Role of oxalate oxidase and apoplastic reactive oxygen species in root growth regulation in water-stressed maize primary roots
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Previous work on maize primary roots under water stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex. These responses involve spatially differential and coordinated regulation of cellular growth processes, including modifications of cell wall extensibility. Results from cell wall proteomic analyses and in-situ imaging showed that apoplastic reactive oxygen species (ROS) levels increase in the apical region of water-stressed roots. To investigate the role of OxO/apoplastic ROS in root growth regulation, transgenic maize lines constitutively expressing a wheat OxO gene were characterized. The results showed that OxO activity in the primary root growth zone is increased in a region-specific manner with different profiles under well-watered and water-stressed conditions, and that these changes are associated with differential effects on root growth in the different treatments. Interestingly, kinematic analysis of spatial growth patterns revealed that the root growth responses in the OxO transgenic lines are primarily due to changes in rates of cell production rather than cell expansion. These results indicate that apoplastic ROS are involved in the regulation of cell production and root growth in well-watered and water-stressed conditions.
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