菌丝桥介入枳根系间抗溃疡病的信号物质响应

Responses of signal substances to canker in trifoliate orange roots through mycorrhizal hyphal bridge

对两室根箱试验装置中一分室(供体室)定植的枳Poncirus trifoliata实生苗接种丛枝菌根(AM)真菌Paraglomus occultum,另一分室(受体室)不作任何处理。定植17周后,将溃疡病病菌Xanthomonas axonopodis(Xac)接种于供体植株,研究不同处理受体植株间的信号物质响应差异,揭示菌丝桥的功能。与不接种处理相比,单接种AM真菌、预先接种AM真菌后再接种Xac均显著提高了供体根系一氧化氮(NO)含量,单接种AM真菌只显著提高了受体根系NO含量;单接种Xac显著降低了供体根系脱落酸(ABA)含量,而单接种AM真菌、双接种(AM真菌+Xac)均增加了供体根系ABA含量。双接种处理显著提高了受体ABA含量;与不接种对照相比,接种处理均降低了供体根系玉米素核苷(ZR)含量,同时单接种AM真菌、双接种处理也降低了受体根系ZR含量;AM真菌显著降低了供体和受体根系茉莉酸(JA)含量,但双接种却显著提高了供体和受体根系JA含量;与不接种对照相比,单接种AM真菌或Xac、双接种处理均显著下调供体根系JA合成基因(PtLOX、PtAOS和PtAOC)的表达,单接种Xac显著下调了受体根系PtLOX和Pt AOC的表达,单接种AM真菌显著下调了受体根系PtAOC的表达,而双接种显著上调了受体根系PtAOS基因的表达。表明菌根真菌的菌丝桥传导JA并诱导受体植株中NO、ABA和ZR含量改变以抵御溃疡病菌危害。

In this study, a two-chambered rootbox experimental installation was used. In which one chamber（donor chamber） was planted with trifoliate orange Poncirus trifoliata seedlings inoculated with an arbuscular mycorrhizal（AM） fungus, Paraglomus occultum, and the another chamber（receptor chamber） was planted with trifoliate orange only without inoculation.In 17 weeks of AMF colonization, Xanthomonas axonopodis（Xac） was inoculated into donor plants, and differences in signal responses were analyzed among receptor seedlings under different treatment conditions to clarify function of mycorrhizal hyphal bridge. Compared with non-inoculated treatment, single-inoculation with AM fungi and Xac inoculation subsequent to AMF inoculation significantly increased root nitric oxide（NO） content in donor plants, while single-inoculation with AM fungi increased root NO content in receptor plants. Single-inoculation with Xac considerably decreased root abscisic acid（ABA） of donor plants, but single-inoculation with AM fungi and double inoculation with AM fungi and Xac both increased root ABA content of donor plants. Double inoculation dramatically increased root ABA content in receptor plants. Compared with non-inoculation treatment, inoculation with AM fungi or Xac significantly decreased root zeatin riboside（ZR） content of the donor. Single-inoculation with AM fungi and double-inoculation with AMF and Xac also decreased root ZR content of the receptor. Single-inoculation with AM fungi had notably lower root jasmonic acid（JA） content in the donor and receptor, while there was higher root JA content in the donor and receptor under double inoculation condition. In comparison with non-inoculation treatment, single-inoculation with AM fungi or Xac and double-inoculation with AMF and Xac without exception down-regulated JA synthetic genes（Pt LOX, Pt AOS and Pt AOC） expression levels in donor plant roots. Single-inoculation with Xac significantly depressed Pt LOX and Pt AOC expression in receptor plant roots. Single-inoculation with AM fungi negatively regulated root Pt AOC expression in the receptor. Double inoculation treatment up-regulated root Pt AOS expression in the receptor. Therefore, these facts indicate that hyphal bridge transfers JA and induces the changes of root NO, ABA, and ZR content of receptor plants to resist Xac.