Salicylate activity. 1. Protection of plants from paraquat injury

Paraquat (1,1'-dimethyl-4,4'-bipyridinium; methylviologen) is a widely used, nonselective contact herbicide that rapidly stimulates free radical generation. It has been found that the addition of sodium salicylate (sodium 2-hydroxybenzoate; NaSA) to paraquat spray solutions significantly decreased herbicidal activity. This protection was observed in tobacco (Nicotiana tabacum) regardless of whether NaSA was foliar-applied along with or prior to paraquat application or NaSA was soil-applied prior to paraquat application. Because salicylic acid (SA) is an inducer of systemic acquired resistance (SAR) to plant disease, paraquat protection by three SAR inducers (acibenzolar-S-methyl, harpin, and probenazole) and selected salicylate derivatives was assessed. Twenty-two of 24 compounds tested decreased herbicidal activity when foliar-applied with paraquat. Protection from paraquat was greatest with 5-chlorosalicylate, and no protection was observed with benzoic acid. NaSA decreased paraquat activity on npr1-2, an Arabidopsis mutant that is compromised in NaSA-induced SAR, and on ein2-1, an ethylene-insensitive Arabidopsis mutant. Thus, salicylate protection from paraquat is independent of disease resistance and ethylene perception. This suggests the existence of an NaSA-mediated pathway capable of protecting plants from reactive oxygen stress.     

Salicylate activity. 2. Potentiation of atrazine

Atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] inhibits photosystem II (PSII) and is commonly used to control weeds in maize. It has been found that addition of sodium salicylate (sodium 2-hydroxybenzoate; NaSA) increased the postemergence herbicidal activity of atrazine against dicotyledonous weeds. NaSA also potentiated the activity of bentazon, another PSII-inhibiting herbicide. NaSA increased atrazine activity when applied either as a tank mix or up to 96 h prior to atrazine application. Other salicylates and the plant disease resistance inducers acibenzolar-S-methyl [benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester] and 2,6-dichloroisonicotinic acid also increased atrazine activity. Among the compounds tested, 3-chloro-5-fluorosalicylate, 4-chlorosalicylate, or 2,6-dichloroisonicotinic acid combined with atrazine yielded the greatest increase in herbicidal activity. Potentiation of atrazine by NaSA was greater at higher temperatures (35 and 25 > 15 degrees C). Also, greater potentiation was observed as the light level decreased. In darkness, NaSA alone or in combination with atrazine caused plant death, whereas atrazine alone had little effect. NaSA increased atrazine activity on npr1-2, an Arabidopsis mutant compromised in SA-induced disease resistance. Atrazine activity was also potentiated by NaSA on the ethylene insensitive mutant ein2-1. This indicates that atrazine potentiation is independent of either salicylate-induced disease resistance or ethylene perception.     

水稻白叶枯病菌蛋白质激发子HarpinXoo诱导植物的防卫反应

摘要：含质粒pHRF4的表达菌株BLHR4在培养基中经IPTG诱导，16 h Harpin表达接近最高量。用不同浓度的HarpinXoo喷雾处理烟草(Nicotiana tabacum L.)、油菜(Brassica campestris L.)和番茄(Lycopersicon esculentum Mill.)，对烟草花叶病毒(TMV)、油菜菌核病(Sclerotinia sclerotiorum (lib.) de Bary)和番茄灰霉病(Botrytis cinerea Pers.)均表现较好的诱导抗病效果。以浓度为100μg/mL的HarpinXoo处理烟草后，分别测定叶片中与防卫反应相关的一些生理指标的变化，结果表明，处理叶片中苯丙氨酸解氨酶（PAL）、过氧化物酶（PO）和多酚氧化酶（PPO）活性都有不同程度的增强。三种酶活性高峰分别在处理后24、12和3 h出现，分别比清水对照增加110.1%、211.2%和273.0%；同时，两个病程相关蛋白（pathogenesis-related protein，PR）基因PR-1b和PR-1a在HarpinXoo处理24 h后被诱导显著表达，36 h时达到最高表达水平。这表明HarpinXoo与HarpinEa一样能够诱导烟草不同抗病信号通路的启动，从而使植株获得抗病性。     

2-fluoroabscisic acid analogues: their synthesis and biological activities

Fluorine was introduced into the 2-position of the side chain of abscisic acid (ABA) analogues by Wittig reaction of alpha-ionone derivatives with ethyl triethylphosphono-2-fluoroacetate. The effects of the fluorinated analogues were evaluated on inhibition of cress seed germination and inhibition of gibberellin-inducible alpha-amylase induction in embryoless barley half-seeds. (2E, 4E)-2-Fluoro-5-(1'-hydroxy-2',6', 6'-trimethyl-2'-cyclohexen-1'-yl)-3-methyl-2,4-pentadienoic acid (5b) showed potent inhibitory activity at the same level as ABA in the cress seed germination test, and 5b also inhibited gibberellin-inducible alpha-amylase induction at 4 x 10(-)(6), 3 times the concentration of ABA (1 x 10(-)(6)) for 50% inhibition of alpha-amylase production. 5b also showed dehydrin induction activity. These results indicate that fluorinated ABA analogues mimic ABA action and can be a lead for a plant growth regulator which regulates plant growth or protects plants from environmental stresses.     

Preparative-scale synthesis of two metabolites isolated from soil treated with zoxium fungicide and kerb herbicide.

The preparation in multigram scale of two metabolites 3-(3,5-dichloro-4-methyl-benzoylamino)-2-hydroxy-3-methyl-pentanoic acid and 3-(3,5-dichloro-benzoylamino)-3-methyl-2-oxo-butyric acid isolated from soil treated with either Zoxium fungicide or Kerb herbicide was efficiently accomplished using a common 5-step synthetic process starting from easily available raw materials.     

Methylene group modifications of the N-(Isothiazol-5-yl)phenylacetamides. Synthesis and insecticidal activity.

It has been shown that oxidation at the alpha-carbon of N-(4-chloro-3-methyl-5-isothiazolyl)-2-[p-[(alpha,alpha, alpha-trifluoro-p-tolyl)oxy]phenyl]acetamide (1) is conveniently brought about using dimethylformamide dimethylacetal to give N-(4-chloro-3-methyl-5-isothiazolyl)-beta-(dimethylamino)-p-[(alpha, alpha,alpha-trifluoro-p-tolyl)oxy]atropamide (2), which has served as a common starting point for a variety of functional group transformations. These transformations were found to proceed in moderate to good yields to give derivatives of 1 that retained much of the efficacy associated with the parent amide and have allowed for an expansion of the SAR to be developed. Examples of enamines, enols, enol (thio)ethers, oximes, and hydrazones were prepared. In particular, the enamines derived from low molecular weight amines and amino acids were most active as broad-spectrum insecticides and were found to be even more active than 1 on root-knot nematode.     

毛白杨抗病相关转录因子基因PtWRKY1的表达特性分析

WRKY转录因子作为植物特有的一类重要转录调控因子,广泛参与植物对生物和非生物胁迫的应答反应及形态发育和组织衰老等,已引起人们的关注。本文以前期克隆得到的毛白杨WRKY转录因子基因（命名为PtWRKY1）为研究对象,开展其基因枪介导洋葱表皮细胞瞬时表达、外源信号分子（水杨酸SA,茉莉酸MeJA,脱落酸ABA）诱导表达、转PtWRKY1基因烟草植株的烟草花叶病毒（TMV）接种实验以及抗病相关基因表达的实时荧光定量RT-PCR（qRT-PCR）分析等研究。结果表明,PtWRKY1基因编码蛋白定位于细胞核,SA、ABA及MeJA处理均可诱导PtWRKY1基因表达,但不同诱导因子对PtWRKY1表达量的影响存在一定差异;同时,TMV侵染实验发现外源PtWRKY1表达能增强转基因烟草抗TMV能力,qRT-PCR分析表明PtWRKY1基因及膜保护性酶（POD,SOD,CAT）基因均受TMV诱导而增强表达。本文研究结果可为后续开展毛白杨转录因子PtWRKY1的功能鉴定及应用奠定基础。     

Effect of exogenous salicylic acid supply on nodule formation of hypernodulating mutant and wild type of soybean

Soybean plant is characterized by a systemic autoregulatory control system of nodulation (autoregulation) by initial infection with rhizobia, and plants commonly display a systemic acquired resistance (SAR) to pathogenic microbe infection related to salicylic acid (SA) signal transmission. We investigated the effect of exogenous SA supply on soybean nodulation to determine whether SA affects the autoregulation of nodulation. Seedlings of the hypernodulating mutants NOD1-3, NOD2-4 and their parent cv. Williams were treated or not treated (control) with a 100 μmS-SA solution at 5 d before the inoculation of Bradyrhizobium japonicum strain USDA110. The nodule dry weight and the number of nodules of the wild type soybean Williams exhibiting autoregulation drastically decreased by the addition of 100 μm SA. The decrease in the nodule number was not caused by the reduction of the rhizobium number in the medium. Salicylic acid inhibited only early nodule formation and did not affect the growth of formed nodules. The inhibitory effect of SA on the nodulation of NOD1-3 and NOD2-4 was significantly less pronounced than that in Williams. These results indicate that SA is directly involved in signal transmission in the autoregulation, and that SA or the SAR induced by SA stimulates the autoregulation of nodulation in soybean.     

Effect of Foliar Applied Plant Elicitors on Microbial and Nematode Populations in the Root Zone of Potato

Abstract

Systemic acquired resistance (SAR) is a process whereby a plant that successfully resists a pathogen becomes highly resistant to subsequent infection not only by the original pathogen but also by a wide variety of pathogens. Most SAR research has focused on resistance in leaves, so much less is known about the effectiveness of foliar applications of SAR compounds in the protection of plant roots and associated microorganisms in soil. This study was conducted to determine if foliar SAR‐inducing applications (BTH or harpin) negatively impact the potato root system beneficial rhizosphere microbial populations and activity or influence pathogenic nematode populations. Foliar applications of benzo (1,2,3) thiadiazole‐7‐carbothioic acid S‐methyl ester (BTH) and the microbial protein harpin applied in various combinations, timings, and rates showed no effects on microbial biomass, culturable bacteria, Pseudomonas populations, or N‐mineralization potentials over 2 years. No stimulatory or inhibitory effects on major bacterial populations were observed, indicating that SAR induction does not have a negative effect on general microbial populations or activities. BTH and harpin both reduced the numbers of lesion nematodes (Pratylenchus spp.) by potato harvest. BTH reduced root knot nematodes, Meloidogyne chitwoodi at the end of the season. In addition, BTH and high‐dose harpin (applied at the 4× rate) reduced the nematode infection index in comparison to the control. The SAR elicitors increased the population densities of nontarget free‐living nematodes in the soil compared to the control. Potato yields were not affected by plant elicitors but BTH and harpin both reduced the number of culled potatoes 26% compared to the control. Future studies are designed to determine if these plant elicitors have any direct effect on rhizosphere diversity or if plants with active defense pathways alter carbon flow and root exudates into the soil.     

Systemic acquired resistance in crop protection: from nature to a chemical approach

Plant natural resistance to potential parasites is regulated by two fundamental mechanisms: the "nonhost" and the "gene-for-gene" resistance, respectively. The latter is relevant when a cultivar resistant (R) gene product recognizes an avirulence gene product in the attacking pathogen and triggers an array of biochemical reactions that halt the pathogen around the site of attempted invasion. To cope with virulent pathogens, plants may benefit by some temporary immunity after a challenge triggering such an array of defense reactions, following a localized necrotizing infection as a possible consequence of a hypersensitive response (HR). This process, mediated by accumulation of endogenous salicylic acid (SA), is called systemic acquired resistance (SAR) and provides resistance, to a certain extent even against unrelated pathogens, such as viruses, bacteria, and fungi, for a relatively long-lasting period. SAR may be more potently activated in plants pretreated with chemical inducers, most of which appear to act as functional analogues of SA. This review summarizes the complex aspects of SAR as a way to prevent crop diseases by activating the plants' own natural defenses. The following outline is taken: (1) introduction through the historical insight of the phenomenon; (2) oxidative burst, which produces high levels of oxygen reactive species in a way similar to the inflammation state in animals and precedes the HR to the pathogen attack; (3) SAR as a coordinate action of several gene products leading to the expression of defenses well beyond the time and space limits of the HR; (4) jasmonic acid (JA) and ethylene as other endogenous factors mediating a different pathway of induced resistance; (5) pathogenesis related proteins (PR proteins) de novo synthesized as specific markers of SAR; (6) exogenous inducers of SAR, which include both synthetic chemicals and natural products; (7) the pathway of signal transduction between sensitization by inducers and PR expression, as inferred by mutageneses, a process that is still, to a large extent, not completely elucidated; (8) prospects and costs; (9) final remarks on the state-of-the-art of the topic reflecting the chemical view of the author, based on the more authoritative ones expressed by the authors of the reviewed papers.     

In vitro study of the relationship between the structure of ginsenoside and its antioxidative or prooxidative activity in free radical induced hemolysis of human erythrocytes

Ginsenoside, the major active component in Panax ginseng, which has been used in traditional Chinese medicine, contains a series of derivatives of the triterpene dammarane being attached by some sugar moieties. To clarify the relationship between the structure of ginsenoside and its properties, 11 individual ginsenosides, along with the central structures of ginsenoside, protopanaxadiol and protopanaxatriol, are used in 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) induced hemolysis of human erythrocytes, a good experimental model to research free radical induced membrane damage and to evaluate the antioxidative or prooxidative activities of various antioxidants conveniently. It is found that the central structures of ginsenosides, either protopanaxadiol or protopanaxatriol, play a prooxidative role in AAPH-induced hemolysis of erythrocytes. As to the individual ginsenoside, if there are no sugar moieties attached to the 20-position of the triterpene dammarane, the ginsenoside acts as a prooxidant, that is, Rg3, Rh2, and Rg2. A glucose attached to the 6-position instead of the 20-position sugar moieties can make the ginsenoside an antioxidant, that is, Rh1. The antioxidants among ginsenosides follow two different mechanisms that can be expressed mathematically by the Boltzmann equation, that is, Rc and Rb1, and a polynomial equation, that is, Re, Rd, R1, Rg1, Rb3, and Rh1. The orders of antioxidative ability are Rc > Rb1 and Re > Rd > R1 > Rg1 > Rb3 > Rh1, respectively.     

Involvement of programmed cell death in suppression of the number of root nodules formed in soybean induced by Bradyrhizobium infection

Legumes establish symbiosis with nitrogen-fixing rhizobia through root nodules to acquire nitrogen. Legumes control nodule number through systemic (autoregulation of nodulation) as well as local regulation. Moreover, plants defend themselves against bacteria and other pathogens through the induction of localized (localized acquired resistance) and systemic (SAR, systemic acquired resistance; ISR, induced systemic resistance) responses. Herein, we show that the number of root nodules is suppressed by programmed cell death (PCD), and is simultaneously controlled by SAR and ISR in soybean (Glycine max [L.] Merr.). The wild-type soybean cultivar Williams 82 showed markedly fewer root nodule primordia and PCD symptoms, including accelerated DNA degradation, enhanced generation of reactive oxygen species (visualized by 3,3′-diaminobenzidine staining), and excessive cell death (detected on staining with trypan blue) compared to the hypernodulation mutant NOD1-3. These results suggest that PCD suppresses the formation of root nodules in wild-type soybean. In addition, microarray and gene ontology analyses showed that essential components of hypersensitive response (HR) or disease resistance, such as resistance (R) genes, mitogen-activated protein kinase cascade, SAR, salicylic acid, jasmonic acid, ethylene, etc., were activated in wild-type plants. These analyses corroborate the above findings, demonstrating that the suppression of root nodule formation by PCD is accompanied by HR, and is simultaneously controlled by SAR and ISR in soybean. These findings provide new insight into the control of nodulation to balance nutritional requirements and energy status in legumes.     

The Induction of Salinity Stress Resistance in Rosemary as Influenced by Salicylic Acid and Jasmonic Acid

This pot study was carried out as a factorial experiment. The foliar application of salicylic acid (SA) and jasmonic acid (JA) both, at three levels and salinity stress at four levels were applied. The results showed that salinity resulted in a significant loss of most morphological traits, protein, total chlorophyll, and catalase activity, whereas leaf proline content, superoxide dismutase activity, peroxidase and chlorophyll b significantly increased. The interaction of the three studied factors influenced protein content and plant weight significantly. Although salinity stress reduced these traits, SA application improved them. Also, SA application entailed the improvements in plant growth, proline, and antioxidant enzymes under salinity stress. Nonetheless, JA application had slight or insignificant impact on the traits. Thus, we can say that rosemary is relatively capable of coping with salinity. But, when the stress is intensified, even the resistance mechanism of the plant fails to counteract the severe stress.     

Deodorization with ku-ding-cha containing a large amount of caffeoyl quinic acid derivatives

Caffeoyl quinic acid (CQA) derivatives in ku-ding-cha, mate, coffee, and related plants were determined by HPLC. One ku-ding-cha contained a large amount of 3,5-dicaffeoylquinic acid (3,5-diCQA, 10.6% in dry weight) as well as 3-CQA (1.7%), 4-CQA (1.1%), 5-CQA (6.3%), 3,4-diCQA (1.8%), and 4,5-diCQA (4.3%). In this ku-ding-cha, the total caffeic acid moiety was 90.3 mmol/100 g of dry weight. The leaves of Ilex latifolia, which is one original species of ku-ding-cha, and another plant of the same genus, I. rotunda, also contained 3,5-diCQA (9.5 and 14.6%), 3-CQA (4.3 and 1.9%), and 5-CQA (4.8 and 3.8%), respectively, whereas raw coffee bean contained 5.5% 5-CQA and other low CQA derivatives. 3,5-DiCQA and 5-CQA with an apple acetone powder (AP) containing polyphenol oxidase showed high capturing activities toward thiols, and two addition compounds between 3,5-diCQA and methane thiol were also identified. Ku-ding-cha indicated extremely strong capturing activities toward methanethiol, propanethiol, and 2-propenethiol in the presence of apple AP. Furthermore, drinking ku-ding-cha reduced the amount of allyl methyl sulfide gas, well-known to persist as malodorous breath long after the ingestion of garlic.     

Synthesis and herbicidal activity of 2-cyano-3-(2-chlorothiazol-5-yl)methylaminoacrylates

A series of 2-cyano-3-(2-chlorothiazol-5-yl)methylaminoacrylates were synthesized as herbicidal inhibitors of PSII electron transport. All of these compounds exhibited good herbicidal activities. In particular, (Z)-ethoxyethyl 2-cyano-3-isopropyl-3-(2-chlorothiazol-5-yl)methylaminoacrylate showed excellent herbicidal activities even at a dose of 75 g/ha. A suitable group at the 3-position of acrylate was essential for high herbicidal activity. 2-Cyanoacrylates containing a 2-chloro-5-thiazolyl group are a novel class of herbicides and display herbicidal activities comparable to existing analogues bearing chloropyridyl or chlorophenyl.     

Exogenous applications of salicylic acid affect quality and yield of strawberry grown under antifrost heated greenhouse conditions

Abiotic stress is becoming more prevalent as the intensity of agriculture and the demand for farmable land are ever increasing. Besides drought and salinity stress, chilling or freezing stress is one of the most important limiting factors of crop production all around the world. Salicylic acid (SA) is a common plant‐produced signal molecule that is responsible for inducing resistance to a number of biotic and abiotic stresses. This study was conducted to determine the effect of foliar SA applications on fruit‐quality characteristics and yield of strawberry under antifrost heated greenhouse conditions in two successive experiments. Spraying of 1 mM SA (1 mM) was done once (SA1), twice (SA2), three times (SA3), or four times (SA4) during the vegetation period with 7 d intervals. Concentrations of chlorophyll and minerals were measured in leaves, and vitamin C (ascorbic acid), total soluble solids (TSS), titratable acidity (TA), and color (a*) in fruits. Fruit weight, early yield, and total yield were also determined. Foliar applications of SA positively affected TSS and ascorbic acid (AA) content of strawberry fruits. Salicylic acid treatments had no effect on TA of strawberry fruits. SA4 treatment gave the greatest a* in fruit and chlorophyll‐concentration values in the leaves. It was shown that SA treatments increased the content of all nutrients in the leaves of strawberry plants, and greater values often were obtained from SA3 and SA4 treatments. The early yield and total yield of strawberry were significantly affected by SA applications, among which SA3 and SA4 resulted in the highest early and total yields. The present study suggests that SA3 and SA4 treatments can ameliorate the deleterious effects of low temperatures on strawberry plants and that SA application may offer an economical and simple method for low‐temperature protection.     

Design, synthesis, and antiviral activity evaluation of phenanthrene-based antofine derivatives

On the basis of our previous structure-activity relationship (SAR) and antiviral mechanism studies, a series of phenanthrene-based antofine derivatives (1-12 and 18-50) were designed targeting tobacco mosaic virus (TMV) RNA and synthesized and systematically evaluated for their antiviral activity against TMV. The bioassay results showed that most of these compounds exhibited good to excellent in vivo anti-TMV activity, of which compounds 19 and 27 displayed higher activity than commercial Ribavirin, thus emerging as potential inhibitors of plant virus. The novel concise structure provides another new template for antiviral studies.     

Structural analogues of homoeriodictyol as flavor modifiers. Part III: short chain gingerdione derivatives

In order to find new flavor modifiers, various short chain gingerdione derivatives were synthesized as structural analogues of the known bitter masker homoeriodictyol and evaluated by a sensory panel for masking and sweetness enhancing activities. 1-(4-Hydroxy-3-methoxyphenyl)hexa-3,5-dione ([2]-gingerdione) and the homologue 1-(4-hydroxy-3-methoxyphenyl)hepta-3,5-dione ([3]-gingerdione) at concentration ranges 50-500 mg kg (-1) showed the most promising masking activity of 20-30% against bitterness of a 500 mg kg (-1) aqueous caffeine solution. Additionally, both compounds were able to reduce the bitterness of a 5 mg kg (-1) quinine solution by about 20%; however, the bitter tastes of salicine, the model peptide H-Leu-Trp-OH, and KCl solutions were not reduced. Whereas for bitter masking activity a vanillyl moiety seems to be important, some of the tested isovanillyl isomers showed an interesting sweet enhancing effect without exhibiting a significant intrinsic sweetness. The isomer 1-(3-hydroxy-4-methoxyphenyl)hexa-3,5-dione ([2]-isogingerdione) at 100 mg kg (-1) caused a significant and synergistic increase of 27% of sweet taste of a 5% sucrose solution.     

Chemical hybridizing agents for chickpea (Cicer arietinum L.): leads from QSAR analysis of ethyl oxanilates and pyridones

In the self-pollinated crops such as chickpea, induction of male sterility by deployment of chemical hybridizing agents (CHAs) facilitating "two-line" approach holds immense potential in heterosis breeding. A total of 40 test CHAs comprising 20 ethyl oxanilates and 20 pyridones were screened as potential CHAs on chickpea (variety BG 1088) at 500, 800, and 1000 ppm. Three test compounds mostly having either F (4)/Br (5)/CF(3) (19) at the para position of the aryl ring from a pool of 20 ethyl oxanilates were identified as the most potent CHAs causing >or=99% induction of pollen sterility and >90% total flower sterility at 1000-ppm test concentration. Among pyridone derivatives, N-(4-chlorophenyl)-5-carbethoxy-4,6-dimethyl, 1,2-dihydropyrid-2-one (26) was found to be the most active. Quantitative structure activity relationship (QSAR) analysis has revealed a direct involvement of Swain-Lupton field constant, F(p), with the target bioactivity which implied that field rather than resonance effect (R) had a positive effect on the activity. The real guiding principle for selectivity was found out to be the hydrophobic parameter pi value. The QSAR models indicated that increased steric bulk at the 4-position on the phenyl ring is associated with enhanced activity. The CHAs appeared to act by mimicking UDP-glucose, the key substrate in the synthesis of callose, or lead to an imbalance in acid-base equilibrium in pollen mother cells resulting in dissolution of callose wall by premature callase secretion.