Molecular analysis of MOS7/Nup88-regulated immune response pathways in Arabidopsis.
Final Report Abstract
Bidirectional transport of macromolecules between the cytoplasm and the nucleus is mediated through nuclear pore complexes (NPCs) that are composed of nucleoporin proteins (NUPs). In Arabidopsis, the NUP88 homolog MOS7 was identified in a genetic screen for components that contribute to auto-immunity of the Resistance (R) gene mutant snc1, and is required for plant immunity to biotrophic and hemi-biotrophic pathogens that depend of living host cell tissue for growth and reproduction. Our recent analyses revealed that NUP88/MOS7 is also essential for full resistance to the necrotrophic fungal pathogen Botrytis cinerea that kills its host to feed on the dead remains. The aim of the funded research project was to understand the function of MOS7 in regulating defense responses against B. cinerea at the molecular and cellular level and to identify novel components of MOS7-regulated immune response pathways. Our functional analyses show that the mos7-1 mutation, causing a four-amino acid deletion, compromises B. cinerea-induced activation of two key immune-regulatory MAP kinases, MPK3 and MPK6, and selectively reduces MPK3 protein levels at the post-transcriptional level. Furthermore, MOS7 contributes to retaining a sufficient abundance of MPK3 inside the nucleus, which is required for full immunity to B. cinerea. We generated a 3D homology model of the MOS7 protein structure and show by co-immunoprecipitation (Co-IP) analysis that MOS7 interacts with NUP98A and NUP98B, two phenylalanine-glycine (FG)-repeat NUPs implicated in regulating the selective permeability barrier of NPCs. Importantly, our protein interaction analysis provided experimental evidence for our structural model that the four amino acid deletion in the mutant MOS7-1 protein impairs this interaction, suggesting that reduced binding of NUP98A/B to mutant MOS7-1 affects the nuclear accumulation of MPK3 and results in the observed immunity defects of mos7-1 plants. We therefore conducted pathogen interaction studies which show a functional involvement of NUP98A and NUP98B in defense against B. cinerea. Together, our analysis uncovered MOS7 and NUP98A/B as in planta interaction partners and novel components of plant immunity towards a necrotrophic pathogen and provides mechanistic insights into how these NUPs coordinate nucleocytoplasmic transport to mount a robust immune response. As part of the funded research project, we also uncovered the genetic requirement of MOS7/NUP88 for manifestation of phenotypes associated with a gain-of-function mutation in the Arabidopsis receptor of fungal chitin, CERK1.
Publications
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(2015). Probing formation of cargo/importin- transport complexes in plant cells using a pathogen effector. Plant J 81, 40-52
Wirthmueller, L., Roth, C., Fabro, G., Caillaud, M.C., Rallapalli, G., Asai, S., Sklenar, J., Jones, A.M.E., Wiermer, M., Jones, J.D.G. and Banfield, M.J.
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(2016). Nucleoporin-regulated MAP kinase signaling in immunity to a necrotrophic fungal pathogen. Plant Physiol 172, 1293-1305
Genenncher, B., Wirthmueller, L., Roth, C., Klenke, M., Ma, L., Sharon A. and Wiermer, M.
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(2017). E3 ligase SAUL1 serves as a positive regulator of PAMP-triggered immunity and its homeostasis is monitored by TNL SOC3. New Phytol 215, 1516-1532
Tong, M., Kotur, T., Liang, W., Vogelmann, K., Kleine, T., Leister, D., Brieske, C., Yang, S., Lüdke, D., Wiermer, M., Zhang, Y., Li, X. and Hoth, S.
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(2017). Nucleoporin NUP88/MOS7 is required for manifestation of phenotypes associated with the Arabidopsis Chitin Elicitor Receptor Kinase1 mutant cerk1-4. Plant Signal Behav 12, e1313378
Genenncher, B., Lipka, V., Petutschnig, E.K. and Wiermer, M.
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(2017). The putative kinase substrate MUSE7 negatively impacts the accumulation of NLR proteins. Plant J 89, 1174-1183
Johnson, K.C.M., Zhao, J., Wu, Z., Roth, C., Lipka, V., Wiermer M. and Li, X.
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(2017). The truncated NLR protein TIR-NBS13 is a MOS6/IMPORTIN-3 interaction partner required for plant immunity. Plant J 92, 808-821
Roth, C., Lüdke, D., Klenke, M., Quathamer, A., Valerius, O., Braus, G. and Wiermer, M.
