Hazelwood, O. S.; Delpit, G.; H.L, T. D.; Sparks, E. E.; Best, N. B.; Ashraf, M. A.

Toxic metal contamination in the environment is pervasive and of significant concern due to its high abundance in agricultural lands across the globe. Future engineering of plants tolerant to toxic metals requires a detailed understanding of plant responses to these toxins, which are currently poorly understood. We discovered that, among four toxic metals, lead (Pb) targets conserved cellular and developmental processes in evolutionary diverse plant systems - the model plant Arabidopsis thaliana and crop plant Zea mays. This study shows that Pb increases the phytohormone auxin, which in turn inhibits cell cycle progression to inhibit root growth and alters root gravitropic responses. Both root growth and gravitropic responses are critical for soil exploration, which is required for plants to live and thrive in harsh environments.