title: Both PHYTOCHROME RAPIDLY REGULATED1 (PAR1) and PAR2 promote seedling photomorphogenesis in multiple light signaling pathways.
abstract: Arabidopsis (Arabidopsis thaliana) seedlings undergo photomorphogenesis in the light and etiolation in the dark. Light-activated photoreceptors transduce the light signals through a series of photomorphogenesis promoting or repressing factors to modulate many developmental processes in plants, such as photomorphogenesis and shade avoidance. CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) is a conserved RING finger E3 ubiquitin ligase, which mediates degradation of several photomorphogenesis promoting factors, including ELONGATED HYPOCOTYL5 (HY5) and LONG HYPOCOTYL IN FAR-RED1 (HFR1), through a 26S proteasome-dependent pathway. PHYTOCHROME RAPIDLY REGULATED1 (PAR1) was first detected as an early repressed gene in both phytochrome A (phyA)-mediated far-red and phyB-mediated red signaling pathways, and subsequent studies showed that both PAR1 and PAR2 are negative factors of shade avoidance in Arabidopsis. However, the role of PAR1 and PAR2 in seedling deetiolation, and their relationships with other photomorphogenesis promoting and repressing factors are largely unknown. Here, we confirmed that both PAR1 and PAR2 redundantly enhance seedling deetiolation in multiple photoreceptor signaling pathways. Their transcript abundances are repressed by phyA, phyB, and cryptochrome1 under far-red, red, and blue light conditions, respectively. Both PAR1 and PAR2 act downstream of COP1, and COP1 mediates the degradation of PAR1 and PAR2 through the 26S proteasome pathway. Both PAR1 and PAR2 act in a separate pathway from HY5 and HFR1 under different light conditions, except for sharing in the same pathway with HFR1 under far-red light. Together, our results substantiate that PAR1 and PAR2 are positive factors functioning in multiple photoreceptor signaling pathways during seedling deetiolation.
authors: Institute of Crop Science , Chinese Academy of Agricultural Sciences, Beijing 100081, China.
authors: Peng
authors: P
authors: Zhou
authors: Meifang
authors: M
authors: Song
authors: Qinghua
authors: Q
authors: Yang
authors: Liang
authors: L
authors: Su
authors: Pei
authors: P
authors: Hou
authors: Lin
authors: L
authors: Guo
authors: Xu
authors: X
authors: Zheng
authors: Yulin
authors: Y
authors: Xi
authors: Fanhua
authors: F
authors: Meng
authors: Yang
authors: Y
authors: Xiao
authors: Li
authors: L
authors: Yang
authors: Jianping
authors: J
authors: Yang
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D064527:Etiolation / Q000528:radiation effects; D018546:Hypocotyl / Q000254:growth & development / Q000528:radiation effects; D008027:Light; D055537:Light Signal Transduction / Q000528:radiation effects*; D008954:Models, Biological; D009024:Morphogenesis / Q000528:radiation effects*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D059748:Proteolysis / Q000528:radiation effects; D034622:RNA Interference / Q000528:radiation effects; D036226:Seedlings / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; C524961:PAR1 protein, Arabidopsis; C524962:PAR2 protein, Arabidopsis