College of Life Sciences, Fujian Agriculture and Forestry University (FAFU), Fuzhou, China.
Department of Plant Biology, Carnegie Institution for Science, Stanford, California, United States of America.
PLoS Genet. 2021 May 14;17(5):e1009540. doi: 10.1371/journal.pgen.1009540. eCollection 2021 May.
Sugar, light, and hormones are major signals regulating plant growth and development, however, the interactions among these signals are not fully understood at the molecular level. Recent studies showed that sugar promotes hypocotyl elongation by activating the brassinosteroid (BR) signaling pathway after shifting Arabidopsis seedlings from light to extended darkness. Here, we show that sugar inhibits BR signaling in Arabidopsis seedlings grown under light. BR induction of hypocotyl elongation in seedlings grown under light is inhibited by increasing concentration of sucrose. The sugar inhibition of BR response is correlated with decreased effect of BR on the dephosphorylation of BZR1, the master transcription factor of the BR signaling pathway. This sugar effect is independent of the sugar sensors Hexokinase 1 (HXK1) and Target of Rapamycin (TOR), but requires the GSK3-like kinase Brassinosteroid-Insensitive 2 (BIN2), which is stabilized by sugar. Our study uncovers an inhibitory effect of sugar on BR signaling in plants grown under light, in contrast to its promotive effect in the dark. Such light-dependent sugar-BR crosstalk apparently contributes to optimal growth responses to photosynthate availability according to light-dark conditions.
糖、光和激素是调节植物生长和发育的主要信号，但这些信号之间的相互作用在分子水平上尚未完全了解。最近的研究表明，在将拟南芥幼苗从光照转移到持续黑暗后，糖通过激活油菜素内酯（BR）信号通路来促进下胚轴伸长。在这里，我们表明糖在光照下生长的拟南芥幼苗中抑制 BR 信号。在光照下生长的幼苗中，BR 诱导下胚轴伸长被增加蔗糖浓度抑制。BR 对 BZR1 的去磷酸化作用的影响降低，BZR1 是 BR 信号通路的主要转录因子，BR 响应的这种抑制与 BR 反应相关。这种糖效应不依赖于糖传感器己糖激酶 1（HXK1）和雷帕霉素靶蛋白（TOR），但需要 BR 不敏感 2（BIN2）GSK3 样激酶，其受糖稳定。我们的研究揭示了光照下生长的植物中 BR 信号对糖的抑制作用，与黑暗中促进作用相反。这种光依赖的糖-BR 串扰显然有助于根据光照-黑暗条件对光合作用产物的可用性做出最佳生长反应。
