The involvement of the N -terminal PHR domain of Arabidopsis cryptochromes in mediating light signaling.

Light is a key environmental cue that fundamentally regulates all aspects of plant growth and development, which is mediated by the multiple photoreceptors including the blue light photoreceptors cryptochromes (CRYs). In Arabidopsis , there are two well-characterized homologous CRYs, CRY1 and CRY2. Whereas CRYs are flavoproteins, they lack photolyase activity and are characterized by an N -terminal photolyase-homologous region (PHR) domain and a C-terminal extension domain. It has been established that the C-terminal extension domain of CRYs is involved in mediating light signaling through direct interactions with the master negative regulator of photomorphogenesis, COP1. Recent studies have revealed that the N -terminal PHR domain of CRYs is also involved in mediating light signaling. In this review, we mainly summarize and discuss the recent advances in CRYs signaling mediated by the N -terminal PHR domain, which involves the N -terminal PHR domain-mediated dimerization/oligomerization of CRYs and physical interactions with the pivotal transcription regulators in light and phytohormone signaling.