An RNA thermoswitch regulates daytime growth in Arabidopsis

Abstract

Temperature is a major environmental cue affecting plant growth and development. Plants often experience higher temperatures in the context of a 24 h day-night cycle, with temperatures peaking in the middle of the day. Here we find that the transcript encoding the bHLH transcription factor PIF7 undergoes a direct increase in translation in response to warmer temperature. Diurnal expression of PIF7 transcript gates this response, allowing PIF7 protein to quickly accumulate in response to warm daytime temperature. Enhanced PIF7 protein levels directly activate the thermomorphogenesis pathway by inducing the transcription of key genes such as the auxin biosynthetic gene YUCCA8, and are necessary for thermomorphogenesis to occur under warm cycling daytime temperatures. The temperature-dependent translational enhancement of PIF7 mRNA is mediated by the formation of an RNA hairpin within its 5' UTR, which adopts an alternative conformation at higher temperature, leading to increased protein synthesis. We identified similar hairpin sequences that control translation in additional transcripts including WRKY22 and the key heat shock regulator HSFA2, suggesting this is a conserved mechanism enabling plants to respond and adapt rapidly to high temperatures.

Acis-regulatory element promoting increased transcription at low temperature in cultured ectothermicDrosophilacells

“…Some cases of APA also change the coding region. In addition, APA can affect formation of RNA secondary structure, which are of crucial importance for thermosensing in plants, bacteria and viruses (Chung et al 2020;Kortmann and Narberhaus 2012;Somero 2018). The broad spectrum of potential APA consequences thwarts reliable bioinformatic predictions of physiological effects.…”

“…In case of vernalization, the process by which wintertime chill stimulates springtime flowering, epigenetic repression of the FLC locus by Polycomb factors is central in Arabidopsis thaliana (Whittaker and Dean 2017;Zhao et al 2020). In thermomorphogenesis, i.e., the morphological changes according to ambient temperature, transcription factors (TFs) of the PIF family, which are controlled by both light and temperature, are crucial (Quint et al 2016;Chung et al 2020). Beyond PIFs, HSF family proteins also induce a large part of the warm transcriptome via eviction of +1 nucleosomes containing the histone H2A variant H2A.Z in temperature responsive genes (Cortijo et al 2017;Kumar and Wigge 2010).…”

In the heat of the day – RNA als Temperaturfühler

“…Um Komponenten zu finden, die auf eine Erhöhung der Außentemperatur reagieren und damit das Wachstum beeinflussen, haben Chung et al Arabidopsis ‐Keimlinge im Tag‐Nacht‐Rhythmus bei einer Temperatur von 17 °C angezogen, bei der die Keimlinge ein kurzes Hypokotyl ausbilden . In diesen Keimlingen haben sie nach temperaturabhängigen Veränderungen im Transkriptom gesucht, also nach Boten‐RNAs (mRNAs), deren Menge sich verändert, wenn die Keimlinge höheren Temperaturen – in diesem Fall 27 °C – ausgesetzt werden, wodurch das Längenwachstum ausgelöst wird.…”

“…Wie Pflanzen die Umgebungstemperatur messen, ist bisher nicht umfassend geklärt. Nun haben Forscher Hinweise darauf gefunden, dass RNA die Temperatur messen kann .…”

Phytochrome B and PCH1 protein dynamics store night temperature information

“…The EVENING COMPLEX, which includes EARLY FLOWERING 3 (ELF3) as one of its components, represses the expression of PIF4 , and direct effects of warm temperature on the complex structure reduce its binding to the PIF4 promoter, de‐repressing its activity (Box et al ., 2015; Ezer et al ., 2017; Silva et al ., 2020). Furthermore, warm temperatures directly modify the conformation of the PIF7 transcript, increasing its translation rate (Chung et al ., 2020). CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) is an E3 ubiquitin ligase required for thermomorphogenesis (Delker et al ., 2014) that increases its nuclear abundance in response to warm temperatures, degrading proteins that antagonise the activity of PIFs such as ELONGATED HYPOCOTYL 5 (HY5) and DELLA proteins (Park et al ., 2017; Blanco‐Touriñán et al ., 2020).…”