Zhang Xuebin, Abrahan Carolina, Colquhoun Thomas A, Liu Chang-Jun
Biology Department, Brookhaven National Laboratory, Upton, New York 11973.
Department of Environmental Horticulture, Plant Innovation Center, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida 32611.
Plant Cell. 2017 May;29(5):1157-1174. doi: 10.1105/tpc.16.00855. Epub 2017 Apr 26.
Flavonoids represent a large family of specialized metabolites involved in plant growth, development, and adaptation. Chalcone synthase (CHS) catalyzes the first step of flavonoid biosynthesis by directing carbon flux from general phenylpropanoid metabolism to flavonoid pathway. Despite extensive characterization of its function and transcriptional regulation, the molecular basis governing its posttranslational modification is enigmatic. Here, we report the discovery of a proteolytic regulator of CHS, namely, KFB, a Kelch domain-containing F-box protein in KFB physically interacts with CHS and specifically mediates its ubiquitination and degradation. exhibits developmental expression patterns in Arabidopsis leaves, stems, and siliques and strongly responds to the dark-to-light (or the light-to-dark) switch, the blue, red, and far-red light signals, and UV-B irradiation. Alteration of expression negatively correlates to the cellular concentration of CHS and the production of flavonoids. Our study suggests that KFB serves as a crucial negative regulator, via mediating CHS degradation, coordinately controlling flavonoid biosynthesis in response to the developmental cues and environmental stimuli.
类黄酮是参与植物生长、发育和适应的一大类特殊代谢产物。查尔酮合酶（CHS）通过引导碳流从一般苯丙烷类代谢进入类黄酮途径，催化类黄酮生物合成的第一步。尽管对其功能和转录调控进行了广泛的表征，但其翻译后修饰的分子基础仍然是个谜。在这里，我们报告了一种CHS的蛋白水解调节因子的发现，即KFB，一种拟南芥中含有Kelch结构域的F-box蛋白。KFB与CHS发生物理相互作用，并特异性介导其泛素化和降解。KFB在拟南芥的叶片、茎和角果中呈现发育表达模式，并对从黑暗到光照（或从光照到黑暗）的转换、蓝光、红光和远红光信号以及UV-B辐射有强烈响应。KFB表达的改变与CHS的细胞浓度和类黄酮的产生呈负相关。我们的研究表明，KFB作为一个关键的负调节因子，通过介导CHS的降解，响应发育线索和环境刺激，协调控制类黄酮的生物合成。
