Phototropin signaling and stomatal opening as a model case

Phototropins are plant-specific light-activated receptor kinases that regulate diverse blue-light-induced responses, and serve to optimize plant growth under various light environments. Phototropins undergo autophosphorylation as an essential step for their signaling and induce a variety of tissue-specific or organ-specific responses, but the divergent mechanisms for these responses are unknown. It is most likely that the phototropins generate a specific output after the event of autophosphorylation. In this report, we will review the common steps of phototropin signaling and the numerous interactive proteins of phototropins, which may act as signal transducers for the diverse responses. We also describe the phototropin-mediated signaling process of stomatal guard cells and its crosstalk with abscisic acid signaling.

Research highlights▶ Phototropins are activated by blue light via autophosphorylation in the activation loop. ▶ Phototropins interact with many partners and generate divergent responses. ▶ Role of phototropins is to optimize plant growth by increasing photosynthesis. ▶ Guard cells are excellent model for investigating phototropin signaling. ▶ Abscisic acid represses phototropin-mediated stomatal opening via inhibiting PP1.