Thermosensory pathway makes a U-turn to respond to heat
Plant organs exhibit a unimodal growth response to temperature, yet the mechanistic links connecting growth-promoting and growth-inhibiting thermal ranges remain unresolved. In Arabidopsis seedlings, warm temperatures promote hypocotyl elongation by relieving phytochrome B (phyB) inhibition, thereby activating the transcription factors PIF4 and PIF7 to drive auxin synthesis. Here, we demonstrate…
Research reveals that plant organs have a surprising U-turn response to heat, moving from growth-promoting to growth-inhibiting thermal ranges. In Arabidopsis seedlings, warm temperatures foster hypocotyl elongation by releasing phytochrome B (phyB) inhibition, leading to the activation of transcription factors PIF4 and PIF7 for auxin synthesis.
However, temperatures exceeding the growth optimum actively hinder growth by reducing auxin levels, signaling, and PIF4 abundance specifically in the cotyledons, where auxin production primarily occurs. Astonishingly, while warm temperatures cause phyB nuclear bodies to shrink, heat stress triggers phyB to form larger condensates, a phenomenon observed in mammalian cells as well, indicating an intrinsic biophysical mechanism.
The study concludes that heat-induced growth inhibition is not simply passive stress damage but an active molecular reversal of the promotive pathway of thermomorphogenesis.
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