Lipoxygenase Metabolites of α-linolenic Acid in the Development of Resistance in Pigeonpea, Cajanus cajan (L.) Millsp, Seedlings Against Fusarium udum Infection

Lipoxygenase (LOX) activity was measured in germinating pigeonpea Cajanus cajan seedlings, resistant (ICP-8863) and susceptible (ICP-2376) to wilt fungus, before and after infection with Fusarium udum. LOX activity was significantly higher in the resistant than in the susceptible cultivars of pigeonpea and was enhanced further in response to infection with Fusarium udum. This increase in LOX activity in the resistant cultivars of pigeonpea appears to be due to the induction of lipoxygenase isozymes in response to infection. Analysis of the endogenous LOX metabolites in pigeonpea seedlings revealed the predominant formation of 13-hydroperoxyoctadecadienoic acid (13-HPODE) in healthy seedlings and 13-hydroperoxyoctadecatrienoic acid (13-HPOTrE) in infected seedlings. Further studies on the effects of LOX metabolites on the growth and multiplication of Fusarium udum showed that HPOTrEs, LOX metabolites of -linolenic acid, are more anti-fungal compared to HPODEs, LOX metabolites of linoleic acid.     

三种酚酸类化合物对莴苣幼苗的化感作用及机理初探

化感物质通过植物体释放到农田土壤中,可对作物生长造成严重影响。酚酸是一类重要的化感物质,由于其相对分子质量小,结构稳定,因而不易降解而累积在土壤中,进而影响作物生长,是引起连作障碍问题的一类主要化合物。为了明确酚酸类物质对植物生长影响的途径,探讨其化感作用机理,以3种结构相似的化合物——苯甲酸、水杨酸和对羟基苯甲酸为研究对象,以莴苣幼苗为活性受体,通过测定化合物对莴苣幼苗根、茎生长的影响,评价了其对植物的毒活性;并借助于荧光显微镜,通过FDA/PI双染色法和DHE染色法,分别研究了3种酚酸类化合物对受体植物根尖细胞活力和活性氧积累的影响。结果表明:3种酚酸类化合物对莴苣幼苗根、茎的生长均表现出低浓度促进、高浓度抑制的作用模式;莴苣幼苗在高浓度酚酸的胁迫下,其体内活性氧大量积累,高浓度的活性氧对莴苣幼苗细胞膜结构等具有显著的破坏作用,进而导致细胞活力降低甚至凋亡,最终抑制植物生长。     

黑松感染松材线虫后几种有机酸含量的变化

 Changes of benzoic acid, phenylacetic acid and salicylic acid contents in stem of 3-4 year old Pinus thunbergii inoculated with Bursaphelenchus xylophilus were studied by HPLC. The results showed that after nematode infection, contents of benzoic acid and salicylic acid in the stem of Pinus thunbergii increased gradually and then decreased when serious disease occurred, while content of phenylacetic acid increased at early stage and decreased at later stage of the disease. The role of benzoic acid, pbenylacetic acid and salicylic acid during the development of the disease was discussed.     

不同原料好氧堆肥过程中碳转化特征及腐殖质组分的变化

为探讨不同畜禽粪便（牛粪和羊粪）为主料，添加不同作物秸秆（玉米秸秆和小麦秸秆）为辅料在堆肥过程中的碳转化特征及腐殖质组分的变化规律，采用条垛式好氧堆肥研究了不同原料组合（T1：牛粪+玉米秸秆；T2：牛粪+小麦秸秆；T3：羊粪+玉米秸秆；T4：羊粪+小麦秸秆）在堆肥过程中总有机碳（TOC）、可溶性有机碳（DOC）和腐殖酸含量的碳转化特征以及胡敏酸（HA）和富里酸（FA）的含量变化规律。结果表明：所有处理的TOC含量随堆肥过程的推进而下降，至堆肥结束时T1~T4处理的TOC含量分别下降了22.1%、21.5%、23.6、23.7%；DOC含量也随堆肥过程的推进而降低，至堆肥第15天时降低至最低，T1~T4处理分别降低至6.57、5.47、4.73 g·kg^-1和4.93 g·kg^-1，但不同处理的变化规律明显不同：以牛粪为主料的T1和T2处理在第10天以前几乎无变化，而以羊粪为主料的T3和T4处理从一开始就迅速下降至最低值，至堆肥第15天时T1~T4处理的降幅分别为32.4%、36.5%、51.8%和39.3%；总腐殖酸(THA)含量的增加始于堆肥的第10天，第15天时达到最高值，最高值分别为25.5%、22.5%、29.8%和30.0%，整个堆肥过程中T3和T4处理显著高于T1和T2处理（P＜0.05）。随堆肥过程的推进，游离腐殖酸(FHA)含量逐渐降低，堆肥结束时降幅为7.6%~18.0%； HA含量逐渐增加，至堆肥结束时增幅为65.4%~197.8%，堆肥过程提高了胡敏酸态碳。T3和T4处理的FHA和HA含量在整个堆肥过程中始终高于牛粪组合T1和T2处理。FA含量随堆肥进程推进逐渐下降，至堆肥结束时降幅为44.9%~54.9%。羊粪中较高含量的纤维素、半纤维素和HA可能是堆肥产品中THA和HA含量较高的主要原因，在以牛粪为主料的堆肥配料中适当加入羊粪可以提高堆肥产品的腐殖酸含量和胡敏酸态碳。     

土壤强还原过程产生的有机酸对土传病原菌的抑制作用

土壤强还原(reductive soil disinfestation,RSD)能有效杀灭土传病原菌,并已在日本、荷兰和美国取得一系列的推广应用,但对于RSD的杀菌机理不甚明了。本试验采用高效液相色谱和荧光定量PCR等技术研究了以玉米秸秆为有机碳源的RSD处理过程中土壤产生的有机酸种类,以及不同浓度的有机酸对土壤病原菌的抑制效果。结果表明:以玉米秸秆为有机碳源的RSD过程中主要产生了乙酸和丁酸;经50mmol/L丁酸溶液处理的土壤中立枯丝核菌、辣椒疫霉、尖孢镰刀菌及茄劳尔氏菌的数量分别为对照的3.5%、38.9%、11.5%和7.9%;10mmol/L的丁酸可以完全抑制尖孢镰刀菌菌丝的生长;5mmol/L的丁酸即可完全抑制尖孢镰刀菌的孢子萌发。本研究结合前人报道表明有机酸,尤其是乙酸和丁酸,对于RSD的杀菌机理起着重要的作用。     

Photochemical behaviour of dichlorprop [(+/-)-2-(2,4-dichlorophenoxy)propanoic acid] in aqueous solution

Aqueous solutions of dichlorprop were irradiated under different conditions of pH, wavelength and oxygenation. The photochemical behaviour was found to be complex and many photoproducts were formed. However, at low concentrations the main photoproducts were 4-chloropyrocatechol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol. Some other photoproducts were identified, namely 2-(4-chloro-2-hydroxyphenoxy)propanoic acid, 2-(3,5-dichloro-2-hydroxyphenyl)propanoic acid and 2,4-dichlorophenyl acetate. From comparison with results previously obtained with mecoprop [2-(4-chloro-2-methylphenoxy)propanoic acid] it appears that the presence of a chlorine atom in position 2 on the ring strongly modifies the photochemical behaviour.     

The role of phytohormones in relation to bakanae disease development and symptoms expression

Fusarium proliferatum, the causal agent of bakanae disease was found to be up-regulated gibberellic acids (GAs) in bakanae diseased rice plants and thereby contributing to the different types of symptoms observed associated with the disease. The up- and down regulation of GAs, IAA and ABA were studied in susceptible (MR 211) and resistant (BR3) varieties artificially inoculated with F. proliferatum at different times after inoculation. The increase in GAs including fungiproduced GA3 and IAA were higher in inoculated MR 211 rice plants (GAs = 26%, IAA = 40.39%) as compared to resistant BR3 (GAs = 19%, IAA = 4.27%), 7 days after inoculation (disease score 1, S-1) in whole plant sample analysis. The increase were higher in both roots and leaves but not in the stem, thus the main symptom observed as stunting of the susceptible plants at disease score 1. However, 14 days after inoculation (disease score 3, S-3), both phytohormones were observed to increase in whole plant sample analysis as well as in all plant parts sampled. This increasing effect was found associated with elongation of internodes and chlorosis of leaves in susceptible plants of MR 211. As the symptoms progressed to disease score 5 (S-5, after 21 days of inoculation) susceptible plants of MR 211 were started to collapse and lodged due to over elongation, and finally dead followed by a decrease in GAs and IAA but an increase in ABA. In resistant variety BR3, marginal up regulation of GAs and IAA were observed only at 21 days after inoculation in stems with no typical symptom of bakanae disease.     

苯甲酸·水杨酸·三唑酮混剂的液相色谱分析

本文介绍了以甲醇 水为流动相,采用C18不锈钢柱,230nm检测波长,对三唑酮、苯甲酸、水杨酸混合物进行液相色谱定量分析的方法。该方法的标准偏差分别为0．027、0．029、0．048;变异系数分别为0．24％、0．67％、0．74％;线性相关系数分别为0．9999、0．9999、0．9999;平均回收率分别为99．82％、100．39％、100．17％。     

曲酸及氯曲酸衍生物的合成及抑菌活性

以曲酸为原料,设计合成了16个曲酸衍生物(QI-01~QI-16)和10个氯曲酸衍生物(QII-01~QII-10),通过核磁共振氢谱及元素分析对其结构进行了表征。初步抑菌活性测定结果表明:所有供试化合物对苹果炭疽病菌Glomerella cingulata和番茄灰霉病菌Botrytis cinerea的菌丝生长均有不同程度的抑制作用,其中化合物QI-07和QI-11对苹果炭疽病菌活性最高,50μg/mL时的抑制率分别为79.3%和86.2%;化合物QII-04、QII-08和QII-09对番茄灰霉病菌活性最高,50μg/mL时的抑制率分别为70.0%、70.0%和76.7%。     

Investigating interactions of salicylic acid and jasmonic acid signaling pathways in monocots wheat

Upon pathogen or insect attack, plants respond with production of a specific blend of the alarm signals salicylic acid (SA) and jasmonic acid (JA), which are recognized as key players in the regulation of the signaling pathways involved. SA and JA responsive genes and SA/JA cross talk were well characterized in dicotyledonous species, but little is known in monocotyledonous plants. Using qRT-PCR, the expression profiles of SA and JA responsive genes were investigated after SA and JA treatments in monocots wheat. The results showed that Glu2 and PR-2 responded almost exclusively to SA, PR-3 and LOX2 responded positively to methyljasmonate (MeJA) treatment, while Lipase and PR-1.1 were induced in response to treatment with SA or MeJA. Furthermore, either by pathogen infection or exogenous application of hormones can activate the antagonistic effect between SA and JA in wheat, which has been well elucidated in dicotyledonous species. The outcomes of SA-JA interactions could be affected by the relative concentration of each hormone. This study shed light on marker genes that can represent SA and JA pathways in wheat and provided some clues for better understanding their interactions in monocot.     

Exogenous salicylic acid treatment delays initial infection and counteracts alterations induced by Maize dwarf mosaic virus in the maize proteome

The phytohormone salicylic acid (SA) was applied to healthy and Maize dwarf mosaic virus (MDMV)-infected maize plants, and differential proteomic analysis was simultaneously performed to evaluate the physiological effects and the SA-maize-virus interaction in the early pathogenesis cycle. MDMV infection reduced photosynthetic rates, while SA increased them, together with plant height and roots in healthy plants. In infected plants, SA increased RuBisCo and stabilized chlorophyll a-b binding protein expression, increased plant height and root volume, delayed symptom expression, and reduced infection rate. Results highlight biochemical pathways involved in the maize-MDMV pathosystem and signal SA as key to maize disease management programs.     

Molecular analysis of resistance mechanisms to Orobanche cumana in sunflower

Resistance to the dicotyledenous parasite Orobanche cumana in sunflower is characterized by a low number of parasitic attachments and a confinement of the parasite in host tissues leading to its necrosis. To help understand what determines such resistance mechanisms, molecular, biochemical and histological approaches were employed before (early response) and after (late response) attachment of the broomrape parasite to susceptible (2603) and resistant (LR1) sunflower genotypes. The expression patterns of 11 defence-related genes known to be involved in different metabolic pathways (phenylpropanoids, jasmonate, ethylene) and/or in resistance mechanisms against microorganisms were investigated. RT-PCR and cDNA blot experiments revealed that the resistant genotype exhibited a stronger overall defence response against O. cumana than the susceptible one, involving marker genes of the jasmonate (JA) and salicylic acid (SA) pathways. Among them, the SA-responsive gene, def. (defensin), appeared to be characteristic of LR1 sunflower resistance. However, no JA accumulation and similar SA contents (250–300 ng g⁻¹ FW) were measured by GC/MS in both genotypes, parasitized or not. In addition, three cDNAs, isolated by a suppression-subtractive hybridization, were shown to be strongly induced only in the resistant genotype 8 days post-inoculation, when the first O. cumana attachments occurred. These genes, putatively encoding a methionine synthase, a glutathione S-transferase and a quinone oxidoreductase, might be involved in detoxification of reactive oxygen species, suggesting the occurrence of an oxidative burst during the incompatible interaction. Finally, host cell-wall modifications leading to parasite-confinement were correlated with more intense callose depositions in the resistant genotype, concomitant with over-expression of the callose synthase cDNA HaGSL1 .     

Synthesis of analogues of the monic acids A and C as potential herbicides

The synthesis of some analogues of pseudomonic acids with simplified ‘left-hand’ side-chains is reported. Tested against isoleucyl tRNA, none was as active as methyl monate A and none was active as a herbicide in glasshouse tests. © 1999 Society of Chemical Industry     

Involvement of phenol metabolism in resistance of Dianthus caryophyllus to Fusarium oxysporum f.sp. dianthi

Three carnation cultivars were investigated for the effect of stem inoculation withFusarium oxysporum f.sp.dianthi on production of phenolic compounds and on fungistatic activity. Carnation stems were characterized by a complex mixture of cell wall-bound phenolics, several of which occurred in considerable amounts. Only very low amounts of phenolic compound were present in the vacuoles.Infection withF. oxysporum f.sp.dianthi induced the production and accumulation of a number of new compounds, both free in the cell sap and bound to the cell wall. In addition, the stem extracts acquired germination-inhibiting properties for conidia of the fungus. The accumulation of several phenolics and the fungistatic activity were roughly correlated to the degree of resistance of the three cultivars. Part of the differences in their resistance toF. oxysporum f.sp.dianthi might be due to an inhibition of the conversion of phenolic acid-type precursors into phytoalexins in the more susceptible cultivars.Samenvatting Drie anjercultivars werden onderzocht op de effecten van stengelinoculatie metFusarium oxysporum f.sp.dianthi op de produktie van fenolische verbindingen en op de fungistatische activiteit van stengelextracten. Anjerstengels bleken een complex mengsel van celwand-gebonden fenolzuren te bevatten, waarvan er verschillende in vrij grote hoeveelheden voorkwamen. Daartegenover waren de hoeveelheden fenolische verbindingen in de vacuole bij gezonde anjerstengels erg laag.Infectie metF. oxysporum f.sp.dianthi induceerde de produktie en accumulatie van een aantal nieuwe verbindingen in het celsap, alsook gebonden aan de celwand. Tevens bleek de remming van de kieming van conidiën vanF. oxysporum f.sp.dianthi onder invloed van deze stengelextracten sterk verhoogd, in vergelijking met de remming veroorzaakt door extracten van gezonde stengels. De accumulatie van een aantal fenolen en de verhoging van de fungistatische activiteit van de extracten waren in grote lijnen gecorreleerd met de uit de praktijk bekende resistentie van de drie cultivars. De verschillen in resistentie tegenF. oxysporum f.sp.dianthi zouden deels kunnen berusten op remming van de omzetting van precursors (fenolzuren) in fytoalexinen in de meer vatbare cultivars.     

三氯异氰尿酸的液相色谱分析

本文介绍了使用反相高效液相色谱，C18柱，以甲醇和冰乙酸水溶液为流动相，紫外检测器，对三氯异氰尿酸制剂进行定量分析的方法。该方法的标准偏差为0.03，变异系数为0．06％，线性相关系效为0．9994，平均回收率为100.3％。     

Rhizobacteria-mediated Induced Systemic Resistance: Triggering, Signalling and Expression

Selected strains of rhizosphere bacteria reduce disease by activating a resistance mechanism in the plant named rhizobacteria-mediated induced systemic resistance (ISR). Rhizobacteria-mediated ISR resembles pathogen-induced systemic acquired resistance (SAR) in that both types of induced resistance render uninfected plant parts more resistant towards a broad spectrum of plant pathogens. Some rhizobacteria trigger the salicylic acid (SA)-dependent SAR pathway by producing SA at the root surface. In other cases, rhizobacteria trigger a different signalling pathway that does not require SA. The existence of a SA-independent ISR pathway has been demonstrated in Arabidopsis thaliana. In contrast to pathogen-induced SAR, ISR induced by Pseudomonas fluorescens WCS417r is independent of SA accumulation and pathogenesis-related (PR) gene activation but, instead, requires responsiveness to the plant hormones jasmonic acid (JA) and ethylene. Mutant analyses showed that ISR follows a novel signalling pathway in which components from the JA and ethylene response are successively engaged to trigger a defensive state that, like SAR, is controlled by the regulatory factor NPR1. Interestingly, simultaneous activation of both the JA/ethylene-dependent ISR pathway and the SA-dependent SAR pathway results in an enhanced level of protection. Thus combining both types of induced resistance provides an attractive tool for the improvement of disease control. This review focuses on the current status of our research on triggering, signalling, and expression of rhizobacteria-mediated ISR in Arabidopsis.     

植物对虫害的系统获得性抗性及抗虫与抗病信号途径间的相互作用

受病原体感染后,植物会获得一种持久广泛的抗性,称为系统获得性抗性,受到昆虫侵害时也会获得类似的系统获得性抗性.植物系统抗虫与抗病信号分子不同,前者是茉莉酸(JA)、甲基茉莉酸(Me-JA)或系统素,而后者是水杨酸(SA).SA介导的系统抗病信号途径与JA等介导的系统抗虫信号途径并非完全独立,而是存在所谓的"交叉对话",但"交叉对话"结果是相互促进还是抑制仍不清楚.植物系统抗性信号及其互作研究无疑会完善植物保护策略.