Figure 2.

Model of lysigenous aerenchyma formation in maize root under waterlogged conditions. Waterlogging promotes biosynthesis and accumulation of ethylene. RBOH expression is upregulated in the cortical cells, the stelar cells and the outer cell layers, whereas MT expression is downregulated specifically in the root cortex. This leads to high accumulation of ROS (including H₂O₂), which initiates PCD and lysis of the cortical cells (i.e., aerenchyma formation). Note that direct scavenging of H₂O₂ by MT proteins remains to be elucidated, but some genetic studies support MT-mediated H₂O₂ reduction. Aer, aerobic conditions; WL, waterlogged conditions; ap, apoplast; cs, cytosol.