Developing grains influence terminal senescence and heat stress response by regulating oxidative stress and defense in wheat flag leaves

Abstract

Heat stress at grain development is a major threat for global wheat production systems. This study investigated the impact of high temperature stress on wheat cultivar HW2041 and its cytoplasmic male sterile (CMS) line during grain development and its effects on leaf senescence and antioxidant defense mechanisms. Late-sown wheat crops experienced extreme high temperature stress, resulting in a shorter grain growth duration compared to normal-sown crops. Heat stress accelerated leaf senescence, as indicated by a faster decline in green flag leaf area, chlorophyll, and protein content. However, the CMS line exhibited delayed senescence and maintained higher levels of these parameters under heat stress. Heat stress also induced oxidative stress, with increased levels of reactive oxygen species (ROS), lipid peroxidation, and protein oxidation. However, the CMS line displayed better antioxidant defense mechanisms, including higher activities of antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POX) and increased levels of ascorbate (AsA) and glutathione (GSH). Moreover, the CMS line exhibited better defense mechanisms in the chloroplast and mitochondria compared to the fertile line, indicating their involvement in regulating senescence and stress responses. Our findings suggest that the CMS line possesses improved heat stress tolerance and a more efficient antioxidant defense system, contributing to delayed senescence and reduced oxidative damage. This study provides valuable insights into the effects of high temperature stress on wheat and highlights the importance of genetic variations in heat stress tolerance.