Mecanismos moleculares e bioquímicos envolvido na germinação de sementes de feijão-caupi (Vigna unguiculata L.) tratadas com inibidor da enzima oxidase alternativa (AOX)

Abstract

Plants have mechanisms that enable them to grow and develop under adverse conditions. Among them, the alternative pathway of mitochondrial respiration mediated by alternative oxidase (AOX) stands out, which is an enzyme seen as a key point of cellular reprogramming and in the control of the formation of reactive oxygen species (ROS) under stress conditions. Germination occurs with intense mitochondrial respiration that can lead to an increase in ROS, which must be controlled to maintain cellular redox homeostasis. The study model was the cowpea (Vigna unguiculata L.), a crop of great importance for human and animal nutrition. Thus, the present study aims to analyze the role of AOX during the germination process of cowpea seeds, relating the biochemical, physiological and molecular processes. For this

purpose, cowpea seeds were treated with variable concentrations (1, 2.5 and 5 mM) of n- propyl gallate (PG) and analyzed at 16, 32 and 48 h after the beginning of germination. Then,

analyses of germination behavior, antioxidant metabolism and transcriptomic analysis were performed to identify differentially expressed genes related to the main metabolic pathways of the germination process. The results revealed that the 5 mM PG concentration caused germination inhibition at 16 h, followed by a reduction in germination at 2.5 and 5 mM at 32 h and subsequent recovery at 48 h. Thus, the 2.5 mM concentration was chosen, which proved to be a borderline concentration capable of altering the germination process, for the analyses of antioxidant metabolism and transcriptomics. Furthermore, the reduction of germination by PG was associated with lower initial H2O2 levels and higher antioxidant activity, while recovery at 48 h was closely related to the consistent upregulation of AOX, mainly AOX1, together with genes related to xenobiotic detoxification and NAD(P)H metabolism. Thus, it is concluded that the inhibition of AOX by PG caused an increase in cellular redox activity that was associated with the reduction of germination during the initial hours, while the upregulation of AOX was closely related to the subsequent recovery of germination at 48 h. Thus, the information obtained in the present study provides basic information on the effect of PG during seed germination and the differential expression profile of the main genes involved in the germination process.