Tonoplast Intrinsic Protein Isoforms as Markers for Vacuolar Functions

Abstract

Plant cell vacuoles may have storage or lytic functions, but biochemical markers specific for the tonoplasts of functionally distinct vacuoles are poorly defined. Here, we use antipeptide antibodies specific for the tonoplast intrinsic proteins ␣ -TIP, ␥ -TIP, and ␦ -TIP in confocal immunofluorescence experiments to test the hypothesis that different TIP isoforms may define different vacuole functions. Organelles labeled with these antibodies were also labeled with antipyrophosphatase antibodies, demonstrating that regardless of their size, they had the expected characteristics of vacuoles. Our results demonstrate that the storage vacuole tonoplast contains ␦ -TIP, protein storage vacuoles containing seed-type storage proteins are marked by ␣ -and ␦ -or ␣ -and ␦ -plus ␥ -TIP, whereas vacuoles storing vegetative storage proteins and pigments are marked by ␦ -TIP alone or ␦ -plus ␥ -TIP. In contrast, those marked by ␥ -TIP alone have characteristics of lytic vacuoles, and results from other researchers indicate that ␣ -TIP alone is a marker for autophagic vacuoles. In root tips, relatively undifferentiated cells that contain vacuoles labeled separately for each of the three TIPs have been identified. These results argue that plant cells have the ability to generate and maintain three separate vacuole organelles, with each being marked by a different TIP, and that the functional diversity of the vacuolar system may be generated from different combinations of the three basic types.

Members of the aquaporin family in the developing pea seed coat include representatives of the PIP, TIP, and NIP subfamilies

“…Vacuoles containing seed-type storage proteins are marked by α-TIPs together with γ -and/or δ-TIPs, whereas those marked by γ -TIP alone have characteristics of lytic vacuoles (Jauh et al, 1999). Being the aquaporins of the tonoplast, TIPs are thought to permit a more rapid transcellular water flow by increasing the effective cross-section of the cytoplasm, and to facilitate osmotic adjustment between cytosol and vacuole.…”

“…Representatives of the PIPs, TIPs, NIPs, and SIPs have been identified in the moss Physcomitrella patens, indicating that the four subfamilies were already established when land plant evolution began (Borstlap, 2002). The PIP subfamily can be further divided into the highly homologous but clearly distinct subgroups PIP1 and PIP2, whereas the TIP subfamily consists of five subgroups, including the α-, γ -, and δ-TIPs which may be markers of different types of vacuoles (Jauh et al, 1999). According to a new nomenclature the subgroups of α-, γ -, and δ-TIPs are now designated TIP3, TIP1, and TIP2, respectively (Johanson et al, 2001;Chaumont et al, 2001).…”

Rice SCAMP1 Defines Clathrin-Coated,trans-Golgi–Located Tubular-Vesicular Structures as an Early Endosome in Tobacco BY-2 Cells

“…Control assays to ascertain the specificity of double labeling experiments were performed as described previously (Jauh et al, 1999;Jiang et al, 2000). Briefly, for labeling experiments with two polyclonal antibodies, primary antibodies were incubated at 48C overnight (in PBS supplemented with 0.1% Triton X-100 [PBST] þ 1% BSA) followed by washing in PBST.…”

Catabolismo de sacarose durante a mobilização do galactomanano e sua importância na estratégia de sobrevivência de plântulas de Sesbania virgata (Cav.) Pers.

“…O vacúolo, por exemplo, é um importante elemento tanto no armazenamento quanto na compartimentalização dos produtos de degradação, sendo essencial nos ciclos de síntese e degradação da sacarose que ocorrem nas células ( evidenciada por diferentes isoformas de proteínas do tonoplasto, que podem ser utilizadas como marcadores de função desses vacúolos (Jauh et al 1999). Neste trabalho, as plântulas crescidas na luz não foram submetidas a uma condição de competição.…”