DELTA-TONOPLAST INTRINSIC PROTEIN DEFINES UNIQUE PLANT VACUOLE FUNCTIONS

Plant cell vacuoles may have either storage or degradative functions. Vegetative storage proteins (VSPs) are synthesized in response to woun ding and to developmental switches that affect carbon and nitrogen sin ks. Here we show that VSPs are stored in a unique type of vacuole that is derived from degradative central vacuoles coincident with insertio n of a new tonoplast intrinsic protein (TIP), delta-TIP, into their me mbranes. This finding demonstrates a tight coupling between the presen ce of delta-TIP and acquisition of a specialized storage function and indicates that TIP isoforms may determine vacuole identity.