Overexpression of Vitreoscilla hemoglobin gene enhances flooding resistance in Brassica napus

Flooding can lead to oxygen deprivation in rapeseed, negatively affecting its growth and development and ultimately reducing yields. Vitreoscilla hemoglobin (VHb), a bacterial hemoglobin with a high oxygen-binding affinity, plays a key role in enhancing oxygen uptake and metabolic efficiency under low-oxygen conditions. Through genetic transformation, we overexpressed the VHb gene in rapeseed, which resulted in significant improvements in survival rate, root length, and biomass under submerged conditions. Additionally, we observed that transgenic plants developed adventitious roots in response to submergence stress. These transgenic plants also exhibited increased activities of ethanol dehydrogenase and pyruvate decarboxylase—enzymes associated with anaerobic respiration. Our findings indicate that VHb enhances flooding tolerance in rapeseed by promoting adventitious root formation and strengthening the plant's capacity for fermentation metabolism under anaerobic conditions.