Asparagine-Guided Regulation of Redox Status and Autophagy in Sugar-Starved Lupin (Lupinus spp.) Embryonic Axes—A Transcriptomic and Proteomic Approach

Abstract

Sugar starvation during seed germination requires coordinated regulation of reserve mobilization, redox homeostasis, and intracellular recycling. In lupin seeds, asparagine is a major nitrogen-rich metabolite, but its role in starvation-induced autophagy and redox regulation remains unclear. Here, isolated embryonic axes of white lupin (Lupinus albus L.) and Andean lupin (Lupinus mutabilis Sweet) were cultured in vitro under sucrose-fed or sugar-starved conditions, with or without asparagine supplementation. Using transcriptomic, proteomic, immunoblot, enzymatic, antioxidant activity, and confocal microscopy analyses, we show that sugar starvation induced redox- and autophagy-related reprogramming, including changes in reactive oxygen species (ROS)-related proteins, catalase accumulation, autophagy-related (ATG) gene expression, vacuolar hydrolase-related responses, and proteolytic activity. Peroxisome-associated components, including glycolate oxidase, acyl-CoA oxidase, and catalase, were strongly affected, indicating dynamic remodeling of peroxisome-related metabolism during starvation. Asparagine modified this response by increasing antioxidant capacity and catalase accumulation under sugar starvation, while reducing detectable autophagosome number, many ATG and vacuolar hydrolase transcripts, and proteolytic activity. Together with previous evidence for asparagine-induced accumulation of autophagic bodies in vacuoles, these results are consistent with asparagine-dependent modulation of several autophagy-related processes rather than with an effect restricted to a single autophagic step. White and Andean lupin shared the same general regulatory framework but differed in response intensity. Thus, asparagine links nitrogen status with redox stabilization, vacuolar catabolism, and autophagy-related dynamics in sugar-starved lupin embryonic axes.