title: The Cyclic Nucleotide-Gated Channel CNGC14 Regulates Root Gravitropism in Arabidopsis thaliana.
abstract: 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, 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 Ca(2+) 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 Ca(2+) changes are required for rapid growth inhibition. Our results support a direct role for CNGC14-dependent Ca(2+) signaling in regulating the early posttranscriptional phase of auxin growth responses in Arabidopsis roots.
authors.affiliation: Department of Biology, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Han-Wei
authors.initials: HW
authors.lastname: Shih
authors.affiliation: Department of Biology, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Cody L
authors.initials: CL
authors.lastname: DePew
authors.affiliation: Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Nathan D
authors.initials: ND
authors.lastname: Miller
authors.affiliation: Department of Biology, Pennsylvania State University, University Park, PA 16802, USA. Electronic address: gbm10@psu.edu.
authors.forename: Gabriele B
authors.initials: GB
authors.lastname: Monshausen
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000235:genetics* / Q000378:metabolism; D018522:Gravitropism; D007210:Indoleacetic Acids / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; C000610582:CNGC14 protein, Arabidopsis; D054815:Cyclic Nucleotide-Gated Cation Channels; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators