The CBF gene family in hexaploid wheat and its relationship to the phylogenetic complexity of cereal CBFs

Abstract

Most temperate plants tolerate both chilling and freezing temperatures whereas many species from tropical regions suVer chilling injury when exposed to temperatures slightly above freezing. Cold acclimation induces the expression of cold-regulated genes needed to protect plants against freezing stress. This induction is mediated, in part, by the CBF transcription factor family. To understand the evolution and function of this family in cereals, we identiWed and characterized 15 diVerent CBF genes from hexaploid wheat. Our analyses reveal that wheat species, T. aestivum and T. monococcum, may contain up to 25 diVerent CBF genes, and that Poaceae CBFs can be classiWed into 10 groups that share a common phylogenetic origin and similar structural characteristics. Six of these groups (IIIc, IIId, IVa, IVb, IVc and IVd) are found only in the Pooideae suggesting they represent the CBF response machinery that evolved recently during colonization of temperate habitats. Expression studies reveal that Wve of the Pooideae-speciWc groups display higher constitutive and low temperature inducible expression in the winter cultivar, and a diurnal regulation pattern during growth at warm temperature. The higher constitutive and inducible expression within these CBF groups is an inherited trait that may play a predominant role in the superior low temperature tolerance capacity of winter cultivars and possibly be a basis of genetic variability in freezing tolerance within the Pooideae subfamily.

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

“…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.…”

“…In hexaploid wheat, for example, there are at least 15 CBF genes in each of the three wheat genomes, including eleven at each of the three Fr-2 loci (Badawi et al 2007). In barley, variation in CBF copy number was found at the Fr-H2 locus and this variation was associated with differences in freezing tolerance ).…”

Advances in physiological and molecular aspects of plant cold tolerance

“…However, while three closely related CBF genes have been reported in Arabidopsis, wheat and some other cereals have undertaken an extension in this family (Pearce et al 2013). Badawi et al (2007) reported that there are at least 15 CBF genes in each of the three hexaploid wheat genomes.…”

Hv-CBF2A overexpression in barley accelerates COR gene transcript accumulation and acquisition of freezing tolerance during cold acclimation

“…The barley genome harbors more than 20 CBF coding sequences in a single genotype (Skinner et al 2005). At least 13 of these colocalize in a cluster on the long arm of chromosome 5 (Skinner et al 2005(Skinner et al , 2006Miller et al 2006;Badawi et al 2007;Francia et al 2007;Knox et al 2010). These CBFs are grouped into two phylogenetic subgroups-HvCBF3/ CBFIII and HvCBF4/CBFIV, both of which are unique to the grasses (Skinner et al 2005;Badawi et al 2007).…”