Isolation and functional analysis of apple MdHMGR1 and MdHMGR4 gene promoters in transgenic <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Cereal grains offer great potential as a storage system for production of highly valuable proteins using biotechnological approaches, but such applications require tight temporal and spatial control of transgene expression. Towards this aim, we have undertaken a detailed analysis of α-kafirin (α-kaf) promoter and α-kaf signal peptide (sp) in transgenic sorghum plants, using green fluorescent protein gene (gfp) as a reporter. Constructs containing either the α-kaf promoter or the constitutive maize ubiquitin-1 (ubi) promoter driving either gfp or sp-gfp translational fusion were introduced into Sorghum bicolor inbred line Tx430 by particle bombardment. We show for the first time that the α-kaf promoter directs endosperm-specific transgene expression, with activity first detected at 10 days post-anthesis (dpa), peaking at 20 dpa, and remaining active through to physiological maturity. Furthermore, we demonstrate for the first time that the α-kafirin sp is sufficient to direct foreign protein to protein bodies in the endosperm. The evidence is also provided for possible mis-targeting by α-kaf sp in vegetative tissues of transgenic lines with ubi-sp-gfp, resulting in loss of reporter gene translational activity that no GFP signal was observed. These results demonstrate that α-kaf promoter and α-kaf sp are well suited for seed bioengineering to produce recombinant proteins in sorghum endosperm or deposit foreign proteins into sorghum protein bodies.     

Allelic differentiation at the <Emphasis Type="Italic">Sg-1</Emphasis> locus for the terminal sugar of the C-22 position of group A saponin in Chinese wild soybean (<Emphasis Type="Italic">Glycine soja</Emphasis> Sieb. &amp; Zucc.)

Group A saponins are thought to be the cause of bitter and astringent tastes in processed foods of soybean (Glycine max), and the elimination of group A saponins is an important breeding objective. The group A saponins include two main Aa and Ab types, controlled by codominant alleles at the Sg-1 locus that is one of several key loci responsible for saponin biosynthesis in the subgenus Glycine soja. However, A0 mutant lacking group A saponin is a useful gene resource for soybean quality breeding. Here, eight Chinese wild soybean A0 accessions were sequenced to reveal the mutational mechanisms, and the results showed that these mutants were caused by at least three kinds of mechanisms involving four allelic variants (sg-1^0-b2, sg-1^0-b3, Sg-1^b-0, and Sg-1^b-01). The sg-1^0-b2 had two nucleotide deletions at positions +?72 and +?73 involving in the 24th and 25th amino acids. The sg-1^0-b3 contained a stop codon (TGA) at the 254th residue. The Sg-1^b-0 and Sg-1^b-01 were two novel A0-type mutants, which likely carried normal structural alleles, and nevertheless did not encode group A saponin due to unknown mutations beyond the normal coding regions. In addition, to reveal the structural features, allelic polymorphism, and mechanisms of the abiogenetic absence of group A (i.e., A0 phenotype), nucleotide sequence analysis was performed for the Sg-1 locus in wild soybean (Glycine soja). The results showed that Sg-1 alleles had a lower conservatism in the coding region; as high as 18 sequences were found in Chinese wild soybeans in addition to the Sg-1^a (Aa) and Sg-1^b (Ab) alleles. Sg-1^a and Sg-1^b alleles were characterized by eight synonymous codons and nine amino acid substitutions. Two evolutionarily transitional allelic sequences (Sg-1^a7 and Sg-1^b2) from Sg-1^a toward Sg-1^b were detected.     

Abscisic Acid-Induced Starch Accumulation in Bioenergy Crop Duckweed <Emphasis Type="Italic">Spirodela polyrrhiza</Emphasis>

Spirodela polyrrhiza, a fast-growing duckweed with high starch and low lignin content, shows promise as a feedstock for bioenergy. Abscisic acid (ABA) is a biological hormone that controls plant growth and stress response. The effects of different ABA concentrations (0, 1.0 × 10^?5, 1.0 × 10^?4, 1.0 × 10^?3, 1.0 × 10^?2, and 1.0 × 10^?1 mg/L) on duckweed biomass growth, carbon dioxide fixation, formation of photosynthetic pigments (Chlorophyll a (Chla), Chlorophyll b (Chlb), and carotenoids), the activities of soluble starch synthase (SSS) and starch branching enzyme (SBE), and the starch content of biomass were investigated in this study. ABA at concentrations lower than 1.0 × 10^?3 mg/L promoted carbon dioxide fixation, whereas it inhibited carbon dioxide fixation at concentrations over 1.0 × 10^?3 mg/L. ABA enhanced SSS and SBE activities at concentrations lower than 1.0 × 10^?2 mg/L. ABA treatment increased the content of Chla, Chlb, and carotenoids and resulted in the enhancement of starch content. Chla content gradually increased with the increasing concentration of ABA (1.0 × 10^?5 to 1.0 × 10^?2 mg/L). After culturing for 10 days, starch content in 1.0 × 10^?2 mg/L ABA medium reached 35.3% of dry weight (DW), which was the highest level in this study. This suggests that there is a great potential to develop a technology to increase starch accumulation in duckweed which can be used as an alternative to corn, sugarcane, or other food crops as a starch source.     

Identification and characterization of <Emphasis Type="Italic">Rht25</Emphasis>, a locus on chromosome arm 6AS affecting wheat plant height,heading time,and spike development

Key message

This study identified Rht25, a new plant height locus on wheat chromosome arm 6AS, and characterized its pleiotropic effects on important agronomic traits.

Abstract

Understanding genes regulating wheat plant height is important to optimize harvest index and maximize grain yield. In modern wheat varieties grown under high-input conditions, the gibberellin-insensitive semi-dwarfing alleles Rht-B1b and Rht-D1b have been used extensively to confer lodging tolerance and improve harvest index. However, negative pleiotropic effects of these alleles (e.g., poor seedling emergence and reduced biomass) can cause yield losses in hot and dry environments. As part of current efforts to diversify the dwarfing alleles used in wheat breeding, we identified a quantitative trait locus (QHt.ucw-6AS) affecting plant height in the proximal region of chromosome arm 6AS (<?0.4 cM from the centromere). Using a large segregating population (~?2800 gametes) and extensive progeny tests (70–93 plants per recombinant family), we mapped QHt.ucw-6AS as a Mendelian locus to a 0.2 cM interval (144.0–148.3 Mb, IWGSC Ref Seq v1.0) and show that it is different from Rht18. QHt.ucw-6AS is officially designated as Rht25, with Rht25a representing the height-increasing allele and Rht25b the dwarfing allele. The average dwarfing effect of Rht25b was found to be approximately half of the effect observed for Rht-B1b and Rht-D1b, and the effect is greater in the presence of the height-increasing Rht-B1a and Rht-D1a alleles than in the presence of the dwarfing alleles. Rht25b is gibberellin-sensitive and shows significant pleiotropic effects on coleoptile length, heading date, spike length, spikelet number, spikelet density, and grain weight. Rht25 represents a new alternative dwarfing locus that should be evaluated for its potential to improve wheat yield in different environments.

     

Prevalence of <Emphasis Type="Italic">VRN1</Emphasis> locus alleles among spring common wheat cultivars cultivated in Western Siberia

With the use of allele-specific primers developed for the VRN1 loci, the allelic diversity of the VRN-A1, VRN-B1, and VRN-D1 genes was studied in 148 spring common wheat cultivars cultivated under the conditions of western Siberia. It was demonstrated that modern Western Siberian cultivars have the VRN-A1a allele, which is widely distributed in the world (alone or in combination with the VRN-B1a and VRN-B1c alleles). It was established that the main contribution in acceleration of the seedling–heading time is determined by a dominant VRN-A1a allele, while the VRNA1b allele, on the contrary, determines later plant heading. Cultivars that have the VRN-A1b allele in the genotype are found with a frequency of 8%. It was shown that cultivars with different allele combinations of two dominant genes (VRN-A1a + VRN-B1c and VRN-A1a + VRN-B1a) are characterized by earlier heading and maturing.     

Genetic dissection of sorghum grain quality traits using diverse and segregating populations

Key message

Coordinated association and linkage mapping identified 25 grain quality QTLs in multiple environments, and fine mapping of the Wx locus supports the use of high-density genetic markers in linkage mapping.

Abstract

There is a wide range of end-use products made from cereal grains, and these products often demand different grain characteristics. Fortunately, cereal crop species including sorghum [Sorghum bicolor (L.) Moench] contain high phenotypic variation for traits influencing grain quality. Identifying genetic variants underlying this phenotypic variation allows plant breeders to develop genotypes with grain attributes optimized for their intended usage. Multiple sorghum mapping populations were rigorously phenotyped across two environments (SC Coastal Plain and Central TX) in 2 years for five major grain quality traits: amylose, starch, crude protein, crude fat, and gross energy. Coordinated association and linkage mapping revealed several robust QTLs that make prime targets to improve grain quality for food, feed, and fuel products. Although the amylose QTL interval spanned many megabases, the marker with greatest significance was located just 12 kb from waxy (Wx), the primary gene regulating amylose production in cereal grains. This suggests higher resolution mapping in recombinant inbred line (RIL) populations can be obtained when genotyped at a high marker density. The major QTL for crude fat content, identified in both a RIL population and grain sorghum diversity panel, encompassed the DGAT1 locus, a critical gene involved in maize lipid biosynthesis. Another QTL on chromosome 1 was consistently mapped in both RIL populations for multiple grain quality traits including starch, crude protein, and gross energy. Collectively, these genetic regions offer excellent opportunities to manipulate grain composition and set up future studies for gene validation.

     

Cloning and expression of <Emphasis Type="Italic">Perilla frutescens FAD2</Emphasis> gene and polymorphism analysis among cultivars

?12 fatty acid desaturase (FAD2) is a key enzyme for linoleic acid and linolenic acid biosynthesis. Perilla frutescens is a special oil plant species with highest linolenic acid content. In this study, based on RACE, two alleles for one FAD2 gene were isolated from P. frutescens cultivar C2: the 3956 bp PfFAD2a and the 3959 bp PfFAD2b, both with a full-length cDNA of 1526 bp, and both encoding a 382aa basic protein. The alleles have identities of over 98%, and their encoded proteins differ only by substitution of a strongly similar residue. Saccharomyces cerevisiae heterologous expression suggested that PfFAD2a/b both encode a bio-functional FAD2 enzyme. Phylogenetic analyses indicated that PfFAD2 shows the highest homologies to FAD2 genes from dicots such as Boraginaceae and Burseraceae. PfFAD2a/b expressions are mainly restricted to developing seeds. PfFAD2a/b expression in the seedling leaf is upregulated by cold (4 °C) and repressed by heat (42 °C). Each of the eight cultivars contains two alleles for one PfFAD2 and 40 SNP sites are found. One allelic gene in cultivars C1 and P1 is pseudogene because of premature stop codon mutation in 5′ coding region. All other normal PfFAD2 genes/allelic genes encode identical or very similar proteins. PfFAD2a/b expression level in developing seeds also varies among the eight cultivars. This study provides systemic molecular and functional features of PfFAD2 and enables its application in the study of plant fatty acids traits.     

Arabidopsis PRC1 core component AtRING1 regulates stem cell-determining carpel development mainly through repression of class I <Emphasis Type="Italic">KNOX</Emphasis> genes

Background

Polycomb repressive complex 2 (PRC2)-catalyzed H3K27me3 marks are tightly associated with the WUS-AG negative feedback loop to terminate floral stem cell fate to promote carpel development, but the roles of Polycomb repressive complex 1 (PRC1) in this event remain largely uncharacterized.

Results

Here we show conspicuous variability in the morphology and number of carpels among individual flowers in the absence of the PRC1 core components AtRING1a and AtRING1b, which contrasts with the wild-type floral meristem consumed by uniform carpel production in Arabidopsis thaliana. Promoter-driven GUS reporter analysis showed that AtRING1a and AtRING1b display a largely similar expression pattern, except in the case of the exclusively maternal-preferred expression of AtRING1b, but not AtRING1a, in the endosperm. Indeterminate carpel development in the atring1a;atring1b double mutant is due to replum/ovule-to-carpel conversion in association with ectopic expression of class I KNOX (KNOX-I) genes. Moreover, AtRING1a and AtRING1b also play a critical role in ovule development, mainly through promoting the degeneration of non-functional megaspores and proper integument formation. Genetic interaction analysis indicates that the AtRING1a/b-regulated KNOX-I pathway acts largely in a complementary manner with the WUS-AG pathway in controlling floral stem cell maintenance and proper carpel development.

Conclusions

Our study uncovers a novel mechanistic pathway through which AtRING1a and AtRING1b repress KNOX-I expression to terminate floral stem cell activities and establish carpel cell fate identities.

     

Molecular characteristics of two new <Emphasis Type="Italic">waxy</Emphasis> mutations in China waxy maize

The waxy gene mutation causes waxy maize grain to have a sticky quality. China has numerous waxy maize landraces and is thought to be the place of origin of waxy maize. The most abundant waxy maize resources in China are located in the Yunnan province and its surrounding areas. We collected 57 waxy maize landraces from Yunnan province and cloned and sequenced the waxy gene from its fourth to eighth exon. Two new waxy gene mutations, named wx-Cin4 and wx-124, were identified. The wx-Cin4 mutation is a 466-bp retrotransposon inserted into exon six. The wx-124 mutation is a 116-bp miniature inverted-repeat transposable element inserted into exon seven. This is the first time a 124-type mutation has been found in a maize waxy gene. The discovery of the two specific waxy mutations from landraces collected in Yunnan province provides new evidence supporting the hypothesis that China is the origin area for waxy maize.     

Molecular characterization and phylogenetic analysis of Wx genes from three Taeniatherum diploid species

In wheat seeds, starch synthase I or the Waxy protein is an enzyme involved in amylose synthesis. The gene encoding this enzyme is Wx and in this study, eight novel Wx alleles were identified in three diploid Taeniatherum species. The variability of these alleles was evaluated, and their nucleotide sequences were compared with those of homologous alleles from wheat. Two types of Taeniatherum Wx alleles were detected in three diploid species Ta. caput-medusae, Ta. asperum, and Ta. crinitum. A phylogenetic analysis indicates that the Taeniatherum Wx alleles were more closely related to Wx alleles from Aegilops species with C, D, M, and U genomes than to Wx alleles of other species. These alleles represent a potential genetic resource that may be useful in wheat breeding programs.     

<Emphasis Type="Italic">FLOURY ENDOSPERM8</Emphasis>, encoding the UDP-glucose pyrophosphorylase 1, affects the synthesis and structure of starch in rice endosperm

Cereal opaque-kernel mutants are ideal genetic materials for studying the mechanism of starch biosynthesis and amyloplast development. Here we isolated and identified two allelic floury endosperm 8 (flo8) mutants of rice, named flo8-1 and flo8-2. In the flo8 mutant, the starch content was decreased and the normal physicochemical features of starch were altered. Map-based cloning and subsequent DNA sequencing analysis revealed a single nucleotide substitution and an 8-bp insertion occurred in UDP-glucose pyrophosphorylase 1 (Ugp1) gene in flo8-1 and flo8-2, respectively. Complementation of the flo8-1 mutant restored normal seed appearance by expressing full length coding sequence of Ugp1. RT-qPCR analysis revealed that Ugp1 was ubiquitously expressed. Mutation caused the decreased UGPase activity and affected the expression of most of genes associated with starch biosynthesis. Meanwhile, western blot and enzyme activity analyses showed the comparability of protein levels and enzyme activity of most tested starch biosynthesis related genes. Our results demonstrate that Ugp1 plays an important role for starch biosynthesis in rice endosperm.     

Natively oxidized amino acid residues in the spinach cytochrome <Emphasis Type="Italic">b</Emphasis><Subscript><Emphasis Type="Italic">6</Emphasis></Subscript><Emphasis Type="Italic">f</Emphasis> complex

The cytochrome b ₆ f complex of oxygenic photosynthesis produces substantial levels of reactive oxygen species (ROS). It has been observed that the ROS production rate by b ₆ f is 10–20 fold higher than that observed for the analogous respiratory cytochrome bc₁ complex. The types of ROS produced (O₂^{??, 1}O₂, and, possibly, H₂O₂) and the site(s) of ROS production within the b ₆ f complex have been the subject of some debate. Proposed sources of ROS have included the heme b _p , PQ _p ^?? (possible sources for O₂^??), the Rieske iron–sulfur cluster (possible source of O₂^?? and/or ¹O₂), Chl a (possible source of ¹O₂), and heme c _n (possible source of O₂^?? and/or H₂O₂). Our working hypothesis is that amino acid residues proximal to the ROS production sites will be more susceptible to oxidative modification than distant residues. In the current study, we have identified natively oxidized amino acid residues in the subunits of the spinach cytochrome b ₆ f complex. The oxidized residues were identified by tandem mass spectrometry using the MassMatrix Program. Our results indicate that numerous residues, principally localized near p-side cofactors and Chl a, were oxidatively modified. We hypothesize that these sites are sources for ROS generation in the spinach cytochrome b ₆ f complex.     

Kernel softness in wheat is determined by starch granule bound Puroindoline proteins

Wheat has a vital position in agriculture because it is a staple food for masses and variation in grain hardness governs its applications. Soft wheats have softer endosperm texture that mills easily, so needs less energy to mill, produces smaller particles, and small amount of starch is damaged after milling as compared to hard wheat. Soft texture results from higher level of friabilin whereas hard texture results from low level of friabilin on starch granule surface. Friabilin, a marker of kernel texture is primarily composed of Puroindolines (PINs) and its genes (Pins) are located on the Hardness (Ha) locus. The Pins are the molecular-genetic basis of kernel softness in wheat. When both Pins are in their ‘wild state’ (Pina-D1a and Pinb-D1a), wheat kernel is soft. Absence or mutation in one of the Pins results in hard grain texture with different effects on end use and milling qualities. Pina-D1b genotypes gave harder grain texture, higher protein content, water absorption of flour, damaged starch granules and greater flour yield than hard wheat. Recently, other Pins like genes, Pin b variant genes located on the long arm of chromosome 7A were reported in bread wheat with more than 70% similarity to Pinb (Pinb-D1a) at the DNA level. Other genes located on chromosomes 1A, 2A, 5A, 7A, 5B, 2D and 6D also affect kernel texture. However the main determinants are the variants in the allelic diversity of Puroindoline family genes. Contemporary studies show that Pins are multifunctional family of genes having a range of functions from grain hardness to natural defense against insects and pathogens such as viruses, bacteria and fungi.     

Analysis of an N-terminal deletion in subunit <Emphasis Type="Italic">a</Emphasis> of the <Emphasis Type="Italic">Escherichia coli</Emphasis> ATP synthase

Subunit a is a membrane-bound stator subunit of the ATP synthase and is essential for proton translocation. The N-terminus of subunit a in E. coli is localized to the periplasm, and contains a sequence motif that is conserved among some bacteria. Previous work has identified mutations in this region that impair enzyme activity. Here, an internal deletion was constructed in subunit a in which residues 6–20 were replaced by a single lysine residue, and this mutant was unable to grow on succinate minimal medium. Membrane vesicles prepared from this mutant lacked ATP synthesis and ATP-driven proton translocation, even though immunoblots showed a significant level of subunit a. Similar results were obtained after purification and reconstitution of the mutant ATP synthase into liposomes. The location of subunit a with respect to its neighboring subunits b and c was probed by introducing cysteine substitutions that were known to promote cross-linking: a_L207C + c_I55C, a_L121C + b_N4C, and a_T107C + b_V18C. The last pair was unable to form cross-links in the background of the deletion mutant. The results indicate that loss of the N-terminal region of subunit a does not generally disrupt its structure, but does alter interactions with subunit b.     

Characterization of an IAA-glucose hydrolase gene <Emphasis Type="Italic">TaTGW6</Emphasis> associated with grain weight in common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

In rice, the TGW6 gene determines grain weight and encodes a protein with indole-3-acetic acid (IAA)-glucose hydrolase activity. Its homolog in wheat, TaTGW6, is considered as a candidate gene related to grain development. To amplify this gene, we designed primers based on a homologous conserved domain of the rice TGW6 gene. Sequence analysis indicated that TaTGW6 comprises only one exon, with 1656 bp in total and an open reading frame of 1035 bp. Three alleles at TaTGW6 locus detected by the primer pair TG23 were designated as TaTGW6-a, TaTGW6-b and TaTGW6-c, respectively. Compared with TaTGW6-a, TaTGW6-b had a 6-bp InDel at the position 170 downstream of initiation codon, and TaTGW6-c was a null mutant. Both TaTGW6-b and TaTGW6-c could significantly increase grain size and weight other than TaTGW6-a; however, the former two alleles showed a low frequency distribution in modern varieties. TaTGW6 was located on chromosome 4AL using a recombinant inbred line population and a set of Chinese Spring nullisomic-tetrasomic lines. It was linked to the SSR locus Xbarc1047 with a genetic distance of 6.62 cM and explained 15.8–21.0 % of phenotypic variation of grain weight in four environments. Association analysis using a natural population and Chinese wheat mini-core collections additionally validated the relationship of TaTGW6 with grain weight; the gene could explain 7.7–12.4 % of phenotypic variation in three environments. Quantitative real-time PCR revealed that TaTGW6-b showed relatively lower expression than TaTGW6-a in immature grain at 20 and 30 days post-anthesis and in mature grain. The low expression of TaTGW6 generally associated with low IAA content, but with high grain weight. The novel functional marker, designated as TG23, can be used for marker-assisted selection to improve grain weight in wheat and also provides insights into the regulatory mechanism underlying grain weight.     

A tomato plastidic ATP/ADP transporter gene <Emphasis Type="Italic">SlAATP</Emphasis> increases starch content in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis>

A plastidic ATP/ADP transporter (AATP) is responsible for importing ATP from the cytosol into plastids. Increasing the ATP supply is a potential way to facilitate anabolic synthesis in heterotrophic plastids of plants. In this work, a gene encoding the AATP protein, named SlAATP, was successfully isolated from tomato. Expression of SlAATP was induced by exogenous sucrose treatment in tomato. The coding region of SlAATP was cloned into a binary vector under the control of 35S promoter and then transformed into Arabidopsis to obtain transgenic plants. Constitutive expression of SlAATP significantly increased the starch accumulation in the transgenic plants. Real-time quantitative PCR (qRT-PCR) analysis showed that constitutive expression of StAATP up-regulated the expression of phosphoglucomutase (AtPGM), ADP-glucose pyrophosphorylase (AtAGPase), granule-bound starch synthase (AtGBSS I and AtGBSS II), soluble starch synthases (AtSSS I, AtSSS II, AtSSS III and AtSSS IV) and starch branching enzyme (AtSBE I and AtSBE II) genes involved in starch biosynthesis in the transgenic Arabidopsis plants. Meanwhile, enzymatic analyses indicated that the major enzymes (AGPase, GBSS, SSS and SBE) involved in the starch biosynthesis exhibited higher activities in the transgenic plants compared to the wild-type (WT). These findings suggest that SlAATP may improve starch content of Arabidopsis by up-regulating the expression of the related genes and increasing the activities of the major enzymes invovled in starch biosynthesis. The manipulation of SlAATP expression might be used for increasing starch accumulation of plants in the future.     

Comparison of alleles at the <Emphasis Type="Italic">Gli-1</Emphasis> loci of common wheat by means of two-dimensional electrophoresis of gliadin and RFLP analysis

Allelic variants of the Gli-1 locus is known to control groups (blocks) of gliadin polypeptides (gliadins). Some allelic variants of blocks that differ in the electrophoretic (acid gel) mobility (EM) of only one gliadin of the block were compared using two-dimensional electrophoresis (SDS-PAGE) and the RFLP procedure. It was found that, in these pairs of similar alleles (Gli-B1f, Gli-B1s, and Gli-D1a as compared with Gli-B1e, Gli-B1n, and Gli-D1c, respectively), faster γ-gliadin had smaller molecular weight (MW). Alleles at the Gli-A1 locus (Gli-A1j, Gli-A1i, Gli-A1a, Gli-A1k, and Gli-A1f) differ in the EM of the γ-gliadin so that Gli-A1j controls the slowest γ-gliadin and Gli-A1f controls the fastest one. We found that, in this order of alleles, faster γ-gliadin always had smaller MW. It was suggested that similar alleles might arise from one another by spontaneous mutations changing the number of repeating sequences or length of the polyglutamine domain present in the γ-gliadin gene thereby influencing MW and EM of encoding polypeptide. Other mechanisms of the mutational appearance of new alleles were found earlier by comparison of allele pairs: Gli-D1a and Gli-D1k (gene silencing) and Gli-D1b and Gli-D1d (gene amplification). We discovered contrasting families of alleles at the Gli-B1 and at the Gli-D1 loci and also two variants of apparently the same allele Gli-D1a that differed in the number of encoded ω-gliadins. Families of alleles at one locus of T. aestivum might inherit from different genotypes of corresponding diploid donor, as we suggested earlier.     

Genetic diversity of <Emphasis Type="Italic">avenin-like b</Emphasis> genes in <Emphasis Type="Italic">Aegilops tauschii</Emphasis> Coss

Avenin-like storage proteins influence the rheological properties and processing quality in common wheat, and the discovery of new alleles will benefit wheat quality improvement. In this study, 13 avenin-like b alleles (TaALPb7D-A–M) were discovered in 108 Aegilops tauschii Coss. accessions. Ten alleles were reported for the first time, while the remaining three alleles were the same as alleles in other species. A total of 15 nucleotide changes were detected in the 13 alleles, resulting in only 11 amino acid changes because of synonymous mutations. Alleles TaALPb7D-E, TaALPb7D-G, and TaALPb7D-J encoded the same protein. These polymorphic sites existed in the N-terminus, Repetitive region (Left), Repetitive region (Right) and C-terminus domains, with no polymorphisms in the signal peptide sequence nor in those encoding the 18 conserved cysteine residues. Phylogenetic analysis divided the TaALPb7Ds into four clades. The Ae. tauschii alleles were distributed in all four clades, while the alleles derived from common wheat, TaALPb7D-G and TaALPb7D-C, belonged to clade III and IV, respectively. Alleles TaALPb7D-G and TaALPb7D-C were the most widely distributed, being present in nine and six countries, respectively. Iran and Turkey exhibited the highest genetic diversity with respect to TaALPb7D alleles, accessions from these countries carrying seven and six alleles, respectively, which implied that these countries were the centers of origin of the avenin-like b gene. The new alleles discovered and the phylogenetic analysis of avenin-like b genes will provide breeding materials and a theoretical basis for wheat quality improvement.