The effect of ellagic acid on the root gravitropic response in Arabidopsis thaliana

Gravitropism is affected by many exogenous factors such as environmental stresses. In the present study, the effect of ellagic acid (EA) on the gravitropic curvature of Arabidopsis thaliana (L.) Heynh. roots was characterized. Exogenous application of EA influenced root gravitropic responses in a concentration-dependent fashion. KI/I staining research revealed that the starch grain in the root cap was reduced by EA treatments. Simultaneously, expression of auxin-responsive reporter gene DR5::GFP showed that the auxin redistribution in roots treated with EA was less sensitive to that of control groups under gravity stimulus. Moreover, the expression of one of the auxin flux-facilitators—PIN2, was also suppressed by EA. Taken together, our results indicated that the effects of EA on root gravitropism were largely dependent on the reduction of starch grain and the disorder of lateral auxin redistribution.