Figure 6.

Patterns of ROS accumulation in anther (A–C) and ovule (D–F) of wild-type and Athemn1 mutant plants of Arabidopsis visualized through NBT staining. A and D, Anther (A) and ovule (D) from a wild-type plant showing no or faint NBT staining (blue) in mature pollen and toward the micropylar end in the ovule. B and E, Anther (B) and ovule (E) from an Athemn1-1 plant showing NBT staining (blue) in pollen and around the egg cell and the central cell (CC) in the ovule. The inset in E shows a magnified view of the embryo sac with unfused polar nuclei (UPN; arrows). C and F, Anther (C) and ovule (F) from an Athemn1-2 plant showing intense NBT (blue) staining in the pollen and around the egg cell and the central cell in the ovule. The inset in F shows a magnified view of the embryo sac with unfused polar nuclei (arrows). G to N, Subcellular localization of the AtHEMN1-GFP fusion protein. Root cells and ovules of an Athemn1-1 mutant plant complemented with the AtHEMN1-GFP fusion construct were examined by confocal microscopy after staining with MitoSOX Red. G, GFP fluorescence in a root cell overexpressing AtHEMN1-GFP. H, DIC image of the cell shown in G. I, MitoSOX Red fluorescence of the cell shown in G. J, Merged image of G to I showing colocalization (yellow) of GFP and MitoSOX Red signals, confirming that AtHEMN1 is targeted to the mitochondria. K, GFP fluorescence in an ovule overexpressing AtHEMN1-GFP. L, DIC image of the ovule shown in K. M, MitoSOX Red fluorescence of the ovule shown in K. N, Merged image of K to M showing colocalization (yellow) of GFP and MitoSOX Red signals corresponding to the mitochondrial cloud around the central cell.