Timing of plant immune responses by a central circadian regulator

Feb 5, 2011Nature

Plant immune responses controlled by the body’s internal clock

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Abstract

Identification of novel genes reveals that programmed cell death (PCD) is central to R-gene-mediated resistance against downy mildew in plants.

New genes involved in R-gene-mediated resistance were identified in Arabidopsis.
Programmed cell death (PCD) significantly contributes to the resistance against downy mildew.
Mutants lacking R-gene-mediated PCD also showed defects in basal resistance.
The circadian regulator CCA1 controls the expression of these defence genes.
Plants may time their immune responses to match pathogen spore dispersal at dawn.

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The principal immune mechanism against biotrophic pathogens in plants is the resistance (R)-gene-mediated defence. It was proposed to share components with the broad-spectrum basal defence machinery. However, the underlying molecular mechanism is largely unknown. Here we report the identification of novel genes involved in R-gene-mediated resistance against downy mildew in Arabidopsis and their regulatory control by the circadian regulator, CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1). Numerical clustering based on phenotypes of these gene mutants revealed that programmed cell death (PCD) is the major contributor to resistance. Mutants compromised in the R-gene-mediated PCD were also defective in basal resistance, establishing an interconnection between these two distinct defence mechanisms. Surprisingly, we found that these new defence genes are under circadian control by CCA1, allowing plants to 'anticipate' infection at dawn when the pathogen normally disperses the spores and time immune responses according to the perception of different pathogenic signals upon infection. Temporal control of the defence genes by CCA1 differentiates their involvement in basal and R-gene-mediated defence. Our study has revealed a key functional link between the circadian clock and plant immunity.

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Timing of plant immune responses by a central circadian regulator

Abstract

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