Microfilament dynamics is required for root growth under alkaline stress in Arabidopsis.

The microfilament (MF) cytoskeleton has crucial functions in plant development. Recent studies have revealed the function of MFs in diverse stress response. Alkaline stress is harmful to plant growth; however, it remains unclear whether the MFs play a role in alkaline stress. In the present study, we find that blocking MF assembly with latrunculin B (Lat B) leads to inhibition of plant root growth, and stabilization of MFs with phalloidin does not significantly affect plant root growth under normal conditions. In high external pH conditions, MF de-polymerization is induced and that associates with the reduction of root growth; phalloidin treatment partially rescues this reduction. Moreover, Lat B treatment further decreases the survival rate of seedlings growing in high external pH conditions. However, a high external pH (8.0) does not affect MF stability in vitro. Taken together, our results suggest that alkaline stress may trigger a signal that leads the dynamics of MFs and in turn regulates root growth.