The Identification of Phenylalanine Ammonia-Lyase(PAL)Genes from Pinus yunnanensis and an Analysis of Enzyme Activity in vitro

Phenylalanine ammonia lyase(PAL)is the rate-limiting and pivotal enzyme of the general phenylpropanoid path-way,but few reports have been found on PAL genes in Pinus yunnanensis.In the present study,three PAL genes were cloned and identified from P.yunnanensis seedlings for thefirst time,namely,PyPAL-1,PyPAL-2,and PyPAL-3.Our results indicated that the open-reading frames of PyPAL genes were 2184,2157,and 2385 bp.Phylogenetic tree analysis revealed that PyPALs have high homology with other known PAL genes in other plants.In vitro enzymatic analysis showed that all three PyPAL recombinant proteins could catalyze the deamination of L-phenylalanine to form trans-cinnamic acid,but only PAL1 and PAL2 can catalyze the conversion of L-tyrosine toρ-coumaric acid.Three PyPAL genes were expressed in different tissues in 1-year-old P.yunnanensis,and such genes had different expression patterns.This study lays a foundation for further understanding of the biosynthesis of secondary metabolites in P.yunnanensis.

Phenylalanine ammonia-lyase gene families in cucurbit species: Structure, evolution, and expression

Phenylalanine ammonia-lyase （PAL）, the first enzyme of phenylpropanoid pathway, is always encoded by multigene families in plants. In this study, using genome-wide searches, 13 PAL genes in cucumber （CsPAL1-13） and 13 PALs in melon （Cm- PALl-13） were identified. In the corresponding genomes, ten of these PAL genes were located in tandem in two clusters, while the others were widely dispersed in different chromosomes as a single copy. The protein sequences of CsPALs and CmPALs shared an overall high identity to each other. In our previous report, 12 PAL genes were identified in watermelon （CIPAL1-12）. Thereby, a total of 38 cucurbit PAL members were included. Here, a comprehensive comparison of PAL gene families was performed among three cucurbit plants. The phylogenetic and syntenic analyses placed the cucurbit PALs as 11 CsPAL-CmPAL-CIPAL triples, of which ten triples were clustered into the dicot group, and the remaining one, CsPAL1-CmPAL8-CIPAL2, was grouped with gymnosperm PALs and might serve as an ancestor of cucurbit PALs. By comparing the syntenic relationships and gene structure of these PAL genes, the expansion of cucurbit PAL families might arise from a series of segmental and tandem duplications and intron insertion events. Furthermore, the expression profiling in different tissues suggested that different cucurbit PALs displayed divergent but overlapping expression profiles, and the CsPAL-CmPAL-CIPAL orthologs showed correlative expression patterns among three cucurbit plants. Taken together, this study provided an extensive description on the evolution and expression of cucurbit PAL gene families and might facilitate the further studies for elucidating the functions of PALs in cucurbit plants.

Genetic diversity and population structure analysis of Pistacia species revealed by phenylalanine ammonia-lyase gene markers and implications for conservation

Information on population genetic structure and crop genetic diversity is important for genetically improving crop species and conserving threatened species. The PAL gene sequence is part of a multigene family that can be utilized to design DNA marker systems for genetic diversity and population structure investigation. In the current study, genetic diversity and population structure of 100 accessions of wild Pistacia species were investigated with 78 PAL markers. A protocol for using PAL sequences as DNA markers was developed. A total of 313 PAL loci were recognized, showing 100% polymorphism for PAL markers. The PAL markers produced relatively more observed and effective alleles in Pistacia falcata and Pistacia atlantica, with a higher Shannon＇s information index and expected heterozygosity in P. atlantica, Pistacia vera and Pistacia mutica. Pairwise assessment of Nei＇s genetic distance and genetic identity between populations revealed a close association between geographically iso- lated populations of Pistacia khinjuk and Pistacia chinensis. The accessions of wild Pistacia species had more genetic relationship among studied groups of species. Analysis of molecular variance indicated 19% among- population variation and 81% within-population variation for the PAL gene based DNA marker. Population structure analysis based on PAL revealed four groups with high genetic admixture among populations. The results establish PAL markers as a functional DNA marker system and provide important genetic information about accessions from wild populations of Pistacia species.

Programmable double-unlock nanocomplex self-supplies phenylalanine ammonia-lyase for precise phenylalanine deprivation of tumors

Essential amino acids(EAAs)deprivation is a potential antitumor approach because EAAs are critical for tumor growth.To efficiently inhibit tumor growth,continuous deprivation of EAAs is required,how-ever,continuous deprivation without precise control will introduce toxicity to normal cells.Herein,a programmable double-unlock nanocomplex(ROCK)was prepared,which could self-supply phenylalanine ammonia-lyase(PAL)to tumor cells for phenylalanine(Phe)deprivation.ROCK was double-locked in physiological conditions when administered systemically.While ROCK actively targeted to tumor cells by integrinαvβ3/5 and CD44,ROCK was firstly unlocked by cleavage of protease on tumor cell membrane,exposing CendR and R8 to enhance endocytosis.Then,hyaluronic acid was digested by hyaluronidase overexpressed in endo/lysosome of tumor cells,in which ROCK was secondly unlocked,resulting in pro-moting endo/lysosome escape and PAL plasmid(pPAL)release.Released pPAL could sustainably express PAL in host tumor cells until the self-supplied PAL precisely and successfully deprived Phe,thereby block-ing the protein synthesis and killing tumor cells specifically.Overall,our precise Phe deprivation strategy effectively inhibited tumor growth with no observable toxicity to normal cells,providing new insights to efficiently remove intratumoral nutrition for cancer therapy.

过氧化物酶和苯丙氨酸解氨酶与苜蓿白粉病抗性的关系

以8个对白粉病有不同抗性的苜蓿品种(Medicgo sativa L.)为材料,研究人工接菌后叶片过氧化物酶(POD)和苯丙氨酸解氨酶(PAL)活性的变化及其与抗病性的关系。结果表明:未接菌的品种间PAL活性差异不显著,而POD活性则差异显著(P<0.05);感病品种POD活显著高于抗病品种;接种白粉病菌后,供试品种间叶片PAL活性和POD活性均升高,其中抗病品种间PAL活性升高幅度显著大于感病品种,其变化与病情指数呈负相关,而POD活性的变化则相反;POD活性和PAL活性与苜蓿品种对白粉病的抗性密切相关。

草酸胁迫对拟南芥抗氧化酶和苯丙氨酸解氨酶的影响

以6周龄拟南芥生态型Columbia-4为材料,在0(CK)、5、10、15、20、25、30、35 mmol.L-1草酸(OA)胁迫48 h后,测定过氧化氢酶(CAT)、超氧化物岐化酶(SOD)、过氧化物酶(POD)和苯丙氨酸解氨酶(PAL)的活性及丙二醛(MDA)的含量,以探讨OA胁迫对模式植物拟南芥活性氧代谢及PAL活性的影响.结果表明:相比于CK,PAL活性极显著地升高;SOD活性也受到诱导,在20 mmol.L-1OA胁迫下,SOD活性最高;CAT和POD的活性与CK相比,受到抑制,在20 mmol.L-1OA胁迫下,二者被抑制的程度最高,并且POD活性较CAT活性被抑制的程度更大;MDA含量与OA浓度呈良好的线性关系(y=0.0279x+1.6567,R2=0.9222***),表明OA浓度越高,对拟南芥细胞的伤害越大.可见,OA有可能通过抑制CAT和POD的活性,导致H2O2等活性氧自由基的累积和膜脂过氧化作用,最终引起对拟南芥叶片的毒害.

高氧气调包装对绿芦笋木质化的影响

以空气包装为对照,研究了60%O2+20%CO2+20%N2、80%O2+20%CO2和100%O2高氧气调包装的绿芦笋在(4±1)℃贮藏28d期间失重率、叶绿素含量、木质素含量、苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)活性的变化。结果表明:高氧气调包装可以减缓绿芦笋的失重,抑制叶绿素的降解、木质素含量的上升,抑制PAL和POD酶活性的上升。80%O2+20%CO2气调包装贮藏条件下绿芦笋失重较小、色泽保持良好、木质化程度较低。该条件可较好地延长绿芦笋货架期并保持其良好的品质。

不同氮素水平下冬小麦叶片酚酸类物质代谢对FACE的响应

利用开放式空气CO2浓度升高（Free Air Carbon-dioxide Enrichment,FACE）平台,研究了低氮（LN）和常氮（NN）水平下,大气CO2浓度升高对冬小麦叶片酚酸类物质代谢的影响。结果表明,CO2浓度升高对小麦叶片水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸含量的影响随供氮水平的不同而有所差异。低氮下小麦通过提高叶片苯丙氨酸解氨酶（PAL）活性（30.1%）而使其含量均显著增加,增幅分别达33.7%、119.6%、26.7%、39.9%和28.6%;而常氮下PAL活性和酚酸类含量变化均未达显著水平。可见,大气CO2浓度升高对冬小麦酚酸类物质代谢的影响受氮水平的调控,在未来CO2浓度升高条件下,选择适宜的施肥水平将显得更为重要。此外,总酚含量与水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸等含量变化趋势基本一致,且总酚含量变化的79.6%~151.4%是由这几种酚酸含量变化引起的,说明CO2浓度升高使水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸等含量增加是总酚含量增加的直接原因。低氮条件下大气CO2浓度升高将通过改变酚酸类物质代谢而间接影响小麦与伴生杂草的关系。

无机铜试剂对棉花苯丙氨酸解氨酶活性的影响

利用无机铜试剂(CIE)在新陆早17和新陆中26两棉花品种的3叶期和蕾期进行叶面喷施,检测棉株叶片内的苯丙氨酸解氨酶(PAL)的活性变化。结果表明,两品种在3叶期和蕾期均表现为PAL活性显著增高,第2天后即开始产生对PAL活性诱导作用,第10天后PAL的活性开始回落至对照组水平;两品种蕾期PAL的诱导活性均明显高于3叶期,且PAL高活性水平持续天数较3叶期长;棉花不同生育期使用CIE,均可增强棉叶PAL的活性;两品种在不同生育期的PAL活性出现峰值的时间、强度不一,显示出品种抗性的差异性。试验表明,CIE可诱导增强棉叶中PAL的活性。

外来物种刺萼龙葵种子生物学研究

研究刺萼龙葵种子生物学,检测种子萌发过程中相关生化指标,测量种子形态及解剖结构,为外来入侵植物刺萼龙葵防治机制提供理论性依据。研究结果表明,刺萼龙葵萌发中种子中的淀粉酶、苯丙氨酸解氨酶活力变化幅度不明显,可溶性多糖、可溶性蛋白质以及游离总氨基酸含量与萌发时间相关;形态及解剖结构上,刺萼龙葵种子长度约为2.125mm、宽度约1.524mm、厚度约0.776mm、大小指数为4.593mm3、种皮厚度约为0.508mm,种皮比重约为42.14%,吸水量约为27.59%;切片观察发现胚发育较完全,胚乳占大部分,胚较小,胚中具有两片大子叶,与其种子活力相关。

Prediction Model of Secondary Substances in Anthocyanins Synthesis of Purple Corn

The aim of this study was to assay the polyphenols,flavonoid,polyphenol oxidase and phenylalnine ammonialyase which were relative to the anthocyanins synthesis of purple corn. The optimization of multiple linear regression model of anthocyanins synthesis was y=4.383 86-0.205 45x1＋5.479 638x2＋0.195 575x4. According to standard partial regression coefficient testing,the result indicated that polyphenols content was negatively correlated with anthocyanins and the relative influence to anthocyanins synthesis was-42.7%; flavonoid content and activity of polyphenol oxidase were positively correlated with anthocyanins of purple corn and the relative influence to anthocyanins synthesis were 71.45% and 73.32% respectively. There was no positive correlation between the activity of phenylalnine ammonialyase and anthocyanins of purple corn. The establishment of multiple linear regression model of anthocyanins synthesis was to provide theory foundation of producing anthocyanins in laboratory.

茉莉酸甲酯处理对鲜切菠萝品质及抗氧化活性的影响

研究茉莉酸甲酯处理对鲜切菠萝贮藏期间品质和抗氧化活性的影响。先将完整的菠萝果实在20℃条件下分别用浓度为0、1、10、100μmol/L的茉莉酸甲酯熏蒸12 h,然后进行鲜切加工并于15℃条件下贮藏48 h。结果表明,茉莉酸甲酯处理可促进鲜切菠萝总酚含量和1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除能力上升,抑制可溶性固形物及可滴定酸含量下降,而对色泽及菌落总数无显著影响(P>0.05)。其中,10μmol/L茉莉酸甲酯处理效果最好,能显著地诱导鲜切菠萝贮藏期间苯丙氨酸解氨酶和肉桂酸-4-羟化酶活力的上升(P<0.05),延缓4-香豆酸辅酶A连接酶活力的下降(P<0.05),从而促进总酚和总黄酮的积累,提高DPPH自由基清除能力。这些结果表明,茉莉酸甲酯处理可保持鲜切菠萝的品质并提高其抗氧化活性。

玉米纹枯病生防菌DZSY21的抗病机制

为明确杜仲内生细菌DZSY21对玉米纹枯病的抗病机制,利用抗生素标记法分析了DZSY21菌体在玉米叶鞘组织中的定殖情况,通过小区接种试验,研究不同生育期玉米叶鞘引入DZSY21对玉米抗纹枯病的作用,并采用分光光度法和荧光定量PCR技术检测不同生育期玉米叶鞘组织中的多酚氧化酶(PPO)、过氧化物酶(POD)和苯丙氨酸解氨酶(PAL)的酶活性以及PR-1、PR-2a基因的表达水平变化。结果表明:菌株DZSY21引入玉米叶鞘后,可在其体内定殖,与玉米叶鞘组织形成和谐的共生关系,在一定程度上增强玉米对纹枯病的抗性;DZSY21在玉米叶鞘的定殖能提高玉米叶鞘组织防御酶PPO、POD和PAL的活性,同时诱导防卫基因表达。该研究结果为揭示生防细菌DZSY21的生防机理及应用提供了科学依据。

过量锰处理对柱花草次级代谢物、酶活性和SgPALs基因表达的影响

以热研二号(RY2)柱花草为材料,分析过量锰处理(100~600μmol/L)对柱花草生长、次级代谢物、多酚氧化酶(PPO)、苯丙氨酸解氨酶(PAL)及SgPALs基因表达的影响,探讨金属锰毒害对柱花草次级代谢途径的影响。结果表明:相对对照锰(5μmol/L)处理,400、600μmol/L锰处理显著抑制柱花草叶片叶绿素浓度、最大光化合速率(F_v/F_m)、地上部和根部生物量。随着外源锰处理浓度(100~600μmol/L)的增加,叶片原花青素、总酚和单宁含量呈现出逐渐增加的趋势,而叶片类黄酮含量逐渐降低。此外,400、600μmol/L锰处理显著增加叶片PAL酶活性,但对PPO活性影响不明显。定量PCR结果表明,过量锰处理对SgPAL1和SgPAL2基因表达影响不明显,但过量锰处理增强了SgPAL3和SgPAL4基因在柱花草叶片中的表达。以上结果说明,柱花草可能通过苯丙氨酸途径调控次级代谢响应金属锰毒胁迫,且SgPAL3和SgPAL4基因可能参与该响应过程。研究结果为探索柱花草响应金属锰毒胁迫机理提供重要依据。

The phenylalanine ammonia-lyase gene family in Isatis indigotica Fort.:molecular cloning,characterization,and expression analysis

Phenolic compounds, metabolites of the phenylpropanoid pathway, play an important role in the growth and environmental adaptation of many plants. Phenylalanine ammonia-lyase(PAL) is the first key enzyme of the phenylpropanoid pathway. The present study was designed to investigate whether there is a multi-gene family in I. Indigotic and, if so, to characterize their properties. We conducted a comprehensive survey on the transcription profiling database by using tBLASTn analysis. Several bioinformatics methods were employed to perform the prediction of composition and physicochemical characters. The expression levels of IiPAL genes in various tissues of I. indigotica with stress treatment were examined by quantitative real-time PCR. Protoplast transient transformation was used to observe the locations of IiPALs. IiPALs were functionally characterized by expression with pET-32a vector in Escherichia colis strain BL21(DE3). Integration of transcripts and metabolite accumulations was used to reveal the relation between IiPALs and target compounds. An new gene(IiPAL2) was identified and both IiPALs had the conserved enzymatic active site Ala-Ser-Gly and were classified as members of dicotyledon. IiPAL1 and IiPAL2 were expressed in roots, stems, leaves, and flowers, with the highest expression levels of IiPAL1 and IiPAL2 being observed in stems and roots, respectively. The two genes responded to the exogenous elicitor in different manners. Subcellular localization experiment showed that both IiPALs were localized in the cytosol. The recombinant proteins were shown to catalyze the conversion of L-Phe to trans-cinnamic acid. Correlation analysis indicated that Ii PAL1 was more close to the biosynthesis of secondary metabolites than IiPAL2. In conclusion, the present study provides a basis for the elucidation of the role of Ii PALs genes in the biosynthesis of phenolic compounds, which will help further metabolic engineering to improve the accumulation of bioactive components in I.indigotica.

Identification of PAL genes related to anthocyanin synthesis in tea plants and its correlation with anthocyanin content

The phenylalanine ammonia-lyase(PAL)gene family in tea plants(Camellia sinensis L.)encodes the enzyme that catalyzes the first reaction of the phenylpropane metabolic pathway.The present study aimed to characterize the PAL genes in tea plants,and get better insights on the CsPALs in anthocyanins accumulation.Seven CsPAL genes were identified and characterized in tea plants by bioinformatics analysis.Systematic analysis of CsPALs was conducted for its phylogenetic relationship,gene structure,chromosomal location,and protein conserved motifs based on tea plant genome.The cis-elements of CsPALs were responsive to light,abiotic stress,hormone,and MYB-binding site.Furthermore,tissuespecific expression analysis showed that CsPAL4 was expressed preferentially in young leaves and buds.Correlation analysis was performed in purple-leaf tea with anthocyanin components,and it was suggested that CsPAL4 was closely related with different anthocyanin accumulated,especially with cyanidin 3-O-galactoside,cyanidin 3-O-glucoside,and delphinidin 3-O-glucoside.Additionally,the putative upstream regulation factors CsMYBs(CsMYB59,CsARR1,CsSRM1,CsMYB101,and CsMYB52)and CsbHLHs(CsbHLH104,CsbHLH3,CsbIM1,CsTCP14,and CsPIF4)could bind to the promoter of CsPALs,thereby activating its transcription.This study provides a theoretical basis for further research to elucidate the functions of the CsPAL genes.

Overexpression of IbPAL1 promotes chlorogenic acid biosynthesis in sweetpotato

Sweetpotato[Ipomoea batatas(L.)Lam.],a food crop with both nutritional and medicinal uses,plays essential roles in food security and health-promoting.Chlorogenic acid(CGA),a polyphenol displaying several bioactivities,is distributed in all edible parts of sweetpotato.However,little is known about the specific metabolism of CGA in sweetpotato.In this study,IbPAL1,which encodes an endoplasmic reticulum-localized phenylalanine ammonia lyase(PAL),was isolated and characterized in sweetpotato.CGA accumulation was positively associated with the expression pattern of IbPAL1 in a tissue-specific manner,as further demonstrated by overexpression of IbPAL1.Overexpression of IbPAL1 promoted CGA accumulation and biosynthetic pathway genes expression in leaves,stimulated secondary xylem cell expansion in stems,and inhibited storage root formation.Our results support a potential role for IbPAL1 in sweetpotato CGA biosynthesis and establish a theoretical foundation for detailed mechanism research and nutrient improvement in sweetpotato breeding programs.

Response dynamics of three defense related enzymes in cotton leaves to the interactive stress of Helicoverpa armigera (Hübner) herbivory and omethoate application

In order to explore the response dynamics of the activities of defense related enzymes in cotton leaves towards the interactive stress of Helicoverpa armigera herbivory and omethoate application, the activities of phenylalanine ammonia-lyase（PAL）, lipoxygenase（LOX）, and polyphenol oxidase（PPO） were examined from 6 to 126 h after cotton leaves were treated 12 h of H. armigera herbivory, and then sprayed with 800 mg L–1 omethoate. The results showed that the changes in the activities of PAL, LOX and PPO that occured under the interactive stress of H. armigera herbivory and omethoate application reflected the interactive effects of the two stresses on cotton defense. The similarity between the response dynamics of PAL, LOX, and PPO activities in cotton leaves under the interactive stress and that under H. armigera herbivory treatment alone showed that the induction of H. armigera herbivory on the activities of PAL, LOX and PPO in cotton leaves played a leading role in the interactive effects, and the effect of omethoate application played only a minor role. A joint factor analysis was performed according to a method which has been used to analyze the joint toxicity of pesticides; this analysis sought to clarify if there was a synergistic, antagonistic, or additive effect on PAL, LOX, and PPO activity in cotton leaves resulting from the interactive H. armigera herbivory and omethoate treatment. In the interactive effect on the response of PAL activity in cotton leaves, antagonistic effects of the omethoate application towards H. armigera herbivory were observed at 6 and 12 h. Synergistic effects were then observed at 18 and 30 h. Antagonistic effects were observed from 54 to 78 h and synergistic effects were finally observed at 126 h. The correlation between H. armigera herbivory and omethoate application in the interactive effect on cotton defense responses of LOX activity also fluctuated from synergism to antagonism during the time course. In the interactive effect on PPO activity, only antagonism was observed between H. armigera herbivory and omethoate application. In the interactive stress of H. armigera herbivory and omethoate application on cotton defense responses, omethoate affected the defense responses of cotton to H. armigera herbivory by producing antagonistic and synergistic effects. These results will be useful to understand the relationship between host plant and herbivorous pest.

Molecular cloning and characterization of three phenylalanine ammonia-lyase genes from Schisandra chinensis

Phenylalanine ammonia-lyase(PAL),which catalyzes the conversion from L-phenylalanine to trans-cinnamic acid,is a well-known key enzyme and a connecting step between primary and secondary metabolisms in the phenylpropanoid biosynthetic pathway of plants and microbes.Schisandra chinensis,a woody vine plant belonging to the family of Magnoliaceae,is a rich source of dibenzocyclooctadiene lignans exhibiting potent activity.However,the functional role of PAL in the biosynthesis of lignan is relatively limited,compared with those in lignin and flavonoids biosynthesis.Therefore,it is essential to clone and characterize the PAL genes from this valuable medicinal plant.In this study,molecular cloning and characterization of three PAL genes(ScPAL1−3)from S.chinensis was carried out.ScPALs were cloned using RACE PCR.The sequence analysis of the three ScPALs was carried out to give basic characteristics followed by docking analysis.In order to determine their catalytic activity,recombinant protein was obtained by heterologous expression in pCold-TF vector in Escherichia coli(BL21-DE3),followed by Ni-affinity purification.The catalytic product of the purified recombinant proteins was verified using RP-HPLC through comparing with standard compounds.The optimal temperature,pH value and effects of different metal ions were determined.Vmax,Kcat and Km values were determined under the optimal conditions.The expression of three ScPALs in different tissues was also determined.Our work provided essential information for the function of ScPALs.

Active changes of lignification-related enzymes in pepper response to Glomus intraradices and/or Phytophthora capsici

The activities of enzymes responsible for lignification in pepper, pre-inoculation with arbuscular mycorrhizal (AM) fungus of Glomus intraradices and/or infection with pathogenic strain of Phytophthora capsici, and the biological control effect of G. intraradices on Phytophthora blight in pepper were investigated. The experiment was carried out with four treatments: (1) plants pre-inoculated with G. intraradices (Gi), (2) plants pre-inoculated with G. intraradices and then infected with P. capsici (Gi+Pc), (3) plants infected with P. capsici (Pc), and (4) plants without any of the two microorganisms (C). Mycorrhizal coloni-zation rate was reduced by about 10% in pathogen challenged plants. Root mortality caused by infection of P. capsici was com-pletely eliminated by pre-inoculation with antagonistic G. intraradices. On the ninth day after pathogen infection, Peroxidase (POD) activity increased by 116.9% in Pc-treated roots but by only 21.2% in Gi+Pc-treated roots, compared with the control, respectively. Polyphenol oxidase (PPO) and Phenylalanine ammonia-lyase (PAL) activities gradually increased during the first 3 d and dramatically decreased in Pc-treated roots but slightly decreased in Gi+Pc-treated roots, respectively. On the ninth day after pathogen infection, PPO and PAL decreased by 62.8% and 73.9% in Pc-treated roots but by only 19.8% and 19.5% in Gi+Pc-treated roots, compared with the control, respectively. Three major POD isozymes (45 000, 53 000 and 114 000) were present in Pc-treated roots, while two major bands (53 000 and 114 000) and one minor band (45 000) were present in spectra of Gi+Pc-treated roots, the 45 000 POD isozyme was significantly suppressed by G. intraradices, suggesting that the 45 000 POD isozyme was induced by the pathogen infection but not induced by the antagonistic G. intraradices. A 60 000 PPO isozyme was induced in Pc-treated roots but not induced in Gi+Pc-treated roots. All these results showed the inoculation of antagonistic G. intraradices alleviates root mortality, activates changes of lignification-related enzymes and induces some of the isozymes in pepper plants infected by P. capsici. The results suggested that G. intraradices is a potentially effective protection agent against P. capsici.