FaSnRK1a mediates salicylic acid pathways to enhance strawberry resistance to Botrytis cinerea

Strawberry is a major fruit crop worldwide because its nutritional and health benefits to human health,but its productivity is limited by Botrytis cinerea.Sucrose nonfermentation 1-related protein kinase 1(SnRK1)has a defense function against pathogens,but the function of SnRK1 in the defense response to B.cinerea in plants is still unclear.In this study,FaSnRK1a-OE and RNAi fruits were constructed and then inoculated with B.cinerea.The result reveals a positive role of Fa SnRK1a in the regulation of resistance to gray mold.FaSnRK1a affects SA content by regulating FaPAL1 and FaPAL2 expressions.The genes related to the SA signaling pathway(FaTGA1 and FaTGA2.1)were significantly increased/decreased in FaSnRK1a-OE or FaSnRK1a-RNAi fruit,respectively.FaSnRK1a interacted with the FaWRKY33.2 protein and negatively regulated FaWRKY33.2 expression,and FaWRKY33.2 acts as a repressor of disease resistance to B.cinerea.Finally,FaSnRK1a regulates the expression of six PR genes and the activities of antioxidant enzymes to boost defense response after B.cinerea inoculation.Our findings showed that FaSnRK1a increases the resistance of strawberry fruit to B.cinerea via SA signaling pathway and interaction with the FaWRKY33.2 transcription factor.

OsbZIP53 Negatively Regulates Immunity Response by Involving in Reactive Oxygen Species and Salicylic Acid Metabolism in Rice

The basic region/leucine zipper(bZIP)transcription factors play important roles in plant development and responses to abiotic and biotic stresses.OsbZIP53 regulates resistance to Magnaporthe oryzae in rice by analyzing APIP5-RNAi transgenic plants.To further investigate the biological functions of OsbZIP53,we generated osbzip53 mutants using CRISPR/Cas9 editing and also constructed OsbZIP53 over-expression transgenic plants.Comprehensive analysis of phenotypical,physiological,and transcriptional data showed that knocking-out OsbZIP53 not only improved disease resistance by inducing a hypersensitivity response in plants,but also regulated the immune response through the salicylic acid pathway.Specifically,disrupting OsbZIP53 increased H2O2 accumulation by promoting reactive oxygen species generation through up-regulation of several respiratory burst oxidase homologs(Osrboh genes)and weakened H2O2 degradation by directly targeting OsMYBS1.In addition,the growth of osbzip53 mutants was seriously impaired,while OsbZIP53 over-expression lines displayed a similar phenotype to the wild type,suggesting that OsbZIP53 has a balancing effect on rice immune response and growth.

Investigating the mechanisms of isochorismate synthase:An approach to improve salicylic acid synthesis and increase resistance to Fusarium head blight in wheat

Salicylic acid(SA),a vital endogenous hormone,plays a crucial role in plant growth and the response to abiotic and biotic stress.Isochorismate synthase(ICS)and phenylalanine ammonia lyase(PAL)are critical rate-limiting enzymes for SA synthesis.Fusarium head blight(FHB)seriously threatens the safety of wheat production,but increasing the content of SA can enhance FHB resistance.However,the pathway of SA synthesis and regulation in wheat remains unknown.In this study,three wheat ICS(TaICSA,TaICSB,and TaICSD)were identified,and their functions were validated in vitro for isomerizing chorismate to isochorismate.The mutation of one or two homoeoalleles of TaICSA,TaICSB,and TaICSD in the wheat variety‘Cadenza’reduced SA levels under ultraviolet treatment and Fusarium graminearum infection,further enhancing sensitivity to FHB.Overexpression of TaICSA can significantly enhance SA levels and resistance to FHB.To further study SA synthesis pathways in wheat and avoid interference with pathogenicity related genes,the leaves of wild-type Cadenza and different TaICS mutant lines were subjected to ultraviolet treatment for transcriptomic analysis.The results showed that 37 PALs might be involved in endogenous SA synthesis,and 82 WRKY and MYB family transcription factors may regulate the expression of ICS and PAL.These results were further confirmed by RT-PCR.In conclusion,this study expands our knowledge of SA biosynthesis and identifies TaICSA,as well as several additional candidate genes that encode transcription factors for regulating endogenous SA levels,as part of an efficient strategy for enhancing FHB resistance in wheat.

Salicylic acid positively regulates maize defenses against lepidopteran insects

In response to insect attack,plants use intricate signaling pathways,including phytohormones,such as jasmonate(JA),ethylene(ET),and salicylic acid(SA),to activate defenses.Maize(Zea mays)is one of the most important staple food crops around the world.Previous studies have shown that the JA and ET signaling play important roles in maize defense against insects,but little is known about whether and how SA regulates maize resistance to insect herbivores.In this study,we ectopically expressed the NahG(salicylate hydroxylase)gene in maize plants(NahG maize)to block the accumulation of SA.It was found that compared with the wild-type(WT)maize,the NahG-maize exhibited decreased resistance to the generalist insects Spodoptera litura and Spodoptera frugiperda and the specialist Mythimna separata,and the compromised resistance in the NahG maize was associated with decreased levels of defensive metabolites benzoxazinoids(Bxs)and chlorogenic acid(CA).Quantification of simulated S.litura feedinginduced JA,JA-isoleucine conjugate(JA-Ile),and ET in the WT and NahG maize indicated that SA does not regulate JA or JA-Ile,but positively controls ET.We provide evidence suggesting that the SA pathway does not crosstalk with the JA or the ET signaling in regulating the accumulation of Bxs and CA.Transcriptome analysis revealed that the bHLH,ERF,and WRKY transcription factors might be involved in SAregulated defenses.This study uncovers a novel and important phytohormone pathway in maize defense against lepidopterous larvae.

Overexpression of auxin/indole-3-acetic acid gene MdIAA24 enhances Glomerella leaf spot resistance in apple(Malus domestica)

Auxin is throughout the entire life process of plants and is involved in the crosstalk with other hormones,yet its role in apple disease resistance remains unclear.In this study,we investigated the function of auxin/indole-3-acetic acid(IAA)gene Md IAA24 overexpression in enhancing apple resistance to Glomerella leaf spot(GLS)caused by Colletotrichum fructicola(Cf).Analysis revealed that,upon Cf infection,35S::Md IAA24 plants exhibited enhanced superoxide dismutase(SOD)and peroxidase(POD)activity,as well as a greater amount of glutathione(reduced form)and ascorbic acid accumulation,resulting in less H_(2)O_(2)and superoxide anion(O_(2)^(-))in apple leaves.Furthermore,35S::Md IAA24 plants produced more protocatechuic acid,proanthocyanidins B1,proanthocyanidins B2 and chlorogenic acid when infected with Cf.Following Cf infection,35S::Md IAA24 plants presented lower levels of IAA and jasmonic acid(JA),but higher levels of salicylic acid(SA),along with the expression of related genes.The overexpression of Md IAA24 was observed to enhance the activity of chitinase andβ-1,3-glucanase in Cfinfected leaves.The results indicated the ability of Md IAA24 to regulate the crosstalk between IAA,JA and SA,and to improve reactive oxygen species(ROS)scavenging and defense-related enzymes activity.This jointly contributed to GLS resistance in apple.

Increase of β -1, 3-Glucanase and Chitinase Activities in Cotton Callus Cells Treated by Salicylic Acid and Toxin of Verticillium dahliae

The different resistance of cotton (Gossypium hirsutum L.) cultivars to crude toxin of Verticillium dah/iae(VD) was correlated with the activities of chitinase and β-1, 3-glucanase in callus cells. The activities of chitinase and β-1, 3-glucanase in the callus cells treated with the VD-toxin were increased to the higher level at earlier time point in resistant cultivars than these in the susceptible cultivars. Exogenous salicylic acid (SA) induced the accumulation of chitinase and β -1,3-glucanase, which resulted in the resistance of callus cells to the VD. toxin. Western blot using a polyclonal antibody against β -1,3-glucanase identified 28 kD protein that was induced by VD-toxin, SA, or VD-toxin plus SA.

Effects of Acetylsalicylic Acid (ASA) and Ethylene Treatments onRipening and Softening of Postharvest Kiwifruit

Kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson cv. Bruno) was used toinvestigate the effects of acetylsalicylic acid (ASA, 1.0 mmol/L, pH 3.5) and ethylene (100 mL/L) treat-ments on changes at endogenous salicylic acid (SA) levels and other senescence-related factors duringfruit ripening and softening at 20 ℃. The level of endogenous SA in ripening fruits declined and a closerelationship was observed between the change at endogenous SA level and the rate of fruit ripening andsoftening. ASA treatment elevated SA level in the fruit, slowed down the increases in lipoxygenase (LOX)and allene oxide synthase (AOS) activities, decreased the O22-. production in the preclimacteric phase andthe early phase of ethylene climacteric rise, maintained the stability of cell membrane, inhibited ethylenebiosynthesis, postponed the onset of the ethylene climacteric, and delayed the process of fruit ripeningand softening. On the contrary, application of ethylene to ripening kiwifruit resulted at a lower SA level, anaccelerated increases in the activities of LOX and AOS and the rate of O22-. production, an elevated relativeelectric conductivity and an advanced onset of ethylene climacteric, and a quicker fruit ripening andsoftening. It is suggested that the effects of ASA on ripening kiwifruit can be attributed to its ability toscavenge O22-. and/or to maintain stability of cell membrane.

Participation of H_2O_2 in Enhancement of Cold Chilling by Salicylic Acid in Banana Seedlings

The possible physiological mechanism of enhancement of cold tolerance by salicylic acid (SA) in banana seedlings ( Musa acuminata cv. Williams 8188) was explored. Measurements of leakage electrolyte after 2 d of recovery at 30/22 ℃ (day/night) following 3 d of cold stress at 7 ℃ showed that pretreatment with hydroponic solution containing SA 0.3-0.9 mmol/L as foliar spray under normal growth conditions (30/22 ℃) could significantly enhance cold tolerance of banana plants. The highest enhancing effect of SA occurred at 0.5 mmol/L and it showed the lowest leakage rate of electrolyte or smaller leaf wilting area after 2 d of recovery at normal temperature from 3 d of 7 ℃ or 5 ℃ cold stress. Higher concentrations (≥2.5 mmol/L) of SA, however, caused more electrolyte leakage, indicating that they aggravated chilling damage. Enhanced cold tolerance by SA could be related to H 2O 2 metabolism. Compared with water_treated seedlings (control), SA 0.5 mmol/L treatment inhibited activities of catalase (CAT) and ascorbate peroxidase (APX), increased peroxidase (POX) activity, but did not affect the activity of superoxide dismutase (SOD) under normal growth conditions, and these changes might lead to an accumulation of H 2O 2, whereas SA pretreatment enhanced the activities of CAT and APX, and reduced the increase in productions of H 2O 2 and thiobarbituric acid_reaction substances (TBARS) during subsequent 7 ℃ cold stress and recovery periods. Exogenous H 2O 2 treatments (1.5 -2.5 mmol/L) also increased cold tolerance of banana seedlings. Furthermore, pretreatment of banana seedlings with dimethylthiourea (a trap for H 2O 2) significantly inhibited cold tolerance induced by SA. These results suggested that endogenous H 2O 2 may be required for SA_enhanced cold tolerance. The significance of the interaction of SA, H 2O 2 and H 2O 2_metabolizing enzymes during cold stress has been discussed.

Effects of Chitosan and Salicylic Acid on Cold Resistance of Litchi under Low Temperature

This paper focused on the effect of spraying chitosan and salicylic acid to Litchi under low temperature stress conditions.The physiology and biochemistry of litchi were studied as well.Results showed that the appropriate concentration of chitosan and salicylic acid treatment could effectively reduce injury caused by low temperature to litchi,compared with water control,chlorophyll,proline,soluble protein content of litchi after treatment and the activity of protective enzyme increasing significantly.However,the accumulation of resistance could significantly be improved.Furthermore,when 1 000 mg/L chitosan combined with 50 mg/L salicylic acid,the litchi acquired the best cold resistance capability.

Effects of Salicylic Acid on Photosynthesis and Chlorophyll Fluorescence Characteristics of Fluecured Tobacco Leaf in Subdued Light

[Objective] This study aimed to test whether salicylic acid （SA） can im-prove the physiological functions of flue-cured tobacco under subdued light condition, and to determine the mechanism of its action. [Method] The tobacco plants under subdued light were foliar-sprayed with 100 mg/L of SA. Then, the physiological in-dices such as plant fresh weight and dry weight, chlorophyl content, photosynthetic parameters and chlorophyl fluorescence parameters were measured. SPSS17.0 and Excellwere adopted for variance analysis and significance test. [Result] The leaf photosynthetic rate （Pn）, stomatal conductance （Gs） and transpiration rate （Tr） of tobacco plants in subdued light were al decreased while the intercellular CO2 con-centration （Ci） was increased, suggesting that non-stomatal limitation led to the de-crease of Pn under weak light intensity stress. SA released the inhibition of tobacco plant growth in weak light, as it elevated the leaf photosynthetic rate, the maximum photochemical efficiency of PSⅡ, potential activity of PSⅡ, effective photochemical efficiency of PSⅡ and photochemical quenching coefficient in weak light significant-ly, and reduced the non-photochemical quenching coefficient. [Conclusion] SA has significant effects on the photosynthetic characteristics of flue-cured tobacco in weak light, and it can improve the synthesis or distribution of photosynthesis product, and the efficiency of light energy, conducive to plant growth and development.

Preparation and Application of Monoclonal Antibodies Specific for Salicylic Acid

Salicylic acid (SA) is widely distributed in many monocots and dicots and has many physiological effects. It can induce heat production in the thermogenic inflorescences of Arum lily([1]), block the biosynthesis of ethylene, and more attractively, it seems to be an important natural signal molecule in the induction of systemic acquired resistance (SAR) in tobacco, cucumber and other plants([2,3]). Studies in recent years showed that SA was also intimately related to the resistance of plants to aboitic stress, for example, SA increased chilling resistance of maize seedlings. Hence, SA has been accepted as a kind of new plant hormones. Up to date, the quantification of SA usually has been performed by HPLC[4,5], which often needs a large quantity of sample and a verbose pretreatment. Compared to HPLC, immunoassays, including radio-immunoassays (RIA) and enzyme-immunoassays (EIA), are easy to perform and have been widely used in the quantification of other plant hormones, such as IAA([6]), ABA([7,8]), GAs([9]), cytokinins et al([10]), and jasmonic acid (JA)([11]), and other low-molecular-weight, none-immunogenic compounds in plants([12]). Till now, only an indirect enzyme-linked immunosorbent assay (ELISA) for SA based on polyclonal antibodies (PAbs) has been developed by our group([13]), although Bennett et al([14]) had prepared SA PAbs using 4-aminosalicylic acid linked to KLH as immunogen in goat. However, the sensitivity of the ELISA we established formerly was relatively low, and also relatively larger quantity of sample is needed than other ELISAs for plant hormones. In this paper, an ELISA for SA based on monoclonal antibody raised against SA-NH-CH2-NH-KLH was introduced, and the fluctuation of SA content in cucumber leaves after inoculated with Pseudomonas syringae pv. syringae was determined.

Nitric Oxide Production is Involved in Inhibition Growth of Salicylate at Chilling Temperature

[Objective] The aim was to investigate whether NO is involved in the inhibitory effect of salicylic acid on the growth at low temperature in Arabidopsis.[Method] The endogenous NO level in roots of wild-type and NahG mutant growing at 22 or 4 ℃ was measured with NO-specific probe DAF-FM DA staining method.[Result] NO level in plants growing at 4 ℃ for a long term could be increased with time;low temperature could induce NO production in wild-type and NahG mutant,and the NO level in NahG mutant with low level of salicylic acid was significantly lower than that in wild-type.[Conclusion] NO was involved in the inhibitory effect of salicylic acid on the growth of Arabidopsis at low temperature.

Comparison of the Effects of H_2O_2 and Salicylic Acid on Alternative Respiratory Pathway in Aged Potato Tuber Slices

The influences of exogenous H 2O 2 and salicylic acid (SA) treatments on the alternative respiratory pathway (ARP) in aged potato (Solanum tuberosum L.) tuber slices were compared. The results showed that both H 2O 2(5.0 mmol/L) and SA (0.1 mmol/L) treatments had a significant inducing effect on ARP capacity (V alt ) and its ratio to total respiration (V alt /V t) in potato slices aged for 24 h. With a monoclonal antibody against the alternative oxidase (AOX), Western blotting results showed that both H 2O 2 and SA treatments increased the AOX expression levels in aged potato tuber slices. However, the results of oxygen isotope discrimination experiments showed that H 2O 2 had no influence on the in vivo ARP activity (ρV alt ) and its contribution to V t(expressed as ρV alt /V t) in potato slices aged for 24 h, but SA had a significant influence on the ρV alt and ρV alt /V t values of the aged potato tuber slices. These results indicate that there are differences between the effects of H 2O 2 and SA on ARP in plant tissues. Both of them possess the ability to induce ARP capacity through inducing AOX expression. However, SA can simultaneously stimulate the operation of ARP, but H 2O 2 can not.

Effects of Exogenous Salicylic Acid Derivative on the Resistance to TMV and Activity of Defense Enzymes of Tobacco

[Objective] This study aimed to evaluate the effects of exogenous salicylic acid derivatives on tobacco resistance to TMV and activity of defense enzymes. [Method] The tobboco leaves were treated by exogenous salicylic acid derivatives. Then, the disease occurrence was observed, and the activity of phenylalanin ammo- nia lyase （PAL） and peroxidase （POX） were measured. [Result] Exogenous salicylic acid derivative increased the activities of PAL and POX, while did not influence the resistance to TMV. [Conclusion] The result provides a theoretical basis for the study of plant disease resistance mechanisms.

Advances in Molecular Mechanism of Microbiological Degradation of Salicylate

Salicylate is a type of pollutant widely and persistently existed in environ- ment. Microbiological degradation of salicylate as one kind of biological remediation methods has the advantages of low cost, good effect and no secondary pollution, and also attracts wide attention both at home and abroad. Currently, many salicy- late-degrading bacteria are isolated and screened, while the molecular mechanism of salicylate metabolism is also worth deep research. The research about molecular mechanism of microorganism degradation was overviewed, various degrading path- ways including catechol meta-cleavage pathway and gentisate pathway were intro- duced, and the latest progress in regulating genes of salicylate degradation was summarized.

Effects of exogenous salicylic acid on growth and H_2O_2-metabolizing enzymes in rice seedlings under lead stress

Salicylic acid （SA） was an essential component of the plant resistance to pathogens and also plays an important role in mediating plant response to some abiotic stress. The possible effects of SA on the growth and H2O2-metabolizing enzymes in rice seedlings under lead stress were studied. When rice seedlings grown in nutrient solution containing Pb^2＋ （0, 0.05, 0.15, 0.25 mmol/L） for 18 d, the plant biomass as well as the chlorophyll content of leaves decreased with increasing Pb concentration. The pre-treatment with SA （treated with 0.1 mmol/L SA for 48 h before Pb stress） partially protected seedlings from Pb toxicity. The chlorophyll contents were significant higher in leaves of Pb-exposed with SA pre-treatment seedlings than in Pb-exposed plants at the same Pb intensity. SA pre-treated alone could significantly increase the length of shoot and root of seedlings but the vigour difference was not marked under long-term exposure to Pb toxicity. SA pre-treated influence the H2O2 level in leaves of seedlings by up-regulating the activity of superoxide dismutase （SOD）, repressing the activity of catalase （CAT） and ascorbate peroxidase （APX） depending on the concentrations of Pb^2＋ in the growth medium. The results supported the conclusion that SA played a positive role in rice seedlings against Pb toxicity.

ATR-FTIR and XPS study on the structure of complexes formed upon the adsorption of simple organic acids on aluminum hydroxide

Information on the binding of organic ligands to metal （hydr）oxide surfaces is useful for understanding the adsorption behaviour of natural organic matter on metal （hydr）oxide. In this study, benzoate and salicylate were employed as the model organic ligands and aluminum hydroxide as the metal hydroxide. The attenuated total reflectance Fourier transform infrared （ATR-FTIR） spectra revealed that the ligands benzoate and salicylate do coordinate directly with the surface of hydrous aluminum hydroxide, thereby forming innersphere surface complexes. It is concluded that when the initial pH is acidic or neutral, monodentate and bridging complexes are to be formed between benzoate and aluminum hydroxide while bridging complexes predominate when the initial pH is alkalic. Monodentate and bridging complexes can be formed at pH 5 while precipitate and bridging complexes are formed at pH 7 when salicylate anions are adsorbed on aluminum hydroxide. The X-ray photoelectron （XP） spectra demonstrated the variation of C 1 s binding energy in the salicyate and phenolic groups before and after adsorption. It implied that the benzoate ligands are adsorbed through the complexation between carboxylate moieties and the aluminum hydroxide surface, while both carboxylate group and phenolic group are involved in the complexation reaction when salicylate is adsorbed onto aluminum hydroxide. The information offered by the XPS confirmed the findings obtained with ATR-FTIR.

Salicylic acid alleviates postharvest chilling injury of sponge gourd(Luffa cylindrica)

Effect of salicylic acid（SA）on chilling injury（CI）of sponge gourd during storage（9 days,9°C）plus shelf life（2 days,20°C）was evaluated in this study.SA treatment at the concentration of 1.5 mmol L^-1 significantly reduced postharvest CI of sponge gourds.Besides,the application of SA could effectively decrease the electrolyte leakage,reduce the accumulation of malondialdehyde（MDA）and total phenolics,enhance the activities of antioxidant enzymes such as superoxide dismutase（SOD）,catalase（CAT）and ascorbate peroxidase（APX）,and inhibit the activities of phenylalanine ammonia-lyase（PAL）and polyphenol oxidase（PPO）.The beneficial effects of SA could be attributed to preserved membrane integrity,inhibited membrane peroxidation,enhanced antioxidant system and suppressed activities of browning related enzymes.In a sense,SA as a postharvest tool may be commercially used in alleviating CI of sponge gourd.

Wheat straw biochar amendment suppresses tomato bacterial wilt caused by Ralstonia solanacearum: Potential effects of rhizosphere organic acids and amino acids

Complex interactions based on host plant, rhizosphere microorganisms and soil microenvironment are presumed to be responsible for the suppressive properties of biochar against soil-borne diseases, although the underlying mechanisms are not well understood. This study is designed to evaluate the efficacy of biochar amendment for controlling tomato bacterial wilt caused by Ralstonia solanacearum, and to explore the interactions between biochar-induced changes in rhizosphere compound composition, the pathogen and tomato growth. The results showed that biochar amendment decreased disease incidence by 61–78% and simultaneously improved plant growth. The positive ‘biochar effect' could be associated with enhanced microbial activity and alterations in the rhizosphere organic acid and amino acid composition. Specifically, elevated rhizosphere citric acid and lysine, but reduced salicylic acid, were induced by biochar which improved microbial activity and rendered the rhizosphere unsuitable for the development of R. solanacearum. In addition, nutrients which were either made more available by the stimulated microbial activity or supplied by the biochar could improve plant vigor and potentially enhance tomato resistance to diseases. Our findings highlight that biochar's ability to control tomato bacterial wilt could be associated with the alteration of the rhizosphere organic acid and amino acid composition, however, further research is required to verify these ‘biochar effects' in field conditions.

Application of advanced oxidation processes for removing salicylic acid from synthetic wastewaters

In this study,advanced oxidation processes(AOPs) such as anodic oxidation(AO),UV/H_2O_2 and Fenton processes(FP) were investigated for the degradation of salicylic acid(SA) in lab-scale experiments.Boron-doped diamond(BDD) film electrodes using Ta as substrates were employed for AO of SA.In the case of FP and UV/H_2O_2,most favorable experimental conditions were determined for each process and these were used for comparing with AO process.The study showed that the FP was the most effective process under aci...