RT Journal Article SR Electronic T1 Synchronization of Circadian Clock Gene Expression in Arabidopsis and Hyaloperonospora arabidopsidis and its Impact on Host-Pathogen Interactions JF bioRxiv FD Cold Spring Harbor Laboratory SP 2024.03.27.586998 DO 10.1101/2024.03.27.586998 A1 Telli, Osman A1 Göl, Deniz A1 Jin, Weibo A1 Cevher-Keskin, Birsen A1 Hong, Yiguo A1 McDowell, John M. A1 Studholme, David J. A1 Tör, Mahmut YR 2024 UL http://biorxiv.org/content/early/2024/03/30/2024.03.27.586998.abstract AB Organisms across all kingdoms have an internal circadian clock running in 24h cycles. This clock affects a variety of processes, including innate immunity in plants. However, the role of pathogen circadian clocks had not been extensively explored. We previously showed that light can influence infection of the oomycete Hyaloperonospora arabidopsidis (Hpa, downy mildew disease) on its natural host Arabidopsis thaliana. Here, we identified Hpa orthologs of known circadian clock genes (CCGs) Drosophila TIMELESS (TIM) and Arabidopsis Sensitive to Red Light Reduced 1 (AtSRR1) genes. Expression of both HpaTIM and HpaSRR1 showed a circadian rhythm when Hpa was exposed to constant light. Contrastingly, these two genes were negatively regulated by constant dark exposure. Furthermore, the expression patterns of HpaTIM and HpaSRR1 correlate with those of AtCCA1 and AtLHY, indicating a synchronisation of biological clock genes between the host and the pathogen. In addition, screening mutants of Arabidopsis Clock Regulated Genes (AtCRGs) with three virulent Hpa isolates revealed that mutations in AtCRGs influenced HpaTIM and HpaSRR1 expression and Hpa development, indicating a functional link between the plant biological clock and virulence. Moreover, sporulation of Hpa was reduced by targeting HpaTIM and HpaSRR1 with short synthesized small interfering RNAs, indicating that the pathogen clock is also relevant to virulence. We propose that plant and pathogen clocks are synchronized during infection and that proper regulation of both clocks are genetically necessary for pathogen virulence.Competing Interest StatementThe authors have declared no competing interest.