Department of Botany and Plant Biology, Section of Biology, Faculty of Sciences, University of Geneva, 30 Quai E. Ansermet, 1211, Geneva 4, Switzerland.
Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Geneva, Switzerland.
Nat Commun. 2020 Mar 12;11(1):1323. doi: 10.1038/s41467-020-15133-y.
UV-B constitutes a critical part of the sunlight reaching the earth surface. The homodimeric plant UV-B photoreceptor UV RESISTANCE LOCUS 8 (UVR8) monomerizes in response to UV-B and induces photomorphogenic responses, including UV-B acclimation and tolerance. REPRESSOR OF UV-B PHOTOMORPHOGENESIS 1 (RUP1) and RUP2 are negative feedback regulators that operate by facilitating UVR8 ground state reversion through re-dimerization. Here we show that RUP1 and RUP2 are transcriptionally induced by cryptochrome photoreceptors in response to blue light, which is dependent on the bZIP transcriptional regulator ELONGATED HYPOCOTYL 5 (HY5). Elevated RUP1 and RUP2 levels under blue light enhance UVR8 re-dimerization, thereby negatively regulating UVR8 signalling and providing photoreceptor pathway cross-regulation in a polychromatic light environment, as is the case in nature. We further show that cryptochrome 1, as well as the red-light photoreceptor phytochrome B, contribute to UV-B tolerance redundantly with UVR8. Thus, photoreceptors for both visible light and UV-B regulate UV-B tolerance through an intricate interplay allowing the integration of diverse sunlight signals.
UV-B 构成了到达地球表面的阳光的重要组成部分。同源二聚体植物 UV-B 光受体 UV 抗性位点 8（UVR8）在 UV-B 的响应下单体化，并诱导光形态发生反应，包括 UV-B 适应和耐受。UV-B 光形态建成抑制物 1（RUP1）和 RUP2 是负反馈调节剂，通过促进 UVR8 基态回复通过再二聚化来发挥作用。在这里，我们表明 RUP1 和 RUP2 是在蓝光响应下被隐花色素光受体转录诱导的，这依赖于 bZIP 转录调节剂伸长的下胚轴 5（HY5）。蓝光下 RUP1 和 RUP2 水平的升高增强了 UVR8 的再二聚化，从而负调控 UVR8 信号，并在多色光环境中提供光受体途径的交叉调控，就像在自然界中一样。我们进一步表明，隐花色素 1 以及红光光受体光敏色素 B 与 UVR8 冗余地有助于 UV-B 耐受。因此，可见光和 UV-B 的光受体通过复杂的相互作用调节 UV-B 耐受，从而整合各种太阳光信号。
