探討阿拉伯芥F-box蛋白EID1透過與phyB以及ELF3交互作用在生物時鐘與下胚軸生長的影響

Abstract

光訊號在植物的生長、發育及環境適應中扮演關鍵角色。除了光以外，生理時鐘亦調控多種生長途徑，並與光訊號路徑整合，以優化植物對環境變化的反應。EMPFINDLICHER IM DUNKELROTEN LICHT 1（EID1）是一個帶有F-box domain的 E3 泛素連接酶，過去研究指出其在番茄中參與生物時鐘節律調控，而在大豆中則透過與時鐘調控因子 Evening Complex（EC）相關的 J complex 交互作用，調節光週期所介導的開花路徑。EID1 在阿拉伯芥中，被視為 phyA 訊號途徑的負向調控者。然而，在阿拉伯芥中，EID1 在整合光訊號與生理時鐘兩條路徑間所扮演的角色仍不清楚。 先前我們實驗室利用 TurboID 鄰近蛋白標記技術，鑑定出可能與EID1有交互作用並與光訊號與時鐘調路徑相關的蛋白質，當中包括phytochrome B（phyB）、EARLY FLOWERING 3（ELF3）以及 GIGANTEA（GI）。本篇論文中，我進一步確定了 EID1 與 phyA、phyB、GI以及 EC 三個核心成員（ELF3、ELF4 與 LUX）之間的交互作用。發現EID1 透過轉譯後機制，在長日照條件下影響 ELF3 蛋白的節律性累積的穩定性。然而EID1 並不影響與ELF3相關的時鐘基因的晝夜節律。在下胚軸伸長的調控方面，EID1 在長日照或短日照的白光條件下皆不影響下胚軸生長；然而，在連續紅光下，EID1 則表現為下胚軸生長的正向調控者。儘管 EID1並不影響 PHYB 蛋白的晝夜節律，但會在特定紅光條件下改變phyB在細胞核中的定位。此外，我們也發現已知與 phyB 核定位相關的蛋白 PCH1.2與 EID1 有物理性的交互作用。綜上所述，本論文結果指出：EID1 可能透過調控 phyB 的核內定位，抑或透過調節 ELF3 的節律性累積，進而參與了在紅光條件下對下胚軸伸長的調控。

Light signaling is fundamental for plant growth, development, and environmental adaptation. In addition to light, the circadian clock also orchestrates various growth pathways and integrates with light signaling networks to optimize plant responses to environmental changes. EMPFINDLICHER IM DUNKELROTEN LICHT 1 (EID1), an F-box E3 ubiquitin ligase, has been implicated in circadian regulation in tomato and photoperiod-mediated flowering pathway in soybean through interaction with the clock regulator Evening Complex (EC)-related J complex. EID1 is known as a negative regulator of the phyA signaling pathway. However, the role of EID1 in integrating light and circadian pathways in Arabidopsis thaliana remains unclear. Previously, our lab employed TurboID-based proximity labeling and identified potential interactions between EID1 and multiple light signaling and clock regulator proteins, including photoreceptor phytochrome B (phyB), EC component EARLY FLOWERING 3 (ELF3), and GIGANTEA (GI). In this study, I determined the interactions between EID1, phyA, phyB, GI, and all three Evening Complex components, including ELF3, ELF4, and LUX ARRHYTHMO (LUX). Notably, EID1 is required to maintain the rhythmic accumulation of ELF3 protein under long-day conditions via a post-translational mechanism, while it does not affect the circadian rhythms of ELF3-related clock genes under diurnal light cycles. For the regulation of hypocotyl elongation, EID1 did not alter hypocotyl elongation under white light in either long- or short-day conditions. However, under continuous red light, EID1 acted as a positive regulator of hypocotyl growth. While EID1 did not influence the diurnal expression of PHYB protein, it affected its nuclear localization under specific red-light conditions. Interestingly, we also found that PCH1.2, a known phyB interactor involved in nuclear translocation, physically interacts with EID1. Together, my findings suggest that EID1 modulates hypocotyl elongation under red light by regulating the nuclear localization of phyB or the rhythmic accumulation of ELF3.