TITLE:
Interactions of Auxinic Compounds on Ca2+ Signaling and Root Growth in Arabidopsis thaliana
AUTHORS:
Neal D. Teaster, Jeffrey A. Sparks, Elison B. Blancaflor, Robert E. Hoagland
KEYWORDS:
Auxinic Compound, Arabidopsis thaliana, Herbicide, Calcium Signaling, FRET Imaging
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.6 No.19,
December
3,
2015
ABSTRACT: Auxinic-like compounds have been widely used as weed control agents. Over the years, the modes
of action of auxinic herbicides have been elucidated, but most studies thus far have focused on
their effects on later stages of plant growth. Here, we show that some select auxins and auxiniclike
herbicides trigger a rapid elevation in root cytosolic calcium levels within seconds of application. Arabidopsis thaliana plants expressing the Yellow-Cameleon (YC) 3.60 calcium reporter were
treated with indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), 1-naphthalene acetic acid (NAA),
and two synthetic herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and mecoprop [2-(4-chloro-
2-methylphenoxy) propanoic acid], followed by monitoring cytosolic calcium changes over a 10 minute
time course. Seconds after application of compounds to roots, the Ca2+ signaling-mediated
pathway was triggered, initiating the plant response to these compounds as monitored and recorded
using Fluorescence Resonance Energy Transfer (FRET)-sensitized emission imaging. Each
compound elicited a specific and unique cytosolic calcium signature. Also primary root development
and elongation was greatly reduced or altered when exposed at two concentrations (0.10
and 1.0 μM) of each compound. Within 20 to 25 min after triggering of the Ca2+ signal, root growth
inhibition could be detected. We speculate that differences in calcium signature among the tested
auxins and auxinic herbicides might correlate with their variation and potency with regard to root
growth inhibition.