Aya Takeuchi

Bio: Aya Takeuchi is an academic researcher from Nagoya University. The author has contributed to research in topics: CLOCK & Circadian clock. The author has an hindex of 2, co-authored 2 publications receiving 152 citations.

Ambient Temperature Signal Feeds into the Circadian Clock Transcriptional Circuitry Through the EC Night-Time Repressor in Arabidopsis thaliana

Abstract: An interlocking multiloop model has been generally accepted to describe the transcriptional circuitry of core clock genes, through which robust circadian rhythms are generated in Arabidopsis thaliana. The circadian clock must have the ability to integrate ambient temperature signals into the clock transcriptional circuitry to regulate clock function properly. Clarification of the underlying mechanism is a longstanding subject in the field. Here, we provide evidence that temperature signals feed into the clock transcriptional circuitry through the evening complex (EC) night-time repressor consisting of EARLY FLOWERING 3 (ELF3, ELF4) and LUX ARRHYTHMO (LUX; also known as PCL1). Chromatin immunoprecipitation assays showed that PSEUDO-RESPONSE REGULATOR7 (PRR7), GIGANTEA (GI) and LUX are direct targets of the night-time repressor. Consequently, transcription of PRR9/PRR7, GI and LUX is commonly regulated through the night-time repressor in response to both moderate changes in temperature (Δ6°C) and differences in the steady-state growth-compatible temperature (16-28°C). A warmer temperature inhibits EC function more, whereas a cooler temperature stimulates it more. Consequently, the expression of these target genes is up-regulated in response to a warm temperature specifically during the dark period, whereas they are reversibly down-regulated in response to a cool temperature. Transcription of another EC target, the PIF4 (PHYTOCHROME-INTERACTING FACTOR 4) gene, is modulated through the same thermoregulatory mechanism. The last finding revealed the sophisticated physiological mechanism underlying the clock-controlled output pathway, which leads to the PIF4-mediated temperature-adaptive regulation of hypocotyl elongation.

The LNK1 night light-inducible and clock-regulated gene is induced also in response to warm-night through the circadian clock nighttime repressor in Arabidopsis thaliana.

Abstract: Ambient temperature has two fundamental impacts on the Arabidopsis circadian clock system in the processes referred to as temperature compensation and entrainment, respectively. These temperature-related longstanding problems have not yet been fully clarified. Recently, we provided evidence that temperature signals feed into the clock transcriptional circuitry through the evening complex (EC) nighttime repressor composed of LUX-ELF3-ELF4, and that the transcription of PRR9, PRR7, GI and LUX is commonly regulated through the nighttime repressor in response to both moderate changes in temperature (∆6 °C) and differences in steady-state growth-compatible temperature (16 °C to 28 °C). These temperature-associated characteristics of the core clock genes might be relevant to the fundamental oscillator functions. Here, we further show that the recently identified LNK1 night light-inducible and clock-controlled gene, which actually has a robust peak at daytime, is induced also by warm-night through the EC nightti...

Phytochromes function as thermosensors in Arabidopsis

Abstract: Plants are responsive to temperature, and some species can distinguish differences of 1°C In Arabidopsis, warmer temperature accelerates flowering and increases elongation growth (thermomorphogenesis) However, the mechanisms of temperature perception are largely unknown We describe a major thermosensory role for the phytochromes (red light receptors) during the night Phytochrome null plants display a constitutive warm-temperature response, and consistent with this, we show in this background that the warm-temperature transcriptome becomes derepressed at low temperatures We found that phytochrome B (phyB) directly associates with the promoters of key target genes in a temperature-dependent manner The rate of phyB inactivation is proportional to temperature in the dark, enabling phytochromes to function as thermal timers that integrate temperature information over the course of the night

Molecular and genetic control of plant thermomorphogenesis

Abstract: Temperature is a major factor governing the distribution and seasonal behaviour of plants. Being sessile, plants are highly responsive to small differences in temperature and adjust their growth and development accordingly. The suite of morphological and architectural changes induced by high ambient temperatures, below the heat-stress range, is collectively called thermomorphogenesis. Understanding the molecular genetic circuitries underlying thermomorphogenesis is particularly relevant in the context of climate change, as this knowledge will be key to rational breeding for thermo-tolerant crop varieties. Until recently, the fundamental mechanisms of temperature perception and signalling remained unknown. Our understanding of temperature signalling is now progressing, mainly by exploiting the model plant Arabidopsis thaliana. The transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4) has emerged as a critical player in regulating phytohormone levels and their activity. To control thermomorphogenesis, multiple regulatory circuits are in place to modulate PIF4 levels, activity and downstream mechanisms. Thermomorphogenesis is integrally governed by various light signalling pathways, the circadian clock, epigenetic mechanisms and chromatin-level regulation. In this Review, we summarize recent progress in the field and discuss how the emerging knowledge in Arabidopsis may be transferred to relevant crop systems.

A prion-like domain in ELF3 functions as a thermosensor in Arabidopsis.

Abstract: Temperature controls plant growth and development, and climate change has already altered the phenology of wild plants and crops1. However, the mechanisms by which plants sense temperature are not well understood. The evening complex is a major signalling hub and a core component of the plant circadian clock2,3. The evening complex acts as a temperature-responsive transcriptional repressor, providing rhythmicity and temperature responsiveness to growth through unknown mechanisms2,4-6. The evening complex consists of EARLY FLOWERING 3 (ELF3)4,7, a large scaffold protein and key component of temperature sensing; ELF4, a small α-helical protein; and LUX ARRYTHMO (LUX), a DNA-binding protein required to recruit the evening complex to transcriptional targets. ELF3 contains a polyglutamine (polyQ) repeat8-10, embedded within a predicted prion domain (PrD). Here we find that the length of the polyQ repeat correlates with thermal responsiveness. We show that ELF3 proteins in plants from hotter climates, with no detectable PrD, are active at high temperatures, and lack thermal responsiveness. The temperature sensitivity of ELF3 is also modulated by the levels of ELF4, indicating that ELF4 can stabilize the function of ELF3. In both Arabidopsis and a heterologous system, ELF3 fused with green fluorescent protein forms speckles within minutes in response to higher temperatures, in a PrD-dependent manner. A purified fragment encompassing the ELF3 PrD reversibly forms liquid droplets in response to increasing temperatures in vitro, indicating that these properties reflect a direct biophysical response conferred by the PrD. The ability of temperature to rapidly shift ELF3 between active and inactive states via phase transition represents a previously unknown thermosensory mechanism.

Genetic and epigenetic control of plant heat responses

Abstract: Plants have evolved sophisticated genetic and epigenetic regulatory systems to respond quickly to unfavorable environmental conditions such as heat, cold, drought, and pathogen infections. In particular, heat greatly affects plant growth and development, immunity and circadian rhythm, and poses a serious threat to the global food supply. According to temperatures exposing, heat can be usually classified as warm ambient temperature (about 22-27℃), high temperature (27-30℃) and extremely high temperature (37-42℃, also known as heat stress) for the model plant Arabidopsis thaliana. The genetic mechanisms of plant responses to heat have been well studied, mainly focusing on elevated ambient temperature-mediated morphological acclimation and acceleration of flowering, modulation of plant immunity and circadian clock by high temperatures, and thermotolerance to heat stress. Recently, great progress has been achieved on epigenetic regulation of heat responses, including DNA methylation, histone modifications, histone variants, ATP-dependent chromatin remodeling, histone chaperones, small RNAs, long non-coding RNAs and other undefined epigenetic mechanisms. These epigenetic modifications regulate the expression of heat-responsive genes and function to prevent heat-related damage. This review focuses on recent progresses regarding the genetic and epigenetic control of heat responses in plants, and pays more attention to the role of the major epigenetic mechanisms in plant heat responses. Further research perspectives are also discussed.