Abstract
In tetrapyrrole biosynthetic pathway, isoforms of glutamyl-tRNA reductase (HEMA2) and Fe-chelatase (FC1) mainly express in non-photosynthetic organs. Previously, we showed that the expression of HEMA2 and FC1 was induced in photosynthetic organs by wounding or ozone exposure. Here, the effects of oxidative stresses on the expression of HEMA2 and FC1 were assessed using reagents generating reactive oxygen species (ROS). Treatment of methyl viologen or Rose Bengal induced the expression of both genes, suggesting ROS generation is involved in the induction. Heme contents in roots of knockout mutant of each gene were about half of respective wild types. In wild types, heme contents were increased by ozone, while in both mutants, the reduction of the ozone-induction was observed. These results suggest the existence of tetrapyrrole biosynthetic pathway, which is normally function for heme biosynthesis in non-photosynthetic organs, but induced in photosynthetic organs under oxidative conditions to supply heme for defensive hemoproteins.
