Gene expression in alloploids: genetic control of lipopurothionins in wheat.

Lipopurothionins are complexes of basic polypeptides and polar lipids found in petroleum ether extracts of wheat endosperm. Location of the structural genes for the protein moiety and of genes probably controlling the lipid moiety has been achieved by analysis of compensated nulli-tetrasomic and ditelosomic lines of Triticum aestivum L. cv. Chinese Spring, as well as of other genetic stocks. There are two electrophoretic variants of the apoprotein designated alpha and beta purothionins. Structural genes for alpha purothionins are located in the long arm of chromosomes 1B and 1D, and for the beta variant in the long arm of 1A. These genes have been tentatively designated Pur-A1, Pur-B1, and Pur-D1. The aminoacid composition of purified alpha and beta purothionins from Triticum aestivum (genomes AABBDD) and T. durum (AABB), and of beta purothionin from T. monococcum (AA) is also consistent with this conclusion and suggests that the alpha purothionin encoded by gene Pur-B1 probably differs from that encoded by gene Pur-D1 in at least three positions of the aminoacid sequence. A gene (or genes) located in the short arm of chromosome 5D markedly affects the level of lipopurothionin but does not affect apoprotein synthesis. It is concluded that they control the lipid moiety which is required for solubility in petroleum ether.