AUX1-mediated root hair auxin influx governs SCFTIR1/AFB-type Ca2+ signaling (Nature Comms)

The phytohormone auxin is transported in a polar fashion through PINs (PIN-FORMED) and PGPs (P–GLYCOPROTEIN) as auxin efflux carriers and AUX1 and LAXs (LIKE-AUX1) as influx carriers. Previous experiments from oat coleoptiles and corn root hairs indicate that one of quickest auxin responses is cell membrane depolarization. In this study, Dindas et al. used Arabidopsis root hair cells as a single cell model system to understand auxin signaling in membrane responses. They found that as a part of the early response auxin is perceived by the auxinol-sensitive cytosolic fraction of the SCF^TIR1/AFB receptor (auxinol acts as a SCF^TIR1/AFB inhibitor). Upon auxin perception, CNGC14 (CYCLIC NUCLEOTIDE GATED CHANNEL 14) activates Ca²⁺-influx and increases cytosolic Ca²⁺ levels. Increased cytosolic Ca²⁺ regulates AUX1-mediated transporter via phosphorylation of AUX1 through Ca²⁺-dependent kinases. The elevated cytosolic Ca²⁺ also regulates the activity of CNGC14 through Ca²⁺-dependent interaction of CNGC14 with calmodulin. (Summary by Arif Ashraf) Nature Comms: 10.1038/s41467-018-03582-5