Abiotic stress treatment reveals expansin like A gene OfEXLA1 improving salt and drought tolerance of Osmanthus fragrans by responding to abscisic acid

Sweet osmanthus(Osmanthus fragrans) is a having general approval aromatic tree in China that is widely applied to landscaping and gardening. However, the evergreen tree adaptability is limited by many environmental stresses. Currently, limited information is available regarding the genetic analysis and functional identification of expansin genes in response to abiotic stress in sweet osmanthus. In this study, a total of 29 expansin genes were identified and divided into four groups by genome-wide analysis from the sweet osmanthus genome. Transcriptome and quantitative Real-time PCR analysis showed that the cell wall-localized protein expansin-like A(OfEXLA1) gene was significantly induced by salt and drought treatment. Histochemical GUS staining of transgenic Arabidopsis lines in which GUS activity was driven with the OfEXLA1 promoter, GUS activity was significantly induced by salt, drought, and exogenous abscisic acid(ABA). In yeast, we found OfEXLA1overexpression significantly improved the population of cells compared with wild-type strains after NaCl and polyethylene glycol(PEG)treatment. Additionally, OfEXLA1 overexpression not only promoted plant growth, but also improved the salt and drought tolerance in Arabidopsis. To gain insight into the role of ABA signaling in the regulation of OfEXLA1 improving abiotic tolerance in sweet osmanthus, four differentially expressed ABA Insensitive 5(ABI5)-like genes(OfABL4, OfABL5, OfABL7, and OfABL8) were identified from transcriptome, and dualluciferase(dual-LUC) and yeast one hybrid(Y1H) assay showed that OfABL4 and OfABL5 might bind to OfEXLA1 promoter to accumulate the OfEXLA1 expression by responding to ABA signaling to improve abiotic tolerance in sweet osmanthus. These results provide the information for understanding the molecular functions of expansin-like A gene and molecular breeding of sweet osmanthus in future.

Overexpression of PbrGA2ox1 enhances pear drought tolerance through the regulation of GA_(3)-inhibited reactive oxygen species detoxification and abscisic acid signaling

Drought stress is a devastating natural disaster driven by the continuing intensification of global warming,which seriously threatens the productivity and quality of several horticultural crops,including pear.Gibberellins(GAs)play crucial roles in plant growth,development,and responses to drought stress.Previous studies have shown significant reductions of GA levels in plants under drought stress;however,our understanding of the intrinsic regulation mechanisms of GA-mediated drought stress in pear remains very limited.Here,we show that drought stress can impair the accumulation of bioactive GAs(BGAs),and subsequently identified PbrGA2ox1 as a chloroplast-localized GA deactivation gene.This gene was significantly induced by drought stress and abscisic acid(ABA)treatment,but was suppressed by GA_(3)treatment.PbrGA2ox1-overexpressing transgenic tobacco plants(Nicotiana benthamiana)exhibited enhanced tolerance to dehydration and drought stresses,whereas knock-down of PbrGA2ox1 in pear(Pyrus betulaefolia)by virus-induced gene silencing led to elevated drought sensitivity.Transgenic plants were hypersensitive to ABA,and had a lower BGAs content,enhanced reactive oxygen species(ROS)scavenging ability,and augmented ABA accumulation and signaling under drought stress compared to wild-type plants.However,the opposite effects were observed with PbrGA2ox1 silencing in pear.Moreover,exogenous GA_(3)treatment aggravated the ROS toxic effect and restrained ABA synthesis and signaling,resulting in the compromised drought tolerance of pear.In summary,our results shed light on the mechanism by which BGAs are eliminated in pear leaves under drought stress,providing further insights into the mechanism regulating the effects of GA on the drought tolerance of plants.

Rice ONAC016 promotes leaf senescence through abscisic acid signaling pathway involving OsNAP

Senescence-induced NAC(senNAC)TFs play a crucial role in senescence during the final stage of leaf development.In this study,we identified a rice senNAC,ONAC016,which functions as a positive regulator of leaf senescence.The expression of ONAC016 increased rapidly in rice leaves during the progression of dark-induced and natural senescence.The onac016-1 knockout mutant showed a delayed leaf yellowing phenotype,whereas the overexpression of ONAC016 accelerated leaf senescence.Notably,ONAC016 expression was upregulated by abscisic acid(ABA),and thus detached leaves of the onac016-1 mutant remained green much longer under ABA treatment.Quantitative RT-PCR analysis showed that ONAC016 upregulates the genes associated with chlorophyll degradation,senescence,and ABA signaling.Yeast one-hybrid and dual-luciferase assays revealed that ONAC016 binds directly to the promoter regions of OsNAP,a key gene involved in chlorophyll degradation and ABA-induced senescence.Taken together,these results suggest that ONAC016 plays an important role in promoting leaf senescence through the ABA signaling pathway involving OsNAP.

VPD modifies CO_(2) fertilization effect on tomato plants via abscisic acid and jasmonic acid signaling pathways

Atmospheric CO_(2)concentration is elevated globally,which has“CO_(2)fertilization effects”and potentially improves plant photosynthesis,yield,and productivity.Despite the beneficial effect of CO_(2)fertilization being modulated by vapor pressure deficit(VPD),the underlying mechanism is highly uncertain.In the present study,the potential roles of hormones in determining CO_(2)fertilization effects under contrasting high and low VPD conditions were investigated by integrated physiological and transcriptomic analyses.Beneficial CO_(2)fertilization effects were offset under high VPD conditions and were constrained by plant water stress and photosynthetic CO_(2)utilization.High VPD induced a large passive water driving force,which disrupted the water balance and consequently caused plant water deficit.Leaf water potential,turgor pressure,and hydraulic conductance declined under high VPD stress.The physiological evidence combined with transcriptomic analyses demonstrated that abscisic acid(ABA)and jasmonic acid(JA)potentially acted as drought-signaling molecules in response to high VPD stress.Increased foliar ABA and JA content triggered stomatal closure to prevent excessive water loss under high VPD stress,which simultaneously increased the diffusion resistance for CO_(2)uptake from atmosphere to leaf intercellular space.High VPD also significantly increased mesophyll resistance for CO_(2)transport from stomatal cavity to fixation site inside chloroplast.The chloroplast“sink”CO_(2)availability was constrained by stomatal and mesophyll resistance under high VPD stress,despite the atmospheric“source”CO_(2)concentration being elevated.Thus,ABA-and JA-mediated drought-resistant mechanisms potentially modified the beneficial effect of CO_(2)fertilization on photosynthesis,plant growth,and yield productivity.This study provides valuable information for improving the utilization efficiency of CO_(2)fertilization and a better understanding of the physiological processes.

Melatonin Alleviates Abscisic Acid Deficiency Inhibition on Photosynthesis and Antioxidant Systems in Rice under Salt Stress

Melatonin and abscisic acid,as major plant hormones,play important roles in the physiological and biochemical activities of crops,but the interaction between the two under salt stress is not yet clear.This study investigated the endogenous levels of melatonin and abscisic acid in rice by using exogenous melatonin,abscisic acid,and their synthetic inhibitors,and examined their interactions under salt stress.The research results indicate that melatonin and abscisic acid can improve rice salt tolerance.Melatonin alleviated the salt sensitivity caused by abscisic acid deficiency,increased antioxidant enzyme activity and antioxidant content in rice treated with abscisic acid synth-esis inhibitors,and reduced total reactive oxygen species content and thiobarbituric acid reactive substance accu-mulation.Melatonin also increased the activity of key photosynthetic enzymes and the content of photosynthetic pigments,maintaining the parameters of photosynthetic gas exchange and chlorophyllfluorescence.In summary,melatonin alleviated the effects of abscisic acid deficiency on photosynthesis and antioxidant systems in rice and improved salt tolerance.This study is beneficial for expanding the understanding of melatonin regulation of crop salt tolerance.

Effects of Abscisic Acid on Cold Resistance in Digitaria sanguinalis(L.)Scop.

[Objectives]This study was conducted to detect the protective effect of abscisic acid on chilling injury of Digitaria sanguinalis(L.)Scop,and whether this effect is related to antioxidant enzymes and osmotic adjustment.[Methods]D.sanguinalis plants were sprayed with abscisic acid solution,and exposed to cold stress at 15℃for 3 d after one day and then at 5℃for 25 to 30 d in a growth chamber.The changes of plant osmotic potential under this treatment were detected.[Results]Under low temperature stress,the osmotic potential of plants in the abscisic acid treatment and the control increased,but the osmotic potential level of the abscisic acid treatment plants was lower.The SOD activity of plants in the ABA treatment and the control decreased under low temperature stress.Under low temperature stress,the activity of catalase and peroxidase in ABA-treated plants was higher than that in control plants.[Conclusions]This study provides a theoretical basis for the impact of abscisic acid on the physiological response of D.sanguinalis to cold injury.

In Vivo Tissue-dependent Abscisic Acid Specific-binding Proteins with High Affinity in Cytosol of Developing Apple Fruits

The in vivo highly tissue-dependent abscisic acid (ABA) specific-binding sites localized in cytosol were identified and characterized in the flesh of developing apple ( Malus pumila L. cv. Starkrimon) fruits. ABA binding activity was scarcely detectable in the microsomes and the cytosolic fraction isolated from the freshly harvested fruits via an in vitro ABA binding incubation of the subcellular fractions. If, however, instead that the subcellular fractions were in vitro incubated in H-3-ABA binding medium, the flesh tissue discs were directly in vivo incubated in H-3-ABA binding medium, a high ABA binding activity to the cytosolic fraction isolated from these tissue discs was detected. The in vivo ABA binding capacity of the cytosolic fraction was lost if the tissue discs had been pretreated with boiling water, indicating that the ABA binding needs a living state of tissue. The in vivo tissue-dependent binding sites were shown to possess protein nature with both active serine residua and thiol-group of cysteine residua in their functional binding center. The ABA binding of the in vivo tissue-dependent ABA binding sites to the cytosolic fraction was shown to be saturable, reversible, and of high affinity. The scatchard plotting gave evidence of two different classes of ABA binding proteins, one with a higher affinity ( Kd = 2.9 nmol/L) and the other with lower affinity ( Kd = 71.4 nmol/L). Phaseic acid, 2-trans-4-trans-ABA or cis-trans-(-)-ABA had substantially no affinity to the binding proteins, indicating their stereo-specificity to bind physiologically active ABA. The time course, pH- and temperature-dependence of the in vivo tissue-dependent binding proteins were determined. It is hypothesized that the detected ABA-binding proteins may be putative ABA-receptors that mediate ABA signals during fruit development.

Effects of Exogenous Abscisic Acid and Water Stress on the Growth Response of Subterranean Clover of Different Genotypes

The response of subterranean clover ( Trifolium subterraneum L.) to different abscisic acid (ABA) concentrations (10 -6 , 10 -5 , 10 -4 mol/L) in nutrient solution and to water stress were studied in growth room. Six cultivars of contrasting yield capacity were compared. Plants remained growing in Hoagland solution or pots until at least four full_developed leaves appeared. The ABA was then applied and the fresh weight, leaf number and length of the largest root were measured at 1, 4, 7 and 11 d after ABA treatment. The above parameters were also measured at 15 d under water stress. In all the tested genotypes ABA caused similar reduction in these growth parameters, as well as a significant decrease of leaf water potential which was dependent on ABA concentration. The average growth reduction after 11 d under 10 -4 mol/L ABA coincided with the range of these crops under water stress in pot experiments. On average of the different genotypes, leaf number, area of full_developed leaf and the dry weight per plant decreased by about 50% whereas the root/shoot ratio increased by 80%.The genotype variation and ranking for this treatment were rather similar to the same genotypes in pot experiments. The genotypes, Clare, Nuba and Seaton Park, showed the best results under both control and ABA treated conditions and water stress conditions. The similarity between the response to ABA in nutrient solution and to water stress opens the possibility to use this approach as a way to quantify the drought resistance of subterranean clover genotypes.

Isolation and Crystal Structure of 1',4'-Trans-diol of Abscisic Acid

1 ′,4′-Trans-diol of abscisic acid was isolated from botrytis cinerea as a colorless crystal. The molecular and crystal structures have been determined by X-ray diffraction analysis. It crystallizes in orthorhombic system, space group P212121 with a = 6.724（3）, b = 17.559（6）, c = 12.265（2）,A,α =β=γ= 90°, V= 1448.1（8）,A^3, Z=4, Dx = 1.222 g/cm^3, F（000） = 576 and μ（MoKa） = 0.087 mm^-1. The final R = 0.0628 and wR = 0.1604 for 2501 independent reflections with Rint - 0.0160 and 1679 observed reflections with 1 〉2σ（I）. There are three intermolecular hydrogen bonds in a unit cell.

K^+channels inhibited by hydrogen peroxide mediate abscisic acid signaling in Vicia guard cells

A number of studies show that environmental stress conditions increase abscisic acid (ABA) and hydrogen peroxide (H2O2) levels in plant cells. Despite this central role of ABA in altering stomatal aperture by regulating guard cell ion transport, little is known concerning the relationship between ABA and H2O2 in signal transduction leading to stomatal movement. Epidermal strip bioassay illustrated that ABA- inhibited stomatal opening and ABA-induced stomatal closure were abolished partly by externally added catalase (CAT) or diphenylene iodonium (DPl), which are a H2O2 scavenger and a NADPH oxidase inhibitor respectively. In contrast, internally added CAT or DPI nearly completely or partly reversed ABA-induced closure in half-stoma. Consistent with these results, whole-cell patch-clamp analysis showed that intracellular application of CAT or DPI partly abolished ABA-inhibited inward K+ current across the plasma membrane of guard cells. H2O2 mimicked ABA to inhibit inward K+ current, an effect which was reversed by the addition of ascorbic acid (Vc) in patch clamping micropipettes. These results suggested that H2O2 mediated ABA-induced stomatal movement by targeting inward K+ channels at plasma membrane.

Exogenous Application of Abscisic Acid or Gibberellin Acid Has Different Effects on Starch Granule Size Distribution in Grains of Wheat

Granule size distribution of wheat starch is an important characteristic that can affect its chemical composition and the functionality of wheat products. Two high-yield winter wheat cultivars were used to evaluate the effects of the application of exogenous ABA or GA during the reproductive phase of the initial grain filling on starch granule size distribution and starch components in grains at maturity. The results indicated that a bimodal curve was found in the volume and surface area distribution of grain starch granules, and a unimodal curve was observed for the number distribution under all treatments. The exogenous ABA resulted in a significant increase in the proportions （both by volume and by surface area） of B-type （〈9.9 Ixm in diameter） starch granules, with a reduction in those of A-type （〉9.9 ~tm） starch granules, while, the exogenous GA3 led to converse effects on size distribution of those starch granules. The exogenous ABA also increased starch, amylose and amylopectin contents at maturity but significantly reduced the ratio of amylose to amylopectin. Application of GA3 significantly reduced starch content, amylopectin content but increased the ratio of amylose to amylopectin. The ratio of amylose to amylopectin showed a significant and negative relationship with the volume proportion of granules 〈9.9 μm, but was positively related to the volume proportion of granules 22.8-42.8 μm.

Cross-talk between calcium-calmodulin and nitric oxide in abscisic acid signaling in leaves of maize plants

Using pharmacological and biochemical approaches, the signaling pathways between hydrogen peroxide （H2O2）, calcium （Ca^2＋）-calmodulin （CAM）, and nitric oxide （NO） in abscisic acid （ABA）-induced antioxidant defense were investigated in leaves of maize （Zea mays L.） plants. Treatments with ABA, H2O2, and CaCl2 induced increases in the generation of NO in maize mesophyll cells and the activity of nitric oxide synthase （NOS） in the cytosolic and microsomal fractions of maize leaves. However, such increases were blocked by the pretreatments with Ca^2＋ inhibitors and CaM antagonists. Meanwhile, pretreatments with two NOS inhibitors also suppressed the Ca^2＋-induced increase in the production of NO. On the other hand, treatments with ABA and the NO donor sodium nitroprusside （SNP） also led to increases in the concentration of cytosolic Ca^2＋ in protoplasts of mesophyll cells and in the expression of calmodulin 1 （CaM1） gene and the contents of CaM in leaves of maize plants, and the increases induced by ABA were reduced by the pretreatments with a NO scavenger and a NOS inhibitor. Moreover, SNP-induced increases in the expression of the antioxidant genes superoxide dismutase 4 （SOD4）, cytosolic ascorbate peroxidase （cAPX）, and glutathione reductase 1 （GR1） and the activities of the chloroplastic and cytosolic antioxidant enzymes were arrested by the pretreatments with Ca^2＋ inhibitors and CaM antagonists. Our results suggest that Ca^2＋-CaM functions both upstream and downstream of NO production, which is mainly from NOS, in ABA- and H2O2-induced antioxidant defense in leaves of maize plants.

Abscisic acid and jasmonic acid are involved in drought priming-induced tolerance to drought in wheat

Drought stress is a limiting factor for wheat production and food security.Drought priming has been shown to increase drought tolerance in wheat.However,the underlying mechanisms are unknown.In the present study,the genes encoding the biosynthesis and metabolism of abscisic acid(ABA)and jasmonic acid(JA),as well as genes involved in the ABA and JA signaling pathways were up-regulated by drought priming.Endogenous concentrations of JA and ABA increased following drought priming.The interplay between JA and ABA in plant responses to drought priming was further investigated using inhibitors of ABA and JA biosynthesis.Application of fluridone(FLU)or nordihydroguaiaretic acid(NDGA)to primed plants resulted in lower chlorophyll-fluorescence parameters and activities of superoxide dismutase and glutathione reductase,and higher cell membrane damage,compared to primed plants(PD)under drought stress.NDGA+ABA,but not FLU+JA,restored priming-induced tolerance,as indicated by a finding of no significant difference from PD under drought stress.Under drought priming,NDGA induced the suppression of ABA accumulation,while FLU did not affect JA accumulation.These results were consistent with the expression of genes involved in the biosynthesis of ABA and JA.They suggest that ABA and JA are required for priming-induced drought tolerance in wheat,with JA acting upstream of ABA.

Effects of Formulated Fertilizer Synergist on Abscisic Acid Accumulation, Proline Content and Photosynthetic Characteristics of Rice under Drought

To investigate the effects of formulated fertilizer synergist on the drought tolerance in rice, pot experiment was conducted to analyze the photosynthetic characteristics and the accumulation of abscisic acid （ABA） and proline in middle-season rice variety Peiliangyou 93. The synergist could improve the net photosynthetic rate, and coordination between the water loss and the CO2 absorption as well as reduce the harmful effect on photosynthetic process under drought conditions. Under drought, the ABA accumulated massively both in roots and leaves, while the ABA content in roots was far higher than that in leaves. The results indicate that synergist could increase the ABA accumulation, but reduce the proline accumulation in rice plant under drought.

RNAi-mediated suppression of the abscisic acid catabolism gene Os ABA8ox1 increases abscisic acid content and tolerance to saline–alkaline stress in rice(Oryza sativa L.)

Saline–alkaline(SA) stress is characterized by high salinity and high alkalinity(high p H), which severely inhibit plant growth and cause huge losses in crop yields worldwide. Here we show that a moderate elevation of endogenous abscisic acid(ABA) levels by RNAi-mediated suppression of Os ABA8 ox1(Os ABA8 ox1-kd), a key ABA catabolic gene, significantly increased tolerance to SA stress in rice plants. We produced Os ABA8 ox1-kd lines in two different japonica cultivars, Dongdao 4 and Nipponbare. Compared with nontransgenic control plants(WT), the Os ABA8 ox1-kd seedlings accumulated 25.9%–55.7% higher levels of endogenous ABA and exhibited reduced plasmalemma injury, ROS accumulation and Na;/K;ratio, and higher survival rates, under hydroponic alkaline conditions simulated by 10, 15, and 20 mmol L-1 of Na;CO;. In pot trials using SA field soils of different alkali levels(p H 7.59, 8.86, and 9.29), Os ABA8 ox1–kd plants showed markedly higher seedling survival rates and more vigorous plant growth, resulting in significantly higher yield components including panicle number(85.7%–128.6%), spikelets per panicle(36.9%–61.9%), branches(153.9%–236.7%), 1000–kernel weight(20.0%–28.6%), and percentage of filled spikelets(96.6%–1340.8%) at harvest time. Under severe SA soil conditions(p H = 9.29, EC = 834.4 μS cm-1),Os ABA8 ox1-kd lines showed an 194.5%–1090.8% increase in grain yield per plant relative to WT plants.These results suggest that suppression of Os ABA8 ox1 to increase endogenous ABA levels provides a new molecular approach for improving rice yield in SA paddies.

A novel impedance immunosensor based on O-phenylenediamine modified gold electrode to analyze abscisic acid

An impedance immunosensor based on O-phenylenediamine modified gold electrode for the determination of phytohormone abscisic acid(ABA) was proposed.The operating pH,absorption time,absorption temperature and concentration of anti-ABA antibody were investigated to optimize the analytical performance.The calibration curve for the determination of ABA was obtained from this impedance immunosensor under optimal conditions.The results showed that the detection limit at about 1 ng/mL in the range of 10-5000 ng/mL...

Phenotype and mechanism analysis of plant dwarfing in pear regulated by abscisic acid

Close planting of dwarf varieties is currently the main cultivation direction for pear trees,and the screening of excellent dwarf varieties is an important goal for breeders.In this study,the dwarfing pear variety‘601D’and its vigorous mutant‘601T’were used to show their biological characteristics and further explore the dwarfing mechanism in‘601D’.The biological characteristics showed that‘601D’had a shorter internode length,a shorter and more compact tree body,thicker and broader leaves,lower stomata density,larger stomata size(dimension),and higher photosynthetic capacity.The biological characteristics of‘601T’showed notable contrasts.The results of endogenous hormone tests indicated that the contents of abscisic acid(ABA),ABA-glucosyl ester,and GA_(4) were higher in‘601D’,but the trans-zeatin content was lower.By transcriptomic analysis,significant differences were found in the biosynthetic and metabolic pathways of ABA.Related transcription factors such as bHLH,WRKY,and homeobox also participated in the regulation of plant dwarfing.We therefore examined three hormones with obvious differences with‘601T’,and found that only ABA could induce‘601T’to return to a dwarfing plant phenotype.Therefore,we conclude that the dwarfing of‘601D’is caused by an excessive accumulation of ABA.This study provides a new theoretical basis for breeding dwarf varieties.

OsbZIP72 Is Involved in Transcriptional Gene-Regulation Pathway of Abscisic Acid Signal Transduction by Activating Rice High-Affinity Potassium Transporter OsHKT1;1

We created CRISPR-Cas9 knock-out and overexpressing OsbZIP72 transgenic rice plants to gain a better understanding of the role and molecular mechanism of OsbZIP72 gene in stress tolerance,which has remained largely elusive.OsbZIP72 was expressed and integrated into rice transgenic plant genomes,and the OsbZIP72 transcript in overexpression lines was elicited by salinity,abscisic acid(ABA)and drought stresses.OsbZIP72 overexpressing plants showed higher tolerance to drought and salinity stresses,while knock-out transgenic lines showed higher sensitivity to these stresses.The differentially expressed genes(DEGs)from RNA-sequencing data encompassed several abiotic stress genes,and the functional classification of these DEGs demonstrated the robust transcriptome diversity in OsbZIP72.Yeast one-hybrid,along with luciferase assay,indicated that OsbZIP72 acted as a transcriptional initiator.Remarkably,electrophoresis mobility assay revealed that OsbZIP72 bound directly to the ABAresponsive element in the OsHKT1;1 promoter region and activated its transcription.Overall,our findings revealed that OsbZIP72 can act as a transcriptional modulator with the ability to induce the expression of OsHKT1;1 in response to environmental stress through an ABA-dependent regulatory pathway,indicating that OsbZIP72 can play a crucial role in the ABA-mediated salt and drought tolerance pathway in rice.

Abscisic acid induces differential expression of genes involved in wound-induced suberization in postharvest tomato fruit

Fruit wounding occurred at harvest and transportation requires rapid suberization as a major part of the healing process to prevent infection and desiccation. The focus of this work was to explore the mediation of abscisic acid(ABA) on woundinduced suberization and to determine expression profiles of specific genes involved in wound-induced suberization in tomato fruit. The measurements of weight loss and fruit firmness suggested wound-induced suberization started at 2 d after wounding. The suberization process with the accumulation of suberin polyphenolics(SPP) and polyaliphatics(SPA) observed through autofluorescence microscopy and Sudan IV staining was accelerated by ABA. Expressions of SlPAL5 and Sl4 CL involved in the synthesis of SPP reached the highest at 4 and 8 d after wounding following ABA application, respectively. Associated with SPA biosynthesis, SlLACS1 and SlLACS2 showed the most abundant transcripts at 8 and 6 d in ABA group, respectively. Transcript levels including SlKCSs, SlCYP86 B1, SlFAR3, and Sl GPATs were up-regulated at 2 d after wounding by ABA. Activities of polyphenol oxidase and lipoxygenase were also enhanced during wound-induced suberization following ABA application. The results in this study proved that ABA accelerated the wound-induced suberization progress by increasing the transcript levels of relevant genes in postharvest tomato fruit.

The heading-date gene Ghd7 inhibits seed germination by modulating the balance between abscisic acid and gibberellins

Seed dormancy of cultivated rice was largely weakened during the progress of domestication.Correct timing and uniformity of seed germination are important for rapid seedling establishment and highyield production.In the present study,we found that the heading-date gene Ghd7 acted as a negative regulator of germination.A mutant of ghd7 showed low sensitivity to exogenous ABA treatment during seed germination.Further investigation revealed reduced accumulation of ABA in mature ghd7 seeds as a consequence of dampened expression of OsNCED genes.Moreover,elevated GA_(3) level was detected in seeds of ghd7 mutant during imbibition course,which was attributed to the induction of genes responsible for the synthesis pathways of bioactive GAs.Thus,Ghd7 inhibits seed germination by increasing the ABA/GA_(3) ratio.Besides revealing pleiotropic effects of Ghd7,our results indicate its role in linking seed germination to growth-phase transition in rice,which would enrich the theoretical basis for future breeding practices.