title: Two jasmonate-inducible myrosinase-binding proteins from Brassica napus L. seedlings with homology to jacalin.
abstract: Two homologous but different cDNAs encoding a 97-kDa and a 70-kDa protein from Brassica napus L. seedlings have been characterized. Both proteins contain sequence motifs with high homology to the IgA binding lectin, jacalin, and the deduced 97-kDa protein contains the peptide sequences of myrosinase-binding protein. The 70-kDa and the 97-kDa protein can both be isolated as a complex containing myrosinase, indicating they indeed are myrosinase-binding proteins. We provide evidence that the 70-kDa protein binds IgA in vitro, and therefore classify the protein as a jacalin-type lectin. Both the 97-kDa and the 70-kDa proteins are encoded by a small number of genes in the Brassica genome. The mRNA for the 97-kDa protein is detected in both light- and dark-grown seedlings, whereas the mRNA for the 70-kDa protein is mainly detected in etiolated seedlings. The transcript levels for both proteins are transient and are rapidly increased by methyl jasmonate. The 70-kDa protein is synthesized de novo during germination and accumulates mainly in the hypocotyl and in the root. By immunogold labeling we show that a few cells scattered in the cotyledons of young seedlings (approx. 5% of total cells), contain protein-body-like structures with the 70-kDa protein. These bodies are present in a 10,000 g pellet from which the 70-kDa protein can be extracted by sodium carbonate. In addition, the 70-kDa protein is detected in the amorphous structures of the vacuole in a few cells of the cotyledon, the hypocotyl and the root.
authors.affiliation: Department of Physiology, Carlsberg Laboratory, Copenhagen Valby, Denmark.
authors.forename: N
authors.initials: N
authors.lastname: Geshi
authors.forename: A
authors.initials: A
authors.lastname: Brandt
mesh_terms: D000595:Amino Acid Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D001937:Brassica / Q000254:growth & development / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003517:Cyclopentanes / Q000494:pharmacology*; D018076:DNA, Complementary; D018525:Germination; D006026:Glycoside Hydrolases / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D037102:Lectins / Q000235:genetics*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D054883:Oxylipins; D037121:Plant Lectins; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000201:enzymology / Q000378:metabolism
chemical_list: C111628:70-kDa protein, Brassica; C111629:97-kDa protein, Brassica; D002352:Carrier Proteins; D003517:Cyclopentanes; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; D037102:Lectins; D054883:Oxylipins; D037121:Plant Lectins; D012333:RNA, Messenger; C043696:jacalin; C011006:jasmonic acid; D006026:Glycoside Hydrolases; C022739:thioglucosidase