Abstract
In tetrapyrrole biosynthetic pathway, isoforms of glutamyl-tRNA reductase (HEMA) and Fe-chelatase (FC) mainly express in non-photosynthetic organs, such as roots and hypocotyls, suggesting they function for heme biosynthesis in these organs. However, the expression of HEMA2 and FC1 was induced in photosynthetic organs by cycloheximide, suggesting that the expression of HEMA2 and FC1 in photosynthetic organs was usually repressed but induced under some stress conditions. To clarify this hypothesis, Arabidopsis HEMA2 or FC1 promoter- GUS construct was subjected to stress conditions. The GUS activity specifically increased in wounded area and the whole body of ozone fumigated leaves, showing that the expression of HEMA2 and FC1 is induced under oxidative stress conditions. cDNA array analysis of wounded leaves revealed that HEMA2, FC1 were rapidly induced within 15 min, and co-induced with heme-proteins related to defense response. The physiological functions of HEMA2 and FC1 under oxidative stress conditions will be discussed.
