Identification and characterization of a phloem-specific beta-amylase.
A monoclonal antibody, RS 5, was raised by injecting sieve elements isolated from tissue cultures of Streptanthus tortuosus (Brassicacae) into BALB/c mice and screening resultant hybridoma supernatants for the labeling of phloem using immunofluorescence microscopy. The RS 5 monoclonal antibody identifies a 57-kD protein on immunoblots, which is present in phloem-forming tissue cultures of S. tortuosus but is absent in cultures that lack phloem. Purified 57-kD protein of S. tortuosus is demonstrated to be a phloem-specific beta-amylase. Partial peptide sequences of the 57-kD protein of S. tortuosus are shown to be 96% identical with the corresponding portions of a deduced sequence reported for a major form of beta-amylase in Arabidopsis thaliana. The RS 5 antibody cross-reacts with the major form of A. thaliana beta-amylase on immunoblots, and the antibody also binds to the sieve elements of A. thaliana using immunofluorescence microscopy. The results suggest that the major form of A. thaliana beta-amylase is a phloem-specific enzyme.
Wang
Q
Q
Department of Biological Sciences, University of Iowa, Iowa City 52242, USA.
Monroe
J
J
Sjölund
R D
RD
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D017360:Arabidopsis / Q000201:enzymology; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000276:immunology / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010944:Plants / Q000201:enzymology*; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014018:Tissue Distribution; D001614:beta-Amylase / Q000276:immunology / Q000302:isolation & purification*
D000911:Antibodies, Monoclonal; D007527:Isoenzymes; D010446:Peptide Fragments; D001614:beta-Amylase