阿拉伯芥LONG HYPOCOTYL IN FAR-RED 1參與光與FAR-RED INSENSITIVE 219/JAR1的茉莉酸訊息傳遞路徑中調控phytochrome B形成光小體之功能性研究

Abstract

植物生長與發育會受到外界光環境與內在荷爾蒙訊息的共同調控，尤其在自然環境中光的變化與植物本身的防禦需求常會互相牴觸，因此植物必須依據環境變化，在生長與防禦之間做出平衡。茉莉酸（jasmonate，JA）作為植物重要的防禦荷爾蒙之一，其訊息傳遞會與光訊號交互作用來調節植物對逆境的反應。前人研究指出，紅光主要的接受器 phytochrome B（phyB）除了參與光形態發生外，也可與 FAR-RED INSENSITIVE 219（FIN219）結合，進一步調控茉莉酸訊息傳遞與光小體（photobody，PB）的形成。在遮陰環境下，非活化態的phyB會與去磷酸化的 FIN219結合，抑制茉莉酸下游訊息傳遞路徑並使得PB無法形成，從而促進阿拉伯芥下胚軸的延長。此外FIN219亦可與轉錄因子LONG HYPOCOTYL IN FAR-RED 1（HFR1）互相調節，共同參與遮陰反應與茉莉酸調控的訊息路徑。綜合以上研究顯示HFR1、phyB與FIN219這三者之間可能存在更廣泛的交互關係與調控網路，以及我們想進一步了解他們對於光與茉莉酸訊息路徑中的交互作用與功能。我們發現HFR1不僅在各種光條件下皆會與phyB、FIN219相互作用，並且在遠紅光、藍光與遮陰環境下三者會協同調控下胚軸的延長。此外HFR1與FIN219之間的交互作用位置會受到外源性茉莉酸（MeJA）處理所影響，反映出HFR1在光與荷爾蒙訊號之間的關鍵功能。本研究也首次揭示HFR1不僅參與光形態發生的調控，還影響phyB所召集形成的PB型態與分布而改變其數量與大小，顯示其對於PB組成與調控中扮演結構性角色。這些結果進一步證實HFR1在phyB介導之光訊號與FIN219的茉莉酸訊息路徑整合中具有多面向調節功能。總結而言，我們的研究證實HFR1參與光與茉莉酸訊息傳遞路徑的調控，並且與phyB、FIN219共同協同調控下胚軸延長與PB的型態，這些結果都表示HFR1是作為整合光與荷爾蒙訊息的核心之一，在植物生長與防禦平衡策略中扮演關鍵角色。本研究建構出HFR1–phyB–FIN219的模組，作為光與荷爾蒙訊號交互作用的嶄新見解，未來將可進一步探討植物生長與防禦相關的下游基因表現，以及檢測花青素與葉綠素的含量變化，以更全面了解此調控網路在植物生理上的功能意義與生態適應策略。

The interaction between light and jasmonates (JAs) is critical in regulating plant growth and defense responses. Previous studies revealed that the inactive Pr form of phytochrome B (phyB) binds to the dephosphorylated FAR-RED INSENSITIVE 219 (FIN219)/JASMONATE RESISTANT1 (JAR1), inhibiting JA signaling pathway and phyB-associated photobodies (PBs) formation under shade. Additionally, FIN219 and the transcription factor LONG HYPOCOTYL IN FAR-RED 1 (HFR1) mutually regulate each other, mediating downstream shade-inducible genes and JA signaling. According to these studies, I want to understand whether HFR1 regulates phyB-associated PBs, the relationship among these three proteins, and the role of HFR1 in light and JA signaling pathways. To figure out these questions, I generated hfr1-201 phyB-1 double mutant, fin219-2 phyB-1 hfr1-201 triple mutant, and overexpression lines. Current study demonstrates that HFR1 participates in far-red, blue, and shade light signaling pathways, co-regulating hypocotyl elongation with phyB and FIN219. Through the transient assay, HFR1 physically interacts with phyB and FIN219 under various light conditions, with exogenous methyl jasmonate (MeJA) influencing their interaction, which suggests that HFR1 plays a significant role in phyB-mediated light signaling and JA signaling. Importantly, we also found that HFR1 mediated phyB-associated PBs formation and pattern under the high R: FR light condition and was influenced by MeJA treatment. Taken together, HFR1 participates in the light and JA signaling pathways and plays a significant role in the trade-offs between growth and defense in Arabidopsis. Shortly, I will have a better understanding and insights into light and hormone-integrated regulatory mechanisms in plants.