytohormones significantly influenced plant sugar metabolism, metabolic profiles, and productivity, thus enabling the control of yield and quality.

Abscisic acid for acute respiratory distress syndrome therapy by suppressing alveolar macrophage pyroptosis via upregulating acyloxyacyl hydrolase expression

ObjectiveAbscisic acid (ABA) is a phytohormone that inhibits airway inflammation in acute respiratory distress syndrome (ARDS) mouse models. However, the molecular mechanism underlying this phenomenon remains unclear. Methods: Serum ABA level in patients and mice was measured via liquid chromatography–tandem mass spectrometry (LC–MS/MS). In-depth molecular mechanism was investigated through transmission electron microscopy, RNA-sequencing, and molecular docking in ARDS mice and cultured primary alveolar macrophages (AMs). ResultsWe found that the serum ABA level was remarkably decreased in ARDS mice and patients. ABA inhibited lipopolysaccharide (LPS)-induced airway inflammation in mice; moreover, it downregulated genes associated with pyroptosis, as shown by RNA-sequencing and lung protein immunoblots. ABA inhibited the formation of membrane pores in AMs and suppressed the cleavage of gasdermin D (GSDMD) and the activation of caspase-11 and caspase-1 in vivo and in vitro; however, the overexpression of caspase-11 reversed the protective effect of ABA on LPS-induced pyroptosis of primary AMs. ABA inhibited intra-AM LPS accumulation while increasing the level of acyloxyacyl hydrolase (AOAH) in AMs, whereas AOAH deficiency abrogated the suppressive action of ABA on inflammation, pyroptosis, and intra-AM LPS accumulation in vivo and in vitro. Importantly, ABA promoted its intracellular receptor lanthionine C-like receptor 2 interacting with transcription factor peroxisome proliferator-activated receptor γ, which ultimately leading to increase AOAH expression to inactivate LPS and inhibit pyroptosis in AMs. ConclusionsABA protected against LPS-induced lung injury by inhibiting pyroptosis in AMs via proliferator-activated receptor γ-mediated AOAH expression.

Difference in the cellular response following THP-1 derived phagocytic monocyte cells exposure to commercial aluminum-based adjuvants and aluminum-containing vaccines

BackgroundAluminum-based adjuvants (ABAs) enhance the immune response following vaccine injection. Their mechanisms of action are not fully understood, and their bio-persistency have been described associated with long-term adverse effects. MethodsWe evaluated and compared the cellular effects of the two main ABAs and whole vaccines on ATP production, ROS generation and cytokines production (IL-6 and IL-10), using THP-1 cells. ResultsABAs altered the cell energy metabolism by increasing ROS production after 24 h and reducing ATP production after 48 h. In addition, both ABAs and whole vaccines induced different kinetics of IL-6 production, whereas only ABAs induced IL-10 secretion. ConclusionThis study showed clearly, for a first time, a difference in cellular response to the ABAs and whole vaccines which should be taken into consideration in future studies focusing on the effect of ABA in vaccines. Future studies on ABAs should also pay attention to mitochondrial function alterations following exposure to ABA-containing vaccines.

Comparative transcriptome analysis of genes involved in paradormant bud release response in 'Summer Black' grape.

Grapevines possess a hierarchy of buds, and the fruitful winter bud forms the foundation of the two-crop-a-year cultivation system, yielding biannual harvests. Throughout its developmental stages, the winter bud sequentially undergoes paradormancy, endodormancy, and ecodormancy to ensure survival in challenging environmental conditions. Releasing the endodormancy of winter bud results in the first crop yield, while breaking the paradormancy of winter bud allows for the second crop harvest. Hydrogen cyanamide serves as an agent to break endodormancy, which counteracting the inhibitory effects of ABA, while H2O2 and ethylene function as signaling molecules in the process of endodormancy release. In the context of breaking paradormancy, common agronomic practices include short pruning and hydrogen cyanamide treatment. However, the mechanism of hydrogen cyanamide contributes to this process remains unknown. This study confirms that hydrogen cyanamide treatment significantly improved both the speed and uniformity of bud sprouting, while short pruning proved to be an effective method for releasing paradormancy until August. This observation highlights the role of apical dominance as a primary inhibitory factor in suppressing the sprouting of paradormant winter bud. Comparative transcriptome analysis revealed that the sixth node winter bud convert to apical tissue following short pruning and established a polar auxin transport canal through the upregulated expression of VvPIN3 and VvTIR1. Moreover, short pruning induced the generation of reactive oxygen species, and wounding, ethylene, and H2O2 collectively acted as stimulating signals and amplified effects through the MAPK cascade. In contrast, hydrogen cyanamide treatment directly disrupted mitochondrial function, resulting in ROS production and an extended efficacy of the growth hormone signaling pathway induction.

Integration of Phosphoproteomics and Transcriptome Studies Reveals ABA Signaling Pathways Regulate UV-B Tolerance in Rhododendron chrysanthum Leaves.

The influence of UV-B stress on the growth, development, and metabolism of alpine plants, such as the damage to DNA macromolecules, the decline in photosynthetic rate, and changes in growth, development, and morphology cannot be ignored. As an endogenous signal molecule, ABA demonstrates a wide range of responses to UV-B radiation, low temperature, drought, and other stresses. The typical effect of ABA on leaves is to reduce the loss of transpiration by closing the stomata, which helps plants resist abiotic and biological stress. The Changbai Mountains have a harsh environment, with low temperatures and thin air, so Rhododendron chrysanthum (R. chrysanthum) seedlings growing in the Changbai Mountains can be an important research object. In this study, a combination of physiological, phosphorylated proteomic, and transcriptomic approaches was used to investigate the molecular mechanisms by which abiotic stress leads to the phosphorylation of proteins in the ABA signaling pathway, and thereby mitigates UV-B radiation to R. chrysanthum. The experimental results show that a total of 12,289 differentially expressed genes and 109 differentially phosphorylated proteins were detected after UV-B stress in R. chrysanthum, mainly concentrated in plant hormone signaling pathways. Plants were treated with ABA prior to exposure to UV-B stress, and the results showed that ABA mitigated stomatal changes in plants, thus confirming the key role of endogenous ABA in plant adaptation to UV-B. We present a model that suggests a multifaceted R. chrysanthum response to UV-B stress, providing a theoretical basis for further elaboration of the mechanism of ABA signal transduction regulating stomata to resist UV-B radiation.

The Effects of Abscisic Acid on Angiogenesis in Both ex vivo and in vivo Assays.

Angiogenesis is a complex biological process wherein novel capillary blood vessels mature from pre-existing vasculature for delivering tissues with oxygen and nutrients. Natural molecules that have anti-angiogenic activity and toxicity can raise the focus on using plant sources as essential therapeutic agent. The current research was intended to estimate the probable anti-angiogenic activity of abscisic acid alone and in combination with prednisolone, a well-known angiostatic glucocorticoid. two months old albino rats were used in this study. ABA and prednisolone stock solutions were prepared and added after embedding aortic rings in growth media. The ex vivo rat aorta ring assay (RAR) was applied to explore the anti-angiogenic effect of ABA. The in vivo chorioallantoic membrane assay (CAM) was applied to quantify the blood vessels inhibition zone by ABA effect. That zone was calculated as the mean inhibition region on eggs in mm ± SD. Abscisic acid screened byex vivo and in vivo assays, revealed a significant dose-dependent blood vessels inhibition in comparison to the negative control with IC50= 7.5µg/ml and a synergism effect when combined with prednisolone. The synergism activity of ABA with prednisolone can significantly inhibit blood vessels growth in RAR and CAM assays. These results shed the light on the potential clinic values of ABA, and prednisolone combination in angiogenesis-dependent tumors.

Genome-Wide Identification and Expression of MAPK Gene Family in Cultivated Strawberry and Their Involvement in Fruit Developing and Ripening.

Studies on many plants have shown that mitogen-activated protein kinases (MAPKs) are key proteins involved in regulating plant responses to biotic and abiotic stresses. However, their involvement in cultivated strawberry development and ripening remains unclear. In this study, 43 FaMAPK gene family members were identified in the genome of cultivated strawberry (Fragaria × ananassa), phylogenetic analysis indicated that FaMAPKs could be classified into four groups. Systematic analysis of the conserved motif, exon–intron structure showed that there were significant varieties between different groups in structure, but in the same group they were similar. Multiple cis-regulatory elements associated with phytohormone response, and abiotic and biotic stresses were predicted in the promoter regions of FaMAPK genes. Transcriptional analysis showed that all FaMAPK genes were expressed at all developmental stages. Meanwhile, the effect of exogenous ABA and sucrose on the expression profile of FaMAPKs was investigated. Exogenous ABA, sucrose, and ABA plus sucrose treatments upregulated the expression of FaMAPK genes and increased the content of endogenous ABA, sucrose, and anthocyanin in strawberry fruits, suggesting that ABA and sucrose might be involved in the FaMAPK-mediated regulation of strawberry fruit ripening. Based on the obtained results, MAPK genes closely related to the ripening of strawberries were screened to provide a theoretical basis and support for future research on strawberries.

Effects of water stress on quality and sugar metabolism in ‘Gala’ apple fruit

Sugar plays an important role in apple fruit development, appearance and quality as well as contributing to a plant's water stress response. Trehalose and the trehalose biosynthetic metabolic pathways are part of the sugar signaling system in plants, which are important regulator of water stress response in apple. The effect of water stress treatments applied to apple trees and the corresponding effects of ABA on developmental fruit quality were examined for indicators of fruit quality during fruit development. The results indicated that the severe water stress treatment (W2) occurring after the last stage of fruit cell division caused a decrease in the color and size of fruit. The moderate water stress (W1) occurring after the last stage of fruit cell enlargement (S2) caused an increase in the content of fructose and sorbitol while the apple fruit shape was not affected. These changes in sugar are related to the activity of sugar metabolic enzymes. While the enzymatic activity of vacuolar acid invertase (vAINV) was higher, that of sucrose-phosphate synthase (SPS) was lower in water stress treated fruit throughout the developmental period. This indicates that enhanced sucrose degradation and reduced sucrose synthesis leads to an overall reduced sucrose content during times of drought. Thus, water stress reduced sucrose content. Whereas the content of endogenous trehalose and ABA were the highest in water stress treated fruit. A moderate water stress (W1) imposed on apple trees via water restriction (60%–65% of field capacity) after the fruit cell enlargement phase of fruit development yielded sweeter fruit of higher economic value.

Abscisic Acid Improves Linoleic Acid Accumulation Possibly by Promoting Expression of EgFAD2 and Other Fatty Acid Biosynthesis Genes in Oil Palm Mesocarp.

Abscisic acid plays an important role in fruit development. However, the effect of ABA on fatty acid biosynthesis in oil palm is still unknown. In this study, ABA treatments (CK, A1–A4) were applied to oil palm fruit at 16 WAP (weeks after pollination), and fatty acids in the mesocarp at 24 WAP were analyzed by GC-MS. Results showed that linoleic acid content under treatment A2 (20 μM ABA) was significantly higher (slightly increased by 8.33%) than the control. Therefore, mesocarp samples of A2, and the control at 16, 20, and 24 WAP was sampled for RNA-Seq. KEGG pathway enrichment analysis showed that 43 genes were differentially expressed in the fatty acid biosynthesis pathway, of which expression of EgFAD2 (unigene 105050201) under 20 μM ABA treatment was 1.84-fold higher than in the control at 20 WAP. Further sequence analysis found that unigene 105050201 had more ABA-responsive elements (ABRE), complete conserved domains, and a C-terminal signaling motif among two FAD2 copies. Furthermore, WGCNA and correlation analysis showed co-expression of EgFAD2 (unigene 105050201) with transcription factors (TFs) (WRI1, AP2-EREBP, bZIP, bHLH, C2C2-Dof, MYB, NAC, and WRKY), ABA signaling genes (PYR, PP2C, SnRK, and ABI5), and other genes involved in fatty acid biosynthesis (FATA, FATB, LACS, SAD, Oleosins, and so on). These results indicated that ABA treatment promoted the expression of FAD2 and other genes involved in fatty acid biosynthesis, which possibly resulted in the accumulation of linoleic acid. This study will be helpful for understanding the possible mechanisms through which ABA affects fatty acid biosynthesis and their accumulation in the mesocarp of oil palm.

Effect of new generation bio-regulators on anthocyanins and berry quality of grape cv. Beauty Seedless

Five-year-old grapevines of Beauty Seedless spaced at 3 m × 3 m distance and trained on the 'Bower' system were sprayed with different plant bioregulators, namely, abscisic acid (ABA: 200 and 400 ppm), ethephon (200 and 400 ppm), benzothiadiazole (BTH: 0.3 and 0.6 mM), prohexadione-calcium (Pro-Ca: 200 and 400 ppm) and control (water spray) at the veraison stage during 2019-20 with the aim of studying their influence on berry physical and biochemical characteristics. The experiment was conducted in the randomised block design with three replications for each treatment. Different berry physical characteristics like weight, length, diameter and firmness were positively influenced with the different treatments except for ethephon (400 ppm) and ABA (400 ppm) treatments, which reduced the berry firmness significantly. Berry biochemical parameters were positively improved by almost all the plant bioregulators, they were most pronounced with ethephon (400 ppm) and ABA (400 ppm). The most prominent effects of ABA and ethephon treatments were noted on the total anthocyanins biosynthesis in the berries, which is major bottleneck under the warm subtropical conditions in different coloured grape genotypes. Hence, application of new generation plant bioregulators such as BTH, Pro-Ca, ABA and ethephon resulted in improvement in berry quality parameters of cv. Beauty Seedless.

Effect of ABA on Photosynthesis and Chlorophyll Fluorescence in Emmenopterys henri Oliv. under High Light

Effect of ABA on Photosynthesis and Chlorophyll Fluorescence in Emmenopterys henri Oliv. under High Light

Effect of ABA on physiological characteristics and expression of salt tolerance-related genes in Tartary buckwheat

Salt-tolerant variety Chuanqiao No. 1 and salt-sensitive variety Chuanqiao No. 2 of Tartary buckwheat were used as experimental materials, and the effect of different concentrations of ABA on physiological characteristics of Tartary buckwheat under salt stress and the optimal ABA concentration on expression of salt tolerance-related genes were analyzed. The results showed that the ABA treatment with appropriate concentration improved the stress resistance of Tartary buckwheat seedlings, and the optimal ABA concentration varies in Chuanqiao No. 1 and Chuanqiao No. 2 with 30 and 20 μM. Under salt stress, the ABA treatment with appropriate concentration increased the fresh weight, root vigor of seedlings and leaf SOD, POD, and CAT activity of Tartary buckwheat, and reduced the leaf plasma membrane permeability of Tartary buckwheat, and the optimal ABA concentration under salt stress varies in Chuanqiao No. 1 and Chuanqiao No. 2 with 40 and 10 μM. The ABA treatment with optimal concentration promoted the expression of FtNHX1, FtSOS1, potassium channel, and four ABA receptor-related genes in the stem and root of two Tartary buckwheat varieties. The expression of salt tolerance-related genes is consistent with the improvement of physiological characteristics in Tartary buckwheat.

Transcriptome-wide identification of squalene epoxidase genes from Glycyrrhiza glabra L.: expression analysis and heterologous expression of GgSQE1 suggest important role in terpenoid biosynthesis.

Squalene epoxidase (SQE) is a crucial regulatory enzyme for the biosynthesis of several important classes of compounds including sterols and triterpenoids. The present paper identified and characterised five SQE genes (GgSQE1 to GgSQE5) from Glycyrrhiza glabra through transcriptome data mining and homology-based cloning, for the first time. The phylogenetic analysis implied their functional divergence. The ORF corresponding to one of the five SQEs, namely, GgSQE1, was cloned and studied for its function in a heterologous system, following transient and stable expressions. The transient expression followed by GgSQE1 encoding protein purification suggested approximately 58.0-kDa protein following the predicted molecular mass of the deduced protein. The gene expression profiling based on qRT-PCR indicated its highest expression (6.4-folds) in the 10-month-old roots. Furthermore, ABA (12.4-folds) and GA3 (2.47) treatments upregulated the expression of GgSQE1 in the shoots after 10 and 12 hours, respectively, which was also reflected in glycyrrhizin accumulation. The inductive effects of ABA and GA3 over GgSQE1 expression were also confirmed through functional analysis of GgSQE1 promoters using GUS fusion construct. Stable constitutive expression of GgSQE1 in Nicotiana tabacum modulated the sterol contents. The study could pave the way for understanding the metabolic flux regulation concerning biosynthesis of related sterols and triterpenoids.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00709-021-01616-2.

Potent Interaction between CMV Reactivation and Gvhd: Immunologic Evidence for Blunting of CMV-Driven Immune Reconstitution in the Setting of Gvhd

Allogeneic hematopoietic cell transplantation (HCT) may be curative for patients with marrow and immune disorders, but graft-vs-host-disease (aGVHD) and infections cause significant morbidity and non-relapse mortality. We have conducted a multicenter, double blind, placebo-controlled phase II trial of costimulation blockade with abatacept (Aba) combined with standard GVHD prophylaxis with a calcineurin inhibitor and methotrexate (CNI + MTX) following HLA matched unrelated donor transplant (n=142). In order to assess the effects of Aba on immune reconstitution, and to assess whether this reconstitution is influenced during CMV reactivation, we longitudinally evaluated post-transplant whole blood samples with multiparameter flow cytometry using markers for CD3, CD4, CD8, CD197 and CD45RA to measure reconstitution of CD4 and CD8 T cell populations and their respective memory subsets over time. Results: We observe that post-transplant CMV reactivation induces a marked expansion of CD8 effector memory (EM) cells, which is similar in magnitude for Aba vs placebo patients. We found that development of moderate (gr 2-4) or severe (gr 3-4) GVHD was not associated with an increased frequency of CMV reactivation, but patients with moderate GVHD showed a blunted expansion of CD8 EM cells compared to those without GVHD, and CD8 EM expansion was essentially absent among CMV reactivating patients with severe aGVHD. Clinical correlates will be presented. Conclusions: Our results suggest that adding abatacept to CNI/MTX does not materially affect reconstitution of T cell immunity in the presence or absence of CMV reactivation, but aGVHD remains a major driver of compromised immune recovery after HCT. Disclosures Watkins: Bristol Myers Squibb: Research Funding. Qayed:Mesoblast: Consultancy; Novartis: Consultancy. Horan:Bristol Myers Squib: Honoraria, Research Funding. Kean:gilead: Research Funding; bluebird bio: Research Funding; fortyseven: Consultancy; magenta: Research Funding; regeneron: Research Funding; hifibio: Consultancy; kymab: Consultancy; Bristol Meyers Squibb: Research Funding; novartis: Consultancy. Langston:Kadmon Corporation: Research Funding; Bristol Myers Squib: Research Funding; Incyte: Research Funding; Chimerix: Research Funding; Takeda: Research Funding; Astellas Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Research Funding.

Effects of ABA on Physiological Characteristics of Tomato under Waterlogging

The effects of waterlogging on antioxidant enzyme activities responses in five different lines, i.e. ABA-deficient mutant (0673) and its control (0535), two ABA over-production transgenic rd29A:NCED1 lines (#2, #7) and Mill. L. cv. New Yorker (WT) were investigated. The waterlogging was mimicked by treating pot plants with flooding. The malondialdehyde (MDA) content, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity in the leaves were evaluated in all treatments. The results showed that after 7 days waterlogging treatment, the malondialdehyde (MDA) was increased in all plants, especially in LA0673. Compared with the LA0673, #2 and #7 significantly increase the activities of SOD, POD and CAT under waterlogging stress. Therefore, ABA could improve the waterlogging tolerance of tomato by increasing the activities of antioxidant enzymes under waterlogging stress.

Isolation of the 9-cis-epoxycarotenoid dioxygenase (NCED) gene from kiwifruit and its effects on postharvest softening and ripening

According to the general consensus, post-ripening effects of ABA on climacteric fruits accelerate the softening process, especially in kiwifruit. In order to further understand the mechanism of ABA action during postharvest ripening of kiwifruit, five ABA synthase genes related to 9-cis-epoxycarotenoid dioxygenase (NCED) were isolated from kiwifruit genome, namely, AcNCED1, AcNCED1.1, AcNCED2, AcNCED3, and AcNCED3.1. Gene expression analysis showed that the expression of AcNCED1 peaked early during postharvest ripening, a finding that was consistent with the trend observed for the changes in ABA content. AcNCED1 expression was induced by ABA and repressed by ABA synthesis inhibitor nordihydroguaiaretic acid. We found cis-elements related to fruit development and ripening in the AcNCED1 promoter sequence. Analysis of AcNCED1 promoter activity showed that ABA and ethylene significantly enhanced the expression of AcNCED1. Furthermore, AcNCED1 silencing inhibited ABA synthesis and delayed kiwifruit softening, whereas transient overexpression of AcNCED1 in tomato accelerated fruit color development relative to controls. These results indicated that AcNCED1 encodes a key enzyme involved in ABA synthesis in kiwifruit, and that it may play an important role in the softening process of fruits early in postharvest.

Effects of exogenous abscisic acid on the growth and cadmium accumulation of lettuce under cadmium-stress conditions

ABSTRACTAbscisic acid (ABA) is an important hormone that can regulate the heavy-metal uptake of plants. In this study, exogenous ABA was applied to lettuce (Lactuca sativa) grown under cadmium (Cd)-stress conditions, and the effects of exogenous ABA on the growth and Cd accumulation of lettuce were evaluated. The results showed that treatment of Cd significantly decreased biomass and increased Cd content of lettuce compared with the control. The shoot biomass increased after spraying 1, 5 and 10 μmol/L ABA, and the root biomass increased after spraying 1–20 μmol/L ABA compared with the treatment of Cd. The Cd content in shoots significantly decreased when exposed to different ABA concentrations. The lowest Cd content in shoots of lettuce was produced by the ABA concentration of 5 μmol/L, with decreased by 23.60% compared with the treatment of Cd. Therefore, spraying ABA effectively alleviated Cd toxicity and reduced Cd uptake in the edible parts of lettuce, and 5 μmol/L ABA was the optimal dose.

ABA and its signaling pathway are involved in the cold acclimation and deacclimation of grapevine buds

The grapevine (Vitis vinifera L.) buds as well as the buds of other deciduous fruit trees acclimate and deacclimate to the cold during the autumn-winter season. Cold acclimation (CA) is characterized by an increase in bud cold-hardiness, while deacclimation (DA) by a loss of it. The mechanisms underlying the transition of the buds from CA to DA are not well understood. In this study, the effect of ABA, LT and ABA + LT on the expression of the genes of the ABA signaling pathway, and the role that these genes and ABA play in the transition of the buds from the CA to the DA was investigated. In vitro experiments carried-out with single-bud cuttings were used to analyze the effect of ABA, LT and ABA + LT treatments on the expression of ABA signaling genes. To study the role of ABA and its signaling pathway in the transition of grapevine buds from CA to DA, applications of ABA and Uniconazole-P (Uni-P), an inhibitor of the enzyme that catabolizes ABA, were performed to the grapevine buds during their period of CA and DA. The results show that : a) VvPP2Cs were the only ABA signaling genes which were induced synergistically by ABA + LT, b) ABA improved the cold-hardiness of the buds only during its period of CA c) Uni-P advanced the appearance of the second peak of ABA in the buds and its transition from the CA to the DA.

Effects of exogenous ABA on translocation of photosynthate to fruit of Fuji apple during late stage of fruit rapid-swelling.

To clarify the effects and underlying mechanism of ABA on sugar accumulation in apple fruits, 13C trace technique was used to examined the effects of different ABA levels (0, 50, 100 and 150 mg·L-1) and fluoridone (ABA biosynthesis inhibitor) on translocation of photosynthate to fruit during late stage of fruit rapid-swelling in five-year-old 'Yanfu3'/M26/Malus hupehensis Rehd. The results showed that the activities of related enzyme in sugar metabolism, the relative expression of sucrose transporter gene MdSUT1, MdSUT2.2 and sorbitol transporter gene MdSOT3 tended to increase first and then decrease with increasing ABA concentration, with a peak in 100 mg·L-1ABA treatment. Fluridone treatment significantly inhibited the enzymes activities of sugar metabolism and the relative expression of sugar transporters. The treatment of 100 mg·L-1ABA significantly reduced leaf 13C content, increased fruit 13C content and increased the transport rate of photosynthate from leaves to fruits compared with other treatments. Our results indicated that exogenous ABA enhanced sink strength of fruit and promoted the transportation of more photosynthate to fruits, which increased the soluble sugar content in fruits.