The study reveals that a conserved serine adjacent to the catalytic glutamate in TIR domains is essential for NAD+‑cleaving activity, and that phosphorylation of this serine by plant calcium‑dependent protein kinases (CPKs) or mammalian kinases (CAMK2D, TBK1) inhibits the activity, thereby preventing growth repression and cell death. This phosphorylation-based mechanism provides a universal means to balance growth and immune defense across species.

The study identifies RAF24, a B4 Raf-like MAPKKK, as a novel regulator of flowering time in Arabidopsis, demonstrating that RAF24 controls the phosphorylation of the ubiquitin ligase HUB2 via SnRK2 kinases, thereby modulating H2Bub1 levels. Phospho‑mimetic and phospho‑ablative HUB2 mutants confirm that phosphorylation at S314 is critical for proper flowering timing.

The study uncovers a feedback mechanism wherein phosphomimic mutation (PetD T4E) or deletion of the N‑terminal five amino acids of the b6f subunit PetD suppresses STT7 kinase activity, leading to a State 1‑locked phenotype and impaired electron transfer, highlighting the essential regulatory role of the PetD N‑terminus in photosynthetic state transitions.