Molecular characterization of vernalization loci VRN1 in wild and cultivated wheats

<p>Abstract</p> <p>Background</p> <p>Variability of the <it>VRN1 </it>promoter region of the unique collection of spring polyploid and wild diploid wheat species together with diploid goatgrasses (donor of B and D genomes of polyploid wheats) were investigated. Accessions of wild diploid (<it>T. boeoticum</it>, <it>T. urartu</it>) and tetraploid (<it>T. araraticum, T. timopheevii</it>) species were studied for the first time.</p> <p>Results</p> <p>Sequence analysis indicated great variability in the region from -62 to -221 nucleotide positions of the <it>VRN1 </it>promoter region. Different indels were found within this region in spring wheats. It was shown that <it>VRN1 </it>promoter region of B and G genome can also contain damages such as the insertion of the transposable element.</p> <p>Some transcription factor recognition sites including hybrid C/G-box for TaFDL2 protein known as the <it>VRN1 </it>gene upregulator were predicted inside the variable region. It was shown that deletions leading to promoter damage occurred in diploid and polyploid species independently. DNA transposon insertions first occurred in polyploid species. At the same time, the duplication of the promoter region was observed in A genomes of polyploid species.</p> <p>Conclusions</p> <p>We can conclude that supposed molecular mechanism of the <it>VRN1 </it>gene activating in cultivated diploid wheat species <it>T. monococcum </it>is common also for wild <it>T. boeoticum </it>and was inherited by <it>T. monococcum</it>. The spring polyploids are not related in their origin to spring diploids. The spring <it>T. urartu </it>and goatgrass accessions have another mechanism of flowering activation that is not connected with indels in <it>VRN1 </it>promoter region. All obtained data may be useful for detailed insight into origin of spring wheat forms in evolution and domestication process.</p

VRN1 genes variability in tetraploid wheat species with a spring growth habit

Abstract Background Vernalization genes VRN1 play a major role in the transition from vegetative to reproductive growth in wheat. In di-, tetra- and hexaploid wheats the presence of a dominant allele of at least one VRN1 gene homologue (Vrn-A1, Vrn-B1, Vrn-G1 or Vrn-D1) determines the spring growth habit. Allelic variation between the Vrn-1 and vrn-1 alleles relies on mutations in the promoter region or the first intron. The origin and variability of the dominant VRN1 alleles, determining the spring growth habit in tetraploid wheat species have been poorly studied. Results Here we analyzed the growth habit of 228 tetraploid wheat species accessions and 25 % of them were spring type. We analyzed the promoter and first intron regions of VRN1 genes in 57 spring accessions of tetraploid wheats. The spring growth habit of most studied spring accessions was determined by previously identified dominant alleles of VRN1 genes. Genetic experiments proof the dominant inheritance of Vrn-A1d allele which was widely distributed across the accessions of Triticum dicoccoides. Two novel alleles were discovered and designated as Vrn-A1b.7 and Vrn-B1dic. Vrn-A1b.7 had deletions of 20 bp located 137 bp upstream of the start codon and mutations within the VRN-box when compared to the recessive allele of vrn-A1. So far the Vrn-A1d allele was identified only in spring accessions of the T. dicoccoides and T. turgidum species. Vrn-B1dic was identified in T. dicoccoides IG46225 and had 11 % sequence dissimilarity in comparison to the promoter of vrn-B1. The presence of Vrn-A1b.7 and Vrn-B1dic alleles is a predicted cause of the spring growth habit of studied accessions of tetraploid species. Three spring accessions T. aethiopicum K-19059, T. turanicum K-31693 and T. turgidum cv. Blancal possess recessive alleles of both VRN-A1 and VRN-B1 genes. Further investigations are required to determine the source of spring growth habit of these accessions. Conclusions New allelic variants of the VRN-A1 and VRN-B1 genes were identified in spring accessions of tetraploid wheats. The origin and evolution of VRN-A1 alleles in di- and tetraploid wheat species was discussed