Plant cell vacuoles may have storage or lytic functions, but biochemical ma
rkers specific for the tonoplasts of functionally distinct vacuoles are poo
rly defined. Here, we use antipeptide antibodies specific for the tonoplast
intrinsic proteins alpha-TIP, gamma-TIP, and delta-TIP in confocal immunof
luorescence experiments to test the hypothesis that different TIP isoforms
may define different vacuole functions. Organelles labeled with these antib
odies were also labeled with anti-pyrophosphatase antibodies, demonstrating
that regardless of their size, they had the expected characteristics of va
cuoles. Our results demonstrate that the storage vacuole tonoplast contains
delta-TIP, protein storage vacuoles containing seed-type storage proteins
are marked by alpha- and delta- or alpha- and delta- plus gamma-TIP, wherea
s vacuoles storing vegetative storage proteins and pigments are marked by d
elta-TIP alone or delta- plus gamma-TIP. In contrast, those marked by I-TIP
alone have characteristics of lytic vacuoles, and results from other resea
rchers indicate that alpha-TIP alone is a marker for autophagic vacuoles. I
n root tips, relatively undifferentiated cells that contain vacuoles labele
d separately for each of the three TIPs have been identified. These results
argue that plant cells have the ability to generate and maintain three sep
arate vacuole organelles, with each being marked by a different TIP, and th
at the functional diversity of the vacuolar system may be generated from di
fferent combinations of the three basic types.