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<p>Plants tailor their architecture to warm temperatures through the central transcription factor PHYTOCHROME-INTERACTING FACTOR 4 (PIF4). Here, we dissect how structured and disordered regions of PIF4 contribute to its function in thermomorphogenesis. A long N-terminal intrinsically disordered region (IDR) enables PIF4 to form low-mobility condensates. Within this IDR, we identify an acidic transactivation domain (TAD) and an extended basic segment that carries a nuclear-localization signal and the canonical basic motif of the basic helix-loop-helix (bHLH) domain. The basic segment is both necessary and sufficient to drive PIF4 condensate formation, while the TAD tunes condensate properties. Strikingly, alanine substitutions that abolish TAD-mediated transactivation, disrupt DNA binding, or greatly reduce phase-separation propensity have no significant effect on thermomorphogenetic hypocotyl elongation. By contrast, substituting twelve basic residues within the basic segment, which disrupts both DNA binding and HLH-mediated oligomerization, abolishes thermo-induced hypocotyl growth. These findings suggest that PIF4’s oligomerization competence contributes significantly to thermomorphogenesis by enabling partner recruitment, allowing DNA-binding and transactivation functions to be supplied in trans.</p>

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Oligomerization-competent PIF4 drives thermomorphogenesis through functional redundancy in transactivation and DNA binding

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月17日

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  • Haibo Xiong,
  • Abhishesh Bajracharya,
  • Ranjeeta Odari,
  • Eden E. Bayer,
  • Alyssa Stoner,
  • Anupa Wasti,
  • Jing Xi,
  • Scott R. Baerson,
  • Meng Chen,
  • Yongjian Qiu

摘要

Plants tailor their architecture to warm temperatures through the central transcription factor PHYTOCHROME-INTERACTING FACTOR 4 (PIF4). Here, we dissect how structured and disordered regions of PIF4 contribute to its function in thermomorphogenesis. A long N-terminal intrinsically disordered region (IDR) enables PIF4 to form low-mobility condensates. Within this IDR, we identify an acidic transactivation domain (TAD) and an extended basic segment that carries a nuclear-localization signal and the canonical basic motif of the basic helix-loop-helix (bHLH) domain. The basic segment is both necessary and sufficient to drive PIF4 condensate formation, while the TAD tunes condensate properties. Strikingly, alanine substitutions that abolish TAD-mediated transactivation, disrupt DNA binding, or greatly reduce phase-separation propensity have no significant effect on thermomorphogenetic hypocotyl elongation. By contrast, substituting twelve basic residues within the basic segment, which disrupts both DNA binding and HLH-mediated oligomerization, abolishes thermo-induced hypocotyl growth. These findings suggest that PIF4’s oligomerization competence contributes significantly to thermomorphogenesis by enabling partner recruitment, allowing DNA-binding and transactivation functions to be supplied in trans.