Genomic analysis and characterisation of adr1, an activated Arabidopsis mutant overexpressing a CC-NBS-LRR gene that confers disease resistance and drought tolerance

• Main Author: Chini, Andrea
• Published: University of Edinburgh 2004
• Subjects: 581.35
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.640530

A transgenic <i>Arabidopsis</i> line containing a chimeric <i>PR-1::luciferase (LUC)</i> reporter gene was subjected to mutagenesis with activation tags. Screening of lines via high throughput LUC imaging identified a number of dominant <i>Arabidopsis</i> mutants that exhibited enhanced <i>PR-1</i> gene expression. Here we report the characterisation of one of these mutants, designated activated disease resistance (<i>adr</i>) 1. This line showed constitutive expression of a number of key defence marker genes and accumulated salicylic acid, but not ethylene or jasmonic acid. Furthermore, <i>adr1</i> plants exhibited resistance against the biotrophic pathogen <i>Peronospora parasitica</i> and <i>Erysiphe cichoracearum</i> but not the necrotrophic fungus <i>Botrytis cineria.</i> Analysis of a series of <i>adr1</i> double mutants suggested that <i>ADR1-</i>mediated resistance against <i>P. parasitica</i> was SA-dependent, while resistance against <i>E. cichoracearum</i> was both SA-dependent and partially NPR1-dependent. The controlled, transient expression of <i>ADR1</i> conveyed striking disease resistance in the absence of yield penalty, highlighting the potential utility of this gene in crop protection. Homologous genes were uncovered in many phylogenetically distant and agronomically important plant species; their sequence analysis revealed a number of consensus motifs unique and distinctive for the ADR1 family. Furthermore, we show that either constitutive or conditional enhanced expression of <i>ADR1</i> conferred significant drought tolerance. Cross-tolerance was not a characteristic of <i>adr1</i> plants; rather they showed increased sensitivity to thermal and salinity stress.  Hence, <i>ADR1</i> activated signalling may antagonise some stress responses. Additionally, a large activation tagged population was screened in order to isolate novel mutants altered in disease susceptibility.  Here we report the characterisation of one mutant, designated activated disease susceptibility (<i>ads</i>) 1. This line was confirmed to concurrently exhibit increased susceptibility to hemi-biotrophic, necrotrophic and non-host pathogens.