Cytokinins influence root gravitropism via differential regulation of auxin transporter expression and localization in Arabidopsis

• DOI: 10.1111/nph.14049
• Publication Date: 2016-06-20T15:52:36Z
• Authors: Marketa Pernisova; Tomas Prat; Peter Grones; Danka Harustiakova; Martina Matonohova; Lukas Spichal; Tomasz Nodzynski; Jiri Friml; Jan Hejatko
• Keywords: Gravitropism; Columella; Root cap; Lateral root; Polar auxin transport

Redirection of intercellular auxin fluxes via relocalization the PIN-FORMED 3 (PIN3) and PIN7 efflux carriers has been suggested to be necessary for root gravitropic response. Cytokinins have also proposed play a role in controlling gravitropism, but conclusive evidence is lacking. We present detailed study dynamics bending early after gravistimulation, which revealed delayed response transgenic lines with depleted endogenous cytokinins (Pro35S:AtCKX) cytokinin signaling mutants. Pro35S:AtCKX lines, as well receptor mutant ahk3, showed aberrations distribution columella cells consistent defects transport machinery. Using vivo real-time imaging PIN3-GFP PIN7-GFP AtCKX3 overexpression ahk3 backgrounds, we observed wild-type-like PIN proteins gravity-induced faster than that PIN3. Nonetheless, cellular PIN3 expression influx carrier AUX1 was affected AtCKX lines. Based on retained sensitivity pin3 pin4 pin7 mutant, propose AUX1-mediated rather columella-located target control gravitropism.