Mineral nutrient content restricts viral RNA accumulation and the systemic spread of Groundnut bud necrosis virus in Vigna unguiculata

Abstract

Groundnut bud necrosis virus (GBNV), a plant virus belonging to the family Bunyaviridae and the genus Orthotospovirus, features a tripartite ambisense RNA genome. It primarily infects crops from the leguminosae and solanaceae families, causing distinctive symptoms such as chlorotic and necrotic spots. Present study aims to elucidate the effect of a few macro- and micro-nutrients supplementation on the progression of viral disease in cowpea plant. Study suggested that supplementation of macro-nutrients (P and K) and micro-nutrient (Zn) reduced viral accumulation and limits the viral spread in plant. Occurrence of oxidative stress and cell death by viral infection was judged by the increased concentration of ROS both at virus inoculated and systemic sites. Plants exhibited a decrease in ROS accumulation and cell death, supplemented with P, K and Zn than Mn supplemented and non-supplemented plants under viral infection. Antioxidant enzymes (CAT, SOD, GR and APX) activities were also increased in the plants supplemented with P, K and Zn than supplemented with Mn and non-supplemented plants. Expression levels of oxidative stress responsive miRNAs along with their corresponding target transcripts were also altered during nutrient supplementation in cowpea plants. Expression of miR319a.2, controlling metacaspase-8 (responsible for initiation of cell death) showed up-regulation, whereas miR398 and miR482 controlling COX-5b (responsible for mitochondrial ROS production) and NBS-LRR (responsible for disease resistance) genes, respectively showed down-regulation in the plants supplemented with P, K and Zn than the plants supplemented with Mn and non-supplemented. The study highlights the accumulation of ROS and PCD, along with the modulation of ROS and PCD-responsive genes during GBNV infection at both the inoculation and systemic sites, influenced by nutrient supplementation. The findings also discuss the potential of nutrient supplementation as a strategy to enhance viral resistance.