Circadian Regulation of the Rice Immune Response during Rice Blast Infection via Metabolic and Calcium Signaling

The circadian clock is crucial in plant immunity and
metabolism,
yet the coordinating mechanisms remain elusive. In the present study,
transcriptome analysis of M. oryzae-infected rice leaves and rhythmic analysis showed reduced amplitudes
of circadian and phytochrome genes, impacting immune response, metabolic
pathways, and calcium signaling. The amplitudes of pattern-triggered
immunity (PTI)-related genes declined, while the rhythmicity of effector-triggered
immunity (ETI)-related genes disappeared. Moreover, alterations in
the phases of metabolic pathways were observed, potentially involved
in immune response regulation like phytohormone biosynthesis. Calcium
signaling exhibited a circadian pattern similar to that of the whole-transcriptome
analysis. The administration of CaCl2 alleviated, whereas
the calcium ion chelator EGTA aggravated, the phenotypes of rice blasts,
suggesting their role in regulating the circadian clock-mediated immune
response in rice. Our study highlighted the significance of circadian
regulation in rice blast-induced immune modulation, which may contribute
to developing immunomodulators and the formulation of chronobiology-based
precise therapeutic regimens.