Identification and Potential Participation of Lipases in Autophagic Body Degradation in Embryonic Axes of Lupin (Lupinus spp.) Germinating Seeds

Autophagy is a fundamental process for plants that plays a crucial role in maintainingcellular homeostasis and promoting survival in response to various environmental stresses. One ofthe lesser-known stages of plant autophagy is the degradation of autophagic bodies in vacuoles. Tothis day, no plant vacuolar enzyme has been confirmed to be involved in this process. On the otherhand, several enzymes have been described in yeast (Saccharomyces cerevisiae), including Atg15, thatpossess lipolytic activity. In this preliminary study, which was conducted on isolated embryonicaxes of the white lupin (Lupinus albusL.) and Andean lupin (Lupinus mutabilisSweet), the potentialinvolvement of plant vacuolar lipases in the degradation of autophagic bodies was investigated. Weidentified in transcriptomes (using next-generation sequencing (NGS)) of white and Andean lupinembryonic axes 38 lipases with predicted vacuolar localization, and for three of them, similarities inamino acid sequences with yeast Atg15 were found. A comparative transcriptome analysis of lupinisolated embryonic axes culturedin vitrounder different sucrose and asparagine nutrition, evaluatingthe relations in the levels of the transcripts of lipase genes, was also carried out. A clear decreasein lipase gene transcript levels caused by asparagine, a key amino acid in lupin seed metabolismwhich retards the degradation of autophagic bodies during sugar-starvation-induced autophagy inlupin embryonic axes, was detected. Although the question of whether lipases are involved in thedegradation of autophagic bodies during plant autophagy is still open, our findings strongly supportsuch a hypothesis.