Peptide AEDL Activates Metabolism and Autophagy in Root Cells of Nicotiana tabacum.

The short peptide AlaGluAspLeu (AEDL) stimulates shoot and root development in Nicotiana tabacum. Growing tobacco in the presence of AEDL was found to induce autophagy and programmed cell death, as demonstrated using immunodetection of the autophagy marker ATG8 and cytochrome c in the cytoplasm, as well as the detection of DNA breaks using the TUNEL assay. A detailed study of the ultrastructure of Nicotiana tabacum root cells grown in the presence of AEDL using transmission electron microscopy revealed fundamental structural differences from control cells. Control cells contained only lytic vacuoles, while in the presence of AEDL, tobacco root meristem cells contained predominantly protein-storing vacuoles and amyloplasts with numerous starch granules in the stroma. Characteristic types of phagophores were identified, forming numerous small autophagosomes with cytoplasmic regions, multivesicular bodies, or concentric membranes, possibly with cytoskeletal elements. Expression of autophagy protein genes revealed a decrease in TOR expression, which promoted autophagy activation and prevented ATG13 phosphorylation. ATG8 gene expression significantly increased in the presence of the AEDL peptide. Schematic diagrams of autophagy processes in root cells of control plants and those grown in the presence of AEDL are presented. Based on these data, it was concluded that stimulation of tobacco plant development in the presence of the AEDL peptide at a concentration of 10-7 M occurs due to the activation of metabolic processes and autophagy. Moreover, the synthesis of metabolites exceeds the required amount of nutrients, which accumulate in vacuoles and leucoplasts.