Plant growth is controlled by integration of hormonal and light-signaling pathways. BZS1 is a B-box zinc finger protein previously characterized as a negative regulator in the brassinosteroid （BR）-signaling pathway ...Plant growth is controlled by integration of hormonal and light-signaling pathways. BZS1 is a B-box zinc finger protein previously characterized as a negative regulator in the brassinosteroid （BR）-signaling pathway and a positive regulator in the light-signaling pathway. However, the mechanisms by which BZS1/BBX20 integrates light and hormonal pathways are not fully understood. Here, using a quantitative proteomic workflow, we identified several BZSl-associated proteins, including light-signaling compo- nents COP1 and HY5. Direct interactions of BZS1 with COPI and HY5 were verified by yeast two-hybrid and co-immunoprecipitation assays. Overexpression of BZS1 causes a dwarf phenotype that is sup- pressed by the by5 mutation, while overexpression of BZSI fused with the SRDX transcription repressor domain （BZS1-SRDX） causes a long-hypocotyl phenotype similar to by5, indicating that BZSI＇s function requires HY5. BZSI positively regulates HY5 expression, whereas HY5 negatively regulates BZS1 protein level, forming a feedback loop that potentially contributes to signaling dynamics. In contrast to BR, strigolactone （SL） increases BZS1 level, whereas the SL responses of hypocoryl elongation, chlorophyll and HY5 accumulation are diminished in the BZSI-SRDX seedlings, indicating that BZS1 is involved in these SL responses. These results demonstrate that BZS1 interacts with HY5 and plays a central role in integrating light and multiple hormone signals for photomorphogenesis in Arabidopsis.展开更多
基金supported by a grant from National Institute of Health (NIH, R01GM066258)“One-hundred Talents Project” of Hebei province, China (E2013100004)supported by the China Scholarship Council
文摘Plant growth is controlled by integration of hormonal and light-signaling pathways. BZS1 is a B-box zinc finger protein previously characterized as a negative regulator in the brassinosteroid （BR）-signaling pathway and a positive regulator in the light-signaling pathway. However, the mechanisms by which BZS1/BBX20 integrates light and hormonal pathways are not fully understood. Here, using a quantitative proteomic workflow, we identified several BZSl-associated proteins, including light-signaling compo- nents COP1 and HY5. Direct interactions of BZS1 with COPI and HY5 were verified by yeast two-hybrid and co-immunoprecipitation assays. Overexpression of BZS1 causes a dwarf phenotype that is sup- pressed by the by5 mutation, while overexpression of BZSI fused with the SRDX transcription repressor domain （BZS1-SRDX） causes a long-hypocotyl phenotype similar to by5, indicating that BZSI＇s function requires HY5. BZSI positively regulates HY5 expression, whereas HY5 negatively regulates BZS1 protein level, forming a feedback loop that potentially contributes to signaling dynamics. In contrast to BR, strigolactone （SL） increases BZS1 level, whereas the SL responses of hypocoryl elongation, chlorophyll and HY5 accumulation are diminished in the BZSI-SRDX seedlings, indicating that BZS1 is involved in these SL responses. These results demonstrate that BZS1 interacts with HY5 and plays a central role in integrating light and multiple hormone signals for photomorphogenesis in Arabidopsis.
