Interactions between the nitrate reductase 2 and catalase 1 fine-tune disease resistance in cassava.

Cassava is one of the most important tuber crops that is used for food, starch and bio-energy. However, cassava is susceptible to a number of diseases, especially cassava bacterial blight (CBB). Nitric oxide (NO) and hydrogen peroxide (H2O2) regulate plant growth and development, as well as stress responses. However, no direct relationships between the enzymes involved in the metabolic enzymes that produce and process these key signaling molecules has been demonstrated. Here, we provide evidence for the interaction between the nitrate reductase 2 (MeNR2) and catalase 1 (MeCAT1) proteins in vitro and in vivo, using yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays, respectively. MeNR2 is a positive regulator and MeCAT1 is a negative regulator of CBB resistance. MeNR2 was localized in the nucleus, cell membrane and peroxisome, while MeCAT1 was localized in the peroxisomes. The interactions between MeNR2 and MeCAT1 also had effects of their respective enzyme activities. Taken together, the data presented here suggested that there is coordination between H2O2 and NO signaling in cassava disease resistance, through the interactions between MeCAT1 and MeNR2.