Plants are frequently challenged by various pathogens. The circadian clock, which is the internal time measuring machinery, has been implicated in regulating plant responses to biotic cues. To better understand the role of the circadian clock in defense control, we tested disease resistance with Arabidopsis mutants disrupted in CCA1 and LHY , two key components of the circadian clock. We found that consistent with their contributions to the circadian clock, cca1 and lhy mutants synergistically affect resistance to both bacterial and oomycete pathogens. Disrupting the circadian clock caused by overexpression of CCA1 or LHY also results in severe disease susceptibility. Thus, our data further demonstrate a direct role of the circadian clock mediated by CCA1 and LHY in defense regulation. We also found that CCA1 and LHY act independently of salicylic acid mediated defense but at least through the down- stream target gene GRP7 to regulate both stomata- dependent and -independent pathways. We further show that defense activation by bacterial infection and the treatment with the elicitor flg22 can also feed back to regulate clock activity. Together our study reveals for the first time reciprocal regulation of the circadian clock and plant innate immunity, significantly expanding our view of complex gene networks regulating plant defense responses and development.
Zhang, Chong; Xie, Qiguang; Anderson, Ryan G.; Ng, Gina; Seitz, Nicjolas C.; Peterson, Thomas; Robertson McClung, C.; McDowell, John M.; Kong, Dongdong; Kwak, June M.; and Lu, Hua, "Crosstalk between the Circadian Clock and Innate Immunity in Arabidopsis" (2013). Open Dartmouth: Faculty Open Access Articles. 2605.