The HAESA family of receptor-like kinases: abscission pathways and emerging functions.

The HAESA (HAE/HSLs) family of leucine-rich repeat receptor-like kinases (LRR-RLKs) represents a central signaling hub and showed high conservation in multiple plants, integrating developmental cues and environmental stresses. Initially characterized for their pivotal role in floral organ abscission through the IDA-HAE/HSL2 ligand-receptor module, subsequent studies have revealed broader functions in root development, seed longevity, stomatal regulation, and responses to both biotic and abiotic stresses. Structural and genetic analyses have uncovered complex regulatory layers, including membrane trafficking, endoplasmic reticulum output control, co-receptor recruitment, and MAPK cascade activation, all of which ensure precise spatiotemporal control of abscission and related processes. Importantly, the multi-functionality of the HAE family proteins reflects a dynamic trade-off between growth and defense, highlighting its role in balancing resource allocation under complex environments. Overall, the HAESA family not only provides fundamental insights into plant signaling networks but also holds potential as a key target for future crop improvement and sustainable agriculture.