Abstract
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.
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Acknowledgements
We thank all the Qiu lab members for their critical comments and suggestions regarding the manuscript. This work was supported by the National Science Foundation (NSF) grants IOS-2200200 and IOS-2239963 to Y.Q., and the National Institutes of Health (NIH) grant R01GM087388 to M.C. The work related to the confocal microscope was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences (NIGMS) of the NIH under award number P20GM130460 to the Imaging Research Core of the Glycoscience Center of Research Excellence (GlyCORE) at the University of Mississippi. We would like to thank Drs. Gregg Roman, Ruofan Cao, and John Adams in the Imaging Research Core of GlyCORE at the University of Mississippi for their assistance with using the Leica SP8 Inverted Confocal Microscope.
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Y.Q. initiated the project in M.C.’s laboratory; Y.Q., H.X., and A.B. conceived the original research plan; Y.Q., S.R.B., and J.X. supervised the experiments; H.X., A.B., R.O., E.E.B, A.S., A.W., J.X., and Y.Q. performed the experiments; H.X., A.B., R.O., J.X., and Y.Q. analyzed the data; M.C. provided instructions, materials, and facilities on the completion of yeast-related data in Fig. 2b and Supplementary Fig. 1; Y.Q., H.X., and A.B. wrote the article with the contributions from all authors; all authors approved the submitted version.
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Xiong, H., Bajracharya, A., Odari, R. et al. Oligomerization-competent PIF4 drives thermomorphogenesis through functional redundancy in transactivation and DNA binding. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70748-x
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DOI: https://doi.org/10.1038/s41467-026-70748-x
