Bark and Leaf Lectins of Sophora japonica Are Sequestered in Protein-Storage Vacuoles

Abstract

The leguminous tree Sophora japonica contains a family of closely related, but distinct, lectins. Different members of this family are independently expressed in seeds, leaves, and bark (CN Hankins, J Kindinger, LM Shannon 1987 Plant Physiol 83: 825-829; 1988 Plant Physiol 86: 67-10). The inter-, and intracellular distribution of the bark and leaf lectins was studied by indirect postembedding immunogold electron microscopy.AMdehyde fixed bark and leaves postifixed with OS04 and embedded in LR White resin permitted sensitive and specific immunogold labeling while maintaining cellular ultrastructure. The The leaf, bark, root, and stem tissue of several different legumes have been described as containing lectins or other immunologically CRM2 (8, 9, 14, 18, 20, 22; see Ref. 3 for review).Partial amino acid sequences of these nonseed lectins or CRM indicate that each of these proteins is closely related to, but not identical to the seed lectin of the same plant (8,9,14). The lectins of legume seeds have been documented to be localized in storage vacuoles or protein bodies (see Ref. 3 for review). In contrast, immunologically related nonseed legume lectins have been localized by light microscopic immunocytochemistry in the vacuoles of soybean root tips (22), the cell wall in Dolichos stems and leaves (4), and the cytoplasm of Dolichos tissue culture and leaf cells (4, 13). The apparent variability of the localization of nonseed legume lectins contrasts with the electron microscopic localization of lectin in the vacuoles of adult wheat roots (17) and the light microscopic localization of lectin in protein-storage vacuoles of the Elder tree (Sambucus) bark (7).Recent amino-terminal protein sequence and immunological cross-reaction data have shown that the seed, leaf, and bark lectins of the legume tree Sophora japonica are distinct but closely related gene products (8, 9). We have used high resolution electron microscopic immunocytochemistry to localize leaf and bark lectins. These observations demonstrate that the leaf and bark lectins are sequestered in protein-storage vacuoles. ' Research in laboratory of L. M. S. is supported by the National Science Foundation.2 Abbreviations: CRM, cross-reacting materials; TBST, tris-buffered saline containing Tween-20. MATERIALS AND METHODSSophora japonica leaf samples were obtained from a tree growing on the U.C. Riverside campus (8) (19). After labeling, the grids were washed with TBST, then with double distilled water, and were stained with 5% aqueous uranyl acetate for 20 min followed by alkaline lead citrate (33 mg ml-1) for 5 min. The grids were examined and photographed with a Hitachi H500 electron microscope.

Sorting of proteins to vacuoles in plant cells

“…acids, and anthocyanins [7,62,121]. They may store proteins; vacuolar storage proteins are most prominent in seeds but may also occur in many different vegetative tissues [27,31,32,106]. Previous concepts of vacuole biogenesis and function hypothesized that protein storage vacuoles represented portions of the central vacuole that subdivided as deposits of storage protein accumulated [17,115].…”

The 32-Kilodalton Vegetative Storage Protein of Salix microstachya Turz

“…In general, they are not homologous to seed storage proteins of the same species (19). Vegetative storage proteins have been localized in protein-storage vacuoles within parenchymal cells of vegetative tissues (6,8,23), the organelles being similar in both ontogeny and structure to protein bodies found in mature dicotyledonous seed storage parenchymal cells (5).…”

“…Vegetative storage proteins have been isolated from various plant organs including soybean pods and leaves (19), potato and yam tubers (7,16), and roots of perennial weeds (4) and from the wood, bark, and leaves of temperate trees (6,8,17,21,24,26). In general, they are not homologous to seed storage proteins of the same species (19).…”

The shoot meristem identity gene TFL1 is involved in flower development and trafficking to the protein storage vacuole

“…Some Arabidopsis vegetative storage proteins are anti-insect acid phosphatases (12). PSVs are found in roots, tubers, bark parenchyma, and paraveinal parenchyma (13)(14)(15) and are probably in the perennial root systems of plants whose shoots die in winter (e.g., perennial grasses) (16)(17)(18)(19)(20). Accumulation of proteins into PSVs and later degradation for renewed growth is important physiologically for many plant cells and organs.…”