Physical and molecular responses to flooding in Brassicaceae

Global flooding events are becoming more frequent due to climate change. Depending on the intensity, flooding can cause below-ground plant tissues to become waterlogged and above-ground plant tissues to become partially or fully submerged, leading to hypoxic environments. These conditions can damage plant tissue, leading to chlorosis and senescence, and typically halting plant growth and development, resulting in significant yield loss. Many economically important Brassicaceae crops are susceptible to flooding stress, such as Brassica napus (canola), Brassica oleracea (broccoli, cabbage, Chinese kale), and Brassica rapa (caisin), as well as the Brassicaceae model species Arabidopsis thaliana, which has led to the characterization of physical and molecular responses of these species under flooding. Additionally, comparative studies with native wetland Brassicaceae species, such as species in the Rorripa genus and Nasturtium officinale (watercress), provide insight into phenotypic and genetic adaptive traits to flooded environments. This review reports the current knowledge of morphological, physiological, and molecular responses of Brassicaceae species under flooding stress, highlighting both interspecies and intraspecies comparisons that reveal shared and distinct adaptations and mechanisms involved in flooding responses. We include a discussion of candidate genes with the potential to improve flooding tolerance in Brassicaceae crops and future directions for this field of research.