Photoperiod Following Inoculation of Arabidopsis with (syn. ) Influences on the Plant-Pathogen Interaction.

In plant-pathogen interactions, a proper light environment affects the establishment of defense responses in plants. In our previous experiments, we found that nonhost resistance (NHR) to Cav. in (L.) Heynh. (Arabidopsis), in diurnal conditions, varies with the inoculation time. Moreover, we indicated that the circadian clock plays an important role in regulating time-of-day differences in NHR to in Arabidopsis. However, the involvement of photoperiod in regulating NHR was still not understood. To determine the photoperiod role, we performed the experiments in continuous light and darkness during the early Arabidopsis- interaction. We found that the light period after the inoculation in the evening enhanced the resistance to penetration. However, the dark period after the inoculation in the morning suppressed the penetration resistance. Furthermore, the genetic analysis indicated that jasmonic acid, reactive oxygen species, and tryptophan-derived metabolite(s) contribute to the photoperiod regulation of NHR in Arabidopsis. The present results denote that photoperiod plays an important role in regulating time-of-day differences in NHR to in Arabidopsis.