Roots of tomato respond to mechanical stimulation by induction of touch genes

Plant roots growing in soil are subjected constantly to friction and mechanical resistance. So far, molecular events associated with the response to mechanical impedance have been studied in plant shoots but not in their roots. Our aim was to identify components of the response mechanism to short and long term mechanical simulation of tomato root apices at the morphological and molecular level. Taking advantage of the unique aeroponic chambers of The Sarah Racine Root Research laboratory we have studied the effect of mechanical impedance on tomato roots. Our results show that mechanical stimulation brought about an increase in the root branching. Both short-term (1 h) and chronic mechanical stimuli resulted in induction of members of the touch gene family, Tch2 and XET encoding calmodulin and xyloglucan endotransglucosylase, respectively, in the apices of tomato roots. The calmodulin calcium-dependent signaling pathway takes part in roots, specifically in response to mechanical stimulation. Plant roots share molecular events with previously identified constituents of the shoot response to mechanical stimulation.