Freezing Tolerance in the Triticeae - Translational Genomics for Crop Breeding: Abiotic Stress, Yield and Quality - page 109

genes show a trend that copy-numbers are higher
in genotypes having a vrn-1 winter allele than
in genotypes having a Vrn-1 spring allele. As
VRN-1 is the key factor required to make
the reproductive transition from the vegetative
growth phase, it will be interesting to bet-
ter understand this association between VRN-1
allelic state and CBF copy-numbers. The appar-
ent increase in copy-numbers of the hard red win-
ter wheats over the soft red winter wheats is also
associated with the greater capacity of the hard
red winter wheats to survive the semi-arid win-
ters of the Great Plains (Knox et al. 2010). It will
be interesting to determine whether this greater
level of winter hardiness is associated only with
the increase in CBF14 copy-number or whether
other loci are similarly affected and perhaps are
even playing a role in potentiating the capacity of
CBF14 to activate its target genes. The increase
in copy-number together with a vernalization-
responsive VRN-1 allele likely could have been
co-selected by breeders, unconsciously, or con-
sciously, since it leads to higher frost hardiness.

ever, the comparison of cold-induced changes in
the transcriptome and metabolome of the two
species is expected to provide new insights into
the consequences of their speciation and poly-
ploidization. The complete sequence of the bar-
ley and wheat genomes will be available in the
near future, allowing this work to progress much
more efficiently. From transcriptome results, it
appears that most of the cold-affected genes are
related to general defense, photosynthetic, and
metabolic processes. In wheat both the effect
of an abrupt decrease in temperature (Monroy
et al. 2007; Kocsy et al. 2010) and of a grad-
ual reduction in temperature (Winfield et al.
2009) were studied. The rationale of the lat-
ter system is the discovery of genes having
different cold-induction threshold temperatures,
which was shown in the case of COR14b gene,
by comparison of wheat genotypes with differ-
ent freezing tolerance (Vagujfalvi et al. 2003;
Galiba et al. 2009). Transcriptome analysis of
cold-acclimated shoots revealed differential reg-
ulation of genes encoding proteins involved in
regulatory and metabolic processes in winter vs.
spring genotypes (Gulick et al. 2005; Monroy
et al. 2007). As between winter and spring
wheats, such differences may also exist between
wheat (more tolerant) and barley, due to their dif-
ferential freezing tolerance. The number of low
temperature-induced genes also depends on the
level of freezing tolerance as it was described in
wheat (Monroy et al. 2007; Kocsy et al. 2010;
Winfield et al. 2010), and a species-dependent
difference in this parameter is also probable. In
wheat many genes (related to flowering and gib-
berellin pathway) were affected by cold either
only in the crown or only in leaves during the
vegetative-to-generative transition as was shown
by microarray analysis (Winfield et al. 2009).
Similarly, different cold-induced changes
were observed in gene expression in leaf and
crown tissues of wheat by the cDNA-AFLP
method (Ganeshan et al. 2011). The cold-
induced alterations in the transcriptome were
studied much less extensively in barley than in
hexaploid wheat. Prolonged cold response was

Wheatvs. Barley Genomics of
FrostTolerance:Common and
Specific Mechanisms

In the first part of this chapter, genomics of freez-
ing tolerance in Triticeae was compared with
an overview of the results obtained by mapping
and sequencing approaches. In addition to the
static aspects of the genomic information such as
DNA sequence or structural variation, functional
genomics focuses on the dynamic aspects such as
gene transcription and translation. Although sev-
eral authors studied the changes in the transcrip-
tome during cold acclimation (Gulick et al. 2005;
Svensson et al. 2006; Monroy et al. 2007; Skin-
ner 2009; Winfield et al. 2009, 2010; Kocsy et al.
2010; Ganeshan et al. 2011; Greenup et al. 2011)
or proteome (Sarhadi et al. 2010; Rinalducci et al.
2011; Vitamvas et al. 2012) of wheat and barley,
so far only two comparative studies investigating
transcriptome in both species have been reported
(Cho et al. 2006; Schreiber et al. 2009). How-