Root-specific induction of early auxin-responsive genes in Arabidopsis thaliana by cis-cinnamic acid

Abstract

cis-Cinnamoyl glucosides are the allelochemicals in Thunberg’s meadowsweet (Spiraea thunbergii). The essential chemical structure responsible for the bioactivity of cis-cinnamoyl glucosides, cis-cinnamic acid (cis-CA), strongly inhibits the root growth of several plant species; however, its mode of action has not been characterized at the gene expression level. We conducted a time–course microarray analysis of gene expression in Arabidopsis in response to 20 µM cis-CA. Comparison of the microarray profiles revealed a 10-fold upregulation of several auxin-responsive GRETCHEN HAGEN-3 (GH3) genes and LATERAL ORGAN BOUNDARIES DOMAIN/ASYMMETRIC LEAVES2-LIKE (LBD) genes from 2 h to 6 h post-treatment. Two early auxin-responsive gene families, the Aux/IAA family (IAA1, IAA5) and the GH3 family (GH3.1, GH3.2, GH3.3), and an LBD gene (LBD16) were markedly upregulated at 2 h after treatment in the roots, but not in the shoots, of Arabidopsis and remained highly expressed for 4 h. The influence of an exogenous application of cis-CA on the indole-3-acetic acid pathway strongly suggests that a root-targeted induction of auxin-responsive genes is involved in the cis-CA-mediated plant growth inhibition.