The cpr5 Mutant of Arabidopsis Expresses Both NPR1-Dependent and NPR1-Independent Resistance

The cpr5 mutant was identified from a screen for constitutive expression of systemic acquired resistance (SAR). This single recessive mutation also leads to spontaneous expression of chlorotic lesions and reduced trichome development. The cpr5 plants were found to be constitutively resistant to two...

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Bibliographic Details
Published in:The Plant cell 1997-09, Vol.9 (9), p.1573-1584
Main Authors: Bowling, Scott A., Clarke, Joseph D., Liu, Yidong, Klessig, Daniel F., Dong, Xinnian
Format: Article
Language:English
Subjects:
Arabidopsis - genetics
Arabidopsis - microbiology
Arabidopsis Proteins
Fungi - pathogenicity
Genes, Recessive
Genetic mutation
Infections
Leaves
Lesions
Mutation
Parasitism
Pathogens
Phenotypes
Plant cells
Plant Proteins - genetics
Plants
Pseudomonas - pathogenicity
Reporter genes
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Summary:The cpr5 mutant was identified from a screen for constitutive expression of systemic acquired resistance (SAR). This single recessive mutation also leads to spontaneous expression of chlorotic lesions and reduced trichome development. The cpr5 plants were found to be constitutively resistant to two virulent pathogens, Pseudomonas syringae pv maculicola ES4326 and Peronospora parasitica Noco2; to have endogenous expression of the pathogenesis-related gene 1 (PR-1); and to have an elevated level of salicylic acid (SA). Lines homozygous for cpr5 and either the SA-degrading bacterial gene nahG or the SA-insensitive mutation npr1 do not express PR-1 or exhibit resistance to P. s. maculicola ES4326. Therefore, we conclude that cpr5 acts upstream of SA in inducing SAR. However, the cpr5 npr1 plants retained heightened resistance to P. parasitica Noco2 and elevated expression of the defensin gene PDF1.2, implying that NPR1-independent resistance signaling also occurs. We conclude that the cpr5 mutation leads to constitutive expression of both an NPR1-dependent and an NPR1-independent SAR pathway. Identification of this mutation indicates that these pathways are connected in early signal transduction steps and that they have overlapping functions in providing resistance.
ISSN:1040-4651
1532-298X
DOI:10.1105/tpc.9.9.1573