Genome-wide identification, characteristics and expression of the prolamin genes in Thinopyrum elongatum

Abstract

Background: Prolamins, unique to Gramineae (grasses), play a key role in the human diet. Thinopyrum elongatum (syn. Agropyron elongatum or Lophopyrum elongatum), a grass of the Triticeae family with a diploid E genome (2n = 2x = 14), is genetically well-characterized, but little is known about its prolamin genes and the relationships with homologous loci in the Triticeae species.

Results: In this study, a total of 19 α-gliadin, 9 γ-gliadin, 19 ω-gliadin, 2 high-molecular-weight glutenin subunit (HMW-GS), and 5 low-molecular-weight glutenin subunit (LMW-GS) genes were identified in the Th. elongatum genome. Micro-synteny and phylogenetic analysis revealed dynamic changes of prolamin gene regions and genetic affinities among Th. elongatum, Triticum aestivum, T. urartu and Aegilops tauschii. The Th. elongatum genome, like the B subgenome of T. aestivum, only contained celiac disease epitope DQ8-glia-α1/DQ8.5-glia-α1, which provided a theoretical basis for the low gluten toxicity wheat breeding. The transcriptome data of Th. elongatum exhibited differential expression in quantity and pattern in the same subfamily or different subfamilies. Dough rheological properties of T. aestivum-Th. elongatum disomic substitution (DS) line 1E(1D) showed higher peak height values than that of their parents, and DS6E(6D) exhibited fewer α-gliadins, which indicates the potential usage for wheat quality breeding.

Conclusions: Overall, this study provided a comprehensive overview of the prolamin gene family in Th. elongatum, and suggested a promising use of this species in the generation of improved wheat breeds intended for the human diet.

Keywords: Celiac disease; Evolution; Expression; Prolamins; Thinopyrum elongatum.

Fig. 1

Characteristic comparisons of prolamin genes. A The number of each prolamin gene subfamily among Th. elongatum, T. aestivum, T. urartu and Ae. tauschii. B Pseudogene rates of α-gliadin, γ-gliadin and LMW-GS gene families among four selected species

Fig. 2

Chromosome location and gene duplication of prolamin genes. Tandem duplicated genes were marked by red, green or blue, respectively

Fig. 3

Micro-synteny analysis of ω-, γ-gliadin and LMW-GS genes. The relationship of these families is indicated by blue, red, and orange lines, respectively

Fig. 4

Phylogenetic tree of α-gliadin genes. The phylogenetic tree was constructed by MEGA X with the maximum likelihood (ML) method and 1000 bootstrap replications. GQ139528.1 was set as outgroup. Different clades are marked with vertical bars and the genes of different species can be judged by their names

Fig. 5

Expression profiles of prolamin genes. The putative functional genes were marked with an asterisk after the gene name

Fig. 6

Electrophoretic map and rheological properties. A A-PAGE electrophoretic patterns of gliadins of CS and DS6E(6D). B 15% SDS-PAGE electrophoretic patterns of glutenins from CS, DS1E(1D). C-D Rheological properties of CS, DS1E(1D) respectively