Characterization of two novel γ-gliadin genes encoded by K genome of Crithopsis delileana and evolution analysis with those from Triticeae

The γ-gliadin-like γ-prolamin genes in the tribe Triticeae

The γ-prolamins are important components of seed storage proteins in wheat and other Triticeae species. Here, the γ-prolamin genes from the diploid Triticeae species were systemically characterized. Most of the γ-prolamins (except 75 K γ-secalins) characterized were defined as γ-gliadin-like γ-prolamins, since they shared same characteristic model structure with γ-gliadins. Over one-third of these putatively functional γ-prolamin peptides contained different number of cysteine residues as compared to the eight residues present in γ-gliadins. Sequence polymorphism and linkage disequilibrium analyses showed the conservation of γ-prolamin genes in Triticeae species under evolutionary selection. Phylogenetic analyses indicated that these γ-prolamin genes can not be clearly separated according to their genomic origins, reflecting the conservation of γ-gliadinlike γ-prolamin genes after the divergence of Triticeae species. A screening of coeliac disease (CD) toxic epitopes shows that the γ-prolamins from some other genomes contain much fewer epitopes than those from the A, S (B) and D genomes of wheat. These findings contribute to better understanding of γ-prolamin family in Triticeae and build a ground for breeding less CD-toxic wheat cultivars.

Isolation and phylogenetic analysis of novel γ-gliadin genes in genus Dasypyrum

As the most ancient member of the wheat gluten family, the γ-gliadin genes are suitable for phylogenetic analysis among wheat and related species. Species in the grass genus Dasypyrum have been widely used for wheat cross breeding. However, the genomic relationships among Dasypyrum species have been little studied. We isolated 22 novel γ-gliadin gene sequences, among which 10 are putatively functional. The open reading frame lengths of these sequences range from 642 to 933 bp, and these putative proteins consist of five domains. Phylogenetic analyses showed that all Dasypyrum γ-gliadin gene sequences clustered in a large group; D. villosum and tetraploid D. breviaristatum γ-gliadin gene sequences clustered in a subgroup, while diploid D. breviaristatum γ-gliadin gene sequences clustered at the edge of the subgroup. All of the Dasypyrum γ-gliadin gene sequences were absent in three major T cell-stimulatory epitopes binding to HLA-DQ2/8 in celiac disease patients. Based on the phylogenetic analyses, we suggest that D. villosum and tetraploid D. breviaristatum evolved in parallel from a diploid ancestor D. breviaristatum.

Isolation and characterization of a Psathyrostachys huashanica Keng 6Ns chromosome addition in common wheat

The development of alien addition lines is important for transferring useful genes from exotic species into common wheat. A hybrid of common wheat cv. 7182 (2n = 6x = 42, AABBDD) and Psathyrostachys huashanica Keng (2n = 2x = 14, NsNs) via embryo culture produced the novel intergeneric disomic addition line 59-11. The seed morphology of 59-11 resembled the parent 7182 and it exhibited extreme agronomic characteristics, i.e., twin stable spikelets, fertile florets, and multi-kernel clusters. Furthermore, 59-11 produced plump kernels with a high seed-setting percentage during the advanced maturation stage. The line was screened based on genomic in situ hybridization, EST-SSR, EST-STS, and gliadin to identify P. huashanica chromatin in the wheat background. The chromosome number and configuration of 59-11 was 2n = 44 = 22 II and we confirmed the 6Ns disomic chromosome additions based on A-PAGE analysis and molecular markers. The results suggested that the production of twin spikelets and multiple kernels per spike in the wheat-P. huashanica addition line was related to homologous group 6 in the wheat chromosome. This is the first report of the introduction of improved spike traits into common wheat from the alien species P. huashanica and it opens up the possibility of increasing the wheat yield based on this enlarged gene pool.