Circadian Rhythms Mediate Jinggangmycin's Suppression of Magnaporthe oryzae Pathogenicity

Circadian rhythms are endogenous regulatory mechanisms evolved by organisms to adapt to periodic light-dark changes. Circadian rhythms can regulate the pathogenicity of fungal pathogens, but the underlying mechanisms remain unclear. Casein kinase 2 (CK2) is an essential component for the normal functioning of fungal circadian rhythms, with the CKa gene encoding its alpha subunit. To investigate the action mechanism of JGM in the pathogenicity of the rice blast fungus via circadian rhythm, ΔMocka and ΔMocka' mutants was generated using gene-editing technology. We observed that the deletion of Mocka resulted in altered amplitudes and phases of circadian rhythm genes relative to the wild type (WT). Additionally, the Mocka deletion influenced the sporulation capacity of Magnaporthe oryzae as well as infectivity. Jinggangmycin (JGM) is an aminoglycoside antibiotic primarily used to control rice sheath blight. The use of JGM has been shown to increase the antioxidant capacity of rice seedlings by enhancing the activity of catalase (CAT) and peroxidase (POD), and it causes the differential expression of rice resistance genes. The deletion of the Mocka gene in M. oryzae weakened its ability to suppress the rice immune response and led to a reduced antioxidant capacity and a significant decrease in callose deposition in rice. Also, the effect of JGM on wild-type M. oryzae was associated with the circadian rhythm. We suggest that Mocka plays a critical role in the pathogenicity of M. oryzae and its circadian rhythm, and the circadian rhythm of the fungus has an impact on the inhibitory effect exerted by JGM. In summary, our findings deepen our understanding of the interconnections between JGM and the rice blast fungus's pathogenicity as well as the pathogenic mechanisms involving circadian rhythm. This research provides a theoretical basis and potential targets for both photoperiod-coordinated precise pesticide application strategies and the development of novel fungicides.