Colocalization of barley lectin and sporamin in vacuoles of transgenic tobacco plants.
Various targeting motifs have been identified for plant proteins delivered to the vacuole. For barley (Hordeum vulgare) lectin, a typical Gramineae lectin and defense-related protein, the vacuolar information is contained in a carboxyl-terminal propeptide. In contrast, the vacuolar targeting information of sporamin, a storage protein from the tuberous roots of the sweet potato (Ipomoea batatas), is encoded in an amino-terminal propeptide. Both proteins were expressed simultaneously in transgenic tobacco plants to enable analysis of their posttranslational processing and subcellular localization by pulse-chase labeling and electron-microscopic immunocytochemical methods. The pulse-chase experiments demonstrated that processing and delivery to the vacuole are not impaired by the simultaneous expression of barley lectin and sporamin. Both proteins were targeted quantitatively to the vacuole, indicating that the carboxyl-terminal and amino-terminal propeptides are equally recognized by the vacuolar protein-sorting machinery. Double-labeling experiments showed that barley lectin and sporamin accumulate in the same vacuole of transgenic tobacco (Nicotiana tabacum) leaf and root cells.
Schroeder
M R
MR
Department of Energy Plant Research Laboratory, Michigan State University, East Lansing 48824-1312.
Borkhsenious
O N
ON
Matsuoka
K
K
Nakamura
K
K
Raikhel
N V
NV
D000595:Amino Acid Sequence; D001692:Biological Transport; D002451:Cell Compartmentation / Q000235:genetics*; D003433:Crosses, Genetic; D001467:Hordeum / Q000235:genetics; D007150:Immunohistochemistry; D037102:Lectins / Q000235:genetics / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D037121:Plant Lectins; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000378:metabolism; D010947:Plants, Toxic; D011058:Pollen; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000235:genetics; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*; D014675:Vegetables / Q000235:genetics
D037102:Lectins; D037121:Plant Lectins; D010940:Plant Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; C076978:barley lectin; C067142:sporamin protein, Ipomoea batatas