Zinc induces mitogen-activated protein kinase activation mediated by reactive oxygen species in rice roots.

It is well known that zinc (Zn) is one of the micronutrients essential for normal growth and development of plants. However, the molecular mechanisms responsible for the regulation of plant growth by Zn are still not completely understood. The aim of this study was to investigate the signalling transduction pathways activated by Zn. We show that Zn elicited a remarkable increase in myelin basic protein (MBP) kinase activities. By immunoblot analysis, we suggest that Zn-activated 40- and 42-kDa MBP kinases are mitogen-activated protein kinases (MAPK). Pre-treatment of rice roots with reactive oxygen species (ROS) scavenger, sodium benzoate, was able to effectively prevent Zn-induced MAPK activation. However, phosphoinositide 3-kinase (PI-3K) inhibitor, LY294002, was unable to inhibit Zn-induced MAPK activation. These results suggest that the ROS may function in the Zn-triggered MAPK signalling pathway in rice roots.