Cell & Molecular Biology Program Event
Ms. Parna Ghosh
Cellular and Molecular Biology
University of Vermont
Role of Heme Oxygenase in regulating expression of ROS-generating enzymes in Medicago truncatula
Tuesday September 10th, 2013
Heme Oxygenase (HO) is an enzyme universally found in animals, plants and microbes. In plants, the role of heme oxygenase in the synthesis of the phytochrome chromophore is well recognized and has been extensively studied; however its role in regulating reactive oxygen species (ROS) in plants is just beginning to be explored, particularly in legumes. Legumes interact with Rhizobium bacteria to form symbiotic nitrogen fixing nodules. ROS plays an important role in the development of roots as well as symbiotic nodules. The ROS regulatory enzymes are localized to organelles such as mitochondria, chloroplasts and peroxisomes as well as in the cytosol and extracellular space (apoplast). The M. truncatula giraffe mutant has a deletion that removes the entire HO coding sequence. We are testing the role of M. truncatula GIRAFFE HO in regulating expression of ROS genes such as plant homologs of NADPH oxidase (RBOHs), superoxide dismutase and a cell wall peroxidase. We found that in roots, the wild-type function of GIRAFFE is to upregulate expression of RBOHA and RBOHC. We are also testing if GIRAFFE regulates expression of the LATD gene that plays a role in regulating several ROS-generating enzymes. We are currently investigating the role of GIRAFFE in the regulation of nodule senescence, since the expression of GIRAFFE HO is highest in a senescing nodule. At present, with changing climatic conditions and exposure to various environmental stresses that can alter ROS homeostasis, characterizing the role of GIRAFFE in the antioxidant machinery of legumes can be useful in improving crop productivity and for enhancing soil fertility.