In the intricate world of plant biology, the timing of flowering—known as the floral transition—is a crucial developmental milestone that determines reproductive success. This transition is exquisitely sensitive to environmental cues, among which photoperiod (day length) and ambient temperature stand as predominant factors. Decades of research have established that plants integrate these signals through complex molecular mechanisms to decide when to shift from vegetative growth to flowering. Yet, despite significant advances, the precise molecular interplay that reconciles temperature and photoperiod signals to fine-tune flowering time has remained only partially understood. A recent breakthrough study offers a compelling glimpse into this enigma, unraveling the dynamic molecular choreography that governs flowering under varying temperatures.
Recent findings, published in Nature Plants by Lee, Kim, Park, and colleagues, shed light on how two pivotal proteins, FKF1 (FLAVIN-BINDING, KELCH REPEAT, F-BOX 1) and GIGANTEA (GI), collaborate to translate temperature cues into developmental decisions via targeted protein degradation. These proteins are central regulators of photoperiodic flowering, historically appreciated for their roles in perceiving day length. However, this work reveals a novel, temperature-dependent functionality for FKF1 and GI, especially in orchestrating the fate of SHORT VEGETATIVE PHASE (SVP), a potent floral repressor.
SVP serves as a molecular brake that delays flowering, ensuring plants do not prematurely commit to reproduction under suboptimal conditions. The study elegantly demonstrates that FKF1, an F-box protein integral to the ubiquitin-proteasome system, teams up with GI to target SVP for 26S proteasome-dependent degradation. This degradation effectively lifts the floral block imposed by SVP, thereby accelerating flowering. Intriguingly, this proteolytic regulation is modulated by ambient temperature and day length, unveiling how environmental information is integrated to drive developmental transitions.
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A striking discovery is the behavior of GI under low-temperature conditions. At reduced temperatures, GI becomes sequestered within liquid-like nuclear condensates, which are membraneless cellular compartments forming via liquid-liquid phase separation. This sequestration effectively immobilizes GI, limiting its availability to interact with FKF1 and thereby preventing SVP degradation. Conversely, elevated temperatures promote FKF1 accumulation and induce the dispersal of GI from these condensates. Freed GI then readily forms a nuclear-dispersed FKF1–GI complex capable of targeting SVP for destruction, culminating in the promotion of flowering.
The study highlights a fascinating aspect of molecular cell biology: the reversible nature of liquid-liquid phase separation as a regulatory mechanism. The temperature-dependent assembly and disassembly of GI-containing nuclear condensates represent a molecular switch that modulates flowering time in response to thermal cues. This switch appears to be finely tuned to environmental fluctuations, ensuring plants flower at the most advantageous time for reproductive success.
What makes this research particularly compelling is the demonstration that mutations in FKF1 and GI significantly diminish temperature sensitivity in flowering regulation. Mutants labeled fkf1-t, gi-2, and a combined fkf1-2 gi-2 double mutant exhibit blunted responses to temperature fluctuations, underscoring the critical involvement of these proteins in thermal-mediated flowering pathways. These genetic insights complement the biochemical findings, reinforcing the conclusion that the FKF1–GI complex is indispensable for integrating temperature signals into the flowering regulatory network.
Delving deeper into the molecular interactions, FKF1’s role as an F-box protein implicates it in forming SCF (Skp, Cullin, F-box) E3 ubiquitin ligase complexes. These complexes ubiquitinate target proteins, marking them for proteasome-mediated degradation. The identification of SVP as a substrate for FKF1-mediated ubiquitination introduces a direct mechanistic link between environmental sensing and the regulation of a floral repressor’s stability.
Moreover, this work challenges existing paradigms by positioning FKF1 and GI not only as photoperiodic sensors but also as seismic signal transducers of temperature fluctuations. The interplay of photoperiodic and thermosensory pathways at the nexus of FKF1 and GI function underlines the sophistication of plant developmental regulation. It suggests that plants have evolved multi-functional molecular hubs capable of integrating multiple environmental signals to optimize developmental timing.
The liquid-liquid phase separation phenomenon observed with GI adds an exciting dimension to our understanding of nuclear protein dynamics. Nuclear condensates have been implicated in a variety of biological processes, from gene regulation to stress responses, but their role in flowering time control had not been previously described. This discovery opens new avenues for exploring how phase separation contributes to plant adaptability and developmental plasticity.
Beyond the fundamental biological insights, the implications of this research extend into agriculture and crop science. With global climate change causing unprecedented fluctuations in temperature, understanding how plants perceive and respond to thermal signals at molecular levels is vital. The FKF1–GI–SVP axis offers a promising target for manipulation, potentially allowing breeders to engineer crops with optimized flowering times adaptable to changing climates.
In summary, the study by Lee and colleagues elucidates a sophisticated molecular mechanism by which ambient temperature modulates plant flowering through the reversible formation of nuclear condensates and the targeted proteolysis of a key floral repressor. At low temperatures, GI is sequestered in nuclear condensates, preventing its interaction with FKF1 and stabilizing SVP to delay flowering. High temperatures trigger FKF1 accumulation and GI dispersal, enabling the FKF1–GI complex to ubiquitinate SVP and promote flowering. This represents a versatile regulatory system that integrates photoperiod and temperature cues to fine-tune the timing of flowering.
This breakthrough advances our understanding of plant developmental biology by revealing how plants couple proteostasis with phase separation dynamics to translate environmental signals into physiological outcomes. It underscores the intricate layers of regulation that plants employ to ensure reproductive success across variable environments. As research continues, exploring the broader applicability of liquid-liquid phase separation in plant signaling and development will likely uncover additional regulatory modules governed by similar principles.
The significance of this research resonates beyond plant science, touching upon fundamental questions about how environmental factors are integrated at the molecular and cellular levels to dictate organismal behavior. The FKF1–GI complex emerges as a vital molecular integrator, harnessing both biochemical and biophysical principles to regulate protein stability and developmental progression. This study exemplifies how innovative molecular and biophysical approaches can illuminate longstanding biological mysteries.
As we grapple with the ecological and agricultural challenges posed by climate change, unlocking the molecular logic underlying temperature-dependent flowering provides a beacon for developing resilient plant varieties. The FKF1–GI-mediated degradation of SVP through phase separation dynamics offers a blueprint for future interventions aiming to optimize flowering time, yield stability, and plant adaptation.
These insights also raise intriguing evolutionary questions. The ability of plants to leverage reversible liquid-liquid phase separation to modulate protein functions suggests an evolutionary advantage by providing rapid, reversible control mechanisms. Such strategies may be widespread in biological systems, offering flexible responses to fluctuating environments.
With the continued integration of molecular genetics, biochemistry, and cell biology, studies like this pave the way toward a holistic understanding of plant responsiveness to multifaceted environmental cues. It is now clear that proteins like FKF1 and GI are not merely static molecular components but dynamic players orchestrating complex developmental decisions via sophisticated regulatory networks sensitive to both time and temperature.
In essence, the research uncovers a molecular narrative in which the stability and localization of key regulatory proteins choreograph flowering time with precision, ensuring plants bloom under conditions most favorable for survival. The versatile FKF1–GI partnership functions as both sensor and effector, translating the subtle language of temperature into decisive biological actions. This elegant molecular mechanism exemplifies the beauty of plant adaptation as a continuous dialogue with the environment at the nexus of protein dynamics and developmental timing.
Subject of Research: Molecular mechanisms integrating photoperiod and temperature cues to regulate flowering time in plants.
Article Title: High-temperature-induced FKF1 accumulation promotes flowering through the dispersion of GI and degradation of SVP.
Article References:
Lee, H.G., Kim, J., Park, KH. et al. High-temperature-induced FKF1 accumulation promotes flowering through the dispersion of GI and degradation of SVP. Nat. Plants (2025). https://doi.org/10.1038/s41477-025-02019-4
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Tags: breakthroughs in plant biology researchenvironmental cues and reproductive successFKF1 and GIGANTEA proteinsflowering mechanisms in plantsflowering time regulation in plantsintegrating temperature and day length signalsmolecular mechanisms in plant developmentNature Plants study on flowering dynamicsphotoperiod and flowering transitionSVP role in floral repressiontargeted protein degradation in plantstemperature effects on flowering
