Brassinosteroid-driven cell expansion: How FERONIA and BIN2 shape plant growth

FERONIA (FER), a member of the Catharanthus roseus receptor-like kinase 1–like (CrRLK1-like) receptor kinase family, was initially identified as a key regulator of female fertility in Arabidopsis. Later studies revealed that FER is a multifunctional protein involved in nearly all aspects of plant growth and development, including cell proliferation, hormone signaling, reproduction, and responses to biotic and abiotic stresses. However, how a single receptor kinase mediates such diverse functions remains unclear. One approach to addressing this question is to investigate FER co-receptors and binding partners, which determine its downstream signaling pathways. Chaudhary and colleagues demonstrated that the interaction between BRASSINOSTEROID-INSENSITIVE 2 (BIN2) and FER plays a crucial role in brassinosteroid (BR)-induced cell expansion. In regions where cells are not actively proliferating or elongating, BR levels are low, allowing BIN2 to phosphorylate FER and suppress its localization on the plasma membrane. Conversely, when BR levels rise, BIN2 is inhibited, leading to FER accumulation on the plasma membrane. This, in turn, promotes reactive oxygen species (ROS) production, reduces cell wall acidification, slows down cell elongation, and helps maintain cell wall integrity during expansion. (Summary by Ching Chan @ntnuchanlab) Molecular Plant 10.1016/j.molp.2025.02.001