|Chu, C - North Dakota State University|
|Tan, C - Oklahoma State University|
|Zhong, S - North Dakota State University|
|Yan, L - Oklahoma State University|
Submitted to: Genes, Genomes, Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2011
Publication Date: 12/1/2011
Citation: Chu, C.G., Tan, C.T., Zhong, S., Xu, S.S., Yan, L. 2011. A novel retrotransposon inserted in the dominant Vm-B1 allele confers spring growth habit in tetraploid wheat (Triticum turgidum L.). Genes, Genomes, Genetics. 1:637:645.
Interpretive Summary: Wheat is traditionally divided into winter and spring wheat based on their requirement for vernalization (exposure of wheat plants at low temperature for inducing flowering). The vernalization requirement in hexaploid bread wheat is mainly determined by three genes VRN-A1, VRN-B1 and VRN-D1 on the long arms of chromosome of 5A, 5B and 5D, respectively. A dominant form (Vrn) at any of the three genes leads to spring growth habit regardless of other vernalization genes, whereas a recessive form (vrn) for all the three genes would lead to winter growth habit. In this study, we observed that a doubled haploid (DH) population derived from a cross of two spring tetraploid wheat lines, a durum cultivar ‘Lebsock’ and a Persian wheat line PI 94749, showed a segregation for winter-spring growth habit. Genetic analysis showed that Lebsock carried the dominant form of Vrn-A1 but the recessive form of vrn-B1, whereas PI 94749 had the recessive form of vrn-A1 but the dominant form of Vrn-B1. The restoration of winter growth habit in the population generated from the two spring parents was due to an incorporation of the two recessive forms vrn-A1 and vrn-B1 in the same line. DNA sequence analysis indicated that DNA variation in VRN-A1 was the same as that previously reported in hexaploid wheat. No difference was found in the previously reported gene region between the dominant and recessive VRN-B1 forms, but a 5,463-bp DNA insertion was detected in the dominant form Vrn-B1. This large insertion was predicted to contain a gene that encodes 1,231 amino acids of a deduced protein, in which the conserved regions belong to retrotransposon (genetic elements that can amplify themselves and insert their copies randomly in a genome) family, and the dominant form Vrn-B1 is thus designated retrotrans_VRN. Markers for the retrotrans_VRN were used to evaluate 154 lines from six tetraploid wheat sub-species, and showed that the retrotrans_VRN frequently exists in Persian wheat, occasionally appear in emmer wheat but rarely occur in other tetraploid wheat sub-species.
Technical Abstract: Wheat is traditionally divided into winter and spring wheat that either has or lacks a vernalization requirement. In this study, a doubled haploid (DH) population derived from a cross between two spring tetraploid wheat (Triticum turgidum L.) genotypes, durum ‘Lebsock’ and Persian wheat accession PI 94749, showed a segregation for winter-spring growth habit. The segregation was controlled by two major QTLs, centered by VRN-A1 and VRN-B1 on chromosomes 5A and 5B, respectively. Experiments from F2 and BC1F2 populations indicated that Lebsock carried the dominant Vrn-A1 but recessive vrn-B1 alleles, whereas PI 94749 had the recessive vrn-A1 but dominant Vrn-B1 alleles. The restoration of winter growth habit in the population generated from the two spring parents was due to an incorporation of the two homozygous recessive alleles vrn-A1 and vrn-B1 in the same line. Sequence analysis indicated that allelic variation in VRN-A1 was the same as that in the previously reported Vrn-A1c in hexaploid wheat. No difference was found in the previously reported allelic region between the dominant Vrn-B1 and recessive vrn-B1 alleles, but a 5,463-bp insertion was detected at the 5’-UTR in the dominant Vrn-B1 allele. This large insertion was predicted to contain an open reading frame encoding 1,231 amino acids of a deduced protein that has several conserved domains in retrotransposon family, and it is thus designated retrotrans_VRN. Marker analysis on 154 accessions from six T. turgidum sub-species showed that the retrotrans_VRN frequently exists in Persian wheat, occasionally appear in cultivated emmer but rarely occur in other tetraploid wheat sub-species.