Barley compatibility factors pivotal for root colonisation and manipulation of basal defence by Piriformospora indica
Final Report Abstract
Within this project we aimed to understand the effect of phospholipid signalling and processes affected by gibberellin (GA) signalling on the establishment of mutualistic symbioses in plant roots with the fungus Piriformospora indica. In genetic and molecular analyses we identified the significance of gibberellins (GA) and Tubby-like proteins (TLPs) for the colonisation of plant roots by P. indica. We further detected in cell biological experiments an initial biotrophic colonisation phase of plant roots by the fungus that was followed by a cell death-associated colonisation phase. Our studies revealed that GA signalling did not generally affect the outcome of immune response (e.g. oxidative burst) but was found to elevate salicylic acid (SA) and suppressing jasmonic acid (JA) signalling. We further found that SA disturbs while JA signalling supports P. indica colonisation. Interestingly, despite enhanced SA and reduced JA signalling, mutants showing constitutive GA signalling showed an improved colonisation. Our data suggest that GA affects other process, e.g. cell death signalling in roots, thereby “overwriting” immunity-related effects of SA and supporting P. indica colonisation. We further detected the dependency of P. indica on TLPs to colonise roots. TLPs are conserved in eukaryotes and form small gene families in plants. Similar to vertebrates, our studies indicated the plasma membrane (PM) localisation of various TLPs and the significance of two conserved amino acids of the Tubby domain for PM binding via phosphatidylinositol 4,5-bisphophate (PIP2). Upon oxidative stress (e.g. salt stress), TLPs are dislodged from the PM by a phospholipase. In contrast to TLP of vertebrates, we detected the translocation of various TLPs to plastids for which the leading sequence and parts of the N-terminal F-box domain were essentially required. TLPs might be part of PM-localised receptor system(s) that are involved in oxidative stress sensing. TLPs might be essentially required to translate stress recognition into adaptive cell responses.
Publications
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(2009) Manipulation of plant innate immunity and gibberellin as factor of compatibility in the mutualistic association of barley roots with Piriformospora indica. Plant Journal 59:461-474
Schäfer, P., Pfiffi, S., Voll, L.M., Zajic, D., Chandler, P.M., Waller, F., Scholz, U., Pons-Kühnemann, J., Sonnewald, S., Sonnewald, U., Kogel, K.H.
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(2009) Phytohormones in plant root-Piriformospora indica mutualism. Plant Signaling & Behavior 4:669-671
Schäfer, P., Pfiffi, S., Voll, L.M., Zajic, D., Chandler, P.M., Waller, F., Scholz, U., Pons-Kühnemann, J., Sonnewald, S., Sonnewald, U., Kogel, K.H.
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(2011) Broad spectrum suppression of innate immunity is required for colonization of Arabidopsis roots by the beneficial fungus Piriformospora indica. Plant Physiology 156:726-40
Jacobs, S., Zechmann, B., Molitor, A., Trujillo, M., Petutschnig, E., Lipka, V., Kogel, K.H., Schäfer, P.
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(2011) STARTS – A stable root transformation system for rapid functional analyses of proteins in roots of the monocot model plant barley. Plant Journal 67:726-735
Imani, J., Li, L., Schäfer, P. ,1, Kogel, K.H.
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(2012) Ethylene in mutualistic symbioses. Plant Signaling and Behaviour 12:1634-38
Khatabi, B., Schäfer, P.
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(2012) Ethylene supports colonization of plant roots by the beneficial fungus Piriformospora indica. PLoS One 7:e35502
Khatabi, B., Molitor, A., Lindermayr, C., Pfiffi, S., Durner, J., von Wettstein, D., Kogel, K.H., Schäfer, P.
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The subcellular localization of Tubby-like proteins and participation in stress signaling and root colonization by the mutualist Piriformospora indica. Plant Physiology 160:349-364
Reitz, M.U., Bissue, J.K., Zocher, K., Attard, A., Hückelhoven, R., Becker, K., Imani, J., Eichmann, R., Schäfer, P.
