Photobodies enable the phase-separation and counterbalance of phytochrome B mediated PIF5 degradation and stabilization

Kim, R. J. A.; Fan, D.; He, J.; Kim, K.; Du, J.; Chen, M.

doi:10.1101/2023.11.12.566724

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bioRxiv · 10.1101/2023.11.12.566724

Photobodies enable the phase-separation and counterbalance of phytochrome B mediated PIF5 degradation and stabilization

Kim, R. J. A.·Fan, D.·He, J.·Kim, K.·Du, J.·Chen, M.

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Abstract

Photoactivation of the plant photoreceptor and thermosensor phytochrome B (PHYB) triggers its condensation into subnuclear photobodies (PBs). However, the function of PBs remains frustratingly elusive. Here, we found that PHYB recruits PHYTOCHROME-INTERACTING FACTOR5 (PIF5) to PBs. Surprisingly, PHYB exerts opposing roles in degrading and stabilizing PIF5. Perturbing PB size by overproducing PHYB provoked a biphasic PIF5 response: while a moderate increase in PHYB enhanced PIF5 degradation, further elevating the PHYB level stabilized PIF5 by retaining more of it in enlarged PBs. These results reveal a PB-mediated light and temperature sensing mechanism, in which PHYB condensation confers the co-occurrence and competition of two antagonistic phase-separated PHYB signaling actions--PIF5 stabilization in PBs and PIF5 degradation in the surrounding nucleoplasm-- thereby enabling an environmentally-sensitive counterbalancing mechanism to titrate nucleoplasmic PIF5 and its transcriptional output. This PB-enabled signaling mechanism provides a framework for regulating a plethora of PHYB-interacting signaling molecules in diverse plant environmental responses.

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Kim, R. J. A., Fan, D., He, J., Kim, K., Du, J., Chen, M.. 2023-11-14. Photobodies enable the phase-separation and counterbalance of phytochrome B mediated PIF5 degradation and stabilization. https://doi.org/10.1101/2023.11.12.566724

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