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.

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.

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.

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.

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.

Exogenous Application of Abscisic Acid (ABA)Enhances Chilling Tolerance in Seedlings ofNapier Grass (Pennisetum purpureum Schum.)

Napier grass, an important forage crop with potentials in multi-purpose applications, is widely grown throughout the tropics and subtropics. Low temperature severely limits its productivity and geographical distribution in temperate regions of the world. In this study, we investigated the effect of exogenous abscisic Acid(ABA) on chilling tolerance of napier grass(Pennisetum purpureum Schum.) seedlings. Seven-day-old napier grass seedlings were cultured in dd H_2O or ABA solution at different concentrations and exposed to 1 ℃ for different time durations. The chilling injury, membrane stability index(MSI) and proline content were estimated from leaf samples. The results showed that there was obvious morphological injury of leaf blighting and restrained growth for the seedlings under chilling stress, but this damage can be largely reduced(by 2/3) when the seedlings were treated by 100 μmol/L ABA in the culture solution, and that the application of exogenous ABA can help to maintain a good stability of leaf cell membrane as expressed by a high MSI value and a low level of proline in leaf cells. These results suggested that exogenous ABA can significantly alleviate chilling injury in napier grass seedlings by maintaining the stability of leaf cell membrane during chilling stress, and that the chilling tolerance was not ensured by a proline accumulation although a passive accumulation of proline was observed in the seedlings under chilling stress. Our results lay a preliminary foundation for future investigations on the molecular mechanisms of ABA induced chilling or freezing tolerance in napier grass.

NaCl Facilitates Cell Wall Phosphorus Reutilization in Abscisic Acid Dependent Manner in Phosphorus Deficient Rice Root

Phosphorus(P) starvation in rice facilitates the reutilization of root cell wall P by enhancing the pectin content. NaCl modulates pectin content, however, it is still unknown whether NaCl is also involved in the process of pectin regulated cell wall P remobilization in rice under P starved conditions. In this study, we found that 10 mmol/L NaCl increased the shoot and root biomasses under P deficiency to a remarkable extent, in company with the elevated shoot and root soluble P contents in rice. Further analysis indicated that exogenous NaCl enhanced the root cell wall P mobilization by increasing the pectin methylesterase activity and uronic acid content in pectin suggesting the involvement of NaCl in the process of cell wall P reutilization in P starved rice roots. Additionally, exogenous NaCl up-regulated the expression of P transporter OsPT6, which was induced by P deficiency, suggesting that NaCl also facilitated the P translocation prominently from root to shoot in P starved rice. Moreover, exogenous abscisic acid(ABA) can reverse the NaCl-mediated mitigation under P deficiency, indicating the involvement of ABA in the NaCl regulated root cell wall P reutilization. Taken together, our results demonstrated that NaCl can activate the reutilization of root cell wall P in P starved rice, which is dependent on the ABA accumulation pathway.

Fiber-specific increase of carotenoid content promotes cotton fiber elongation by increasing abscisic acid and ethylene biosynthesis

Cotton fiber is a raw material for the global textile industry and fiber quality is essential to its industrial application.Carotenoids are plant secondary metabolites that may serve as dietary components,regulate light harvesting,and scavenge reactive oxygen species.Although carotenoids accumulate predominantly in rapidly elongating cotton fibers,their roles in cotton fiber development remain poorly understood.In this study,a fiber-specific promoter proSCFP was applied to drive the expression of GhOR1Del,a positive regulator of carotenoid accumulation,to upregulate the carotenoid level in cotton fiber in planta.Fiber length,strength,and fineness were increased in proSCFP:GhOR1Del transgenic cotton and abscisic acid(ABA)and ethylene contents were increased in elongating fibers.The ABA downstream regulator GhbZIP27a stimulated the expression of the ethylene synthase gene GhACO3 by binding to its promoter,suggesting that ABA promoted fiber elongation by increasing ethylene production.These findings suggest the involvement of carotenoids and ABA signaling in promoting cotton fiber elongation and provide a strategy for improving cotton fiber quality.

Identification and Expression Analysis of Abscisic Acid Signal Transduction Genes in Hemp Seeds

Abscisic acid(ABA)is involved in regulating diverse biological processes,but its signal transduction genes and roles in hemp seed germination are not well known.Here,the ABA signaling pathway members,PYL,PP2C and SnRK2 gene families,were identified from the hemp reference genome,including 7 CsPYL(pyrab-actin resistance1-like,ABA receptor),8 CsPP2CA(group A protein phosphatase 2c),and 7 CsSnRK2(sucrose nonfermenting1-related protein kinase 2).The content of ABA in hemp seeds in germination stage is lower than that in non-germination stage.Exogenous ABA(1 or 10μM)treatment had a significant regulatory effect on the selected PYL,PP2C,SnRK2 gene families.CsAHG3 and CsHAI1 were most significantly affected by exogenous ABA treatment.Yeast two-hybrid experiments were performed to reveal that CsPYL5,CsSnRK2.2,and CsSnRK2.3 could interact with CsPP2CA7 and demonstrate that this interaction was ABA-independent.Our results indicated that CsPYL5,CsSnRK2.2,CsSnRK2.3 and CsPP2CA7 might involve in the ABA signaling transduction pathway of hemp seeds during the hemp seed germination stages.This study suggested that novel genetic views can be brought into investigation of ABA signaling pathway in hemp seeds and lay the foundation for further exploration of the mechanism of hemp seed germination.

甜菜BvABF基因家族全基因组鉴定及其ABA处理下表达模式分析

ABA响应元件结合因子(ABRE binding factor,ABF)作为植物中bZIP转录因子的一个独特亚家族,在脱落酸(abscisic acid,ABA)依赖型和非依赖型信号通路中发挥重要作用。为挖掘和鉴定糖料作物甜菜BvABF基因家族生物学功能及其表达模式,本研究采用生物信息学方法,预测了蛋白理化特性、系统进化、染色体位置、基因结构、保守基序、顺式作用元件、二级结构和蛋白互作网络等,并通过qRT-PCR方法分析了在100μmol·L^(-1) ABA处理下BvABF在根和叶中的表达模式。结果表明,从甜菜中鉴定出6个BvABF基因家族成员,将其分为A、B和C簇,它们均含有一个bZIP区域。BvABF分布在1、3、6、7和9号染色体,含有3~4个外显子。BvABF蛋白拥有4个含有潜在磷酸化位点(R-X-X-S/T)的保守区域C1、C2、C3和C4,在C端含有一个碱性区域和4个重复的由亮氨酸(Leu)残基组成的七肽重复序列。BvABF基因家族启动子含有多种激素和光响应元件,其中4个基因含有ABA响应元件(ABA-responsive element,ABRE);另外,干旱诱导的响应元件(MBS)、低温响应元件(LTR)和厌氧响应元件(anaerobic responsive element,ARE)等也存在于该基因家族。此外,BvABF可能与磷酸化相关蛋白(PP2CCNBD-X2、SRK2I、SRK2E-X1和PP2C50)和ABA受体(PYL2、PYL4和PYR1)发生互作。进一步对BvABF在ABA处理下甜菜不同组织中的表达模式分析发现,所有BvABF基因在甜菜根和叶中均受ABA诱导和调控,且不同基因在ABA处理下呈现出不同的表达模式。这些结果表明,BvABFs在糖料作物甜菜响应ABA过程中扮演着重要角色。

外源GA3和ABA对烤烟内源激素调控效应和常规化学成分的影响

本文从激素和基因水平探究外源激素赤霉素(GA3)和脱落酸(ABA)的作用机理,研究其对烤烟生长发育及产量和质量的影响,为田间施用外源激素提供理论依据。采用大田试验,材料为中烟100(ZY100)和NC71,喷施不同浓度配比的GA3和ABA,测定不同时期烟株的农艺性状、基因表达量、生理特性、内源激素含量及烤后烟叶化学成分。结果表明,与未喷施GA3处理相比,喷施GA3后ZY100株高升高20%,NC71株高升高31%;喷施ABA后ZY100株高降低17%,NC71株高降低10%。喷施GA3后ZY100和NC71内源赤霉素含量分别升高20%和30%;喷施外源GA3后ZY100和NC71烟株内CPS、GA20ox和PSY的基因表达量均上调,GA2ox基因表达量下调。喷施GA3提高了ZY100和NC71烟株体内叶绿素以及可溶性蛋白的含量,降低了丙二醛含量,提高了烤后烟叶总糖含量、钾含量、钾氯比,降低了烟碱含量和氯含量,显著提高了烤烟的经济性状。

Research and Applicationon Plant Hormone--Abscisic Acid, ABA

Abscisic Acid (ABA), along with ethylene, gibberellins, cytokinins and auxins, is regarded as five kinds of important plant hormone. ABA was first isolated from cotton bud by Addcott Ohhuma’s group in 1963. Until 1965, its plane structure was determined. It was formally named as Abscisic acid in "the International Conference of Plant Regulator" in 1967. Scientists all over the world have made a long-term unremitting effort

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.

脱落酸ABA受体的功能以及翻译后修饰研究进展

脱落酸(Abscisic Acid,ABA)作为植物六大激素之一,在植物应对干旱、渗透等逆境胁迫条件下,维持植物体本身内环境的稳态中都起重要作用.ABA受体RCARs/PYR/PYLs结合ABA后抑制PP2C的活性来激活ABA信号转导途径.ABA受体作为ABA信号传递中的核心成员,其翻译后修饰对其功能有重要意义.本文主要总结了ABA受体的功能以及泛素化、硝基化和磷酸化修饰对其功能的精细调控的研究进展,并对该领域需解决的问题进行了展望.总结发现,ABA受体的不同修饰对其功能的影响不同,因此其翻译后修饰的研究可能对培育抗逆农作物品种具有理论指导意义.

外源ABA对藜麦种子萌发及ABA相关基因表达的影响

穗发芽会导致藜麦籽粒产量和品质严重受损,而脱落酸(ABA)与种子萌发和休眠密切相关。该研究以易穗发芽的‘大黑藜3’(BBQ3)、‘白藜6’(WQ6)和抗穗发芽的‘小黑藜1’(SBQ1)和‘白藜4’(WQ4)为试验材料,在种子萌发3 d内施加不同浓度ABA和氟啶酮(FL),探究ABA和FL对两种粒色藜麦种子萌发、ABA含量以及ABA合成基因NCED、裂解基因8′OH和信号转导基因ABI3表达的影响。结果表明:(1)各藜麦种子萌发均受到各浓度外源ABA抑制,并以25μmol·L^(-1)浓度效果最佳,同时受到外源低浓度FL促进,且施用2.5μmol·L^(-1)浓度即可;外源ABA和FL处理的SBQ1和WQ4发芽率降低和升高幅度分别小于BBQ3和WQ6。(2)对照组SBQ1和WQ4种子内源ABA含量分别显著高于BBQ3和WQ6;外源ABA处理可显著提高藜麦种子内源ABA含量,且WQ4显著高于WQ6,种皮略厚的SBQ1内源ABA含量显著低于BBQ3;外源FL处理下4份材料种子内源ABA含量均有所下降,但只有SBQ1达到显著水平。(3)对照组中,SBQ1和WQ4萌发种子中NCED、8′OH、ABI3基因的表达量分别高于BBQ3和WQ6;外源ABA处理下,SBQ1萌发种子中NCED和ABI3表达量在12 h才显著上调,BBQ3的3个基因表达量均在6 h时就显著上调,同时WQ4的3个基因表达量上调时间也迟于WQ6;在外源FL处理下,SBQ1中3个基因表达量均上调,但NCED表达量明显低于8′OH,BBQ3中NCED和ABI3的表达量下调,8′OH表达量显著上调;FL对WQ4中NCED和8′OH的表达主要起抑制作用,对ABI3无显著调控作用,而对WQ6中8′OH基因表达的促进作用高于NCED基因。(4)黑藜和白藜中种子发芽率、ABA含量与NCED、ABI3基因的表达量均显著相关。研究发现,抗穗发芽藜麦材料种子发芽率低于易穗发芽材料,ABA含量高于易穗发芽材料;外源ABA可显著抑制种子萌发,且易穗发芽藜麦材料对ABA的敏感性高于抗穗发芽材料,ABA敏感性高材料的相关基因表达对ABA的响应早于其他材料;FL对种子萌发有促进作用,但可能不是直接通过抑制NCED、ABI3的表达和促进8′OH的表达来调控ABA合成,而是通过影响其他关键结合位点进行调控。

ABA调控种子发育的研究进展

种子发育是一个复杂的生物学过程,受各种遗传和外界因素的调节,显著影响农作物特别是禾谷类作物的种子活力和产量与质量。脱落酸(ABA)是调控种子发育和萌发最重要的植物激素之一,其活性水平、信号转导及其LAFL网络在种子发育包括胚胎发生和成熟过程的调控中起关键作用。该文主要综述了近年来ABA调控种子发育的研究取得的重要进展,包括ABA代谢和信号转导对种子发育的调控,ABA与种子成熟转录因子(AFL-B3、FUS3、ABI3、LEC2等)的作用,以及ABA在种子发育中的作用机制,并提出了需要进一步研究的科学问题,为深入理解种子发育的分子机制提供参考,从而提高种子的活力、产量和质量。

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.

Effects of Abscisic Acid Treatment on Berry Coloration and Expression of Flavonoid Biosynthesis Genes in Grape

In order to enhance berry coloration of bright-red grape cultivars, the effects of abscisic acid (ABA) treatment on the quantity and composition of anthocyanins as well as the expression of genes related to flavonoid biosynthesis in the berry were examined. Exogenous ABA treatment increased anthocyanin content, especially petunidin- and malvidin-type anthocyanins. Quantitative real-time PCR analysis revealed that ABA treatment around véraison resulted in the upregulation of genes encoding enzymes responsible for both general flavonoid and anthocyanin biosynthesis. On the other hand, the gene expressions of enzymes involved in proanthocyanidin synthesis were drastically decreased at véraison and remained extremely low even with ABA treatment. Thus, increases in the total amount and composition ratios of petunidin- and malvidin-type anthocyanins were mainly caused by ABA-induced upregulation of uridine diphosphate glucose flavonoid glucosyl transferase, glutathione S-transferase 4, O-methyl transferase and flavonoid 3’, 5’ hydroxylase expression, resulting in the deep coloration of berry of skin.