Phylogenetic relationship of a new class of LMW-GS genes in the M genome of Aegilops comosa

Abstract

A new class of low molecular weight glutenin subunit (LMW-GS) genes was isolated and characterized from Aegilops comosa (2n = 2x = 14, MM). Although their DNA structure displayed high similarity to LMW-i type genes, there are some key differences. The deduced amino acid sequences of their mature proteins showed that the first amino acid residue of each gene was leucine and therefore they were designated as LMW-l type subunits. An extra cysteine residue was present in the signal peptide and the first cysteine residue of mature proteins located at the end of repetitive domain. Additionally, a long insertion of 10-22 residues (LGQQPQ(5-17)) occurred in the end of the C-terminal II. Comparative analysis demonstrated that LMW-l type glutenin genes possessed a great number of single-nucleotide polymorphisms and insertions/deletions. A new classification system was proposed according to the gene structure and phylogenetic analysis. In this new system, LMW-GS is classified into two major classes, LMW-M and LMW-I, with each including two subclasses. The former included LMW-m and LMW-s types while the latter contained LMW-l and LMW-i types. Analysis of their evolutionary origin showed that the LMW-l genes diverged from the group 2 of LMW-m type genes at about 12-14 million years ago (MYA) while LMW-i type evolved from LMW-l type at approximately 8-12 MYA. The LMW-s type was a variant form of group 1 of LMW-m type and their divergence occurred about 4-6 MYA. In addition to homologous recombination, non-homologous illegitimate recombination could be an important molecular mechanism for the origin and evolution of LMW-GS gene family. The secondary structure prediction suggested that the novel LMW-l type subunits, such as AcLMW-L1 and AcLMW-L2, may have positive effects on dough properties.

Wheat seed storage proteins: Advances in molecular genetics, diversity and breeding applications

“…tauschii demonstrated common ancestors of the other Glu-D-1-1 alleles in an associated star-like phylogeny, suggestingM A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPTthat there were at least four independent origins of bread wheat(Zhang et al 2008b). In addition to unequal homologous recombination, duplication and deletion of large fragments occurring in Glu-D-1-1 and Glu-3 alleles were attributed to illegitimate recombination(Zhang et al 2008b;Wang et al 2011). The time of the duplication event of x-and y-type subunits could extend to MYA, suggesting that during the origin of cultivated wheat the A and B genomes did not evolve simultaneously, and that they might have been introgressed into hexaploid at different times and rates(Blatter et al 2004).…”

Low‐molecular‐weight glutenin subunits from the 1U genome of Aegilops umbellulata confer superior dough rheological properties and improve breadmaking quality of bread wheat

“…The single‐nucleotide polymorphisms (SNPs) and insertions and deletions (InDels) presented in LMW‐GS genes were identified by means of multiple alignments and Bioedit 7.0. Prediction of secondary structure of the deduced amino acid sequences was carried out by PSIPRED server (http://bioinf.cs.ucl.ac.uk/psipred) on the basis of Wang et al …”

“…Although the typical N‐terminal domain of LMW‐i type subunits is absent, it can also be expressed normally in wheat endosperm as LMW‐m and LMW‐s . In addition to the three types of subunits, a new LMW‐l type subunit was identified in Aegilops species, where the first amino acid residue is leucine …”

“…17 Although the typical N-terminal domain of LMW-i type subunits is absent, it can also be expressed normally in wheat endosperm as LMW-m and LMW-s. 18,19 In addition to the three types of subunits, a new LMW-l type subunit was identified in Aegilops species, where the first amino acid residue is leucine. 20 The extensive allelic variations at Glu-3 loci are considered not only to provide useful information on the origin and evolutionary relationships of bread wheat and related species, but also have great significance for processing qualities of bread wheat. The recombination between polymorphic LMW-GS genes located at the Glu-3 loci was identified, enabling a better understanding the genetic diversity of Glu-3 loci.…”

Diploid genome differentiation conferred by RNA sequencing-based survey of genome-wide polymorphisms throughout homoeologous loci in Triticum and Aegilops

“…comosa belong to the section Comopyrum, and have limited distribution in northwestern Turkey and from northwestern Turkey to Greece, respectively [27]. Comopyrum species are utilized for identifying novel alleles of glutenin subunit genes [28,29]. Despite their usefulness as genetic resources, little genome information has been accumulated from these three Aegilops species.…”