Common mycorrhizal networks activate salicylic acid defense responses of trifoliate orange(Poncirus trifoliata)  

作　　者：Yi-Can Zhang Ying-Ning Zou Li-Ping Liu Qiang-Sheng Wu 

机构地区：[1]College of Horticulture and Gardening, Yangtze University, Jingzhou 434025, China [2]Institute of Root Biology, Yangtze University, Jingzhou 434025, China [3]Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove 50003, Czech Republic

出　　处：《Journal of Integrative Plant Biology》2019年第10期1099-1111,共13页植物学报（英文版）

基　　金：supported by the Plan in Scientific and Technological Innovation Team of Outstanding Young Scientists, Hubei Provincial Department of Education (T201604)

摘　　要：Citrus canker, caused by Xanthomonas axonopo-dis pv. citri ('Xac'), is an important quarantine disease in citrus crops. Arbuscular mycorrhizal fungi (AMF) form symbiotic interactions with host plants and further affect their disease resistance, possibly by modulating the activity of salicylic acid (SA), a key phytohormone in disease resistance. Common mycorrhizal networks (CMNs) can interconnect plants, but it is not yet clear whether CMNs promote resistance to citrus canker and, if so, whether SA signaling is involved in this process. To test this possibility, we used a two-chambered rootbox to establish CMNs between trifoliate orange (Poncirus trifoliata) seedlings in chambers inoculated (treated) or not (neighboring) with the AMF, Paraglomus occultum. A subset of the AMF-inoculated seedlings were also inoculated with Xac (+AMF+Xac). At 2 d post-inoculation (dpi), compared with the +AMF-Xac treatment, neighboring seedlings in +AMF+Xac treatment had lower expression levels of the SA biosynthetic genes, PtPAL, PtEPS1, and PtPBS3, but higher SA levels, which attributed to the upregulation of PtPAL and PtPBS3 in treated seedlings and the transfer of SA, via CMNs, to the neighboring seedlings. At 4 dpi, the pathogenesis-related (PR) protein genes, PtPR1, PtPR4, and PtPR5, and the transcriptional regulatory factor gene, PtNPR1, were activated in neighboring seedlings of+AMF+Xac treatment. At 9 dpi, root phenylalanine ammo-nia-lyase activity and total soluble phenol and lignin concentrations increased in neighboring seedlings of+AMF+Xac treatment, likely due to the linkage and signal transfer, via CMNs. These findings support the hypothesis that CMNs transfer the SA signal from infected to neighboring healthy seedlings, to activate defense responses and affording protection to neighboring plants against citrus canker infection.Citrus canker, caused by Xanthomonas axonopodis pv. citri(‘Xac’), is an important quarantine disease in citrus crops. Arbuscular mycorrhizal fungi(AMF) form symbiotic interactions with host plants and further affect their disease resistance, possibly by modulating the activity of salicylic acid(SA), a key phytohormone in disease resistance. Common mycorrhizal networks(CMNs) can interconnect plants, but it is not yet clear whether CMNs promote resistance to citrus canker and, if so, whether SA signaling is involved in this process. To test this possibility, we used a two-chambered rootbox to establish CMNs between trifoliate orange(Poncirus trifoliata) seedlings in chambers inoculated(treated) or not(neighboring) with the AMF, Paraglomus occultum. A subset of the AMF-inoculated seedlings were also inoculated with Xac(tAMFtXac). At 2 d postinoculation(dpi), compared with the tAMFàXac treatment,neighboring seedlings in tAMFtXac treatment had lower expression levels of the SA biosynthetic genes, Pt PAL, Pt EPS1,and Pt PBS3, but higher SA levels, which attributed to the upregulation of Pt PAL and Pt PBS3 in treated seedlings and the transfer of SA, via CMNs, to the neighboring seedlings. At4 dpi, the pathogenesis-related(PR) protein genes, Pt PR1,Pt PR4, and Pt PR5, and the transcriptional regulatory factor gene, Pt NPR1, were activated in neighboring seedlings oftAMFtXac treatment. At 9 dpi, root phenylalanine ammonia-lyase activity and total soluble phenol and lignin concentrations increased in neighboring seedlings oftAMFtXac treatment, likely due to the linkage and signal transfer, via CMNs. These findings support the hypothesis that CMNs transfer the SA signal from infected to neighboring healthy seedlings, to activate defense responses and affording protection to neighboring plants against citrus canker infection.

关 键 词：PONCIRUS trifoliata MYCORRHIZAL salicylic acid DEFENSE RESPONSES 

分 类 号：Q[生物学]