Abstract
Plant-parasitic nematodes secrete a series of effectors to promote parasitism by modulating host immunity, but the detailed molecular mechanism is ambiguous. Animal parasites secrete macrophage migration inhibitory factor (MIF)-like proteins for evasion of host immune systems, in which their biochemical activities play essential roles. Previous research demonstrated that MiMIF-2 effector was secreted by Meloidogyne incognita and modulated host immunity by interacting with annexins. In this study, we show that MiMIF-2 had tautomerase activity and protected nematodes against H2O2 damage. MiMIF-2 expression not only decreased the amount of H2O2 generation during nematode infection in Arabidopsis, but also suppressed Bax-induced cell death by inhibiting reactive oxygen species burst in Nicotiana benthamiana. Further, RNA-seq transcriptome analysis and RT-qPCR showed that the expression of some heat-shock proteins was down regulated in MiMIF-2 transgenic Arabidopsis. After treatment with flg22, RNA-seq transcriptome analysis indicated that the differentially expressed genes in MiMIF-2 expressing Arabidopsis were pointed to plant hormone signal transduction, compound metabolism and plant defense. RT-qPCR and metabolomic results confirmed that salicylic acid (SA) related marker genes and SA content were significantly decreased. Our results provide a comprehensive understanding of how MiMIF-2 modulates plant immunity and broaden knowledge of the intricate relationship between M. incognita and host plants.
Highlights
Root-knot nematodes (RKNs; Meloidogyne spp.) are one of the most destructive obligate parasites of plants, infecting more than 5500 plant species and leading to over 70 billion dollars losses annually [1,2]
Our results showed that rMiMIF-2 formed a trimer in non-denaturing western blotting and catalyzed the tautomerization of p-hydroxyphenylpyruvate, but the activity was much weaker than that of HuMIF
A previous study indicated that the initiator methionine of migration inhibitory factor (MIF) was cleaved, exposing the proline residue, which was essential for MIF tautomerase activity [46]
Summary
Root-knot nematodes (RKNs; Meloidogyne spp.) are one of the most destructive obligate parasites of plants, infecting more than 5500 plant species and leading to over 70 billion dollars losses annually [1,2]. MIF-like proteins from Helminths and Protozoa were shown to play crucial roles in modulating host immune responses and their enzyme activities were investigated. Recent report confirmed that the MiMIF-2 was a MIF-like protein and expressed in the M. incognita hypodermis and secreted into plant tissues. It is fascinating to study whether MiMIF-2 possesses tautomerase and oxidoreductase activity during interaction with plant host cells. FoglelonwesisniglentrceeadtmbyenRtNwAiitthha1n0-imn MthoHse2Otre2a,tnedemwaitthodGeFsPvdiasRbNiliAtyowr abus f3fe0r%(Fliogwureer3iDn,JE2).sTiongwethheicr,h MiMIF gethneesse sreilseunltcsesdhobwyeRd NthAatiMthiManIFi-n2 wthaossienvtorelvaetdedinwanitthioxGidFaPntdascRtiNviAty.or buffer (Figure 3D,E) Together, these results showed that MiMIF-2 was involved in antioxidant activity. By analyzing the data of differentially expressed genes that involved in the pathways of plant–pathogen interaction, plant hormone signal transduction and phenylalanine metabolism, some defense-associated genes were down regulated, for example PR1, FRK1, WRK29 and PAL. MiMIF-2 expdreetsesrminingedAinraobnied-wopaysiAs NaOftVeAr wtriethaDtmunennettt’swmiuthltipfllegc2o2mp2a4risho.nsTtehste(ablpahrar0e.0p5)r.esents the average of three inde3.pDeinsdcuesnsitomn easurements. *, ** indicating the significant difference from the wild type was determined in one-way ANOVA with Dunnett’s multiple comparisons test (alpha 0.05)
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