Two distinct jacalin-related lectins with a different specificity and subcellular location are major vegetative storage proteins in the bark of the black mulberry tree.
Using a combination of protein isolation/characterization and molecular cloning, we have demonstrated that the bark of the black mulberry tree (Morus nigra) accumulates large quantities of a galactose-specific (MornigaG) and a mannose (Man)-specific (MornigaM) jacalin-related lectin. MornigaG resembles jacalin with respect to its molecular structure, specificity, and co- and posttranslational processing indicating that it follows the secretory pathway and eventually accumulates in the vacuolar compartment. In contrast, MornigaM represents a novel type of highly active Man-specific jacalin-related lectin that is synthesized without signal peptide or other vacuolar targeting sequences, and accordingly, accumulates in the cytoplasm. The isolation and cloning, and immunocytochemical localization of MornigaG and MornigaM not only demonstrates that jacalin-related lectins act as vegetative storage proteins in bark, but also allows a detailed comparison of a vacuolar galactose-specific and a cytoplasmic Man-specific jacalin-related lectin from a single species. Moreover, the identification of MornigaM provides the first evidence, to our knowledge, that bark cells accumulate large quantities of a cytoplasmic storage protein. In addition, due to its high activity, abundance, and ease of preparation, MornigaM is of great potential value for practical applications as a tool and bioactive protein in biological and biomedical research.
Van Damme
Els J M
EJ
Laboratory for Phytopathology and Plant Protection, Catholic University Leuven, 2001 Leuven, Belgium.
Hause
Bettina
B
Hu
Jialiang
J
Barre
Annick
A
Rougé
Pierre
P
Proost
Paul
P
Peumans
Willy J
WJ
D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D031625:Morus / Q000235:genetics / Q000378:metabolism*; D024301:Plant Bark / Q000235:genetics / Q000378:metabolism*; D037121:Plant Lectins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D043244:Ribonuclease III; D012639:Seeds / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D018076:DNA, Complementary; D037121:Plant Lectins; D010940:Plant Proteins; C043696:jacalin; C402383:DCL1 protein, Arabidopsis; D043244:Ribonuclease III