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Articles

Differential Accumulation of Proteinase Inhibitor I in Normal and Crown Gall Tissue of Tobacco, Tomato, and Potato ¹

Clarence I. Kado^b

^a Department of Agricultural Chemistry and Program in Biochemistry and Biophysics, Washington State University, Pullman, Washington 99163, Department of Plant Pathology, University of California, Davis, California 95616

A proteinase inhibitor (inhibitor I) is induced in crown gall tumors of tobacco (Nicotiana tabacum) initiated through infection with the tumorinducing bacterium, Agrobacterium tumefaciens, strains B6 or CG-14. Uninfected tissues do not contain immunologically detectable quantities of inhibitor I. Inhibitor I synthesis in tobacco crown gall tumors paralleled tumor growth at the average rate of about 4.5 µg of inhibitor I per 200 mg of fresh tissue per day. Infection of variegated tobacco mutant Dp-I with A. tumefaciens strain CG-14 produced tumors with 25% more inhibitor than tumors induced with strain B6. Unlike tobacco, tumors induced by either bacterial strain on potato (Solanum tuberosum) and on tomato (Lycopersicum esculentum) did not accumulate inhibitor I. Consequently, inhibitor I accumulation is modulated by the type of plant host used in spite of familial relatedness (Solanaceae) and the strain of A. tumefaciens used for infection.

Immunological and electrophoretic properties of inhibitor I from tobacco crown gall tumor, callus, etiolated, and variegated tissues were compared. Agar immunodiffusion assays showed no apparent differences among precipitin reaction lines between inhibitor I of tumor, callus, variegated, and etiolated tissues. The immunoelectrophoretic mobilities of inhibitor I of tumor, variegated, and etiolated tissues were the same, but differed from that of either normal or crown gall callus tissues. These results suggest that different isoinhibitors of inhibitor I could account for the observed differences in electrophoretic mobilities, or that modification of the inhibitor has occurred sometime during, or after, its synthesis.

³ To whom reprint requests should be addressed.

¹ This work was supported in part by the United States Department of Agriculture Cooperative States Research Service Grant 316-15-30, National Science Foundation Grant GB-37972, and National Institutes of Health Grant CA-11526 from the National Cancer Institute. College of Agriculture Research Center, Scientific Paper No. 4494, Project 1791.