The 2NS chromosomal translocation enhances redox homeostasis and mitigates oxidative stress during Magnaporthe oryzae Triticum infection in wheat

Abstract

Wheat blast, caused by the hemibiotrophic fungus Magnaporthe oryzae Triticum (MoT), is a destructive disease that poses a severe threat to global wheat production. The 2NS chromosomal translocation, introgressed from Aegilops ventricosa into the Bangladeshi wheat variety BARI Gom 33 (BG33), was found to confer moderate-to-high resistance to MoT under field conditions. Despite the deployment of 2NS chromosomal segment for providing resistance to wheat blast, the underlying mechanisms remain largely unknown. This study aimed to elucidate the physiological and biochemical bases of resistance in BG33, specifically regarding its capacity to nullify infection-induced oxidative stress. Comparative analysis between the resistant variety (BG33) and a susceptible variety (BARI Gom 26, BG26) revealed that BG33 maintained significantly lower accumulation of reactive oxygen species (ROS), including hydrogen peroxide (H₂O₂), and exhibited reduced lipid peroxidation (malondialdehyde, MDA) and lipoxygenase (LOX) activity post-inoculation. BG33 also retained higher photosynthetic pigment integrity (chlorophyll and carotenoids), indicating superior protection against oxidative cellular damage. Most importantly, BG33 displayed enhanced antioxidant activity both constitutively and in response to MoT-induced oxidative stress. Basal levels of catalase (CAT), peroxidase (POD), glutathione peroxidase (GPX), ascorbate peroxidase (APX), glutathione- S -transferase (GST), and proline were 1.3–2.5-fold higher in BG33 than in BG26. Upon MoT infection, BG33 further upregulated enzymatic antioxidants, including superoxide dismutase, CAT, APX, GPX, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase and proline by 1.2–2.0-fold, establishing a robust state of redox homeostasis that was absent in BG26. These findings suggest that a multi-tiered antioxidant defense system mitigating the oxidative burst in the 2NS translocation, may in part be responsible for preserving cellular function and thus reduces fungal prolifearation. This study also provides evidence that the wheat genotype possessing enhanced constitutive or inducible antioxidant potentially through 2NS translocation can contribute to the resistance against wheat blast compared to ones lacking 2NS translocation. Future research should focus on identifying and cloning the key 2NS regulatory genes governing these antioxidant pathways.