丛枝菌根真菌响应桉树茄科雷尔氏菌侵染进程基因的筛选与鉴定

Screening and identification of AMF genes in Eucalyptus grandis during the infection course of Ralstonia solanacearum

【背景】桉树(Eucalyptus)青枯病危害严重,丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)与桉树共生影响桉树对青枯病的抗性,而AMF响应桉树青枯菌侵染的机制仍不清楚。【目的】探索AMF响应桉树茄科雷尔氏菌(Ralstonia solanacearum)的侵染机制。【方法】以非菌根化和异形根孢囊霉(Rhizophagus irregularis)菌根化巨桉(Eucalyptus grandis)分别受茄科雷尔氏菌侵染0、24、48和96 h接种后(hour post-inoculated,hpi)的根系组织为研究对象,基于转录组测序筛选和鉴定菌根化巨桉根系中异形根孢囊霉响应茄科雷尔氏菌侵染的基因信息。【结果】与对应非菌根化桉树受茄科雷尔氏菌侵染的时间点相比,菌根化桉树中异形根孢囊霉响应青枯菌侵染显著差异表达基因为3382-5989个,随青枯侵染时间进程的增加,异形根孢囊霉特异性响应茄科雷尔氏菌侵染差异表达基因数量逐渐增多。茄科雷尔氏菌侵染24 hpi时,异形根孢囊霉显著富集共生体生长、孢子形成和凋亡信号通路、铁载体等相关基因;茄科雷尔氏菌侵染48hpi时,异形根孢囊霉主要提高自身跨膜运输的能力,促进自身钾、氮等养分吸收与交换等;茄科雷尔氏菌侵染96hpi时,异形根孢囊霉主要调控氧化还原反应和黄酮类等抗菌物质合成。【结论】菌根化桉树中AMF主要调控其生长加强生态位和营养(如氮、钾、铁)竞争、分泌抗菌物质、激活防御反应以响应青枯菌的侵染,所鉴定的相关基因信息为研究AMF-桉树-青枯菌互作机制提供一定的资源和参考。

[Background]Bacterial wilt is a serious disease attacking Eucalyptus.Arbuscular mycorrhizal fungi(AMF)affect the resistance of Eucalyptus to bacterial wilt,the mechanism of which remains unclear.[Objective]To explore the responding mechanism of AMF of Eucalyptus grandis during the infection course of Ralstonia solanacearum.[Methods]In this study,the non-mycorrhizal root tissue and the Rhizophagus irregularis-colonized root tissue of E.grandis were sampled at the time points of 0,24,48,and 96 hour post inoculation(hpi)of R.solanacearum.The genes involved in the response of R.irregularis in E.grandis roots to R.solanacearum infection were screened and identified by transcriptome sequencing.[Results]Compared with the non-mycorrhizal root tissue,R.irregularis showed 3382-5989 differentially expressed genes at different time points of E.grandis infection by R.solanacearum.The number of specifically differentially expressed genes of R.irregularis in response to R.solanacearum infection gradually increased over the infection time.R.irregularis significantly enriched the genes involved in AMF symbiont growth,sporulation,and apoptosis signaling pathways and siderophores at 24 hpi.At 48 hpi,R.irregularis mainly improved the transmembrane transport and promoted the absorption and exchange of nutrients such as potassium and nitrogen.At 96 hpi,R.irregularis mainly regulated the redox reaction and the synthesis of antibacterial substances such as flavonoids.[Conclusion]The AMF of E.grandis mainly regulate the plant growth,enhance the niche and nutrient(such as nitrogen,potassium,and iron)competition,secrete antimicrobial substances,and activate the defense response to R.solanacearum infection.The identified genes provide resources and references for further deciphering the mechanism of AMF-Eucalyptus-R.solanacearum interaction.