Detection of y-type Subunit at the Glu-A1 Locus in Some Swedish Bread Wheat Lines

Electrophoretic and reversed phase high performance liquid chromatographic (RP-HPLC) analyses were performed
on gluten proteins extracted from flours milled from two different Swedish bread wheat lines; these lines have been reported to
possess a novel high M(r) glutenin subunit controlled by a gene at the Glu-A1 locus, referred to as 21*. Although RP-HPLC
indicated that subunit 21* has a surface hydrophobocity similar to that of the commonly occurring allelic subunits 1 or 2*, it
differs from them in isoelectric point, being more basic when analysed by two dimensional gel electrophoresis (IEF/SDSPAGE).
RP-HPLC separations of high ill, glutenin subunits showed the presence of an additional peak, tile behaviour of which
was similar to that of y-type subunits encoded by genes at the Glu-A1y locus and present only in wild wheats T. urartu (AA) or
T. dicoccoides (AABB). Based on chromatographic results and on the tight linkage observed with subunit 21*, it is suggested
that the additional component (indicated as 21*y), present in the breeding Lines analysed, corresponds to the y-type subunit
encoded at the Glu-A1 locus. Genes encoding the subunits 21* and 21*y were also analysed by polymerase chain reaction
(PCR). Contrary to what was observed for the polypeptide itself. the gene corresponding to subunit 21* was similar in size to
that encoding subunit 2* and shorter than that corresponding to subunit 1. Moreover, the amplification product corresponding to
tile active 21*y gene was shorter than that of the allelic inactive gene present in the bread wheat cultivar Cheyenne. As reported
for other high M(r) glutenin subunits, gene size differences observed were due to a different length of the repetitive region.
Because cultivated polyploid wheats have been shown to have only the x-type subunit at the Glu-il? locus, ii is speculated that
the new combination, with both x- and y-type subunits expressed, might have been introgressed during breeding processes from
the wild wheat progenitors T. urartu or T. dicoccoides, which have genotypes expressing both types of subunits.