Abstract
Tracheary element (TE) differentiation involves the morphological events such as secondary wall formation and programmed cell death which are spatiotemporally regulated. To elucidate the regulation mechanism of TE morphogenesis, we paid attention to the generation of reactive oxygen species (ROS) which are well-known signal molecules in the process of hypersensitive response. We found, by nitroblue tetrazolium (NBT) staining, that superoxide was generated on the cell surface at an apex of immature TEs and TE precursor cells. The area of superoxide generation was consistent with the initiation area of secondary wall formation recognized by FITC-WGA. When DPI, a suicide inhibitor of NADPH oxidase, was added prior to the secondary wall formation, superoxide generation at the apex and subsequent TE differentiation were suppressed, suggesting that local superoxide generated by NADPH oxidase plays a role in the initiation of secondary wall.
