Figure 8.

Model for the protective function of cytokinin in the light stress response. HL causes the inhibition of the active PSII and the production of ROS, which can also inhibit D1 repair (dotted black lines). Plants have evolved several mechanisms, such as ROS scavenging and the D1 repair cycle, to counteract the destructive effect of too much light (light gray boxes and solid black lines). Cytokinin (CK) has protective functions in the light stress response by promoting both ROS scavenging and D1 repair (gray lines), which is mediated by the AHK2 and AHK3 receptors and the type B response regulators ARR1 and ARR12 acting downstream of the receptors. The involvement of ARR1 and ARR12 has been concluded based on the results shown in Figure 7B.