A cluster of 11 CBF transcription factors is located at the frost tolerance locus Fr-A m 2 in Triticum monococcum

Abstract

Due to the adverse effects of cold temperatures on winter wheat, frost tolerance is an important trait for breeding programs in regions with severe winters. Frost tolerance locus Fr-A(m)2 was recently discovered in diploid wheat (Triticum monococcum L.). This locus was mapped as a QTL on chromosome 5A(m) in the same region as a QTL for the level of transcription of the cold-regulated gene COR14b at 15 degrees C. A CBF transcription factor was mapped in the center of these two overlapping QTLs. However, since the CBF gene family in wheat has numerous members, it was possible that multiple CBF genes were present at Fr-A(m)2. To investigate this possibility we initiated a systematic characterization of the CBF family in T. monococcum. Here we report the molecular characterization of thirteen TmCBF genes. Nine of them were numbered according to the closest barley HvCBF gene, and the other four that have no clear barley orthologues were assigned numbers TmCBF15 to TmCBF18. TmCBF5 and TmCBF18 were mapped on T. monococcum chromosomes 7A(m) and 6A(m), respectively, and are thus not candidates for the Fr-A(m)2 gene. The remaining eleven TmCBF genes are clustered at the Fr-A(m)2 locus within five different Bacterial Artificial Chromosome (BAC) clones. These BACs were mapped using a high-density map and recombination events were found between most BACs. Lines carrying these recombination events will be useful to identify which of the CBF genes is responsible for the differences in frost tolerance between the T. monococcum parental lines at the Fr-A(m)2 locus.

Large deletions in the CBF gene cluster at the Fr-B2 locus are associated with reduced frost tolerance in wheat

“…An in-depth study of the CBF gene family in T. monococcum identified 15 CBF genes, eleven of which are present as a cluster at the Fr-2 locus on chromosome 5A m (Miller et al 2006). A subsequent high-density mapping study of this region suggested that the CBF12, CBF14 and CBF15 genes were most likely to account for the observed differences in cold tolerance within the specific T. monococcum mapping population used in this study (Knox et al 2008).…”

“…The CBF gene cluster on chromosome 5B of wheat, showing the gene order in the proximal cluster as proposed by Miller et al (2006) (see Discussion for further details on alternative gene orders at this locus). Also shown are the regions of the CBF cluster included in the six-, nine-and eleven-gene deletions identified in this study Survival rates of hexaploid lines with a spring and winter growth habit following exposure to −6 °C in artificial freezing experiments.…”

“…Whereas Arabidopsis has three CBF genes present as a tandem cluster, wheat and other members of the Pooideae family have undergone a large expansion of this gene family, with eleven genes at the Fr-2 locus, eight of which are Pooideae-specific (Badawi et al 2007;Miller et al 2006;Skinner et al 2005). This expansion has been dated to coincide with a period of global cooling during the Eocene-Oligocene transition approximately 33 MYA (Sandve and Fjellheim 2010) and it has been proposed that the increase in the number of CBF genes and diversity at this locus may have occurred as a result of selection pressure for improved frost tolerance by this period of lower temperatures.…”

“…1), but the orientation of the four linked CBF genes in the proximal cluster (which were all present in a single BAC clone) could not be established due to the lack of recombination among these genes. A CBF-17-CBF-9-CBF-4-CBF-2 order was initially proposed to maximize the physical proximity of the more similar paralogs (Miller et al 2006) but the alternative order (CBF-2-CBF-4-CBF-9-CBF-17) was later favored by Knox et al (2008) to be consistent with the CBF gene order found in barley (Francia et al 2007). If we assume that these large deletions within the Fr-B2 cluster arise from distinct single deletion events, the most likely order of the proximal cluster is CBF17-CBF9-CBF4-CBF2 as initially suggested by Miller et al (2006) and as presented in Fig.…”

C-Repeat Binding Factor and Dehydrin Genes are Induced Co-Ordinately in Drought Tolerance Response of Wheat Cultivars

“…Cbf14 and Cbf15 genes of wheat were first identified in Triticum monococcum L. and mapped to a major locus determining frost tolerance in this species (Miller et al, 2006). Cbf14 and Cbf15 of Triticum aestivum were functionally tested by transformation of barley, proving the role of these genes in freezing tolerance (Soltész et al, 2013).…”