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. 1995 Nov;109(3):743–750. doi: 10.1104/pp.109.3.743

Identification and characterization of a phloem-specific beta-amylase.

Q Wang 1, J Monroe 1, R D Sjölund 1
PMCID: PMC161373  PMID: 8552713

Abstract

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.

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Selected References

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