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

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