HK2 — Arabidopsis thaliana

Summary

AT5G35750 (HK2, AHK2) encodes a transmembrane histidine kinase cytokinin receptor with osmosensor activity, classified as EC 2.7.13.3. The protein contains CHASE, histidine kinase, and receiver domains characteristic of two-component system sensors. In Arabidopsis, HK2 is associated with cytokinin perception and transport, embryonic root morphogenesis, vasculogenesis, secondary growth, and regulation of chlorophyll catabolism. It has been linked to numerous agronomic traits including seed yield, seed size, leaf size and number, stem length and diameter, shoot fresh weight, root mass density, lateral root length, photosynthetic rate, water use efficiency, and responses to far-red and red light. The gene is also connected to salt and freezing tolerance, ethylene and auxin sensitivity, cell cycle and elongation traits, floral organ size, and sporogenesis. HK2 localizes to the plasma membrane, endoplasmic reticulum, plastid, cytosol, and nucleus.