病原菌Pst DC3000侵染拟南芥导致自噬和光合作用的抑制

在病原菌侵染下,植物体是如何通过超敏反应限制病原菌扩增的,到目前为止还不清楚。最近的研究显示自噬起了必要的作用,可见,研究自噬和超敏反应的机制非常重要。本研究通过观察在非寄主病原菌突变体丁香假单胞菌番茄致病变种(Pseudomonas syringae pv.tomatoDC3000,Pst DC3000)的侵染下,拟南芥光合功能的变化及自噬现象出现的情况,以为进一步研究植物抗病机理提供实验基础。以野生型拟南芥为材料,采用光谱分析和叶绿素荧光成像分析手段,研究不同浓度的Pst DC3000侵染对拟南芥离体叶片光合功能的影响;以转基因野生型拟南芥(绿色荧光蛋白标记的自噬基因8a)幼根为材料,应用共聚焦显微镜,研究不同浓度的Pst DC3000诱导拟南芥自噬的情况。实验发现,OD600=0.2的Pst DC3000侵染,可显著诱导拟南芥叶片活性氧的积累和迸发,并会引起拟南芥叶片光合作用效率的下降。同时发现,该病原菌处理2 h,可导致拟南芥根中自噬小体的产生。用2',7'-二氯二氢荧光素二乙酯(2',7'-dichlorodihydrofluorescein diacetate,H2DCFDA)标记活性氧,检测了P...     

拟南芥转录因子bHLH17负调控茉莉素介导的抗性反应

植物激素茉莉素作为抗性信号调控植物对腐生性病原菌和昆虫的抗性, 作为发育信号调控植物根的生长、雄蕊发育、表皮毛形成和叶片衰老。茉莉素受体COI1识别茉莉素分子, 进而与JAZ蛋白互作并诱导其降解, 继而调控多种茉莉素反应。拟南芥(Arabidopsis thaliana) IIId亚组bHLH转录因子(bHLH3、bHLH13、bHLH14和bHLH17)是JAZ的一类靶蛋白。与野生型相比, IIId亚组bHLH转录因子的单突变体对灰霉菌和甜菜夜蛾的抗性无明显差异, 而四突变体对灰霉菌和甜菜夜蛾的抗性增强。该文通过高表达bHLH17并研究其对灰霉菌和甜菜夜蛾的抗性反应, 结果显示, 被灰霉菌侵染的bHLH17高表达植株较野生型表现出更严重的病症。取食bHLH17高表达植株叶片的甜菜夜蛾幼虫体重大于取食野生型叶片的幼虫体重。bHLH17高表达抑制了茉莉素诱导的抗性相关基因(Thi2.1)和伤害响应基因(VSP2、AOS、JAZ1、JAZ9和JAZ10)的表达。原生质体转化实验显示bHLH17通过其N端行使转录抑制功能。研究结果表明, IIId亚组bHLH转录抑制因子bHLH17高表达会负调控茉莉素介导的对灰霉菌和甜菜夜蛾的抗性。     

褪黑素调节烟草丁香假单胞菌抗性的功能研究

为分析褪黑素(N-乙酰-5-甲氧基色胺)在植物先天免疫中的功能及调控机理,研究以病原菌丁香假单胞杆菌(Pseudomonas syringae pv.tomato DC3000,Pst DC3000)—烟草互作系统为模型,检测了病原菌侵染对烟草褪黑素相关基因表达的影响,并探讨了褪黑素对植物叶片病原菌生长以及气孔开度和活性氧自由基(reactive oxygen species,ROS)含量的影响以及调控机理。结果表明:(1)Pst DC3000处理提高了烟草褪黑素合成(NtSNAT1)和受体(NtPMTR1)基因表达,且外源褪黑素处理降低了叶片中的病原菌含量。(2)与野生型植物相比,过表达大豆GmSNAT1基因显著提高了转基因烟草中内源褪黑素含量和NtPMTR1的表达,且转基因烟草叶片中的Pst DC3000菌落数显著下降。(3)外源褪黑素和细菌鞭毛蛋白多肽flg22处理诱导了野生型和转基因烟草保卫细胞中ROS产生和气孔关闭,且转基因植物对褪黑素和flg22诱导的气孔关闭和ROS产生比野生型烟草更加敏感。综上所述,研究表明褪黑素可能通过受体NtPMTR1介导的信号途径促进保卫细胞ROS产生,诱导气孔关闭,从而降低病原菌Pst DC3000的入侵。     

茉莉酸介导丛枝菌根真菌诱导番茄抗早疫病的机制

丛枝菌根真菌的定殖可以提高寄主植物的抗病性,但机制并不十分清楚。利用番茄茉莉酸信号转导途径前系统素过表达材料35S::PS、茉莉酸合成突变体spr2、茉莉酸信号识别突变体jai1及其野生型CM 4个不同基因型材料,分别在根系接种丛枝菌根真菌摩西斗管囊霉(Funneliformis mosseae, Fm),待菌根形成后,在叶片外源喷施10 mL 0.5μmol/L茉莉酸甲酯(MeJA)和接种番茄早疫病病原菌(Alternaria solani, As),比较不同基因型抗病防御反应以及对早疫病抗性的差异。结果表明:预先接种菌根真菌的CM和35S::PS番茄,在叶片接种病菌5 d和10 d后,其叶片中过氧化物酶(POD)、多酚氧化酶(PPO)和脂氧合酶(LOX)活性以及丙二烯氧化物环化酶基因(AOC)和茉莉酸信号受体基因(COI1)的转录水平显著高于只接种早疫病菌的处理、只接种菌根菌的处理以及未进行任何处理的健康植株,其早疫病发病率和病情指数也显著降低;外源喷施MeJA可增强预先接种菌根菌的CM和35S::PS番茄植抵抗早疫病的能力。与此同时,对预先接种菌根菌的spr2番茄外源喷施MeJA...     

转GhB301基因烟草的防御酶活性及抗病相关基因表达分析

为了明确棉花ERF-B3亚族转录因子基因GhB301在烟草异位表达后(抗枯萎病中)的功能,该研究以过表达GhB301基因烟草和野生型烟草为材料,采用枯萎病菌孢子悬浮液接菌方法,分析病原菌侵染前后防御酶活性变化以及防卫相关基因的表达变化与抗病性的关系。结果显示:(1)棉花枯萎病菌处理15d后,2个转基因株系烟草叶片黄化程度与野生型相比较轻。(2)棉花枯萎病菌处理后,过表达GhB301转基因烟草和野生型烟草叶片过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)的活性较未接菌对照显著提高,并且酶活峰值出现均早于野生型材料;转基因材料叶片的POD、PAL、PPO活性均在处理3d后达到峰值,而野生型材料叶片的POD、PAL活性在处理5d后才达到峰值。(3)接种棉花枯萎病菌后活性氧相关基因、乙烯(ET)/茉莉酸(JA)途径相关基因、病程相关基因的表达量在转基因株系OE1和OE2中均受到明显影响。研究推测,GhB301在烟草中的异位表达激活了防卫相关基因的表达,提高了防御酶的活性,从而增强了烟草对枯萎病菌的抗性。     

外源水杨酸和茉莉酸诱导巨峰葡萄抗根瘤蚜

【目的】水杨酸和茉莉酸在植物诱导防御虫害反应中发挥着重要作用。本研究旨在探讨水杨酸和茉莉酸诱导葡萄对根瘤蚜的抗性。【方法】以盆栽巨峰为试材,在接种葡萄根瘤蚜Daktulosphaira vitifoliae的同时喷施水杨酸和茉莉酸,测定和评估了对根瘤蚜生长发育及产卵量的影响,以及对葡萄根系抗氧化相关酶［过氧化物酶(POD)和过氧化氢酶(CAT）］活性、丙二醛（MDA）含量、新梢生长量及光合速率的影响。【结果】水杨酸和茉莉酸诱导处理显著降低了根瘤蚜卵量及下代1,2龄若蚜总数,接种35 d后根瘤蚜的产卵量分别减少了41.35％和50.00％,1龄和2龄若蚜总数分别减少了42.31％和50.00％;根瘤蚜侵染后根系中POD和CAT活性均呈先升高后降低的趋势,且水杨酸和茉莉酸诱导处理在各测定时期均高于仅接种根瘤蚜处理;水杨酸和茉莉酸处理的根系中MDA含量在各测定时期均低于仅接种根瘤蚜处理;水杨酸和茉莉酸处理降低了根瘤蚜侵染对植株地上部生长及光合的抑制。接种处理后第30天,仅接种根瘤蚜处理的植株地上部生长量减少了48.11%,光合速率降低了58.77％,而水杨酸和茉莉酸处理后的新梢生长量分别减少了31.57％和25.71％,光合速率分别降低了32.89％和24.67％。【结论】叶片喷洒茉莉酸和水杨酸能够降低根瘤蚜种群密度,并提高葡萄根系活性氧清除能力和防御酶活性,缓解树势衰退。     

AtWRKY63基因过表达拟南芥对核盘菌抗性的研究

为研究草酸在核盘菌致病过程中可能的作用,以模式植物拟南芥为材料,采用30mmol/L草酸喷施3周龄拟南芥,发现草酸显著诱导拟南芥AtWRKY63的表达。通过构建AtWRKY63过表达载体转化拟南芥,获得过表达AtWRKY63的纯系转基因植株,再用核盘菌活体接种拟南芥,结果表明过表达AtWRKY63植株对核盘菌的抗性显著增强。组织化学染色结果表明,AtWRKY63是通过诱导植物的氧爆发,抑制核盘菌菌丝的生长来抵御核盘菌的侵染;qRT-PCR对拟南芥转录水平分析表明,AtWRKY63可能激活了过表达植株的水杨酸与茉莉酸依赖的抗病信号途径,从而增强对核盘菌的抗性。     

拟南芥AZI1基因对酿酒酵母细胞生长和蒜薹灰霉菌侵染的抑制作用

本工作采用酿酒酵母细胞表达载体pESC和植物细胞表达载体pPZP211分析了拟南芥AZI1基因对真菌的抗性功能。半乳糖诱导产生的AZI1蛋白可以使酵母细胞的生长能力明显降低。DAB和台酚蓝染色结果显示用蒜薹灰霉菌孢子处理Col-0野生型植株叶片后被侵染部位只能产生少量H2O2,病原体可以扩散,而AZI1基因过表达植株叶片在侵染部位有大量H2O2产生,着色较深,表明转化体能够以局部细胞的死亡来阻止病原体侵染周围的细胞。在Col-0野生型植株中,AZI1基因的表达受外源水杨酸诱导,24h后达到峰值。以上结果说明AZI1基因在拟南芥对生物胁迫因素的应答过程中具有重要作用。     

拟南芥抵抗丁香假单胞杆菌过程中AZI1基因功能研究

AZI1属于脂转移蛋白家族,它在拟南芥抵抗病原菌侵染过程中可能起着传递信号物质的作用。该实验以过表达和T-DNA插入突变体及野生型拟南芥植株为材料,通过RNA印迹、蛋白质免疫印迹和原位免疫组织化学方法,研究了拟南芥壬二酸诱导基因AZI1对丁香假单胞杆菌的抗性功能。结果表明:(1)AZI1基因可以被丁香假单胞杆菌、H2O2和乙烯利诱导,它可能参与水杨酸和乙烯介导的抗菌途径。(2)蛋白质免疫印迹实验结果显示,丁香假单胞杆菌侵染叶片的叶柄渗出液中存在AZI1蛋白及其同源物EARLI1,并能够与其他蛋白质形成复合体,说明AZI1有可能通过维管组织移动到个体的其他部位,与信号分子的转移有关。(3)AZI1及其同源物EARLI1主要在花序茎的木质化部位表达,过表达AZI1基因能够促进木质素的合成,提高拟南芥对丁香假单胞杆菌的抗性。     

桃蚜取食行为对大气CO_2浓度升高的响应

【目的】近年来随着人类活动的增加,温室气体尤其是大气CO_2浓度升高造成的虫害爆发已成为国际上关注的焦点,因此,研究拟南芥Arabidopsis thaliana上桃蚜取食行为的变化对大气CO_2浓度升高的响应意义重大。【方法】本研究以拟南芥和绿色桃蚜Myzus persicae为研究对象,利用野生型拟南芥Col-0,茉莉酸途径信号传导缺失突变体(jar1)、水杨酸途径信号传导缺失突变体(npr1)、乙烯途径信号传导缺失突变体(ein2-5)为材料,以大气CO_2浓度升高为影响因子,利用刺吸式电位仪(EPG)记录了桃蚜在不同处理的拟南芥上的取食波形。【结果】研究结果发现:CO_2浓度升高缩短了Col-0和jar1植株上蚜虫首次刺探时间和首次到达韧皮部的时间,却延长了npr1和ein2-5上蚜虫首次到达韧皮部的时间,降低了jar1植株上蚜虫总的刺探时间且增加了其总的取食韧皮部时间,但没有改变其它基因型植株上蚜虫总的刺探和取食时间;同时增加了野生型植株上蚜虫的刺探频率,却没有影响其它基因型植株上的刺探频率。【结论】CO_2浓度升高降低了野生型植株和jar1植株抗性,有利于蚜虫到达韧皮部;却增加了npr1和ein2-5上的植物抗性,从而不利于蚜虫到达韧皮部。     

Differential inducible defense mechanisms against bacterial speck pathogen in Arabidopsis thaliana by plant-growth-promoting-fungus Penicillium sp. GP16-2 and its cell free filtrate

Although a wealth of information is available regarding resistance induced by plant growth-promoting rhizobacteria (PGPR), not much is known about plant growth-promoting fungi (PGPF). Hence, the goal of the present research was to provide more information on this matter. In Arabidopsis thaliana L., root colonizing PGPF Penicillium sp. GP16-2 or its cell free filtrate (CF) elicited an induced systemic resistance (ISR) against infection by Pseudomonas syringae pv. tomato DC3000 (Pst), leading to a restriction of pathogen growth and disease development. We demonstrate that signal transduction leading to GP16-2-mediated ISR requires responsiveness to JA and ET in a NPR1-dependent manner, while CF-mediated ISR shows dispensability of SA, JA, ET and NPR1-dependent signaling (at least individually). In addition, root colonization by GP16-2 is not associated with a direct effect on expression of known defense-related genes, but potentiates the activation of JA/ET-inducible ChitB, which only becomes apparent after infection by Pst. However, CF-mediated ISR was partly associated with the direct activation of marker genes responsive to both SA and JA/ET signaling pathways and partly associated with priming, leading to activation of JA-/ET-inducible ChitB and Hel genes. These suggest that CF may contain one or more elicitors that induce resistance by way where at least SA, JA and ET may play a role in defense signaling in Arabidopsis. Therefore, defense gene changes and underlying signaling pathways induced by Penicillium sp. GP16-2 root colonization and its CF application are not the same and only partially overlap.     

Role of ethylene signalling in growth and systemic resistance induction by the plant growth‐promoting fungus Penicillium viridicatum in Arabidopsis

The plant growth‐promoting fungi (PGPF) have long been known to improve plant growth and suppress plant diseases. The PGPF Penicillium viridicatum GP15‐1 elicited plant growth and induced systemic resistance (ISR) in Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000 (Pst), leading to a restriction of pathogen growth and disease development. Examination of local and systemic genes indicated that GP15‐1 did not modulate the expression of any of the tested defence‐related marker genes involved in salicylic acid (SA), jasmonic acid (JA) and ethylene signalling pathways. Subsequent challenge of GP15‐1‐colonized plants with Pst bacterium primed Arabidopsis plants for enhanced activation of the JA‐inducible Atvsp (vegetative storage protein) gene at a later stage of infection. To assess the contribution of different signalling pathways in GP15‐1‐elicited plant growth and ISR, Arabidopsis genotypes implicated in SA signalling expressing the nahG transgene (NahG) or carrying disruption in NPR1 (npr1), JA signalling (jar1) and ethylene signalling (ein2) were tested. The GP15‐1‐induced plant growth and ISR were fully compromised in an ein2 mutation. Root colonization assay revealed that the inability of the ein2 mutant to express GP15‐1‐induced plant growth and ISR was not associated with reduced root colonization by GP15‐1. In conclusion, our results demonstrate the ethylene signalling pathway is involved in plant growth promotion and ISR elicitation by the PGPF P. viridicatum GP15‐1 in Arabidopsis. These results provide evidence that ethylene signalling has a substantial role in plant growth and disease resistance.     

Alternative Functions of Arabidopsis YELLOW STRIPE-LIKE3: From Metal Translocation to Pathogen Defense

YELLOW STRIPE-LIKE1 (YSL1) and YSL3 are involved in iron (Fe) and copper (Cu) translocation. Previously, we reported that upregulation of YSL1 and YSL3 under excess Cu caused high accumulation of Cu in the siz1 mutant, impaired in small ubiquitin-like modifier (SUMO) E3 ligase. Interestingly, the siz1 mutant contains high levels of salicylic acid (SA), involved in plant defense against biotrophic pathogens. In this study, we found that YSL1 and YSL3 were upregulated by SA. SA-regulated YSL3 but not YSL1 depended on NONEXPRESSOR OF PR1 (NPR1). Susceptibility to the pathogen Pseudomonas syringe pv. tomato (Pst) DC3000 was greater for ysl3 than the wild type. Also, during Pst DC3000 infection, YSL3 was positively regulated by SA signaling through NPR1 and the upregulation was enhanced in the coi1 mutant that defective in the jasmonic acid (JA) receptor, CORONATINE INSENSITIVE1. This line of evidence indicates that the regulation of YSL3 is downstream of SA signaling and interplays with JA signaling for involvement in pathogen-induced defense. We provide new insights into the biological function of the metal transporter YSL3 in plant pathogen defense.     

Tomato SlSAP3, a member of the stress-associated protein family,is a positive regulator of immunity against Pseudomonas syringae pv. tomato DC3000

Tomato stress-associated proteins (SAPs) belong to A20/AN1 zinc finger protein family, some of which have been shown to play important roles in plant stress responses. However, little is known about the functions and underlying molecular mechanisms of SAPs in plant immune responses. In the present study, we reported the function of tomato SlSAP3 in immunity to Pseudomonas syringae pv. tomato (Pst) DC3000. Silencing of SlSAP3 attenuated while overexpression of SlSAP3 in transgenic tomato increased immunity to Pst DC3000, accompanied with reduced and increased Pst DC3000-induced expression of SA signalling and defence genes, respectively. Flg22-induced reactive oxygen species (ROS) burst and expression of PAMP-triggered immunity (PTI) marker genes SlPTI5 and SlLRR22 were strengthened in SlSAP3-OE plants but were weakened in SlSAP3-silenced plants. SlSAP3 interacted with two SlBOBs and the A20 domain in SlSAP3 is critical for the SlSAP3-SlBOB1 interaction. Silencing of SlBOB1 and co-silencing of all three SlBOB genes conferred increased resistance to Pst DC3000, accompanied with increased Pst DC3000-induced expression of SA signalling and defence genes. These data demonstrate that SlSAP3 acts as a positive regulator of immunity against Pst DC3000 in tomato through the SA signalling and that SlSAP3 may exert its function in immunity by interacting with other proteins such as SlBOBs, which act as negative regulators of immunity against Pst DC3000 in tomato.     

拟南芥钙调素结合蛋白参与胁迫响应的研究

采用实时荧光定量RT-PCR和Northern blotting技术检测了野生型拟南芥中CBP60g基因对丁香假单胞菌和非生物胁迫的响应,并对丁香假单胞菌接种后,野生型拟南芥、cbp60g-1突变体和CBP60g过表达转基因植物中抗逆相关基因的表达变化进行检测。结果显示:(1)在野生型拟南芥中CBP60g基因的表达能被丁香假单胞菌、高盐、冷和机械损伤所诱导。(2)经丁香假单胞菌诱导后病程相关基因PR5和AIG1的表达在过表达转基因植物中明显高于野生型。(3)受干旱和ABA诱导的AtMYB2基因的表达在过表达转基因植物中也高于野生型。研究表明,CBP60g同时参与了拟南芥对生物和非生物胁迫响应。     

Brassinosteroids are involved in ethylene‐induced Pst DC3000 resistance in Nicotiana benthamiana

• Plant immunity is regulated by a huge phytohormone regulation network. Ethylene(ET) and brassinosteroids (BRs) play critical roles in plant response to biotic stress; however, the relationship between BR and ET in plant immunity is unclear.
• We used chemical treatments, genetic approaches and inoculation experiments to investigate the relationship between ET and BR in plant defense against Pst DC3000 in Nicotiana benthamiana.
• Foliar applications of ET and BR enhanced plant resistance to Pst DC3000 inoculation, while treatment with brassinazole (BRZ, a specific BR biosynthesis inhibitor) eliminated the ET induced plant resistance to Pst DC3000. Silencing of DWARF 4(DWF4, a key BR biosynthetic gene), BRASSINOSTEROID INSENSITIVE 1 (BRI1, aBR receptor) and BRASSINOSTEROID-SIGNALING KINASE 1 (BSK1, downstream of BRI1) also neutralised the ET‐induced plant resistance to Pst DC3000. ET can induce callose deposition and reactive oxygen species (ROS) accumulation to resistPst DC3000, BRZ‐treated and gene‐silenced were completely eliminate this response.
• Our results suggest BR is involved in ET‐induced plant resistance, the involvement of ET in plant resistance is possibly by the induction of callose deposition and ROS accumulation, in a BR‐dependent manner.

     

Arabidopsis DAL1 and DAL2, two RING finger proteins homologous to Drosophila DIAP1, are involved in regulation of programmed cell death

Programmed cell death (PCD) is a precise, genetically controlled cellular process with important roles in plant growth, development, and response to biotic and abiotic stress. However, the genetic mechanisms that control PCD in plants are unclear. Two Arabidopsis genes, DAL1 and DAL2 (for Drosophila DIAP1 like 1 and 2), encoding RING finger proteins with homology to DIAP1 were identified, and a series of experiments were performed to elucidate their roles in the regulation of PCD and disease resistance. Expression of DAL1 and DAL2 genes was induced in Arabidopsis plants after inoculation with virulent and avirulent strains of Pseudomonas syrinage pv. tomato (Pst) DC3000 or after infiltration with fumonisin B1 (FB1). Plants with mutations in the DAL1 and DAL2 genes displayed more severe disease after inoculation with an avirulent strain of Pst DC3000, but they showed similar disease severity as the wild-type plant after inoculation with a virulent strain of Pst DC3000. Significant accumulations of reactive oxygen species (ROS) and increased cell death were observed in the dal1 and dal2 mutant plants after inoculation with the avirulent strain of Pst DC3000. The dal mutant plants underwent extensive PCD upon infiltration of FB1 and displayed higher levels of ROS accumulation, callose deposition, and autofluorescence than the wild-type plants. Our data suggest that DAL1 and DAL2 may act as negative regulators of PCD in Arabidopsis.     

Functions of pipecolic acid on induced resistance against Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000 in tomato plants

Amino acid metabolic pathways are involved in the plant immune system. Pipecolic acid (Pip), a lysine-derived non-protein amino acid, acts as an important regulator of disease resistance. Here, we report the functions of Pip on tomato disease resistance. Tomato seedlings treated with 0.5 mM Pip showed increased resistance to Pst DC3000 and B. cinerea compared with the control. After pathogen infection, the expression of defence-related genes increased in plants pretreated with Pip, while reactive oxygen species (ROS) accumulation decreased. These data demonstrated that exogenous application of Pip induced resistance against Pst DC3000 and B. cinerea in tomatoes, possibly through the regulation of ROS accumulation and defence-related gene expression.     

Priming for enhanced defence responses by specific inhibition of the Arabidopsis response to coronatine

The priming agent β-aminobutyric acid (BABA) is known to enhance Arabidopsis resistance to the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000 by potentiating salicylic acid (SA) defence signalling, notably PR1 expression. The molecular mechanisms underlying this phenomenon remain unknown. A genome-wide microarray analysis of BABA priming during Pst DC3000 infection revealed direct and primed up-regulation of genes that are responsive to SA, the SA analogue benzothiadiazole and pathogens. In addition, BABA was found to inhibit the Arabidopsis response to the bacterial effector coronatine (COR). COR is known to promote bacterial virulence by inducing the jasmonic acid (JA) response to antagonize SA signalling activation. BABA specifically repressed the JA response induced by COR without affecting other plant JA responses. This repression was largely SA-independent, suggesting that it is not caused by negative cross-talk between SA and JA signalling cascades. Treatment with relatively high concentrations of purified COR counteracted BABA inhibition. Under these conditions, BABA failed to protect Arabidopsis against Pst DC3000. BABA did not induce priming and resistance in plants inoculated with a COR-deficient strain of Pst DC3000 or in the COR-insensitive mutant coi1-16. In addition, BABA blocked the COR-dependent re-opening of stomata during Pst DC3000 infection. Our data suggest that BABA primes for enhanced resistance to Pst DC3000 by interfering with the bacterial suppression of Arabidopsis SA-dependent defences. This study also suggests the existence of a signalling node that distinguishes COR from other JA responses.