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Title: Identification and characterisation of genes which underpin non-host disease resistance in Arabidopsis
Author: Kang, Jeong-Gu
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2007
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A pathosystem using Arabidopsis and wheat powdery mildew, Blumeria graminis f. sp. tritici (Bgt), for which Arabidopsis is a non-host, was employed to initiate the genetic dissection of non-host resistance (NHR). The EMS mutagenised population from the Arabidopsis line containing the GST1:LUC transgene, which can facilitate a high throughput mutant screening strategy, have been screened using an ultra low light imaging camera system. Following a mutant screen of approximately 100,000 M2 plants, a number of candidates have been identified that compromise the induction of the LUC transgene in response to attempted Bgt infection. Through this screening, nhr1 was isolated as a putative factor for non-host pathogen recognition. This mutant showed severely compromised GST1 induction and less hypersensitive cell death in response to Bgt inoculation, while exhibiting little difference against other host bacterial and fungal pathogens including Pseudomonas syringae p.v. tomato and Hyaloperonospora parasitica. In addition, nhr1 was sugar dependent in germination. We identified ads3 (ACTIVATED DISEASE SUSCEPTIBILTY 3), an Arabidopsis mutant showing drought resistant as well as disease susceptible phenotype against host and non-host pathogens. ads3 is emf1-D by enhanced expression of Embryonic Flower 1 (EMF1), which had been known as repressor of floral transition in plant. The susceptibility of emf1-D was recapitulated in transgenic Arabidopsis plants ectopically expressing EMF1. Conversely, conditionally decreased EMF1 level in the transgenic plant conveyed disease resistance. emf1-D was drought resistant and hypersensitive to abscisic acid (ABA). We show that ectopic expression of EMF1 modulates a ABA signalling, resulting in susceptibility to pathogens. The other plant link, which is the translationally controlled tumor protein (TCTP) over-expressing line, showed reduced NHR against Bgt. A leucine rich repeat receptor-like kinase (LRK) was isolated as a putative TCTP-interacting protein, and the KO line of the LRK showed less or delayed resistant response to non-host as well as host fungal pathogens. furthermore, the TCTP over-expressing line exhibited hypersensitivity towards ABA. These results suggest that ABA signalling could play a critical role in non-host resistance in plants.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available