Barley Plants Overexpressing Ferrochelatases (Hvfc1 And Hvfc2) Show Improved Photosynthetic Rates And Have Reduced Photo-Oxidative Damage Under Drought Stress Than Non-Transgenic Controls

We investigated the roles of twoFerrochelatases (FCs), which encode the terminal enzyme for heme biosynthesis, in drought and oxidative stress tolerance in model cereal plant barley (Hordeum vulgare). Three independent transgenic lines ectopically overexpressing either barleyFC1orFC2were selected and evaluated under well-watered, drought, and oxidative stress conditions. BothHvFC1andHvFC2overexpressing transgenics showed delayed wilting and maintained higher photosynthetic performance relative to controls, after exposure to soil dehydration. In each case,HvFCoverexpression significantly upregulated the nuclear genes associated with detoxification of reactive oxygen species (ROS) upon drought stress. Overexpression ofHvFCs, also suppressed photo-oxidative damage induced by the deregulated tetrapyrrole biosynthesis mutanttigrina(d12). Previous studies suggest that onlyFC1is implicated in stress defense responses, however, our study demonstrated that bothFC1andFC2affect drought stress tolerance. As FC-derived free heme was proposed as a chloroplast-to-nuclear signal, heme could act as an important signal, stimulating drought responsive nuclear gene expression. This study also highlighted tetrapyrrole biosynthetic enzymes as potential targets for engineering improved crop performance, both in well-watered and water-limited environments.