The perception and signaling transduction of extracellular auxin in plants

Auxin plays a crucial role essentially in all aspects of plant growth and development. Different auxin signaling mechanisms may explain its remarkable functional diversity, but the underlying mechanism is not well understood. We identified TMK-mediated extracellular auxin signaling mechanisms that interpret auxin signals through post-translational regulation of substrates. In Arabidopsis, extracellular auxin is perceived by a co-receptor complex containing both TMKs and ABPs and then triggers auxin signaling cascades that participate in most properties of cellular responses including cell wall acidification, cytoskeleton organization, auxin homeostasis, etc. Our observations reveal complex mechanisms of extracellular auxin signaling in plant development.