AHK3 notes (Q9C5U1, At1g27320, ORE12)

2026-10-05 review session (cytokinin two-component signaling module)

• Identity checked: UniProt Q9C5U1 AHK3_ARATH, At1g27320.
• Deep research tooling failed in this environment; review based on cached publications.
• Cytokinin receptor, dominant in leaves; mediates leaf longevity via ARR2 phosphorylation PMID:16407152. The ore12 allele is a gain-of-function missense in the extracellular domain.
• ER localization of functional AHK3 fusions and AHK3-AHK4 interaction in vivo PMID:21841169.
• Phosphate-starvation and sugar signaling PMID:15923327.
• R. fascians: AHK3/AHK4 needed for disease symptoms PMID:19129491 -> GO:0042742 'defense response to bacterium' marked over-annotated (susceptibility, not defense).
• ISM extracellular region and HDA nucleus judged non-functional locations (REMOVE / MARK_AS_OVER_ANNOTATED).
• Proposed NEW: GO:0009885.