Roos Jonas, Bejai Sarosh, Mozūraitis Raimondas, Dixelius Christina
Department of Plant Biology, Linnean Centre for Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences, PO Box 7080, SE-75007, Uppsala, Sweden.
Plant J. 2015 Feb;81(4):572-85. doi: 10.1111/tpj.12752.
The fungus Verticillium longisporum is a soil-borne plant pathogen of increasing economic importance, and information on plant responses to it is limited. To identify the genes and components involved in the early stages of infection, transcripts in roots of V. longisporum-challenged Arabidopsis Col-0 and the susceptible NON-RACE SPECIFIC DISEASE RESISTANCE 1 (ndr1-1) mutant were compared using ATH1 gene chips. The analysis revealed altered transcript levels of several terpene biosynthesis genes, including the monoterpene synthase TPS23/27. When transgenic 35S:TPS23/27 and TPS23/27-amiRNA plants were monitored the over-expresser line showed enhanced fungal colonization whereas the silenced genotype was indistinguishable from Col-0. Transcript analysis of terpene biosynthesis genes suggested that only the TPS23/27 pathway is affected in the two transgenic genotypes. To confirm changes in monoterpene production, emitted volatiles were determined using solid-phase microextraction and gas chromatography-mass spectrometry. Levels of all identified TPS23/27 monoterpene products were significantly altered in the transgenic plants. A stimulatory effect on conidial germination and hyphal growth of V. longisporum was also seen in co-cultivation with 35S:TPS23/27 plants and upon exposure to 1,8-cineole, the main product of TPS23/27. Methyl jasmonate treatments of myc2-1 and myc2-2 mutants and analysis of TPS23/27:uidA in the myc2-2 background suggested a dependence on jasmonic acid mediated by the transcription factor MYC2. Taken together, our results show that TPS23/27-produced monoterpenes stimulate germination and subsequent invasion of V. longisporum in Arabidopsis roots.
长孢轮枝菌是一种土壤传播的植物病原体，其经济重要性日益增加，而关于植物对其反应的信息有限。为了鉴定参与感染早期阶段的基因和成分，使用ATH1基因芯片比较了长孢轮枝菌侵染的拟南芥Col-0和易感的非种族特异性抗病性1（ndr1-1）突变体根中的转录本。分析揭示了几个萜类生物合成基因转录水平的改变，包括单萜合酶TPS23/27。当监测转基因35S:TPS23/27和TPS23/27-amiRNA植物时，过表达株系显示出真菌定殖增强，而沉默基因型与Col-0没有区别。萜类生物合成基因的转录分析表明，只有TPS23/27途径在这两种转基因基因型中受到影响。为了确认单萜产量的变化，使用固相微萃取和气相色谱-质谱法测定了释放的挥发性物质。在转基因植物中，所有鉴定出的TPS23/27单萜产物的水平都有显著改变。在与35S:TPS23/27植物共培养以及暴露于TPS23/27的主要产物1,8-桉叶素时，也观察到对长孢轮枝菌分生孢子萌发和菌丝生长的刺激作用。茉莉酸甲酯处理myc2-1和myc2-2突变体以及对myc2-2背景下的TPS23/27:uidA分析表明，其依赖于转录因子MYC2介导的茉莉酸。综上所述，我们的结果表明，TPS23/27产生的单萜刺激了长孢轮枝菌在拟南芥根中的萌发和随后的侵染。
