The B-, G- and S-genomic Chi genes in family Triticeae

Abstract

As result of a close evolutionary relationship between Triticeae B, G, and S genomes, the exchange of genetic material between them is possible and may be beneficial for broadening the genetic diversity of cultivated bread wheat. However, the extent to which regulatory networks are conserved remains poorly researched. Here, the structural organization and transcriptional activity of the B, S, and G genome copies of a gene encoding flavonoid biosynthesis enzyme chalcone-flavanone isomerase (CHI) were explored using introgression lines which differ from the wild type by carrying a non-bread wheat Chi-1 gene. Chi-S1, Chi-G1, and Chi-B1 all mapped to a comparable region of chromosomes 5S, 5G, and 5B, respectively. Nucleotide sequences of Aegilops speltoides Chi-S1 and Triticum timopheevii Chi-G1 were determined and compared with T. aestivum Chi-B1 sequences. The enzymes encoded by these three genes shared the same predicted tertiary structure and active sites. However, the replacement of Chi-B1 by Chi-S1 or Chi-G1 in a wheat background resulted in a significant decrease in the global amount of the Chi-1 transcript present in the seedling shoot indicating divergence in regulation of expression of the orthologous Chi-1 genes among Triticeae ssp.

Keywords

• aegilops speltoides
• chalcone-flavanone isomerase
• flavonoid biosynthesis
• gene cloning and mapping
• triticum aestivum
• triticum timopheevii
• wheat genome evolution