The journey of cardosin A in young Arabidopsis seedlings leads to evidence of a Golgi-independent pathway to the protein storage vacuole

The aspartic proteinase cardosin A is a vacuolar enzyme found to accumulate in protein storage and lytic vacuoles the flowers bodies seeds of native plant cardoon. Cardosin was first isolated several decades ago has since been extensively characterized, both terms tissue distribution biochemistry. In system, roles have attributed A, such as reproduction, reserve mobilization, membrane remodeling. To participate diverse events, must travel different compartments within cell: vacuoles, cytoplasmic (and eventually outside cell). Several studies approached expression Arabidopsis thaliana Nicotiana tabacum with promising results for use these systems study trafficking. poly-sorting mechanism uncovered this protein, two sorting determinants, mediating routes, described. conventional C-terminal domain, which delivers vacuole via Golgi, second more unconventional signal—the plant-specific insert (PSI)—that mediates Golgi-independent route. hypothesis that signals are activated according cell needs organs high metabolic activity investigated here. An line expressing under an inducible promoter used understand dynamics regarding accumulation during seed germination events. Using antibodies against regions combining them immunofluorescence immunocytochemistry assays young seedling tissues, detected along secretory pathway vacuole, often associated endoplasmic reticulum. More interestingly, upon treatment drug Brefeldin still indicating intact can bypass Golgi contrary what observed N. . This good starting point further research involving fluorescent fusions exploring detail relationship between trafficking development.