Homoeologous chromosomal location of the genes encoding thionins in wheat and rye

Thionins are high sulphur basic polypeptides present in the endosperm of Gramineae. In wheat there are three thionins encoded by genes located in the long arms of chromosomes 1A, 1B and 1D. Rye has one thionin encoded by a gene which has been assigned to chromosome 1R after analysis of the Imperial-Chinese Spring rye-wheat disomic addition lines. Commercial varieties and experimental stocks with a 1B/1R substitution carry the thionin from rye ( R) instead of the B thionin from wheat. The R thionin gene is not located in the large chromosomal segment representing most of the short arm of chromosome 1R

Thiocalsin: a thioredoxin-linked, substrate-specific protease dependent on calcium.

We describe a protease, named "thiocalsin," that is activated by calcium but only after reductive activation by thioredoxin, a small protein with a redox-active disulfide group that functions widely in regulation. Thiocalsin appeared to be a 14-kDa serine protease that functions independently of calmodulin. The enzyme, purified from germinating wheat grain, specifically cleaved the major indigenous storage proteins, gliadins and glutenins, after they too had been reduced, preferentially by thioredoxin. The disulfide groups of the enzyme, as well as its protein substrates, were reduced by thioredoxin via NADPH and the associated enzyme, NADP-thioredoxin reductase. The results broaden the roles of thioredoxin and calcium and suggest a joint function in activating thiocalsin, thereby providing amino acids for germination and seedling development