CHARACTERIZATION OF THE WHEAT MR 15000 GRAIN-SOFTNESS PROTEIN AND ANALYSIS OF THE RELATIONSHIP BETWEEN ITS ACCUMULATION IN THE WHOLE SEED AND GRAIN SOFTNESS
Cj. Jolly et al., CHARACTERIZATION OF THE WHEAT MR 15000 GRAIN-SOFTNESS PROTEIN AND ANALYSIS OF THE RELATIONSHIP BETWEEN ITS ACCUMULATION IN THE WHOLE SEED AND GRAIN SOFTNESS, Theoretical and Applied Genetics, 86(5), 1993, pp. 589-597
The Mr 15000 protein associated with water-washed wheat starch granule
s from soft wheats was shown to be heterogeneous: it could be divided
into a fraction containing one or more alpha-amylase inhibitor subunit
s and a fraction largely composed of a previously uncharacterised poly
peptide(s) referred to as the ''grain-softness protein'' (GSP). The ma
jor N-terminal sequence and sequences of peptides derived from proteas
e digests of GSP are reported. An antiserum specific for GSP was used
to show that GSP accumulated in both hard and soft wheat grains, but t
he GSP in soft grains associated more strongly with starch granules th
an the GSP in hard grains. A positive correlation between grain softne
ss and accumulation of GSP in the seed was demonstrated for a range of
cultivars. This differs from the qualitative relationship, based on t
he isolated starch fraction, between GSP and grain softness that has a
lready been reported. Analysis of wholemeal extracts with the antiseru
m demonstrated that the accumulation of GSP in the seed was dependent
on the short arm of chromosome 5D, which also encodes the Ha locus. In
addition, examination of near-isogenic lines differing in hardness in
dicated that the gene(s) controlling GSP was (were) linked with the Ha
locus. The findings indicate that GSP may be the product of the Ha lo
cus and thus be the major factor that determines the milling character
istics of bread wheats.