The Cyclic Nucleotide-Gated Channel CNGC14 Regulates Root Gravitropism in Arabidopsis thaliana

• Published in: Current biology Vol. 25; no. 23; pp. 3119 - 3125
• Main Authors: Shih, Han-Wei, DePew, Cody L., Miller, Nathan D., Monshausen, Gabriele B.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 07.12.2015
• Subjects: Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Cyclic Nucleotide-Gated Cation Channels - genetics; Cyclic Nucleotide-Gated Cation Channels - metabolism; Gravitropism; Indoleacetic Acids - metabolism; Plant Growth Regulators - metabolism; Plant Roots - genetics; Plant Roots - growth & development; Signal Transduction
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2015.10.025

In plant roots, auxin inhibits cell expansion, and an increase in cellular auxin levels on the lower flanks of gravistimulated roots suppresses growth and thereby causes downward bending. These fundamental features of root growth responses to auxin were first described over 80 years ago [1], but our understanding of the underlying molecular mechanisms has remained scant. Here, we report that CYCLIC NUCLEOTIDE-GATED CHANNEL 14 (CNGC14) is essential for the earliest phase of auxin-induced ion signaling and growth inhibition in Arabidopsis roots. Using a fluorescence-imaging-based genetic screen, we found that cngc14 mutants exhibit a complete loss of rapid Ca2+ and pH signaling in response to auxin treatment. Similarly impaired ion signaling was observed upon gravistimulation. We further developed a kinematic analysis approach to study dynamic root growth responses to auxin at high spatiotemporal resolution. These analyses revealed that auxin-induced growth inhibition and gravitropic bending are significantly delayed in cngc14 compared to wild-type roots, where auxin suppresses cell expansion within 1 min of treatment. Finally, we demonstrate that auxin-induced cytosolic Ca2+ changes are required for rapid growth inhibition. Our results support a direct role for CNGC14-dependent Ca2+ signaling in regulating the early posttranscriptional phase of auxin growth responses in Arabidopsis roots. •CNGC14 regulates auxin- and gravity-induced Ca2+ signaling in Arabidopsis roots•cngc14 mutants exhibit delayed growth responses to auxin and gravitropic stimulation•Rapid auxin-induced inhibition of Arabidopsis root growth requires Ca2+ signaling The development of root system architecture is strongly influenced by gravity. Shih et al. reveal that the cyclic nucleotide-gated channel CNGC14 is required for the initial phase of Arabidopsis root gravitropism. Loss of CNGC14 function suppresses rapid auxin-dependent growth inhibition by abolishing Ca2+ signaling in gravistimulated roots.