Fig. 8: A working model of UV-B responses in Arabidopsis and rice.
From: Nuclear accumulation of rice UV-B photoreceptors is UV-B- and OsCOP1-independent for UV-B responses
In response to UV-B light (left panel), monomerization of the Arabidopsis UV-B receptor AtUVR8 leads to the nuclear accumulation of active AtUVR8, which interacts with AtCOP1 and other signaling factors including MYB and WRKY transcription factors, resulting in the expression of growth- and stress-related genes and regulation of plant development and acclimation. The rice UV-B receptors OsUVR8a and OsUVR8b are constitutively present in the nucleus via their NLS; in response to UV-B light (right panel), OsUVR8a and OsUVR8b also monomerize and activate transcription of growth- and stress-related genes to regulate plant development and acclimation. However, OsUVR8a and OsUVR8b accumulate in the nucleus independently of UV-B light and OsCOP1, and may mediate UV-B responsive gene expression in concert with transcription factors such as MYB and basic helix-loop-helix (bHLH) family members. OsUVR8a and OsUVR8b have weak interaction with OsCOP1 which is a repressor in rice UV-B responses. UV-B light predominantly upregulates the expression of growth-related genes and downregulates that of stress-related genes in Arabidopsis, whereas these transcriptional patterns are reversed in rice.
