2.4 Heat priming and BRs promote the accumulation of
dephosphorylated BES1 during memory phase
HS activates BES1 via dephosphorylation (Albertos et al., 2022), so we
are curious about whether the state can be sustained in the memory
phase. We executed a transient expression experiment on N.
benthamiana leaves to explore the subcellular distribution of BES1
after heat priming. As shown in Fig. 3A, BES1 was diffused in the
nucleus and cytoplasm prior priming, after exposure to 44℃ for 90 min,
more BES1-GFP was shuttled to the nucleus, and the accumulation of BES1
in the nucleus could be maintained for another 2-3 d. BRs signal
transduction activates BES1/BZR1 through releasing the inhibition of
BIN2 thus promotes dephosphorylation of BES1, so we suppose BRs mediate
thermomemory through promoting the accumulation of activated BES1 during
the memory phase. We detected the abundance of de-phosphorylated BES1 in
seedlings grown on solid plate medium with or without BL application
during the memory phase. As shown in Fig. 3B, BL application strengthens
the accumulation of dephosphorylated BES1, whereas BRZ (brassinazole, a
specific inhibitor of BR synthesis) treatment impairs dephosphorylation.
These results indicate that heat priming promotes the accumulation of
dephosphorylated BES1 in the nucleus, BRs signal transduction further
enhances this process.