RNA Biology and Molecular Physiology

Circadian Clock Control of Pathogen Defense

Circadian control of immune responses has been well documented in mammals.

We are interested in the impact of the circadian clock on plant immune responses and in the consequences of an impaired endogenous timing system on plant defense.

Flg22-triggered oxidative burst is higher upon infiltration in the subjective morning than upon infiltration in the subjective evening.

Time-of-day dependence is lost in the arrhythmic mutant lux/pcl1 mutant

Flg22-triggered expression of WRKY22 is higher upon infiltration in the subjective morning than upon infiltration in the subjective evening.

Time-of-day dependence is lost in the arrhythmic mutant lux/pcl1 mutant.

When Pseudomonas syringae DC3000 (avrRpt2) bacteria are syringe-infiltrated into the leaf, defense gene induction varies with a circadian rhythm with a peak in the subjective morning.

When bacteria are syringe-infiltrated into the leaf, bacterial growth is suppressed more strongly after morning inoculation than after evening inoculation (A).

When bacteria are spray-inoculated onto the leaf surface bacterial growth is suppressed more strongly after evening inoculation than after morning inoculation (B).

Thus, the circadian clock differentially controls two aspects of defense, the preinvasive defense through closure of stomata later in the day, and the postinvasive defense.