VRN-B1 VARIABILITY IN TRITICUM SPP. REVEALED BY IN-SILICO APPROACH AND MOLECULAR MARKERS

Author(s)
Angione, Giuseppina
Esposito, Salvatore
Date Issued
2024
Type
conferenceObject
Abstract
The Vernalization gene (Vrn-1) encodes a MADS-box transcription factor that regulates vernalization-induced flowering in cereals, promoting the vegetative-to-reproductive phase transition under the effect of low temperature. Mutations in promoter or intron regions account for the differences between dominant and recessive alleles, controlling vernalization response and wheat growth habit (spring vs winter). Several alleles at Vrn-1 homoeologous loci were identified, that offer diverse effects in regulating important traits (heading date, flowering time, plant height, grain yield, and yield-related traits). Although genetic mapping has allowed the identification of Vrn-1 homoalleles, gene length still represents a limitation for developing functional markers, starting from sequence polymorphisms present in allelic variants. As a result, many molecular markers were developed by amplifying short fragments, leading to a puzzling in the allele nomenclature. In this work, the Vrn-B1 gene along with its promoter sequence was investigated in fifteen Triticum chromosome assembled genomes, including twelve bread wheat (T. aestivum L.), a spelt wheat (T. spelta cv. PI190962), a wild emmer (T. dicoccoides cv. Zavitan), and a durum wheat reference genome (T. durum cv. Svevo). In addition, ~190 Triticum spp. accessions, including spring, facultative, and winter genotypes of different tetraploid wheat species (T. turgidum, T. carthlicum, T. turanicum, T. polonicum,T. dicoccoides, T. dicoccum, and T. durum) were screened with a set of molecular markers available in the literature.The in-silico approach found one Vrn-B1 copy per genome, with 56% of recessive alleles on chromosome 5B. Interestingly, two bread wheat genotypes (Sy Mattis and Arinarfold) harbored the recessive allele vrn-B1 on chromosome 7B, suggesting either translocation events or misassembled regions in these two genotypes. The dominant allele Vrn-B1a was found in Mace, Kariega, and Landmark, whereas Lancet had the dominant Vrn-B1f and PI190962 (T. spelta) Vrn-B1c. However, despite observed intronic variability, the promoter region was highly conserved within T. aestivum genotypes, since all sequences were identical to the promoter of Triple Dirk C, classified as recessive vrn-B1 at the intron level. By contrast, several sequence polymorphisms were identified among different species. The molecular screening of tetraploid wheat species confirmed the high abundance of the recessive allele, with the only exception for Farvento, the first T. dicoccum genotype harboring the Vrn-B1f allele and suggesting a common origin of this allele.Our findings reveal key insights into Vrn-B1 loci genomic rearrangements and the evolutionary origins of dominant wheat alleles in Triticum spp. The discovery of a common origin for Vrn-B1f and the ongoing targeted resequencing using long and ultralong reads will further clarify the complete structure of Vrn-B1, offering new avenues for wheat genetic research and breeding
Handle
Conference(s)
LXVII SIGA Annual Congress