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Darkness and gulliver2 / phy B mutation decrease the abundance of phosphorylated BZR 1 to activate brassinosteroid signaling in A rabidopsis
Author(s) -
Kim Bokyung,
Jeong Yu Jeong,
Corvalán Claudia,
Fujioka Shozo,
Cho Seoae,
Park Taesung,
Choe Sunghwa
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12423
Subject(s) - chemistry , phosphorylation , abundance (ecology) , darkness , brassinosteroid , biochemistry , biology , mutant , botany , gene , arabidopsis , fishery
Summary Light is essential for plant survival; as such, plants flexibly adjust their growth and development to best harvest light energy. Brassinosteroids ( BR s), plant growth‐promoting steroid hormones, are essential for this plasticity of development. However, the precise mechanisms underlying BR ‐mediated growth under different light conditions remain largely unknown. Here, we show that darkness increases the activity of the BR ‐specific transcription factor, BZR 1, by decreasing the phosphorylated (inactive) form of BZR 1 in a proteasome‐dependent manner. We observed that COP 1, a dark‐activated ubiquitin ligase, captures and degrades the inactive form of BZR 1. In support of this, BZR 1 is abundant in the cop1‐4 mutant. The removal of phosphorylated BZR 1 in darkness increases the ratio of dephosphorylated to phosphorylated forms of BZR 1, thus increasing the chance of active homodimers forming between dephosphorylated BZR 1 proteins. Furthermore, a transcriptome analysis revealed the identity of genes that are likely to contribute to the differential growth of hypocotyls in light conditions. Transgenic misexpression of three genes under the 35 S promoter in light conditions resulted in elongated petioles and hypocotyls. Our results suggest that light conditions directly control BR signaling by modulating BZR 1 stability, and consequently by establishing light‐dependent patterns of hypocotyl growth in A rabidopsis.