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also observed genetic polymorphism and nucleotide diversity of puroindoline genes
in einkorn wheat and
T. urartu
accessions. A new translocation lines (5A
m
S.5AS)
from CS background carries puroindolines and
GSP-1
alleles that confer softer ker-
nel texture. Massa et al. (
2004
) analyzed 50 accessions of
Ae. tauschii
which held
enormous diversity at
Ha
locus. Simeone et al. (
2006
) identified putative puroin-
doline proteins with 22 and 28 amino acid replacements while working on diploid
species. In some accessions of
Ae. speltoides
and
Ae. searsii
, a stop codon at final
Tryptophane of
PINA
was observed while in other accessions one-residue was de-
leted inin
PINB
(Lillemo et al.
2002
).
StructureofGenesatHaLocus
The intronless coding regions of the
Pina-D1
and
Pinb-D1
genes of bread wheat are
447 bp long. The genes are 70.2 % identical in the coding regions but only ~53 %
identical in the 30 un-translated region (Gautier et al.
1994
). The physical order
of these genes within BAC clones was identified as
Pinb-Pina-Gsp-1
in
T. mono-
coccum
(Tranquilli et al.
1999
)
and
Ae. tauschii
(Turnbull et al.
2003
). There are
several reports where additional partial copy of
Pina-D1
has been found on 5DL.
Bahve and Morris (
2008
) discussed in detail the gene expression their regulation
and promoter sequences of puroindolines. The characterization of nucleotide se-
quence in A and B genome of tetraploid wheat, the 50 boundary of the
Ha
locus was
defined by
Gsp
gene. A gene cluster known as Gene7 and Gene8 was also validated
by the presence of the 30 boundary. Therefore, a ca 55 kb gDNA segment is defined
as the
Ha
locus having the
Pina
,
Pin
b, two
Pinb
degenerated copies, Gene3 (only in
D-genome) and Gene5. Chantret et al. (
2005
) identified a deletion of 38 kb in com-
mon wheat instead of Gene3 and Gene5. Instead these genes were annotated in dip-
loid progenitors of hexaploid wheat. In barley, analysis of
Ha
locus identified some
genes clusters were found conserved between wheat and barley (Caldwell et al.
2004
). Some rearrangements were observed in barley hordoindolines (equivalents
of puroindilines) like upstream position of gene from GC2 instead of downstream
(as in wheat) and they are also in the opposite orientation. However, in barley grain
hardiness is focused to their resistance to pest and disease invasion rather than mill-
ing attributes.
The other important part of
Ha
locus is
Gsp-1
gene which is tightly linked to
Pina
and
Pinb
on chromosome 5DS. Unlike Pin genes,
GSP-1
genes are present on
all three group 5 chromosomes in wheat (Chantret et al.
2005
). The nucleotide cod-
ing region of these genes consists of 495 nucleotides without introns and resembles
90-100 % with one another and ~42 % with Pin genes (Bhave and Morris
2008
).
Some studies suggest multiple
Gsp-1
copies per genome in at least some genomes/
accessions (Gollan et al.
2007
) whereas mapping studies show only one gene at the
Ha
locus (Chantret et al.
2005
).
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