Effect of plant root exudates and tetronic acid on [Ca2+]
and nod gene expression in M. loti. A, Analysis of gene expression by semi-quantitative RT-PCR during control conditions (lane 1, white bars) and after 1 h treatment with L. japonicus root exudates (lane 2, black bars) or 1.5 mM tetronic acid (lane 2, striped bars). Relative transcript abundance was normalized against 16S rRNA. Data are the means ± SEM of three independent experiments. B, Monitoring of [Ca2+]i changes in M. loti cells challenged (arrow) with L. japonicus root exudates (black trace) or 1.5 mM tetronic acid (grey trace).