PIF4 and ELF3 Act Independently in Arabidopsis thaliana Thermoresponsive Flowering

Abstract

Plants have evolved elaborate mechanisms controlling developmental responses to environmental stimuli. A particularly important stimulus is temperature. Previous work has identified the interplay of PIF4 and ELF3 as a central circuit underlying thermal responses in Arabidopsis thaliana. However, thermal responses vary widely among strains, possibly offering mechanistic insights into the wiring of this circuit. ELF3 contains a polyglutamine (polyQ) tract that is crucial for ELF3 function and varies in length across strains. Here, we use transgenic analysis to test the hypothesis that natural polyQ variation in ELF3 is associated with the observed natural variation in thermomorphogenesis. We found little evidence that the polyQ tract plays a specific role in thermal responses beyond modulating general ELF3 function. Instead, we made the serendipitous discovery that ELF3 plays a crucial, PIF4-independent role in thermoresponsive flowering under conditions more likely to reflect field conditions. We present evidence that ELF3 acts through the photoperiodic pathway, pointing to a previously unknown symmetry between low and high ambient temperature responses. Moreover, in analyzing two strain backgrounds with different thermal responses, we demonstrate that responses may be shifted rather than fundamentally rewired across strains. Our findings tie together disparate observations into a coherent framework in which multiple pathways converge in accelerating flowering in response to temperature, with some such pathways modulated by photoperiod.

Variability in a Short Tandem Repeat Mediates Complex Epistatic Interactions in Arabidopsis thaliana

“…For instance, the degree of huntingtin polyQ expansion is strongly correlated with Huntington's disease severity (Andrew et al 1993). In contrast, there is little evidence for any monotonic relationship between a ELF3-polyQ-related phenotype and ELF3-polyQ length (Undurraga et al 2012;Press et al 2014Press et al , 2016. Indeed, all indications are that the mapping between ELF3-polyQ tract length and phenotype is nonmonotonic and strongly contingent on genetic background, unlike the classic polyQ disease models.…”

Arabidopsis thaliana ambient temperature responsive lncRNAs

“…Current research on the role of ambient temperature in plant development is mainly focused on identification and characterization of protein coding genes involved in this process. For example, MADS-box transcription factor genes, the bHLH transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4) [ 20 – 23 ], the TEMPRANILLO genes [ 24 ] and the MYB transcription factor EARLY FLOWERING MYB PROTEIN (EFM) [ 25 ] have been shown to regulate ambient temperature-mediated flowering. PIF4, together with the photoreceptor phytochrome B (phyB), also plays an important role in thermo-morphogenesis [ 26 – 28 ].…”

The Genetic Control of Reproductive Development under High Ambient Temperature

“…PIF4 binding to the promoter of FT and consequent transcriptional activation of FT is promoted by an improved chromatin accessibility through temperature-dependent histone modifications at the FT promoter (Kumar and Wigge, 2010;Kumar et al, 2012). However, high temperature also accelerated flowering in pif4 mutants under long photoperiods, suggesting that a PIF4-independent thermoresponsive flowering pathway acts through components of the photoperiod pathway (Koini et al, 2009;Press et al, 2016).…”