Victor Breno Faustino Bezerra¹, João Victor Dourado Alves Brito¹, Lorenna Maria Neves Freitas¹, Gabriela Oliveira Matos¹, Murilo Siqueira Alves¹

The imminent scenario of climate change and long periods of drought, along with problems such as hunger and malnutrition, is being aggravated. As a result, interest in and the search for new crop alternatives have increased. Among them, cowpea (Vigna unguiculata [L.] Walp.) is perceived as a great option to address these problems, given its high productivity combined with a high concentration of carbohydrates and proteins, both in its grains and in its leaves, shoots and pods, as well as its expressive resistance to abiotic stresses, especially water scarcity. However, cowpea is mainly susceptible to pathogens, and among them the main one that generates major losses in terms of productivity is the Cowpea Severe Mosaic Virus (CPSMV). Among the known mechanisms in plants linked to pathogen responses, programmed cell death (PCD) is highly linked to the production of reactive oxygen species (ROS) and the process of hypersensitive response (HR). Ferroptosis is a non-apoptotic and recently discovered type of PCD, where cell death occurs through the reaction between cytosolic accumulated Fe⁺² and H₂O₂, which ultimately lead to lipid peroxidation and cell death. The aim of this study was to identify evidence of the ferroptosis process during the infection of susceptible and resistant cowpea cultivars with CPSMV. To this end, plants of the cultivars Pitiúba and Marataoã were infected with CPSMV while still in the first expanded trefoil, and others were only mechanically damaged. Among the infected plants after the 12-hour period, the ferroptosis inhibitor ferrostatin (Fer-1) was applied, and all treatments were collected from uninoculated opposite leaves 48 hours post inoculation (hpi). In order to evaluate the damage caused by the pathogen's systemic infection, markers such as malonaldehyde (MDA) and hydrogen peroxide (H₂O₂) were quantified. The Pitiúba cultivar showed a decrease in hydrogen peroxide content in the infected plants treated with Fer-1, while the infected plants showed a greater accumulation of H₂O₂. While the Marataoã plants showed the same content among all treatments. The MDA content of all the cultivars remained the same among treatments. This shows a lower level of lipid peroxidation in the infected leaves of both cultivars, but the H₂O₂ content in Pitiúba showed a possible relationship with the ferroptosis process after treatment with the inhibitor. In addition to the biochemical markers of stress, the activity of enzymes related to the redox state of plant cells was also assessed. Thus, the activity of the enzyme catalase (CAT) was measured between the two cultivars, with a lower activity observed in the Pitiúba cultivar after treatment with Fer-1, while in Marataoã only a decrease was observed in infected plants. Activity of superoxide dismutase (SOD) was also evaluated, showing differences only in infected Marataoã plants. While the activity of ascorbate peroxidase (APX) was observed to be reduced in Pitiúba plants treated with Fer-1, the same was observed in Marataoã. Therefore, it was possible to observe a difference in both stress indicator molecules and enzymes in the contrasting cultivars, indicating some kind of regulation linked to ferroptosis, which could be related to a mechanism of resistance to CPSMV in cowpea plants.

Agradecimentos: I would therefore like to thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for supporting the study, as well as the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), which made this work possible.