II. 26. Location to barley chromosomes of genes for some major grain protease inhibitors.
J. Hejgaard and S. Bjørn, Department of Biochemistry and Nutrition, Technical University of Denmark, DK-2800 Lyngby, Denmark, and G. Nielsen, Agricultural Research Department, Risø National Laboratory, DK-4000 Roskilde, Denmark.
Chromosome location of structural genes coding for protease inhibitors was based on wheat-barley addition lines obtained from Dr. A.K.M.R. Islam, Adelaide. Inhibitors in wheat and barley grain extracts were separated by isoelectric focusing, and different types of inhibitors were detected by specific negative-staining procedures and identified with monospecific antibodies (Hejgaard 1981).
A gene coding for a specific subtilisin inhibitor (SI) (Yoshikawa et al. 1976) was located on chromosome 2, and a gene for the major endosperm trypsin inhibitor (TI) (Mikola and Suolinna 1969) was on chromosome 3. For these two inhibitor loci we propose the designations Isa 1 (inhibitor of subtilisin amylosaccharitics) and Itc 1 (inhibitor of trypsin and chymotrypsin), respectively. In spite of the high resolution and sensitivity of the techniques used, expressions of gene coding for the two homologous, but immunochemically distinct, inhibitors of both chymotrypsin and microbial serine proteases (CI-1 and CI-2) (Hejgaard and Boisen 1980) could not be detected in grains of the addition lines studied. A wheat addition line containing barley chromosome 5 was, however, unavailable, but a wheat with a translocated barley 5S chromosome was included in the experiments. Thus, the results indicate that genes for the two inhibitors CI-1 and CI-2 are located on the long arm of barley chromosome 5, but further confirmation is needed. To reduce confusion we already now propose the loci designations Ica 1 and Ica 2 (inhibitor of chymotrypsin and Aspergillus proteinasae) for the two lysine-rich chymotrypsin inhibitors CI-1 and CI-2, respectively.
References:
Hejgaard, J. 1981. Isoelectric focusing of subtilisin inhibitors: Detection and partial characterization of cereal inhibitors of chymotrypsin and microbial proteases. Anal. Biochem. 116:444-449.
Hejgaard, J. and S. Boisen. 1980. High-lysine proteins in Hiproly barley breeding: Identification, nutritional significance and new screening methods. Hereditas 93:311-320.
Mikola, J. and E. M. Suolinna. 1969. Purification and properties of a trypsin inhibitor from barley. European J. Biochem. 9:555-560.
Yoshikawa, M., T. Iwasaki, M. Fujii and M. Oogaki. 1976. Isolation and some properties of a subtilisin inhibitor from barley. J. Biochem. 79:765-773.