FCA mediates thermal adaptation of stem growth by attenuating auxin action in Arabidopsis

Abstract

Global warming is predicted to profoundly affect plant distribution and crop yield in the near future. Higher ambient temperature can influence diverse aspects of plant growth and development. In Arabidopsis, the basic helix-loop-helix transcription factor PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) regulates temperature-induced adaptive responses by modulating auxin biosynthesis. At high temperature, PIF4 directly activates expression of YUCCA8 (YUC8), a gene encoding an auxin biosynthetic enzyme, resulting in auxin accumulation. Here we demonstrate that the RNA-binding protein FCA attenuates PIF4 activity by inducing its dissociation from the YUC8 promoter at high temperature. At 28°C, auxin content is elevated in FCA-deficient mutants that exhibit elongated stems but reduced in FCAoverexpressing plants that exhibit reduced stem growth. We propose that the FCA-mediated regulation of YUC8 expression tunes down PIF4-induced architectural changes to achieve thermal adaptation of stem growth at high ambient temperature.

The population genomic signature of environmental selection in the widespread insect-pollinated tree species Frangula alnus at different geographical scales

“…Auxin is an important plant hormone, modulating many aspects of plant growth, development and responses to biotic and abiotic stress (Wolters and Jürgens, 2009;Peleg and Blumwald, 2011). Variation at loci underlying auxin expression may thus have profound fitness consequences, as has been demonstrated in the context of temperature stress (for example, Swindell et al, 2007;Lee et al, 2014), plant-pathogen interactions (Kazan and Manners, 2009) and symbiotic interactions (for example, Reddy et al, 2006). We correspondingly observed a significant association between SNP a2 and temperature at the regional scale (Table 2).…”

Phytochromes and Phytochrome Interacting Factors

“…While in shade, HFR1, PAR1 (PHYTOCHROME RAP-IDLY REGULATED1), and PAR2 interact with PIF4 and subsequently prevent PIF4 from activating its target genes ( Fig. 2; Hornitschek et al, 2009;Hao et al, 2012;Lee et al, 2014;Nieto et al, 2015). Besides hypocotyl elongation, PIF4 also controls several physiological and development aspects, such as stomatal development in response to light quality, circadian gating, chlorophyll degradation and leaf senescence in darkness, freezing tolerance, and anthocyanin biosynthesis under red-light conditions Casson et al, 2009;Lee and Thomashow, 2012;Sakuraba et al, 2014;Song et al, 2014;Liu et al, 2015;Zhang et al, 2015;Zhu et al, 2016a).…”

PIF4 and ELF3 Act Independently in Arabidopsis thaliana Thermoresponsive Flowering

“…Several independent studies have recently found that elevated temperatures, specifically during dark periods [29], inhibit the activity of the EC by an unknown mechanism [14–16], leading to increased expression of PIF4 and its targets [11,27]. This increased PIF4 activity leads to several morphological temperature responses through various signaling pathways [13,27]. PIF4 is also required for the acceleration of flowering at 27°C under short photoperiods [9,29], though these observations have been disputed [30,31].…”

“…However, others have implicated different candidates, such as FCA [13], and mathematical modeling has suggested that ELF3/EC complex regulation alone is insufficient to explain PIF4 thermal regulation [14,34]. The exact mechanisms of this response have yet to be unraveled.…”