Gil Kyung-Eun, Park Mi-Jeong, Lee Hyo-Jun, Park Young-Joon, Han Shin-Hee, Kwon Young-Ju, Seo Pil Joon, Jung Jae-Hoon, Park Chung-Mo
Department of Chemistry, Seoul National University, Seoul, 08826, Korea.
Plant J. 2017 Jan;89(1):128-140. doi: 10.1111/tpj.13351. Epub 2016 Dec 5.
The circadian clock control of CONSTANS (CO) transcription and the light-mediated stabilization of its encoded protein coordinately adjust photoperiodic flowering by triggering rhythmic expression of the floral integrator flowering locus T (FT). Diurnal accumulation of CO is modulated sequentially by distinct E3 ubiquitin ligases, allowing peak CO to occur in the late afternoon under long days. Here we show that CO abundance is not simply targeted by E3 enzymes but is also actively self-adjusted through dynamic interactions between two CO isoforms. Alternative splicing of CO produces two protein variants, the full-size COα and the truncated COβ lacking DNA-binding affinity. Notably, COβ, which is resistant to E3 enzymes, induces the interaction of COα with CO-destabilizing E3 enzymes but inhibits the association of COα with CO-stabilizing E3 ligase. These observations demonstrate that CO plays an active role in sustaining its diurnal accumulation dynamics during Arabidopsis photoperiodic flowering.
生物钟对CONSTANS（CO）转录的调控以及光介导的其编码蛋白的稳定性，通过触发开花整合因子开花位点T（FT）的节律性表达，协同调节光周期开花。CO的昼夜积累由不同的E3泛素连接酶依次调节，使得在长日照下CO在下午晚些时候达到峰值。我们在此表明，CO的丰度不仅受E3酶的靶向作用，还通过两种CO异构体之间的动态相互作用进行主动自我调节。CO的可变剪接产生两种蛋白质变体，全长的COα和缺乏DNA结合亲和力的截短型COβ。值得注意的是，对E3酶有抗性的COβ会诱导COα与使CO不稳定的E3酶相互作用，但会抑制COα与使CO稳定的E3连接酶的结合。这些观察结果表明，在拟南芥光周期开花过程中，CO在维持其昼夜积累动态方面发挥着积极作用。
