Plant Physiol. Drug Metab Dispos
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Plant Physiology 80:1-6 (1986)
© 1986 American Society of Plant Biologists

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Articles

Lectins in Castor Bean Seedlings 1

Suzanne M. Harley2 and Harry Beevers

Biology Department, University of California, Santa Cruz, California 95064

The amounts of the two lectins (ricin and Ricinus communis agglutinin) in tissues of castor bean seedlings were followed during germination and early growth. For measurement, lectins in extracts were separately eluted from Sepharose columns; an antibody to the agglutinin was also used to detect the lectins by immunodiffusion. The endosperm of the dry seed contains 3.5 mg total lectin (5.6% of the total seed protein), which declines by 50% by day 4 and more rapidly thereafter as the tissue is completely consumed. The cotyledons of the dry seed also contain lectins but the amounts are less than 1% of those in the endosperm, and, as in the endosperm, they are constituents of the albumin fraction of the isolated protein bodies. No lectins were detected in the green cotyledons of 10-day seedlings that had been exposed to light from day 5. The embryonic axes of 2-day seedlings contained very small amounts of lectins but they were not detectable in the aerial parts of seedlings grown for 3 weeks or in cells from endosperm grown in tissue culture.

The ability of proteinases and glycosidases (isolated from endosperm of 4-day seedlings) to hydrolyze the lectins was examined. No hydrolysis of the two lectins was observed, but the subunits, separated by reduction with 2-mercaptoethanol, were hydrolyzed slowly by a proteinase and some release of mannose was observed in the presence of the glycosidases. Ricin was converted to its subunits by cysteine and an enzyme in an endosperm extract accelerated chain separation by glutathione.

2 Predoctoral fellowship from the National Science Foundation. Present address: Biology Department, University of California, Los Angeles, CA 90024.

1 Supported by National Science Foundation Grant PCM 78-19575 from the United States National Science Foundation.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1986 by the American Society of Plant Biologists