Abstract text: Plant-specific inserts (PSIs) are unique protein domains found in some plant aspartic proteinases (APs), including cardosins A and B. Previous work demonstrated that the PSI of cardosin A (PSI A) mediates an unconventional trafficking route that bypasses the Golgi. Unconventional pathways (either to the vacuole or to the cell wall) occur frequently when plants face adverse conditions, however little is known regarding the mechanisms behind these routes. The objective of this study was to investigate whether SEC24 isoforms involved in COPII-mediated transport from the endoplasmic reticulum to the Golgi participate in the unconventional trafficking of PSI A. To address this, PSI A-mCherry was transiently expressed in A. thaliana mutant lines carrying altered versions of SEC24A, SEC24B, and SEC24C, and its subcellular localization analysed to assess the impact of each mutation on PSI trafficking. No significant differences were observed in the sec24b and sec24c mutants, however, in the sec24a mutant, PSI A-mCherry was found in large perinuclear aggregates, suggesting that SEC24A, unlike SEC24B and SEC24C, may play a role in the export of PSIs from the endoplasmic reticulum in an unconventional manner. This study suggests that COPII (or SEC24A alone) can be involved in the regulation of unconventional (Golgi-bypassing) routes.