Both plants and animals rely on nucleotide-binding domain leucine-rich repeat-containing (NLR) proteins to respond to invading pathogens and activate immune responses. An emerging concept in NLR biology is that “sensor” NLR proteins are often paired with “helper” NLR proteins to mediate immune signalling. However, the degree to which NLRs form signalling networks beyond sensor and helper pairs is poorly understood. In this thesis, I discovered that a large NLR immune signalling network with a complex architecture mediates immunity to oomycetes, bacteria, viruses, nematodes, and insects. Helper NLRs in the NRC (NLR-required for cell death) family are functionally redundant but display distinct specificities towards diverse sensor NLRs. Several sensor NLRs, including Rx, Bs2 and Sw5b, signal via interchangeable NRC2, NRC3 or NRC4, whereas some other sensor NLRs have a more limited downstream spectrum. For example, Prf signals via interchangeable NRC2 or NRC3 but not NRC4, and Rpi-blb2 signals via only NRC4. These helper/sensor NLRs form a unique phylogenetic superclade, with the NRC clade sister to the sensor NLR clades. The network has emerged over 100 million years ago from an NLR pair that diversified into up to one half of the NLRs of asterids. I propose that this NLR network increases evolvability and robustness of immune signalling to counteract rapidly evolving plant pathogens.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:705124 |
| Date | January 2016 |
| Creators | Wu, Chih-Hang |
| Publisher | University of East Anglia |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ueaeprints.uea.ac.uk/62253/ |
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