cDNA cloning and nucleotide sequences of a1 and a2 thionins from hexaploid wheat endosperm

Abstract

Thionins are homologous ‘ys-nch proteins Of about kD that have been isolated from different tissues in a wide range Table 1. Characteristics ofcDNAs encoding a, and az thionins from hexaplo;d ,,,heat of plant taxa and are active against plant pathogens both in vitro and in vivo (Fernindez de Caleya et al., 1972; Garcia- Olmedo et al., 1992; Carmona et al., 1993). The available amino acid sequences (either directly determined or deduced from cDNAs) have been classified into five well-defined Organism: Loci Products: Relevant Feature of the Products: Triticum aestivum L. cv Chinese Spring. Pur-57, a, thionin; Pur-DI, a2 thionin. structural types. Two of these types, I and V, are present in wheat endosperm (Castagnaro et al., 1992; Garcia-Olmedo et al., 1992). Type I corresponds to those thionins included in the original purothionin mixture obtained from wheat flour by Balls and co-workers (Balls et al., 1942). This mixture was resolved through CM-cellulose chromatography into two components, a and /3 purothionins (Redman and Fisher, 1968). The presence of structural genes for the a purothionin fraction in the long arms of chromosomes 1B and 1D of hexaploid wheat and for the /3 component in the long arm of chromosome 1A was subsequently demonstrated (Fernindez de Caleya et al., 1976). The a purothionin fraction was later resolved by ion-exchange chromatography into two compo- nents, a1 and az, whose amino acid sequences differ in six positions (Jones and Mak, 1977) and whose genes are respec- tively located on chromosomes 1B and 1D (Fernandez de Caleya et al., 1976).