B1 Locus Research Articles

A high prevalence of Toxoplasma in Australian chickens

A small survey was undertaken of commercially reared free-range chickens in Western Australia using serology and molecular detection. Eighteen out of 20 serum samples showed antibody responses with titers of 1:64 in 5 chickens and ≥1:128 in 13 chickens. DNA extracted from 22 out of 50 tissue samples, 10 brains and 12 spleens, were positive by nested PCR, and sequencing at the B1 locus on DNA from 3 brain and 3 spleen samples confirmed that 2 isolates were Toxoplasma gondii, Type I, and 4 Type II/III. The high prevalence of Toxoplasma infection found in commercial, free-range chickens raises public health issues with respect to both exposure in the workplace, during carcass processing, and subsequent transmission during food handling and/or consumption as food. The results of this study emphasize the need for more data on the incidence of Toxoplasma infection in domestic animals and humans in Australia.

Maize Unstable factor for orange1 Is Required for Maintaining Silencing Associated with Paramutation at the pericarp color1 and booster1 Loci

To understand the molecular mechanisms underlying paramutation, we examined the role of Unstable factor for orange1 (Ufo1) in maintaining paramutation at the maize pericarp color1 (p1) and booster1 (b1) loci. Genetic tests revealed that the Ufo1-1 mutation disrupted silencing associated with paramutation at both p1 and b1. The level of up regulation achieved at b1 was lower than that at p1, suggesting differences in the role Ufo1-1 plays at these loci. We characterized the interaction of Ufo1-1 with two silenced p1 epialleles, P1-rr′ and P1-prTP, that were derived from a common P1-rr ancestor. Both alleles are phenotypically indistinguishable, but differ in their paramutagenic activity; P1-rr′ is paramutagenic to P1-rr, while P1-prTP is non-paramutagenic. Analysis of cytosine methylation revealed striking differences within an enhancer fragment that is required for paramutation; P1-rr′ exhibited increased methylation at symmetric (CG and CHG) and asymmetric (CHH) sites, while P1-prTP was methylated only at symmetric sites. Both silenced alleles had higher levels of dimethylation of lysine 9 on histone 3 (H3K9me2), an epigenetic mark of silent chromatin, in the enhancer region. Both epialleles were reactivated in the Ufo1-1 background; however, reactivation of P1-rr′ was associated with dramatic loss of symmetric and asymmetric cytosine methylation in the enhancer, while methylation of up-regulated P1-prTP was not affected. Interestingly, Ufo1-1–mediated reactivation of both alleles was accompanied with loss of H3K9me2 mark from the enhancer region. Therefore, while earlier studies have shown correlation between H3K9me2 and DNA methylation, our study shows that these two epigenetic marks are uncoupled in the Ufo1-1–reactivated p1 alleles. Furthermore, while CHH methylation at the enhancer region appears to be the major distinguishing mark between paramutagenic and non-paramutagenic p1 alleles, H3K9me2 mark appears to be important for maintaining epigenetic silencing.

The maize b1 paramutation control region causes epigenetic silencing in Drosophila melanogaster

Paramutation is an epigenetic process in which a combination of alleles in a heterozygous organism results in a meiotically stable change in expression of one of the alleles. The mechanisms underlying paramutation are being actively investigated, and examples have been described in both plants and mammals, suggesting that it may utilize epigenetic mechanisms that are widespread and evolutionarily conserved. Paramutation at the well-studied maize b1 locus requires a control region consisting of seven 853 bp tandem repeats. To study the conservation of the epigenetic mechanisms underlying seemingly unique epigenetic processes such as paramutation, we created transgenic Drosophila melanogaster carrying the maize b1 control region adjacent to the Drosophila white reporter gene. We show that the b1 tandem repeats cause silencing of the white reporter in Drosophila. A single copy of the tandem repeat sequence is sufficient to cause silencing, and silencing strength increases as the number of tandem repeats increases. Additionally, transgenic lines with the full seven tandem repeats demonstrate evidence of either pairing-sensitive silencing and silencing in trans, or epigenetic activation in trans. These trans-interactions are dependent on repeat number, similar to maize b1 paramutation. Also, as in maize, the tandem repeats are bidirectionally transcribed in Drosophila. These results indicate that the maize b1 tandem repeats function as an epigenetic silencer and mediate trans-interactions in Drosophila, and support the hypothesis that the mechanisms underlying such epigenetic processes are conserved.

Locus- and domain-dependent control of DNA methylation at mouse B1 retrotransposons during male germ cell development.

In mammals, germ cells undergo striking dynamic changes in DNA methylation during their development. However, the dynamics and mode of methylation are poorly understood for short interspersed elements (SINEs) dispersed throughout the genome. We investigated the DNA methylation status of mouse B1 SINEs in male germ cells at different developmental stages. B1 elements showed a large locus-to-locus variation in methylation; loci close to RNA polymerase II promoters were hypomethylated, while most others were hypermethylated. Interestingly, a mutation that eliminates Piwi-interacting RNAs (piRNAs), which are involved in methylation of long interspersed elements (LINEs), did not affect the level of B1 methylation, implying a piRNA-independent mechanism. Methylation at B1 loci in SINE-poor genomic domains showed a higher dependency on the de novo DNA methyltransferase DNMT3A but not on DNMT3B, suggesting that DNMT3A plays a major role in methylation of these domains. We also found that many genes specifically expressed in the testis possess B1 elements in their promoters, suggesting the involvement of B1 methylation in transcriptional regulation. Taken altogether, our results not only reveal the dynamics and mode of SINE methylation but also suggest how the DNA methylation profile is created in the germline by a pair of DNA methyltransferases.

Identification of Novel Genetic Markers Associated with Clinical Phenotypes of Systemic Sclerosis through a Genome-Wide Association Strategy

The aim of this study was to determine, through a genome-wide association study (GWAS), the genetic components contributing to different clinical sub-phenotypes of systemic sclerosis (SSc). We considered limited (lcSSc) and diffuse (dcSSc) cutaneous involvement, and the relationships with presence of the SSc-specific auto-antibodies, anti-centromere (ACA), and anti-topoisomerase I (ATA). Four GWAS cohorts, comprising 2,296 SSc patients and 5,171 healthy controls, were meta-analyzed looking for associations in the selected subgroups. Eighteen polymorphisms were further tested in nine independent cohorts comprising an additional 3,175 SSc patients and 4,971 controls. Conditional analysis for associated SNPs in the HLA region was performed to explore their independent association in antibody subgroups. Overall analysis showed that non-HLA polymorphism rs11642873 in IRF8 gene to be associated at GWAS level with lcSSc (P = 2.32×10−12, OR = 0.75). Also, rs12540874 in GRB10 gene (P = 1.27 × 10−6, OR = 1.15) and rs11047102 in SOX5 gene (P = 1.39×10−7, OR = 1.36) showed a suggestive association with lcSSc and ACA subgroups respectively. In the HLA region, we observed highly associated allelic combinations in the HLA-DQB1 locus with ACA (P = 1.79×10−61, OR = 2.48), in the HLA-DPA1/B1 loci with ATA (P = 4.57×10−76, OR = 8.84), and in NOTCH4 with ACA P = 8.84×10−21, OR = 0.55) and ATA (P = 1.14×10−8, OR = 0.54). We have identified three new non-HLA genes (IRF8, GRB10, and SOX5) associated with SSc clinical and auto-antibody subgroups. Within the HLA region, HLA-DQB1, HLA-DPA1/B1, and NOTCH4 associations with SSc are likely confined to specific auto-antibodies. These data emphasize the differential genetic components of subphenotypes of SSc.

Cytological and genetic mapping of the gene for four-awned phenotype in Triticum carthlicum Nevski

A striking feature of Triticum carthlicum Nevski (2n = 4x = 28, AABB genome) is an awn-like appendage on the glume, so all the spikelets appear four-awned. From the word “tetraaristatus” (four-awned), the locus was named “t” to distinguish it from the b1 locus on chromosome 5A and b2 locus on chromosome 6B for awn formation. The aims of present study was to determine the chromosomal location of the t locus in tetraploid wheat T. carthlicum, and (2) to assess linkage relationships of t, Rht12 using microsatellite markers in T. carthlicum. Combined cytological evidence and microsatellite mapping showed that t was located on the chromosome 5AL. The alignment of the gene was Xgwm291–(6.4 cM)–t–(6.7 cM)–Xgwm410 in F2 of T. carthlicum #521/LD222, and Xhbg219–(12.4 cM)–t–(5.1 cM)–Xgwm410–(6.2 cM) –Rht12 in F2 of ANW 16C/#521 on the 5AL. The t locus was different from b1 locus, because it was known that the semi-dwarf Rht12 gene was completely linked with b1 gene. We discussed that the four-awned phenotype of T. carthlicum was introduced from Triticum aestivum L. ssp. carthlicoides.

The tumour-suppressive miR-29a/b1 cluster is regulated by CEBPA and blocked in human AML

Background:CCAAT/enhancer-binding protein-α (CEBPA) is crucial for normal granulopoiesis and is frequently disrupted in acute myeloid leukaemia (AML). Increasing evidence suggests that CEBPA exerts its effects, in parts, by regulating specific microRNAs (miRNAs), as previously shown for miR-223. The aim of this study was to investigate the genome-wide pattern of miRNAs regulated by CEBPA in myeloid cells.Methods:In Kasumi-1 cells, conditionally expressing CEBPA, we assessed the expression of 470 human miRNAs by microarray analysis. We further investigated the microarray results by qRT-PCR, luciferase reporter assays, and chromatin immunoprecipitation assays.Results:In all, 18 miRNAs were more than two-fold suppressed or induced after CEBPA restoration. Among these 18 miRNAs, we focused on CEBPA-mediated regulation of the tumour-suppressive miR-29b. We observed that miR-29b is suppressed in AML patients with impaired CEBPA function or loss of chromosome 7q. We found that CEBPA selectively regulates miR-29b expression on its miR-29a/b1 locus on chromosome 7q32.3, whereas miR-29b2/c on chromosome 1q32.2 is not affected.Conclusion:This study reports the activation of the tumour-suppressive miR-29b by the haematopoietic key transcription factor CEBPA. Our data provide a rationale for miR-29b suppression in AML patients with loss of chromosome 7q or CEBPA deficiency.

The role of DNA methylation, nucleosome occupancy and histone modifications in paramutation

Paramutation is the transfer of epigenetic information between alleles that leads to a heritable change in expression of one of these alleles. Paramutation at the tissue-specifically expressed maize (Zea mays) b1 locus involves the low-expressing B' and high-expressing B-I allele. Combined in the same nucleus, B' heritably changes B-I into B'. A hepta-repeat located 100-kb upstream of the b1 coding region is required for paramutation and for high b1 expression. The role of epigenetic modifications in paramutation is currently not well understood. In this study, we show that the B' hepta-repeat is DNA-hypermethylated in all tissues analyzed. Importantly, combining B' and B-I in one nucleus results in de novo methylation of the B-I repeats early in plant development. These findings indicate a role for hepta-repeat DNA methylation in the establishment and maintenance of the silenced B' state. In contrast, nucleosome occupancy, H3 acetylation, and H3K9 and H3K27 methylation are mainly involved in tissue-specific regulation of the hepta-repeat. Nucleosome depletion and H3 acetylation are tissue-specifically regulated at the B-I hepta-repeat and associated with enhancement of b1 expression. H3K9 and H3K27 methylation are tissue-specifically localized at the B' hepta-repeat and reinforce the silenced B' chromatin state. The B' coding region is H3K27 dimethylated in all tissues analyzed, indicating a role in the maintenance of the silenced B' state. Taken together, these findings provide insight into the mechanisms underlying paramutation and tissue-specific regulation of b1 at the level of chromatin structure.

Paramutation: Epigenetic Instructions Passed Across Generations

PARAMUTATION is the fascinating ability of specific DNA sequences to communicate in trans to establish meiotically heritable expression states. Intriguingly, newly silenced sequences continue to issue instructions to naive alleles in subsequent generations. The term “paramutation” was first coined in the 1950s by Alexander Brink to describe this puzzling phenomenon at the r1 locus in maize (Brink 1956); an interaction between specific alleles in heterozygotes led to heritable decreases in gene expression of one allele. Not only was the reduced expression state stable through meiosis, but also the low-expressing allele could induce silencing of another high-expressing allele in subsequent generations. The frequency of the change was 100% and the stability of the change was lower than typical mutations; hence the term “paramutation.” A few years later, Ed Coe, Jr., described another maize example in which interaction between alleles at the b1 locus also led to heritable silencing (Coe 1959) and Rudolf Hagemann described interactions at the sulfurea locus in tomato (Hagemann 1969). Since that time other examples of paramutation have been identified in maize and in other species (reviewed in Chandler and Stam 2004; Stam and Mittelsten Scheid 2005; Chandler 2007), yet the two maize loci where paramutation was initially described, r1 and b1, remain the most extensively characterized and best understood. The r1 and b1 loci encode closely related, functionally equivalent transcription factors that activate the anthocyanin pigment biosynthetic pathway (Goff et al. 1990; Ludwig et al. 1990). They are likely related to each other through a duplication resulting from an ancient allotetraploidization event during maize evolution (Gaut and Doebley 1997). The two loci have multiple alleles with distinct expression patterns, which regulate the distribution of anthocyanin pigments during development (Styles et al. 1973; Coe 1979). Recent work demonstrates a key role for RNA in mediating both r1 and b1 paramutation, as the mop1 gene that encodes an RNA-dependent RNA polymerase (RDR; Alleman et al. 2006) is absolutely required for paramutation at both loci (Dorweiler et al. 2000). Yet, there are striking differences in the properties of r1 and b1 paramutation, which hint at distinct mechanisms. In this article, the most striking differences between r1 and b1 paramutation are described and potential mechanisms are discussed relative to our current understanding of the role of RNA interference (RNAi) in mediating transcriptional silencing.

Type X Toxoplasma gondii in a wild mussel and terrestrial carnivores from coastal California: New linkages between terrestrial mammals, runoff and toxoplasmosis of sea otters

Sea otters in California are commonly infected with Toxoplasma gondii. A unique Type X strain is responsible for 72% of otter infections, but its prevalence in terrestrial animals and marine invertebrates inhabiting the same area was unknown. Between 2000 and 2005, 45 terrestrial carnivores (lions, bobcats, domestic cats and foxes) and 1396 invertebrates (mussels, clams and worms) were screened for T. gondii using PCR and DNA sequencing to determine the phylogeographic distribution of T. gondii archetypal I, II, III and Type X genotypes. Marine bivalves have been shown to concentrate T. gondii oocysts in the laboratory, but a comprehensive survey of wild invertebrates has not been reported. A California mussel from an estuary draining into Monterey Bay was confirmed positive for Type X T. gondii by multilocus PCR and DNA sequencing at the B1 and SAG1 loci. This mussel was collected from nearshore marine waters just after the first significant rainfall event in the fall of 2002. Of 45 carnivores tested at the B1, SAG1, and GRA6 typing loci, 15 had PCR-confirmed T. gondii infection; 11 possessed alleles consistent with infection by archetypal Type I, II or III strains and 4 possessed alleles consistent with Type X T. gondii infection. No non-canonical alleles were identified. The four T. gondii strains with Type X alleles were identified from two mountain lions, a bobcat and a fox residing in coastal watersheds adjacent to sea otter habitat near Monterey Bay and Estero Bay. Confirmation of Type X T. gondii in coastal-dwelling felids, canids, a marine bivalve and nearshore-dwelling sea otters supports the hypotheses that feline faecal contamination is flowing from land to sea through surface runoff, and that otters can be infected with T. gondii via consumption of filter-feeding marine invertebrates.

Transplacental toxoplasmosis in a wild southern sea otter ( Enhydra lutris nereis)

In September 2004, a neonatal sea otter pup was found alive on the beach in northern Monterey Bay, CA. Efforts to locate the mother were unsuccessful. Due to a poor prognosis for successful rehabilitation, the pup was euthanized. Postmortem examination revealed emaciation, systemic lymphadenopathy and a malformation of the left cerebral temporal lobe. On histopathology, free tachyzoites and tissue cysts compatible with Toxoplasma gondii were observed in the brain, heart, thymus, liver, lymph nodes and peri-umbilical adipose. The presence of T. gondii within host tissues was associated with lymphoplasmacytic inflammation and tissue necrosis. Immunofluorescent antibody tests using postmortem serum were positive for anti- T. gondii IgM and IgG (at 1:320 and 1:1280 serum dilution, respectively), but were negative for IgG directed against Sarcocystis neurona and Neospora caninum (<1:40 each). Brain immunohistochemistry revealed positive staining for tachyzoites and tissue cysts using antiserum raised to T. gondii, but not S. neurona or N. caninum. T. gondii parasite DNA was obtained from extracts of brain and muscle by PCR amplification using the diagnostic B1 locus. Restriction enzyme digestion followed by gel electrophoresis and DNA sequencing confirmed the presence of Type X T. gondii, the strain identified in the majority of southern sea otter infections.

An RNA-dependent RNA polymerase is required for paramutation in maize

Paramutation is an allele-dependent transfer of epigenetic information, which results in the heritable silencing of one allele by another. Paramutation at the b1 locus in maize is mediated by unique tandem repeats that communicate in trans to establish and maintain meiotically heritable transcriptional silencing. The mop1 (mediator of paramutation1) gene is required for paramutation, and mop1 mutations reactivate silenced Mutator elements. Plants carrying mutations in the mop1 gene also stochastically exhibit pleiotropic developmental phenotypes. Here we report the map-based cloning of mop1, an RNA-dependent RNA polymerase gene (RDRP), most similar to the RDRP in plants that is associated with the production of short interfering RNA (siRNA) targeting chromatin. Nuclear run-on assays reveal that the tandem repeats required for b1 paramutation are transcribed from both strands, but siRNAs were not detected. We propose that the mop1 RDRP is required to maintain a threshold level of repeat RNA, which functions in trans to establish and maintain the heritable chromatin states associated with paramutation.

Human leukocyte antigen (HLA) DR4 is not associated with differences in overall survival (OS), progression free survival (PFS), or graft-vs-host-disease (GVHD) following allogeneic hematopoietic stem cell transplantation (allo HSCT) for myeloid malignancies

6552 Background: HLA DR4 is associated with autoimmune disorders and with response to cyclosporine immunosuppression in T-cell Large Granular Lymphoproliferative Disorder (BJH 2003;123(3)). We have earlier reported association of DR 15 positivity with decreased acute GVHD (aGVHD) in patients undergoing allo HSCT for myeloid malignancies (Blood, 2005 Nov 10;Epub). Therefore we investigated the role of HLA DR4 on graft-versus-leukemia effect and GVHD in HLA-matched allo HSCT performed for myeloid malignancies. Methods: A retrospective review of 119 consecutive related and 48 consecutive unrelated allo HSCT patients (pts) treated between 1992 and 2003 at RPCI was performed to investigate the influence of HLA DR4 on OS, PFS and the incidence of grade 2–4 aGVHD and chronic GVHD (cGVHD). HLA DR B1 locus typing was determined by either molecular (n=108) or serologic (n=59) methods. The proportion of patients with one or two HLA DR4 antigens was 26% (43/167) which is similar to the range seen in general Caucasian population. Pt characteristics included: AML (n=84), CML (n=63), and MDS (n=20); median age 43 years (range 11–66); Male (n=104), Female (n=63); Caucasian (&gt;95%); Total Body Irradiation (TBI) conditioning regimens (n=124); Busulfan (Bu)/Cyclophosphamide (Cy) (n=22), Bu/TBI (n=27), Cy/TBI (n=13), Etoposide/Cy/TBI (n=84), or other combinations (n=21). Results: There was no difference in OS and the PFS between the HLA DR4 positive vs negative groups in any disease or donor subgroups (p=0.4 and 0.6). GVHD prophylaxis was similar in the two groups but aGVHD and cGVHD incidence was not different in the two groups (p=0.8 and 0.9) Conclusions: HLA DR 4 is not associated with differences in GVHD or outcomes unlike the previous finding that HLA DR15 is associated with decreased acute GVHD in myeloid malignancies. These results suggest that there are differential effects of HLA DR antigens on the incidence of GVHD and outcomes in myeloid and lymphoid malignancies. Understanding these differences may facilitate the design of pt specific GVHD prophylaxis following allo HSCT. No significant financial relationships to disclose.

Defining the primary route for lutein synthesis in plants: the role of Arabidopsis carotenoid beta-ring hydroxylase CYP97A3.

Lutein, a dihydroxy derivative of alpha-carotene (beta,epsilon-carotene), is the most abundant carotenoid in photosynthetic plant tissues where it plays important roles in light-harvesting complex-II structure and function. The synthesis of lutein from lycopene requires at least four distinct enzymatic reactions: beta- and epsilon-ring cyclizations and hydroxylation of each ring at the C-3 position. Three carotenoid hydroxylases have already been identified in Arabidopsis, two nonheme diiron beta-ring monooxygenases (the B1 and B2 loci) that primarily catalyze hydroxylation of the beta-ring of beta,beta-carotenoids and one heme-containing monooxygenase (CYP97C1, the LUT1 locus) that catalyzes hydroxylation of the epsilon-ring of beta,epsilon-carotenoids. In this study, we demonstrate that Arabidopsis CYP97A3 (the LUT5 locus) encodes a fourth carotenoid hydroxylase with major in vivo activity toward the beta-ring of alpha-carotene (beta,epsilon-carotene) and minor activity on the beta-rings of beta-carotene (beta,beta-carotene). A cyp97a3-null allele, lut5-1, causes an accumulation of alpha-carotene at a level equivalent to beta-carotene in wild type, which is stably incorporated into photosystems, and a 35% reduction in beta-carotene-derived xanthophylls. That lut5-1 still produces 80% of wild-type lutein levels, indicating at least one of the other carotene hydroxylases, can partially compensate for the loss of CYP97A3 activity. From these data, we propose a model for the preferred pathway for lutein synthesis in plants: ring cyclizations to form alpha-carotene, beta-ring hydroxylation of alpha-carotene by CYP97A3 to produce zeinoxanthin, followed by epsilon-ring hydroxylation of zeinoxanthin by CYP97C1 to produce lutein.

Identification and characterization of stripe rust resistance gene Yr34 in common wheat

An uncharacterized source of seedling resistance to Puccinia striiformis f.sp. tritici was identified in an advanced wheat breeding line WAWHT2046. Genetic analysis based on a WAWHT2046/Carnamah-derived double haploid (DH) population demonstrated monogenic inheritance of seedling stripe rust resistance in WAWHT2046. The gene controlling stripe rust resistance in line WAWHT2046 was tentatively designated YrWA. The chromosome 5AL located awn inhibitor gene B1, possessed by WAWHT2046, also showed monogenic inheritance when the DH population was scored for the presence and absence of awns. Joint segregation analysis at the B1 and YrWA loci indicated genetic linkage between the two loci. A recombination value of 12.2 cM was computed using Mapmanager. This association located YrWA in the chromosome arm 5AL. Molecular mapping using microsatellite markers placed YrWA distal to B1. All molecular markers mapped proximal to the awn inhibitor locus B1. As no other stripe rust resistance gene is reported to be located in the chromosome arm 5AL, YrWA was permanently designated as Yr34. Yr34 produced an intermediate (23C) seedling infection type and expressed very low stripe rust response (10R-MR) on adult plants in the field, similar to the resistance gene Yr17. In addition to Yr34, this mapping population segregated for three genetically independent adult plant stripe rust resistance genes. The detection of DH lines with completely susceptible response, higher than that shown by the Yr34-lacking parent Carnamah, suggested that both parents contributed adult plant resistance. The use of WAWHT2046 as a parent in breeding programs would also contribute APR in addition to Yr34.

Silent Celiac Disease in Chronic Hepatitis C

To assess the impact of interferon treatment on celiac disease onset in hepatitis C patients and to clarify its clinical relevance and outcome. Hepatitis C is associated with autoimmunity, which can be exacerbated by interferon treatment. Cases of celiac disease activation during interferon treatment have been reported. Retrospective evaluation of 534 hepatitis C patients with or without symptoms compatible with celiac disease onset during interferon treatment and 225 controls. Anti-transglutaminase antibodies were assayed. HLA-DQA1 and -B1 loci were typed. Upper gastrointestinal endoscopy was applied to confirm the diagnosis in antibody-positive patients. Anti-transglutaminase antibodies were detected before treatment in 1.3% of hepatitis C patients and in 0.4% of controls (not significant). Eighty-six percent of patients with anti-transglutaminase antibodies showed activation of celiac disease while on interferon. Symptoms ranged from mild to severe, and interferon had to be discontinued in 2 of 7 (29%) patients. Symptoms disappeared in 6 of 7 patients after interferon withdrawal. Onset of symptoms compatible with celiac disease during interferon therapy was significantly associated with the presence of anti-transglutaminase antibodies (OR 53). In hepatitis C patients, the activation of silent celiac disease during interferon treatment is almost universal and should be suspected, but it uncommonly requires interferon treatment discontinuation. Symptoms subside after interferon withdrawal.

Reduced Amylose Effects on Bread and White Salted Noodle Quality

ABSTRACTAmylose content in wheat endosperm is controlled by three Wx loci, and the proportion of amylose decreases with successive accumulation of Wx null alleles at the three loci. The proportion of amylose is believed to influence end‐use quality of bread and Asian noodles. The objectives of this study were to determine influence of the allelic difference at Wx‐B1 locus on bread quality, bread firmness, and white salted noodle texture in a spring wheat cross segregating for the Wx‐B1 locus and in a set of advanced spring wheat breeding lines differing in allelic state at the Wx‐ B1 locus. In addition, we examined the relationship between amylose content and flour swelling properties on bread and noodle traits. Fifty‐four recombinant inbred lines of hard white spring wheat plus parents were grown in replicated trials in two years, and 31 cultivars and breeding lines of hard spring wheat were grown in two locations. Bread and white salted noodles were processed from these trials. The presence of the Wx‐B1 null allele reduced amylose content by 2.4% in a recombinant inbred population and 4.3% in a survey of advanced breeding lines and cultivars compared with the normal. The reduced amylose was accompanied by an average increase in flour swelling power (FSP) for the Wx‐B1 null group of 0.8 g/g for the cross progeny and 2.3 g/g for the cultivar survey group. The Wx‐B1 allelic difference did not affect flour protein in cross progeny where the allelic difference was not confounded with genetic background. Bread from the Wx‐B1 null groups on average had increased loaf volume and was softer than the normal group for the cross progeny and cultivar survey group. The Wx‐B1 allelic difference altered white salted noodle texture, most notably noodle springiness and cohesiveness where the Wx‐B1 null groups was more springy and more cohesive than the normal groups for both sets of genetic materials. Flour protein was more highly related to loaf volume than were FSP or amylose. Both flour protein and FSP were positively related to noodle textural traits, but especially noodle springiness and cohesiveness.

Inheritance of Seed Color in Flax

Seed color of flax (Linum usitatissimum L.) is used in Canada to identify the two main market types. Traditional, high linolenic acid flax must have brown seed, while solin or zero linolenic acid flax must be yellow‐seeded. The objective of this study was to determine the allelic–gene relationship of the dominant yellow gene, the variegated recessive gene, and various spontaneous and unknown recessive yellow genes in flax. Eleven flax cultivars or lines, four spontaneous recessive yellow seed mutants (YSED2, YSED4, S95407, and S96071), one recessive yellow European line (G‐1186/94), two dominant yellow seed lines (CPI84495 and YSED18), one variegated line (M96006), and three brown lines (‘ED47’, ‘Vimy’, and ‘CDC Bethune’) were crossed in all possible combinations, excluding reciprocals. Test crosses were performed with four USDA‐ARS introductions (‘Minerva’, ‘Bolley Golden’, ‘Crystal’, and ‘Bionda’) possessing the four different seed color genes, to determine which locus controlled the yellow–variegated seed color. Test cross data indicated that YSED2, YSED4, S95407, and S96071 possessed the same recessive allele of the g locus producing yellow seed. The European yellow line, G‐1186/94, had a recessive allele at the d locus producing yellow seed, and a dominant yellow Y1 allele was carried by CPI84495 and YSED18. The variegated seed color was conditioned by a second recessive allele of the b1 locus, designated as b1vg Segregation analysis indicated that all the four loci governing seed color were inherited independently except for a possible weak linkage between g and b1vg The recessive genes (g, d, and b1vg), when homozygous recessive, were epistatic to the other loci carrying dominant alleles.

Microsatellite monitoring of recombination around the Vrn‐B1 locus of wheat during early backcross breeding

AbstractThe length of chromosomal segments retained around the Vrn‐B1 gene controlling sensitivity to vernalization in wheat (Triticum aestivum L.) was studied in the first and third backcrosses by using microsatellite markers. Eleven polymorphic markers located on chromosome 5B were used for microsatellite analysis. It was shown in the first backcross that plants with a donor segment around the gene of interest not longer than 50% of chromosome 5B could be selected. When selection is not molecular‐marker assisted, the length of the chromosomal donor segment with the target gene may reach 94% of chromosome 5B even in plants of the third backcross generation. The considerable length differences in the 5B microsatellite loci between the winter and spring lines of wheat studied indicate that these markers are promising in marker‐assisted backcrossing or marker‐assisted selection for the Vrn‐B1 gene using different combinations of Spring and Winter genotypes.

Acid phosphatase polymorphism within and among populations of Cauliflower (Brassica oleracea var botrytis)

Eighty-one lines of cauliflower (Brassica oleracea var. botrytis) from 12 populations used to produce commercial hybrids in Brazil were screened for polymorphism in the acid phosphatase system, in order to evaluate the usefulness of this marker for the determination of the parental contamination level in hybrid seeds. Little polymorphism was detected in the examined lines, but the system appeared to be very useful for hybrid identification, since the only condition required was polymorphism between the two parental lines. If the analyzed lines were used for hybrid production, 8.4% and 12.3% of the possible crosses would result in hybrids which can be positively identified using the APS-1 and B1 loci, respectively. If only one plant of each homozygous type (SS or FF) was analyzed in each population, 41% and 50% of the possible crosses would result in hybrids which can be positively identified using the APS-1 and B1 loci, respectively.