Functional characterisation and validation of nonhost components in Triticeae species for durable resistance against fungal diseases (DURESTrit)
Plant Physiology
Final Report Abstract
Nonhost resistance (NHR) is the most durable and broadly acting form of resistance plants possess to ward off the majority of pathogens regularly occurring within their environment. In order to exploit NHR in future crop protection concepts, we need to understand how the minority of adapted host pathogens can circumvent or suppress NHR and what defense- or accommodation-related proteins, signalling pathways or structural components of their host plants are targeted in order to establish disease. Because NHR is operating at the species level, corresponding sources of resistance can only in exceptional cases be crossed with related crop plants. Therefore, gene technological approaches to transfer NHR components across species barriers are an attractive alternative to traditional or markerassisted breeding. In the ERA-NET consortium TritNONHOST, plus a number of related projects e.g. funded within the German GABI program (BMBF), we previously identified a number of genes and genetic loci in barley and wheat that are associated or correlated with NHR to three major fungal pathogens including powdery mildews. A sub-set of those belonging to the group of receptor-like kinases (RLKs) were successfully validated in transient over-expression or gene silencing assays in barley and wheat, thereby providing an important source for the DURESTrit consortium. We have functionally tested three RLK genes (HvLEMK1, HvRLK7 and HvRLK10) by generating and characterizing stable transgenic RNAi lines in barley and stable over-expression lines in wheat. Results of pathogen assays with this set of transgenic lines indicated that it might be difficult to transfer NHR from barley into wheat using these RLKs. While transient over-expression of the barley RLKs in the wheat cv. Kanzler gave a positive resistance phenotype towards the wheat powdery mildew pathogen, the same phenotype could not be replicated in wheat cv. Fielder, suggesting that the wheat genetic background influences limits efficacy of transfer of NHR from barley to wheat. Putative mutants of RLKs from RNA-guided Cas9 technology were obtained in barley, providing additional resources whereby the role of these genes in NHR can be determined. The genetic fine mapping and physical mapping of (1) a major QTL located on 2HL from cultivated barley, (2) a NHR gene from a 2HS H. bulbosum introgression and (3) a large-effect QTL for NHR to the wheat powdery mildew in barley (Rbgtq1) resulted in the generation of valuable genetic material and the genetic and in part physical delimitation of novel sources of NHR. A library of synthetic secreted effector protein genes from the barley powdery mildew fungus was generated and used for targeted interaction assays with plant RLK candidate proteins. This part of the project was linked to the NSF-funded project “Host targets of fungal effectors as keys to durable disease resistance”. Besides RLKs, a selected subset of candidate genes with differential regulation in host- versus nonhost interactions or belonging to potentially relevant protein families were also tested by transient expression/silencing assays in barley. The results obtained within DURESTrit deepen our understanding of NHR in cereals and provide novel materials and know-how for the exploitation of NHR by translational research.
Publications
- 2015. Broadly conserved fungal effector BEC1019 suppresses host cell death and enhances pathogen virulence in powdery mildew of barley (Hordeum vulgare L.). Molecular Plant-Microbe Interactions 28: 968-983
Whigham, E., Qi, S., Mistry, D., Surana, P., Xu, R., Fuerst,G.S., Pliego, C., Bindschedler, L.V., Spanu, P., Dickerson J.A., Innes, R., Nettleton, D., Bogdanove, A.J., and Wise, R.P.
(See online at https://doi.org/10.1094/MPMI-02-15-0027-FI) - 2015. RNA–protein interactions in plant disease: hackers at the dinner table. New Phytologist 207: 991-995
Spanu P.D.
(See online at https://doi.org/10.1111/nph.13495) - 2016. An LRR/malectin receptor-like kinase mediates nonhost resistance in barley and enhances quantitative resistance in wheat. Frontiers in Plant Science 7: 1836
Stefanato F., Gordon A., Ereful N., Caldararu O.F., Petrescu A.-J., Kumlehn J., Boyd L.A., Schweizer P.
(See online at https://doi.org/10.3389/fpls.2016.01836) - 2016. Nutrient supplements boost yeast transformation efficiency. Scientific Reports 6: 35738
Yu, S.-C., Dawson, A, Henderson, A.C., Lockyer, E.J., Read, E., Sritharan, G., Ryan, M., Sgroi, M., Ngou, P.M., Woodruff, R., Zhang, R., Ren Teen Chia, T., Liu, Y., Xiang, Y., and Spanu, P.D.
(See online at https://doi.org/10.1038/srep35738) - 2017. A comparative analysis of nonhost resistance across the two Triticeae crop species wheat and barley. BMC Plant Biology 17: 232
Delventhal R., Rajaraman J., Stefanato F.L., Rehman S., Aghnoum R., McGrann G.R.D., Bolger M., Usadel B., Hedley P.E., Boyd L.A., Niks R.E., Schweizer P., Schaffrath U.
(See online at https://doi.org/10.1186/s12870-017-1178-0) - 2017. Editorial: Biotrophic plant-microbe interactions. Frontiers in Plant Science 8: 192
Spanu, P.D., and Panstruga, R.
(See online at https://doi.org/10.3389/fpls.2017.00192) - 2018. Effectors involved in fungal– fungal interaction lead to a rare phenomenon of hyperbiotrophy in the tritrophic system biocontrol agent– powdery mildew–plant. New Phytologist 217: 713-725
Laur J., Bojarajan R.G., Labbé C., Lefebvre F., Spanu P.D., Bélanger R.R.
(See online at https://doi.org/10.1111/nph.14851) - 2018. Evolutionarily conserved partial gene duplication in the Triticeae tribe of grasses confers pathogen resistance. Genome Biology
Rajaraman, J., Douchkov, D., Lück, S., Hensel, G., Nowara, D., Pogoda, M., Rutten, T., Meitzel, T., Brassac, J., Höfle, C., Hückelhoven, R., Klinkenberg, J., Trujillo, M., Bauer, E., Schmutzer, T., Himmelbach, A., Mascher, M., Lazzari, B., Stein, N., Kumlehn, J., Schweizer, P.
(See online at https://doi.org/10.1186/s13059-018-1472-7) - 2018. Mapping resistance to powdery mildew in barley reveals a large-effect nonhost resistance QTL. Theoretical and Applied Genetics 131: 1031–1045
Romero, C.C.T., Vermeulen, J.P., Vels, A., Himmelbach, A., Mascher, M., and Niks, R.E.
(See online at https://doi.org/10.1007/s00122-018-3055-0) - 2018. Why did filamentous plant pathogens evolve the potential to secrete hundreds of effectors to enable disease? Molecular Plant Pathology 19: 781-785
Thordal-Christensen, H., Birch, P.R.J., Spanu, P.D., and Panstruga, R.
(See online at https://doi.org/10.1111/mpp.12649) - 2018. Yeast transformation efficiency is enhanced by TORC1- and eisosome-dependent signalling
Yu, S., Kümmel, F., Skoufou-Papoutsaki, M., and Spanu, P.D.
(See online at https://doi.org/10.1101/244889)
