Identification and characterisation of genes which underpin non-host disease resistance in Arabidopsis

• Main Author: Kang, Jeong-Gu
• Published: University of Edinburgh 2007
• Subjects: 571.2
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.653198

A pathosystem using <i>Arabidopsis </i>and wheat powdery mildew, <i>Blumeria graminis </i>f. sp. <i>tritici </i>(<i>Bgt</i>), for which <i>Arabidopsis </i>is a non-host, was employed to initiate the genetic dissection of non-host resistance (NHR). The EMS mutagenised population from the <i>Arabidopsis </i>line containing the <i>GST1:LUC </i>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 <i>LUC </i>transgene in response to attempted <i>Bgt </i>infection. Through this screening, <i>nhr1 </i>was isolated as a putative factor for non-host pathogen recognition. This mutant showed severely compromised <i>GST1</i> induction and less hypersensitive cell death in response to <i>Bgt </i>inoculation, while exhibiting little difference against other host bacterial and fungal pathogens including <i>Pseudomonas syringae </i>p.v. tomato and <i>Hyaloperonospora parasitica. </i>In addition, <i>nhr1 </i>was sugar dependent in germination. We identified <i>ads3 </i>(<i>ACTIVATED DISEASE SUSCEPTIBILTY 3</i>), an <i>Arabidopsis </i>mutant showing drought resistant as well as disease susceptible phenotype against host and non-host pathogens. <i>ads3 </i>is <i>emf1-D </i>by enhanced expression of Embryonic Flower 1 (EMF1), which had been known as repressor of floral transition in plant. The susceptibility of <i>emf1-D </i>was recapitulated in transgenic <i>Arabidopsis </i>plants ectopically expressing <i>EMF1. </i>Conversely, conditionally decreased <i>EMF1 </i>level in the transgenic plant conveyed disease resistance. <i>emf1-D </i>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 <i>Bgt. </i>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.