Wheat Substitution Lines Research Articles

Metabolism of halauxifen acid is regulated by genes located on wheat chromosome 5A

Abstract Allohexaploid wheat (Triticum aestivum L.) is tolerant to halauxifen-methyl (HM) via rapid detoxification of the phytotoxic form of HM, halauxifen acid (HA), to non-phytotoxic metabolites. Previous research utilizing ‘Chinese Spring’ (CS) wheat, alien substitution (i.e., endogenous chromosome pair substituted with a homoeologous pair from diploid Sears’ goatgrass (Aegilops searsii M. Feldman & M. Kislev) (AS), or nullisomic-tetrasomic (NT) lines indicated plants lacking chromosome 5A are more sensitive than CS to HM. We hypothesized the increased HM sensitivity of these plants results from losing gene(s) on chromosome 5A associated with HA metabolism, which leads to a reduced HA detoxification rate relative to CS. To compare HA abundance among AS, CS, alien substitution, and NT lines during a time course, two excised-leaf studies using unlabeled HM and liquid chromatography–mass spectrometry analyses were performed. Aegilops searsii accumulated more HA than CS did, and each substitution line at 8, 12, and 24 h after treatment (HAT). Furthermore, only the wheat substitution line lacking chromosome 5A displayed greater abundance of HA relative to CS (2.4- to 3.8-fold, depending on the time point). In contrast, HA abundances in lines possessing chromosome 5A were not different than HA abundances in CS at all time points. When NT lines were compared with CS, the nullisomic 5D-tetrasomic 5A (N5D-T5A) line displayed similar HA abundance, whereas the nullisomic 5A-tetrasomic 5D (N5A-T5D) accumulated approximately 3-fold more HA at 12 and 24 HAT. These results biochemically support the hypothesis that genes encoding HA-detoxifying enzyme(s) are located on wheat chromosome 5A and corroborate findings from previous greenhouse phenotypic experiments. Future experimentation is needed to identify and characterize genes and enzymes on wheat chromosome 5A involved with HA detoxification, which may include cytochrome P450 monooxygenases, unknown oxidases, UDP-dependent glucosyltransferases, or, potentially, transcription factors that regulate expression of these genes associated with HA detoxification.

Disomic Substitution of 3D Chromosome with Its Homoeologue 3E in Tetraploid Thinopyrum elongatum Enhances Wheat Seedlings Tolerance to Salt Stress

The halophytic wild relatives within Triticeae might provide valuable sources of salt tolerance for wheat breeding, and attempts to use these sources of tolerance have been made for improving salt tolerance in wheat by distant hybridization. A novel wheat substitution line of K17-1078-3 was developed using common wheat varieties of Chuannong16 (CN16), Zhengmai9023 (ZM9023), and partial amphidiploid Trititrigia8801 (8801) as parents, and identified as the 3E(3D) substitution line. The substitution line was compared with their parents for salt tolerance in hydroponic culture to assess their growth. The results showed that less Na+ accumulation and lower Na+/K+ ratio in both shoots and roots were achieved in K17-1078-3 under salinity compared to its wheat parents. The root growth and development of K17-1078-3 was less responsive to salinity. When exposed to high salt treatment, K17-1078-3 had a higher photosynthesis rate, more efficient water use efficiency, and greater antioxidant capacity and stronger osmotic adjustment ability than its wheat parents. In conclusion, a variety of physiological responses and root system adaptations were involved in enhancing salt tolerance in K17-1078-3, which indicated that chromosome 3E possessed the salt tolerance locus. It is possible to increase substantially the salt tolerance of wheat by the introduction of chromosome 3E into wheat genetic background.

The karyotype of Aegilops geniculata and its use to identify both addition and substitution lines of wheat

BackgroundThe annual allotetraploid species Aegilops geniculata harbors a number of traits relevant for wheat improvement. An effective cytogenetic method has yet to be developed to distinguish between each of its 14 chromosomes.ResultsA fluorescence in situ hybridization (FISH) approach was adopted to describe the karyotype of Ae. geniculata. Each of its 14 chromosomes was unequivocally recognized using a cocktail of three probes, namely pTa-713, (AAC)5 and pTa71. FISH karyotyping was then used to detect and characterize selections from an Ae. geniculata × bread wheat wide cross of a chromosome 1Mg disomic addition line and three 4Mg(4B) substitution lines. The identity of the addition line was confirmed by the presence of Glu-M1, detected both using an SDS-PAGE separation of endosperm proteins and by applying a PCR assay directed at the Glu-M1 locus. The status of the substitution lines was validated by genotyping using a wheat single nucleotide polymorphism chip.ConclusionFISH karyotyping based on pTa-713, (AAC)5 and pTa71 will be useful for determining the contribution of Ae. geniculata to derivatives of an Ae. geniculata × wheat wide cross. SNP chip-based genotyping is effective for confirming the status of whole chromosome wheat/alien substitution lines.

New resistance sources to Russian wheat aphid (Diuraphis noxia) in Swedish wheat substitution and translocation lines with rye (Secale cereale) and Leymus mollis

Andersson S.C., Johansson E., Baum M., Rihawi F., El Bouhssini M. (2015): New resistance sources to Russian wheat aphid ( Diuraphis noxia ) in Swedish wheat substitution and translocation lines with rye ( Secale cereale ) and Leymus

Comparison of redox and gene expression changes during vegetative/generative transition in the crowns and leaves of chromosome 5A substitution lines of wheat under low-temperature condition.

The aim of our experiments was to investigate the effect of chromosome 5A on the thiol-dependent redox environment and on the transcription of cold- and vernalization-related genes during the vegetative/generative transition in crowns and leaves of wheat. Chinese Spring, a moderately freezing-tolerant variety, and its more and less tolerant substitution lines - [CS(Ch5A)] and [CS(Tsp5A)], respectively - with different combinations of vernalization alleles were compared. At low temperature, the amount of cystine and glutathione disulphide and the related redox potentials increased in the crowns but not in the leaves. In the crowns of the substitution lines, the concentration and redox state of thiols were different only at the vegetative and double ridge (start of the generative transition) stages. The expression of the vernalization-related VRN1 gene increased significantly during the transition both in the crowns and leaves. The transcription of the freezing tolerance-related CBF14, COR14b and COR39 genes markedly increased in both organs after 2 weeks at 4 °C when the seedlings were still in the vegetative stage. This increment was greater in CS(Ch5A) than in CS(Tsp5A). The Ch5A chromosome in CS genetic background enhanced the expression of CBF regulon even in the generative phase in crown that is the key organ for overwintering and freezing tolerance. At certain developmental stages, both the thiol and the transcript levels differed significantly in the two substitution lines.

Identification of chromosomes controlling yield stability in wheat using component and path analysis

In order to identify the chromosomes controlling yield and yield stability, 21 wheat substitution lines along with their parents: genotypes Chinese Spring (recipient) and Chayan (donor) and genotype Sardary, as control, were used in a randomized complete block design with three replications under two different conditions (rainfed and irrigated) for two consecutive cropping seasons (2007 – 2009) at the Agricultural College of Razi University, Kermanshah, Iran. The results of descriptive diagram and combined analysis of variance showed highly significant differences for genotypes (G), environments (E) and GE interaction, indicating variability between G, E and their effects in the GE interaction and possible detection of the chromosomes controlling yield and yield stability in wheat. Chromosome substitution lines 3B, 4B, 1D and 2D showed higher yield and yield components in different environments which indicated these chromosomes might carry quantitative trait locus (QTLs) associated with controlling adaptation. Component analysis illustrated that chromosomes 1A, 5A, 7A, 5B and 7D had higher components C3 (thousand-seed weight, TSW) and higher MCi (multiplied coefficient of variation) can be identified as the key responsible chromosomes for yield instability. Chromosomes 1A, 3B, 6B, 1D and 2D had the highest and chromosomes 2A, 3A and 5D had lowest path coefficient V3 (TSW). Therefore, higher grain yield and yield stability of chromosomes 1A, 5A, 7A, 3B, 5B, 6B, 1D, 2D and 7D are because of higher genotypic component coefficients TSW. In this study, chromosomes with negative effects on yield and yield stability were mainly located on genome A and chromosomes with positive effects were found on genome B.

The determination of chromosomes involved in controlling epicuticular wax, water statues and stomatal characteristics using selected wheat substitution lines under water-stress conditions

Some selected chromosomal substitution lines were used to determine the role of their relevant chromosomes in affecting variation of epicuticular wax, water statues and stomatal characteristics under water-deficit conditions. Recipient and donor parents of the substitution lines were Chinese spring (CS) and Timstein, respectively. Analyses of variance revealed highly significant variations among the candidate substitution lines for leaf relative water content (LRWC), excised leaf water lost and grain weight. However, no significant variation was found for epicuticular wax (ECW). In the case of stomatal characteristics, analyses of variance indicated significant variation for stomatal frequency only and no significant variation was found for other stomatal characteristics. Comparison between the substitution lines and their recipient parent (CS) revealed that none of the substitution lines was significantly different with the recipient parent (CS) for ECW, thus indicating none of the candidate chromosomes involved in controlling this character. However, the results indicated the effects of chromosomes 1A, 3D and 7D from donor parent (Tim) in controlling LRWC. Chromosomes 7D of Timstein also had a significant effect in enhancing LRWC when substituted into CS background. In addition, it was observed that none of the characters correlated with grain yield in water-stressed experiments.

Gene expression analysis in the roots of salt-stressed wheat and the cytogenetic derivatives of wheat combined with the salt-tolerant wheatgrass, Lophopyrum elongatum

Using microarray analysis, we identified regulatory and signaling-related genes with differential expression in three genotypes with varying degrees of salt tolerance, Triticum aestivum , the amphiploid, and the wheat substitution line DS3E(3A). Lophopyrum elongatum is among one of the most salt-tolerant members of the Triticeae; important genetic stocks developed from crosses between wheat and L. elongatum provide a unique opportunity to compare gene expression in response to salt stress between these highly related species. The octaploid amphiploid contains the entire genome of T. aestivum and L. elongatum, and the disomic substitution line DS3E(3A) has chromosome 3A of wheat replaced by chromosome 3E of L. elongatum. In this study, microarray analysis was used to characterize gene expression profiles in the roots of three genotypes, Triticum aestivum, the octaploid amphiploid, and thewheat DS3E(3A) substitution line, in response to salt stress. We first examined changes in gene expression in wheat over a time course of 3days of salt stress, and then compared changes in gene expression in wheat, the T. aestivum×L. elongatum amphiploid, and in the DS3E(3A) substitution line after 3days of salt stress. In the time course experiment, 237 genes had 1.5 fold or greater change at least one out of three time points assayed in the experiment. The comparison between the three genotypes revealed 304 genes with significant differences in changes of expression between the genotypes. Forty-two of these genes had at least a twofold change in expression in response to salt treatment; 18 of these genes have signaling or regulatory function. Genes with significant differences in induction or repression between genotypes included transcription factors, protein kinases, ubiquitin ligases and genes related to phospholipid signaling.

Grain yield and grain protein percentage of common wheat lines with wild emmer chromosome-arm substitutions

Wild emmer wheat, Triticum turgidum subsp. dicoccoides, (2n = 4× = 28; genome BBAA), the progenitor of domesticated wheat, is genetically closely related to durum and common wheat. This wild taxon has characteristics that would be valuable if transferred to domesticated wheat. A series of chromosome-arm substitution lines (CASLs) of wild emmer wheat were produced in the background of an Israeli common wheat cultivar. These CASLs were evaluated in a pot experiment and in field trials in Israel and California for their grain yield (GY) and its components and for grain protein percentage. In addition, the extent of genetic interactions (epistatic effects) between “wild” and “domesticated” alleles, within and between homoeologous groups 1 and 7 as expressed in grain and protein yields and other quantitative traits, were determined. The research has shown that wild emmer wheat harbors genetic variability for quantitative traits and that the “wild” genes interact among themselves in a non-additive way in the common genetic background. Several chromosome arms improve GY and protein percentage in common wheat, but their effects will be presumably enhanced when combination of genes from several “wild” arms are integrated into a single “domesticated” genotype. Hence, the interaction between these genes and those in the recipient common wheat must be accounted for when higher yield or protein content is desired. The results of this study indicate on the potential of this material for breeding and genetic analysis, and support the idea of pyramiding genes from a wild species.

The influence of Vrn-B1a and Vrn-B1c alleles on the length of developmental phases of substitution and near-isogenic lines of common wheat

The influence of Vrn-B1a and Vrn-B1c alleles on the length of developmental phases of substitution and near-isogenic lines of common wheat

The antioxidant enzymes activity in leaves of inter-varietal substitution lines of wheat (Triticum aestivum L.) with different tolerance to soil water deficit

Understanding of the genetic basis of physiological properties, which are most relevant to water-deficit tolerance would be helpful for genomic-assisted improvement of bread wheat. A set of bread wheat inter-varietal single chromosome substitution lines (ISCSLs) of variety ‘Janetzkis Probat’ (JP) in the genetic background of ‘Saratovskaya’ 29 (S29) were used to reveal the critical chromosomes in wheat genome controlling tolerance to water deficit. The same lines were involved in the identification of chromosomes associated with the activity of antioxidant enzymes that are closely related to the detoxification of H2O2 [catalase (CAT), ascorbate peroxidase, dehydroascorbate reductase and glutathione reductase (GR)]. The recipient cultivar S29 was highly drought tolerant while the donor JP was sensitive. Using non-metric multidimensional scaling of yield components and indices of drought tolerance/susceptibility chromosomes 2A and 4D, substitution in the genetic background of S29 was found to lead to a critical decrease of water-deficit tolerance. The drop of tolerance correlated with a sharp decline of cumulative activity of the catalase and the enzymes of ascorbate–glutathione cycle in wheat leaves. Clear evidence was obtained for the involvement of genes present on the homoeologous group 2 chromosomes in the control of GR and CAT activity. Substitution of the chromosome 4D had a significant reducing impact on the CAT activity level.

Dissection of rye chromosomes by the gametocidal system

Chromosome mutations occur in common wheat carrying a monosome of gametocidal (Gc) chromosomes 2C and 3C(SAT). These Gc chromosomes have been known to induce chromosomal breakage in a rye chromosome 1R added to common wheat. We attempted to introduce the two Gc chromosomes into the other six rye chromosome (2R to 7R) addition or substitution lines of common wheat to establish a set of chromosomal rearrangement-inducing lines for rye chromosomes. We obtained critical plants that had a pair of rye chromosomes and one Gc chromosome for 2R, 3R, 4R and 6R, and semi-critical plants that were monotelodisomic and monosomic for 5R. Chromosomal aberrations are expected to occur in the progeny of these plants. Besides we established self-fertile disomic 2C addition lines of common wheat that were disomic substitution for 3R, disomic addition for 6R, monotelodisomic for 5R, and monosomic for 7R. We can produce the critical plants of the respective rye chromosomes by crossing above lines to the respective wheat-rye disomic addition or substitution lines. During the cytological screening in this study, we found Gc-induced chromosomal aberrations for every rye chromosome. The stocks reported here can be used to produce dissection lines for each of the rye chromosomes in common wheat by the Gc system.

Identification of a novel homolog for a calmodulin-binding protein that is upregulated in alloplasmic wheat showing pistillody

Intracellular signaling pathways between the mitochondria and the nucleus are important in both normal and abnormal development in plants. The homeotic transformation of stamens into pistil-like structures (a phenomenon termed pistillody) in cytoplasmic substitution (alloplasmic) lines of bread wheat (Triticum aestivum) has been suggested to be induced by mitochondrial retrograde signaling, one of the forms of intracellular communication. We showed previously that the mitochondrial gene orf260 could alter the expression of nuclear class B MADS-box genes to induce pistillody. To elucidate the interactions between orf260 and nuclear homeotic genes, we performed a microarray analysis to compare gene expression patterns in the young spikes of a pistillody line and a normal line. We identified five genes that showed higher expression levels in the pistillody line. Quantitative expression analysis using real-time PCR indicated that among these five genes, Wheat Calmodulin-Binding Protein 1 (WCBP1) was significantly upregulated in young spikes of the pistillody line. The amino acid sequence of WCBP1 was predicted from the full-length cDNA sequence and found to encode a novel plant calmodulin-binding protein. RT-PCR analysis indicated that WCBP1 was preferentially expressed in young spikes at an early stage and decreased during spike maturation, indicating that it was associated with spikelet/floret development. Furthermore, in situ hybridization analysis suggested that WCBP1 was highly expressed in the pistil-like stamens at early to late developmental stages. These results indicate that WCBP1 plays a role in formation and development of pistil-like stamens induced by mitochondrial retrograde signaling.

Heading time of substitution and near-isogenic lines of common wheat with dominant alleles Vrn-B1a and Vrn-B1c

Heading time of substitution and near-isogenic lines (NILs) with Vrn-B1a and Vrn-B1c alleles was studied without vernalization and after 30-day vernalization in the greenhouse and in the field. Without vernalization, both in the greenhouse and in the field, plants with Vrn-B1c allele headed several days earlier, than plants with Vrn-B1a. However, plants with Vrn-B1a allele responded to vernalization by more pronounced heading acceleration than Vrn-B1c plants. The weak Vrn-B1a allele dominated in F1 hybrids from the cross between two NILs with Vrn-B1c and Vrn-B1a alleles. These observations confirm the multiple allelism of the Vrn-B1 gene, responsible for the spring growth habit in wheat.

The performance of single chromosome substitution lines of bread wheat subjected to salinity stress

The parents (the landrace Chinese spring (CS) and a synthetic hexaploids (S6x)) and 17 derived single chromosome substitution lines (SL) were grown in parallel in the field under non-saline (1.0 dSm−1) and saline (12.0 dSm−1) conditions, and evaluated for a set of phenotypic traits. The performance of CS indicated it to have borderline salinity tolerance with respect to all of the traits except for leaf area (for which it behaved in as a salinity sensitive type). The SL 4D was early in booting, ear emergence, flowering and maturity, while 5D and 2B SLs were both late. The 2B SL produce 33% more ears than CS. The 5D SL under-performed with respect to ear weight, grain number per ear, grain weight per ear and 1000-grain weight both under non-saline and saline conditions. Under saline conditions, four SLs (1A>5A>1D>2B) outperformed Cs for ear length, and six SLs (1D>6A>4B>3A>3B>3D) showed an improved grain weight. The grains produce by the 2B SL were smaller than those of CS. Leaf area developed better in four SLs (4D>2B>1A>7D) than in CS.

Tolerance of prolonged drought among a set of bread wheat chromosome substitution Lines

Variation in tolerance of prolonged drought was identified among a set of single chromosome bread wheat substitution lines, involving the replacement of each cv. Chinese Spring chromosome in turn with its homologue from a synthetic hexaploid (Triticum dicoccoides × Aegilops tauschii). Water stress was applied under controlled conditions by limiting the supply of water to 30% from 100% aqueous soil. The reaction to the resulting long-term drought stress was quantified by three indices, based on grain yield components. Enhanced drought tolerance was associated with the presence of donor chromosomes 1A, 5A, 1D, 3D, 5D and 6D, and enhanced susceptibility with chromosomes 3A, 4B and 7D.

Physical mapping of puroindoline b-2 genes and molecular characterization of a novel variant in durum wheat (Triticum turgidum L.)

The puroindoline genes (Pina and Pinb) are the functional components of the common or bread wheat (Triticum aestivum L.) grain hardness locus that are responsible for kernel texture. In this study, four puroindoline b-2 variants were physically mapped using nulli-tetrosomic lines of bread wheat cultivar Chinese Spring and substitution lines of durum wheat (Triticum turgidum L.) cultivar Langdon. Results indicated that Pinb-2v1 was on 7D of Chinese Spring, Pinb-2v2 on 7B of Chinese Spring, Pinb-2v3 on 7B of Chinese Spring and Langdon, and Pinb-2v4 on 7A of Chinese Spring and Langdon. A new puroindoline b-2 variant, designated Pinb-2v5, was identified at the puroindoline b-2 locus of durum wheat cultivar Langdon, with a difference of only five single nucelotide polymorphisms compared with Pinb-2v4. Sequencing results indicated that, in comparison with the Pinb-2v3 sequence (AM99733 and GQ496618 with one base-pair modification of G to T at 6th position, designated Pinb-2v3a) in bread wheat cultivar Witchta, the coding region of Pinb-2v3 in 12 durum wheat cultivars had a single nucleotide change from T to C at the 311th position, resulting in a corresponding amino acid change from valine to alanine at the 104th position. This new allele was designated Pinb-2v3b. The study of puroindoline b-2 gene polymorphism in CIMMYT and Italian durum wheat germplasm and discovery of a novel puroindoline b-2 variant could provide useful information for further understanding the molecular and genetic basis of kernel hardness and illustrating gene duplication events in wheat.

Molecular markers show a complex mosaic pattern of wheat-Thinopyrum intermedium translocations carrying resistance to YDV

Thinopyrum intermedium translocations derived from the wheat (Triticum aestivum L.) substitution line P-29 were previously characterized by RFLP. We have further analyzed these lines and additional related germplasm with publicly available STS and SSRs. Primers which showed a polymorphism between wheat and P-29, were tested in all recombinant and nulli-tetrasomic lines confirming their position on chromosome 7D. The resulting 7D/7E chromosome maps appeared as a mosaic of wheat and Th. intermedium chromatin sections. To verify the composition of the translocation lines suggested by the RFLP-PCR map, F(2) progeny of two crosses (CS/216-1 and CS/260-1) were analyzed with molecular markers. Both populations gave an unexpectedly diverse number of recombinant individuals, suggesting that interstitial translocations occur more frequently than previously thought. This analysis also showed that there is a wide range in the number and position of the interstitial translocations within a given line such as the mosaic chromosome in recombinant line 260-1/CS-26, which has four Th. intermedium chromosome segments. Phenotypic data of the two populations suggested the presence of one gene which we have called Bdv3 to differentiate it from the previously reported orthologous gene Bdv2. Using the PCR-based molecular markers identified in this study, 5 out of 12 elite lines that showed good yields and no YDV symptoms contained Th. intermedium chromatin. Due to the multiple components involved in the YDV disease complex, combining selection for YDV resistance with the molecular markers and maps identified in this study will increase the efficiency of introgressing Th. intermedium chromatin containing YDV resistance or other beneficial traits into elite wheat germplasm.

Chromosomal Location of Traits Associated with Wheat Seedling Water and Phosphorus Use Efficiency under Different Water and Phosphorus Stresses

The objective of this study was to locate chromosomes for improving water and phosphorus-deficiency tolerance of wheat at the seedling stage. A set of Chinese Spring-Egyptian Red wheat substitution lines and their parent Chinese Spring (recipient) and Egyptian Red (donor) cultivars were measured to determine the chromosomal locations of genes controlling water use efficiency (WUE) and phosphorus use efficiency (PUE) under different water and phosphorus conditions. The results underlined that chromosomes 1A, 7A, 7B, and 3A showed higher leaf water use efficiency (WUEl = Pn/Tr; Pn = photosynthetic rate; Tr = transpiration rate) under W-P (Hoagland solution with 1/2P), -W-P (Hoagland solution with 1/2P and 10% PEG). Chromosomes 7A, 3D, 2B, 3B, and 4B may carry genes for positive effects on individual plant water use efficiency (WUEp = biomass/TWC; TWC = total water consumption) under WP (Hoagland solution), W-P and -W-P treatment. Chromosomes 7A and 7D carry genes for PUE enhancement under WP, -WP (Hoagland solution with 10% PEG) and W-P treatment. Chromosome 7A possibly has genes for controlling WUE and PUE simultaneously, which indicates that WUE and PUE may share the same genetic background. Phenotypic and genetic analysis of the investigated traits showed that photosynthetic rate (Pn) and transpiration rate (Tr), Tr and WUEl showed significant positive and negative correlations under WP, W-P, -WP and -W-P, W-P, -WP treatments, respectively. Dry mass (DM), WUEP, PUT (phosphorus uptake) all showed significant positive correlation under WP, W-P and -WP treatment. PUE and phosphorus uptake (PUT = P uptake per plant) showed significant negative correlation under the four treatments. The results might provide useful information for improving WUE and PUE in wheat genetics.

Class D and Bsister MADS-box genes are associated with ectopic ovule formation in the pistil-like stamens of alloplasmic wheat (Triticum aestivum L.)

Homeotic transformation of stamens into pistil-like structures (pistillody) has been reported in cytoplasmic substitution (alloplasmic) lines of bread wheat (Triticum aestivum L.) that have the cytoplasm of a related wild species, Aegilops crassa. An ectopic ovule differentiates in the pistil-like stamen in the alloplasmic wheat. The SEEDSTICK (STK)-like class D MADS-box gene, wheat STK (WSTK), was expressed in the primordia of ectopic ovules in the pistil-like stamens as well as in the true pistil, suggesting that ectopic ovule formation results from WSTK expression in the pistil-like stamens of alloplasmic wheat. The ectopic ovule is abnormal as it fails to form complete integuments. Based on the expression pattern of WSTK and B(sister) MADS-box gene, WBsis (wheat B ( sister )), we conclude that WSTK plays a role in determination of ovule identity in the pistil-like stamen, but complete ovule development fails due to aberrant expression of WBsis.