Inheritance and molecular characterization of broad range tolerance to herbicides targeting acetohydroxyacid synthase in sunflower

Ahasl1 is a multilallelic locus where all the induced and natural mutations for herbicide tolerance were described thus far in sunflower (Helianthus annuus L.). The allele Ahasl1-1 confers moderate tolerance to imidazolinone (IMI), Ahasl1-2, and Ahasl1-3 provides high levels of tolerance solely to sulfonylurea (SU) and IMI, respectively. An Argentinean wild sunflower population showing plants with high level of tolerance to either an IMI and a SU herbicide was discovered and used to develop an inbred line designated RW-B. The objectives of this work were to determine the relative level and pattern of cross-tolerance to different AHAS-inhibiting herbicides, the mode of inheritance, and the molecular basis of herbicide tolerance in this line. Slight or no symptoms observed after application of different herbicides indicated that RW-B possesses a completely new pattern of tolerance to AHAS-inhibiting herbicides in sunflower. Biomass response to increasing doses of metsulfuron or imazapyr demonstrated a higher level of tolerance in RW-B with respect to Ahasl1-1/Ahasl1-1 and Ahasl1-2/Ahasl1-2 lines. On the basis of genetic analyses and cosegregation test, it was concluded that tolerance to imazapyr in the original population is inherited as a single, partially dominant nuclear gene and that this gene is controlling the tolerance to four different AHAS-inhibiting herbicides. Pseudo-allelism test permitted us to conclude that the tolerant allele present in RW-B is an allelic variant of Ahasl1-1 and was designated as Ahasl1-4. Nucleotide and deduced amino acid sequence indicated that the Ahasl1-4 allele sequence of RW-B has a leucine codon (TTG) at position 574 (relative to the Arabidopsis thaliana AHAS sequence), whereas the enzyme from susceptible lines has a tryptophan residue (TGG) at this position. The utilization of this new allele in the framework of weed control and crop rotation is discussed.     

Molecular and biochemical characterization of an induced mutation conferring imidazolinone resistance in sunflower

A partially dominant nuclear gene conferring resistance to the imidazolinone herbicides was previously identified in the cultivated sunflower (Helianthus annuus L.) line CLHA-Plus developed by seed mutagenesis. The objective of this study was to characterize this resistant gene at the phenotypic, biochemical and molecular levels. CLHA-Plus showed a complete susceptibility to sulfonylureas (metsulfuron, tribenuron and chlorsulfuron) but, on the other hand, it showed a complete resistance to imidazolinones (imazamox, imazapyr and imazapic) at two rates of herbicide application. This pattern was in close association with the AHAS-inhibition kinetics of protein extracts of CLHA-Plus challenged with different doses of imazamox and chlorsulfuron. Nucleotide and deduced amino acid sequence comparisons between resistant and susceptible lines indicated that the imidazolinone-resistant AHAS of CLHA-Plus has a threonine codon (ACG) at position 122 (relative to the Arabidopsis thaliana AHAS sequence), whereas the herbicide-susceptible enzyme from BTK47 has an alanine residue (GCG) at this position. Since the resistance genes to AHAS-inhibiting herbicides so far characterized in sunflower code for the catalytic (large) subunit of AHAS, we propose to redesignate the wild type allele as ahasl1 and the incomplete dominant resistant alleles as Ahasl1-1 (previously Imr1 or Ar _pur ), Ahasl1-2 (previously Ar _kan ) and Ahasl1-3 (for the allele present in CLHA-Plus). The higher tolerance level to imidazolinones and the lack of cross-resistance to other AHAS-inhibiting herbicides of Ahasl1-3 indicate that this induced mutation can be used to develop commercial hybrids with superior levels of tolerance and, at the same time, to assist weed management where control of weedy common sunflower is necessary.     

Validation of the <Emphasis Type="Italic">VRN-H2</Emphasis>/<Emphasis Type="Italic">VRN-H1</Emphasis> epistatic model in barley reveals that intron length variation in <Emphasis Type="Italic">VRN-H1</Emphasis> may account for a continuum of vernalization sensitivity

The epistatic interaction of alleles at the VRN-H1 and VRN-H2 loci determines vernalization sensitivity in barley. To validate the current molecular model for the two-locus epistasis, we crossed homozygous vernalization-insensitive plants harboring a predicted “winter type” allele at either VRN-H1 (Dicktoo) or VRN-H2 (Oregon Wolfe Barley Dominant), or at both VRN-H (Calicuchima-sib) loci and measured the flowering time of unvernalized F₂ progeny under long-day photoperiod. We assessed whether the spring growth habit of Calicuchima-sib is an exception to the two-locus epistatic model or contains novel “spring” alleles at VRN-H1 (HvBM5A) and/or VRN-H2 (ZCCT-H) by determining allele sequence variants at these loci and their effects relative to growth habit. We found that (a) progeny with predicted “winter type” alleles at both VRN-H1 and VRN-H2 alleles exhibited an extremely delayed flowering (i.e. vernalization-sensitive) phenotype in two out of the three F₂ populations, (b) sequence flanking the vernalization critical region of HvBM5A intron 1 likely influences degree of vernalization sensitivity, (c) a winter habit is retained when ZCCT-Ha has been deleted, and (d) the ZCCT-H genes have higher levels of allelic polymorphism than other winterhardiness regulatory genes. Our results validate the model explaining the epistatic interaction of VRN-H2 and VRN-H1 under long-day conditions, demonstrate recovery of vernalization-sensitive progeny from crosses of vernalization-insensitive genotypes, show that intron length variation in VRN-H1 may account for a continuum of vernalization sensitivity, and provide molecular markers that are accurate predictors of “winter vs spring type” alleles at the VRN-H loci.     

Validation of <Emphasis Type="Italic">DGAT1</Emphasis>-<Emphasis Type="Italic">2</Emphasis> polymorphisms associated with oil content and development of functional markers for molecular breeding of high-oil maize

The gene encoding acyl-CoA:diacylglycerol acyltransferase (DGAT1-2) is a key quantitative trait locus that controls oil content and oleic acid composition in maize kernels. Here we re-sequenced the DGAT1-2 region responsible for oil variation in a maize landrace set and in 155 inbred lines (35 high-oil and 120 normal lines). The high-oil DGAT1-2 allele was present in most Northern Flint and Southern Dent populations but was absent in five of eight Corn Belt Dent open-pollinated populations and in most of the earlier inbred lines. Loss of the high-oil DGAT1-2 allele possibly resulted from genetic drift in the early twentieth century when a few Corn Belt Dent populations were selected for the development of high-grain-yield inbred lines. Association analysis detected significant effects of two PCR-based functional markers (HO06 and DGAT04; developed based on DGAT1-2 polymorphisms) on kernel oil content and oleic acid composition using the 155 inbred lines. Zheng58 and Chang7-2, the parent inbred lines of elite hybrid Zhengdan958, were used to transfer the favorable allele from the high-oil line By804 using marker-assisted backcrossing with the two functional markers. In BC5F2:3 populations, oil content of the three genotypes (−/−, +/−, and +/+) was, respectively, 3.37, 4.20, and 4.61% (Zheng58 recipient line) and 4.14, 4.67, and 5.25% (Chang7-2 recipient line). Oil content of homozygous kernels containing the high-oil DGAT1-2 allele increased by 27–37% compared with recurrent parents. Hence, these functional markers can be used to re-introduce the high-oil DGAT1-2 allele into modern inbred lines for increased oil content through marker-assisted backcrossing.     

Identification of a new <Emphasis Type="Italic">Vrn</Emphasis>-<Emphasis Type="Italic">B1</Emphasis> allele using two near-isogenic wheat lines with difference in heading time

We conducted a molecular analysis of the Vrn-B1 gene in two near-isogenic lines (NILs) carrying the dominant Vrn-B1 ^S and Vrn-B1 ^Dm alleles from the Saratovskaya 29 and Diamant 2 cultivars, respectively. These lines are characterized by different times of ear emergence. PCR analysis and subsequent sequencing of the regulatory regions of Vrn-B1 revealed the full identity of the promoter region in both alleles. Simultaneously, we found significant differences in the structure of the first intron of the Vrn-B1 ^S allele when compared to Vrn-B1 ^Dm ; specifically, the deletion of 0.8 kb coupled with the duplication of 0.4 kb. We suggest that these changes in intron 1 of Vrn-B1 ^S caused earlier ear emergence in the corresponding NIL. The unusual structure of intron 1 within the Vrn-B1 ^S allele was described for the first time in this study. The allele Vrn-B1 ^Dm was almost identical with the previously studied sequence of the Vrn-B1a allele of T. aestivum, Triple Dirk B. We designated the new Vrn-B1 ^S allele as Vrn-B1c. PCR analysis of the Vrn-B1 gene in 26 spring wheat cultivars of both Russian and foreign breeding revealed that 16 of them contain the Vrn-B1a allele and 6 contain the Vrn-B1c allele. Other cultivars studied contained the recessive vrn-B1 gene, except for Novosibirskaya 67. This study demonstrates that the traditional system of Vrn-1 markers does not fully encompass the allelic diversity of these genes because none of the cultivars containing the Vrn-B1c allele gave a PCR product using the previously developed set of primers for identification of the Vrn-B1 locus. We showed that the newly characterized Vrn-B1c allele is widely distributed among different genotypes of spring wheat. The findings indicate the impact of structural changes in the first intron of Vrn-1 on the vernalization response and heading time.     

Development of PCR markers for <Emphasis Type="Italic">Tamyb10</Emphasis> related to <Emphasis Type="Italic">R</Emphasis>-<Emphasis Type="Italic">1,</Emphasis> red grain color gene in wheat

The grain color of wheat affects not only the brightness of flour, but also tolerance to preharvest sprouting. Grain color is controlled by dominant R-1 genes located on the long arm of hexaploid wheat chromosomes 3A, 3B, and 3D (R-A1, R-B1, and R-D1, respectively). The red pigment of the grain coat is composed of catechin and proanthocyanidin (PA), which are synthesized via the flavonoid biosynthetic pathway. We isolated the Tamyb10-A1, Tamyb10-B1, and Tamyb10-D1 genes, located on chromosomes 3A, 3B, and 3D, respectively. These genes encode R2R3-type MYB domain proteins, similar to TT2 of Arabidopsis, which controls PA synthesis in testa. In recessive R-A1 lines, two types of Tamyb10-A1 genes: (1) deletion of the first half of the R2-repeat of the MYB region and (2) insertion of a 2.2-kb transposon belonging to the hAT family. The Tamyb10-B1 genes of recessive R-B1 lines had 19-bp deletion, which caused a frame shift in the middle part of the open reading frame. With a transient assay using wheat coleoptiles, we revealed that the Tamyb10 gene in the dominant R-1 allele activated the flavonoid biosynthetic genes. We developed PCR-based markers to detect the dominant/recessive alleles of R-A1, R-B1, and R-D1. These markers proved to be correlated to known R-1 genotypes of 33 varieties except for a mutant with a single nucleotide substitution. Furthermore, double-haploid (DH) lines derived from the cross between red- and white-grained lines were found to necessarily carry functional Tamyb10 gene(s). Thus, PCR-based markers for Tamyb10 genes are very useful to detect R-1 alleles.     

<Emphasis Type="Italic">KIR</Emphasis> haplotype content at the allele level in 77 Northern Irish families

There has been an explosion in population studies determining the frequency of KIR genes. However, there is still limited knowledge of allele and haplotype frequencies in different populations. The present study aims to determine the haplotype frequencies using allele information on ten genes and presence/absence of the other seven genes in the parents of 77 families. There were 26 of 154 different genotypes without using allele information and 143 of 154 different genotypes using allele information. These genotypes came from 96 of 308 different haplotypes. Of these, 41 were A and 55 were B. Forty-nine haplotypes occurred only once. In total, 181 (58.8%) of haplotypes were A and 127 (41.2%) were B. Three different haplotypes carried two copies of KIR2DL4, two different haplotypes were truncated with both KIR2DL4 and KIR3DL1/S1 missing, and three different haplotypes were negative for both KIR2DL2 and KIR2DL3; two of these haplotypes carried KIR2DS2. A further haplotype, present in two individuals, appeared to have two alleles of KIR2DL5A present. The percentages of individuals who were homozygous for the A haplotype, heterozygous for the A and B haplotype and homozygous for the B haplotype were 35.1%, 47.4% and 17.5% respectively. The genes KIR3DL1, KIR2DS4 and KIR2DL3 were present on 31, 32 and 15 different B haplotypes, respectively, and 64, 65 and 40 of the total B haplotypes, respectively. Sixty B haplotypes had both KIR3DL1 and KIR2DS4, and four haplotypes had KIR2DS4 and KIR2DL3. However, in 40 of 41 different and 180 of 181 total A haplotypes, KIR3DL1, KIR2DS4 and KIR2DL3 were all present (we did not allele-type for KIR2DL1 and therefore could not determine presence/absence on those haplotypes). At the allele level, homozygosity was found in 22.1%, 9.7% and 12.6% for KIR2DL4, KIR3DL2 and KIR3DL1 genes, respectively, but 62.6% and 53% for KIR2DL3 and KIR2DS4 genes, respectively, despite the fact that no one allele dominated the frequency in any of these genes.     

Allelic polymorphism of the CGG repeat region in the <Emphasis Type="Italic">FMR1</Emphasis> gene in patients with impaired natural and stimulated ovulation

The frequency of heterozygote carriers of risk zone alleles of the FMR1 gene (40–47 CGG repeats) was significantly higher in the group of patients with ovarian dysfunctions compared to control group I. The frequency of these alleles shows an increasing tendency in patients poorly responding to superovulation induction in IVF cycles. The average number of oocytes and follicles obtained from the stimulation of superovulation was significantly decreased in FMR1 gene heterozygous risk zone allele carriers as compared to patients with normal alleles of the FMR1 gene. The general average dosage of exogenous gonadotrophin necessary for superovulation induction was significantly higher in heterozygote carriers of FMR1 gene risk zone alleles than in patients with normal genotype. As well, the FMR1 gene risk zone alleles can be one of the hereditary susceptibility factors of impaired natural and stimulated ovulation.     

Rye-derived powdery mildew resistance gene <Emphasis Type="Italic">Pm8</Emphasis> in wheat is suppressed by the <Emphasis Type="Italic">Pm3</Emphasis> locus

Genetic suppression of disease resistance is occasionally observed in hexaploid wheat or in its interspecific crosses. The phenotypic effects of genes moved to wheat from relatives with lower ploidy are often smaller than in the original sources, suggesting the presence of modifiers or partial inhibitors in wheat, especially dilution effects caused by possible variation at orthologous loci. However, there is little current understanding of the underlying genetics of suppression. The discovery of suppression in some wheat genotypes of the cereal rye chromosome 1RS-derived gene Pm8 for powdery mildew resistance offered an opportunity for analysis. A single gene for suppression was identified at or near the closely linked storage protein genes Gli-A1 and Glu-A3, which are also closely associated with the Pm3 locus on chromosome 1AS. The Pm3 locus is a complex of expressed alleles and pseudogenes embedded among Glu-A3 repeats. In the current report, we explain why earlier work indicated that the mildew suppressor was closely associated with specific Gli-A1 and Glu-A3 alleles, and predict that suppression of Pm8 involves translated gene products from the Pm3 locus.     

Cell selection and inheritance of imidazolinone resistance in sugarbeet (Beta vulgaris)

 Sugarbeets are sensitive to imidazolinone herbicide residues applied to rotational crops. Two imidazolinone-resistance (IMI-R) sugarbeet traits were developed by somatic cell selection to overcome rotation restrictions for sugarbeets where imidazolinones have been applied. Sir-13 is an IMI-R/SU-S (sulfonylurea-sensitive) variant selected from an imidazolinone-sensitive (IMI-S) sugarbeet clone, REL-1. A second variant, 93R30B, resistant to imidazolinone as well as to sulfonylurea herbicides (IMI-R/SU-R), was selected from a plant homozygous for a previously described sulfonylurea-specific resistance trait, Sur (IMI-S/SU-R). The IMI-R alleles (Sir-13 and 93R30B) were found to be corresponding allelic variants at the same ALS locus and both were tightly associated with the Sur allele. Each resistant allele is dominant to the sensitive wild-type allele; however, incomplete dominance is shown among resistance alleles. Diploid sugarbeet contains a single ALS gene copy, limiting the ability to stack these resistance traits in the same plant by traditional breeding. Received: 1 May 1997 / Accepted: 30 June 1997     

Evidence for Gene Duplication and Allelic Codominance (not Hierarchical Dominance) at the Mating‐Type Locus of the Ciliate,Euplotes crassus

The high‐multiple mating system of Euplotes crassus is known to be controlled by multiple alleles segregating at a single locus and manifesting relationships of hierarchical dominance, so that heterozygous cells would produce a single mating‐type substance (pheromone). In strain L‐2D, now known to be homozygous at the mating‐type locus, we previously identified two pheromones (Ec‐α and Ec‐1) characterized by significant variations in their amino acid sequences and structure of their macronuclear coding genes. In this study, pheromones and macronuclear coding genes have been analyzed in strain POR‐73 characterized by a heterozygous genotype and strong mating compatibility with L‐2D strain. It was found that POR‐73 cells contain three distinct pheromone coding genes and, accordingly, secrete three distinct pheromones. One pheromone revealed structural identity in amino acid sequence and macronuclear coding gene to the Ec‐α pheromone of L‐2D cells. The other two pheromones were shown to be new and were designated Ec‐2 and Ec‐3 to denote their structural homology with the Ec‐1 pheromone of L‐2D cells. We interpreted these results as evidence of a phenomenon of gene duplication at the E. crassus mating‐type locus, and lack of hierarchical dominance in the expression of the macronuclear pheromone genes in cells with heterozygous genotypes.     

Procedures for identifying S-allele genotypes of Brassica

Summary Procedures are described for efficient selection of: (1) homozygous and heterozygous S-allele genotypes; (2) homozygous inbreds with the strong self- and sib-incompatibility required for effective seed production of single-cross F₁ hybrids; (3) heterozygous genotypes with the high self- and sib-incompatibility required for effective seed production of 3- and 4-way hybrids.From reciprocal crosses between two first generation inbred (I₁) plants there are three potential results: both crosses are incompatible; one is incompatible and the other compatible; and both are compatible. Incompatibility of both crosses is useful information only when combined with data from other reciprocal crosses. Each compatible cross, depending on whether its reciprocal is incompatible or compatible, dictates alternative reasoning and additional reciprocal crosses for efficiently and simultaneously identifying: (A) the S-allele genotype of all individual I₁ plants, and (B) the expressions of dominance or codominance in pollen and stigma (sexual organs) of an S-allele heterozygous genotype. Reciprocal crosses provide the only efficient means of identifying S-allele genotypes and also the sexual-organ x S-allele-interaction types.Fluorescent microscope assay of pollen tube penetration into the style facilitates quantitation within 24–48 hours of incompatibility and compatibility of the reciprocal crosses. A procedure for quantitating the reciprocal difference is described that maximizes informational content of the data about interactions between S alleles in pollen and stigma of the S-allele-heterozygous genotype.Use of the non-inbred I_o generation parent as a known heterozygous S-allele genotype in crosses with its first generation selfed (I₁) progeny usually reduces at least 7 fold the effort required for achieving objectives 1, 2, and 3, compared to the method of making reciprocal crosses only among I₁ plants.Identifying the heterozygous and both homozygous S-allele genotypes during the I₁ generation facilitates, during subsequent inbred generations, strong selection for or against modifier genes that influence the intensity of self- and sib-incompatibility. Selection for strong self and sib incompatibility can be effective for both homozygous inbreds and also for the S-allele heterozygote, thus facilitating production of single-cross F₁ hybrids and also of 3-and 4-way hybrids.Department of Plant Breeding and Biometry paper No. 690     

Association of SULT1A1 and UGT1A1 polymorphisms with breast cancer risk and phenotypes in Russian women

Estrogens are critical for breast cancer initiation and development. Sulfotransferase 1A1 (SULT1A1) and UDP-glucuronosyltransferase 1A1 (UGT1A1) conjugate and inactivate both estrogens and their metabolites, thus preventing estrogen-mediated mitosis and mutagenesis. SULT1A1 and UGT1A1 are both polymorphic, and different alleles encode functionally different allozymes. We hypothesize that low-activity alleles SULT1A1*2 and UGT1A1*28 are associated with higher risk for breast cancer and more severe breast tumor phenotypes. We performed a case-control study, which included 119 women of Russian ancestry with breast cancer and 121 age-matched Russian female controls. We used PCR followed by pyrosequencing to determine the SULT1A1 and UGT1A1 genotypes. Allele UGT1A1*28 was present at a higher frequency than the wild-type UGT1A1*1 allele in breast cancer patients as compared to controls (P = 0.002, OR = 1.79, CI 1.23–2.63). Consistently, the frequency of genotypes that contain allele UGT1A1*28 in the homozygous or the heterozygous state was greater in breast cancer patients as compared with the frequency of the wild-type UGT1A1*1/*1 genotype (P = 0.003, OR = 4.00, CI 1.49–11.11 and P = 0.014, OR = 2.04, CI 1.14–3.57, respectively). Individuals carrying allele UGT1A1*28 in the homo-or heterozygous state had larger breast tumors (>2 cm) as compared to the group with high-activity genotypes (P = 0.011, IR = 3.44, CI 1.42–8.36). No association was observed between any of the SULT1A1 genotypes and breast cancer risk or phenotypes. Our data suggest that UGT1A1, but not SULT1A1, genotypes are important for breast cancer risk and phenotype in Russian women. Published in Russian in Molekulyarnaya Biologiya, 2006, Vol. 40, No. 2, pp. 263–270. The article was translated by the authors.     

Molecular differentiation of null alleles at <Emphasis Type="Italic">ZCCT</Emphasis>-<Emphasis Type="Italic">1</Emphasis> genes on the A,B, and D genomes of hexaploid wheat

A dominant allele of the vernalization gene Vrn-2 is the wild type conferring winter growth habit, whereas a recessive vrn-2 allele confers spring growth habit. The recessive vrn-2 allele is mutated due to the deletion of the complete gene (a null form) or alternation of a key amino acid in the VRN-2 protein (a nonfunctional form) in diploid wheat or tetraploid wheat. VRN-2 is also denoted ZCCT due to the presence of a zinc finger and a CCT domain in its protein. There are two paralogous ZCCT genes at the VRN-2 locus in diploid Triticum monococcum and three paralogous ZCCT genes on each of the A and B genomes in tetraploid wheat, but little is known about the allelic variation in VRN-2 in hexaploid wheat. In the study reported here, we performed a one-shot PCR to simultaneously amplify the promoter regions of the three ZCCT-1 genes from hexaploid wheat, including the 302-bp fragment from ZCCT-A1, the 294-bp fragment from ZCCT-B1, and the 320-bp fragment from ZCCT-D1. Each amplicon could be differentiated by electrophoresis in an acrylamide/bisacrylamide gel. This PCR marker for different lengths of the three ZCCT-1 genes was used to search for null alleles in hexaploid wheat. A null allele was found in each of ZCCT-A1, ZCCT-B1, and ZCCT-D1 among 74 cultivars and genetic stocks of U.S. hexaploid wheat. Among 54 Chinese wheat cultivars, breeding lines, and landraces, we identified three accessions carrying a single null allele at ZCCT-A1, three accessions carrying a null allele at ZCCT-B1, and one accession carrying a double null allele at both ZCCT-A1 and ZCCT-D1. The potential application of these natural ZCCT-1 mutant materials in wheat breeding programs and studies on the genetics of wheat is discussed.     

The Estimation of GC Repeats in Promoter P1 of <Emphasis Type="Italic">IGF</Emphasis>-<Emphasis Type="Italic">1</Emphasis> Gene and Their Influence on IGF-1 Plasma Levels in Stable Angina Patients

Increased plasma levels of insulin-like growth factor 1 (IGF-1) are observed in advanced arteriosclerosis, but the reasons for these elevated levels remain unknown. One possibility to explain them is variation in the sequences that control IGF-1 gene expression. The goal of this study was to determine the effect of molecular variants of the IGF-1 P1 promoter on IGF-1 serum levels and to determine the impact of IGF-1 levels on the severity of coronary atherosclerosis. Methods: Blood samples were collected from 101 consecutive patients undergoing routine angiography. Genomic DNA was isolated from the nucleated cells of the blood plasma as described (2). Based on the presence of conformational differences in the DNA strand and on the absence of single nucleotide polymorphisms, the DNA from 38 patients was further analyzed by the “allelic ladder” method to determine the number of repeated GC dinucleotides in the P1 promoter of the IGF-1 gene. In addition, we analyzed serum growth hormone levels in order to examine the effect on systemic IGF-1 synthesis. Results: Conformational differences in the P1 promoter of the IGF-1 gene were observed in 38 out of the 101 patients. Several genotypes, depending on the number of GC repeats, were observed (11/19,17/19,18/19,18/21,19/19,19/20,19/21). Interestingly, a family history of coronary artery disease was seen less often among individuals heterozygous for the GC repeats. A lower IGF-1 levels were seen in non-variant carriers (homozygous genotypes for 19 or 21 repeats of GC, or heterozygous genotype 19/21) when compared to the variant group (other heterozygous genotypes then 19/21) (181.6 ± 47.9 ng/mL vs. 227.7 ± 73.7, p = 0.026). A correlation between IGF-1, IGF-binding protein number 3, and growth hormone levels (p = ns) was not observed, and there were no significant differences in the growth hormone levels in the studied group of patients (p = ns).     

A new insight into arable weed adaptive evolution: mutations endowing herbicide resistance also affect germination dynamics and seedling emergence

Background and Aims

Selective pressures exerted by agriculture on populations of arable weeds foster the evolution of adaptive traits. Germination and emergence dynamics and herbicide resistance are key adaptive traits. Herbicide resistance alleles can have pleiotropic effects on a weed''s life cycle. This study investigated the pleiotropic effects of three acetyl-coenzyme A carboxylase (ACCase) alleles endowing herbicide resistance on the seed-to-plant part of the life cycle of the grass weed Alopecurus myosuroides.

Methods

In each of two series of experiments, A. myosuroides populations with homogenized genetic backgrounds and segregating for Leu1781, Asn2041 or Gly2078 ACCase mutations which arose independently were used to compare germination dynamics, survival in the soil and seedling pre-emergence growth among seeds containing wild-type, heterozygous and homozygous mutant ACCase embryos.

Key Results

Asn2041 ACCase caused no significant effects. Gly2078 ACCase major effects were a co-dominant acceleration in seed germination (1·25- and 1·10-fold decrease in the time to reach 50 % germination (T₅₀) for homozygous and heterozygous mutant embryos, respectively). Segregation distortion against homozygous mutant embryos or a co-dominant increase in fatal germination was observed in one series of experiments. Leu1781 ACCase major effects were a co-dominant delay in seed germination (1·41- and 1·22-fold increase in T₅₀ for homozygous and heterozygous mutant embryos, respectively) associated with a substantial co-dominant decrease in fatal germination.

Conclusions

Under current agricultural systems, plants carrying Leu1781 or Gly2078 ACCase have a fitness advantage conferred by herbicide resistance that is enhanced or counterbalanced, respectively, by direct pleiotropic effects on the plant phenology. Pleiotropic effects associated with mutations endowing herbicide resistance undoubtedly play a significant role in the evolutionary dynamics of herbicide resistance in weed populations. Mutant ACCase alleles should also prove useful to investigate the role played by seed storage lipids in the control of seed dormancy and germination.     

Generation of mice with a novel conditional null allele of the <Emphasis Type="Italic">Sox9</Emphasis> gene

Sox9 is expressed in multiple tissues during mouse development and adulthood. Mutations in the Sox9 gene or changes in expression levels can be attributed to many congenital diseases. Heterozygous loss-of-function mutations in the human SOX9 gene cause Campomelic dysplasia, a semi-lethal skeletal malformation syndrome. Disruption of Sox9 by conventional gene targeting leads to perinatal lethality in heterozygous mice, hence hampering the feasibility to obtain the homozygous Sox9 null mice for in vivo functional studies. In this study, we generated a conditional allele of Sox9 (Sox9 ^tm4.Tlu ) by flanking exon 1 with loxP sites. Homozygous mice for the Sox9 ^tm4.Tlu allele (Sox9 ^flox/flox ) are viable, fertile and indistinguishable from wildtype (WT) mice, indicating that the Sox9 ^tm4.Tlu allele is a fully functional Sox9 allele. Furthermore, we demonstrated that Cre-mediated recombination using a Col2a1-Cre line resulted in specific ablation of Sox9 activity in cartilage tissues.     

Polymorphism of the <Emphasis Type="Italic">BoLA-DRB3</Emphasis> gene in the Mongolian,Kalmyk, and Yakut cattle breeds

Polymorphism of the BoLA-DRB3 gene was studied with the use of the PCR-RFLP technique in three cattle breeds (Mongolian, Kalmyk, and Yakut) representing the Bos taurus turano-mongolicus group. 35 BoLA-DRB3.2 alleles were detected in the Mongolian breed and 34 alleles in the Kalmyk breed. The frequencies of alleles in both populations are distributed rather evenly: the frequencies of the most widely represented alleles (*18, *20, and *28) in the Mongolian cattle varied from 7.75 to 8.45%. The most frequent alleles in the Kalmyk cattle were *28 (14.52%), *24 (7.26%), and *12 (6.45%). Only five alleles were identified in the Yakut cattle breed. The prevailing allele was *29 (77.3%); a relatively frequent allele was *1 (13.1%), and the remaining three alleles constituted only 9.6%. Such a low level of diversity of BoLA-DRB3 gene alleles was not observed earlier in any other cattle breed. The Mongolian and Kalmyk breeds showed a wide diversity of BoLA-DRB3 genotypes (56 and 51 genotypes, respectively) and a high level of expected heterozygosity (H _e = 0.953 and 0.946, respectively). Both breeds had a deficiency of heterozygotes (Mongolian cattle: H _o = 0.775, D = −0.187; Kalmyk cattle: H _o = 0.708, D = −0.252). A low level of genotypic diversity for the BoLA-DRB3 locus (only seven genotypes; the frequency for the genotype *29/*29 is 71.4%) and a very low level of observed heterozygosity (H _o = 0.12) were revealed in the Yakut breed. BoLA-DRB3.2 alleles associated with resistance to persistent lymphocytosis caused by the bovine leukemia virus (total frequencies 15.49 and 24.19%) and to various forms of mastitis (total frequencies 12.68 and 20.96%, respectively) were identified in the Mongolian and Kalmyk animals. In the Yakut breed, alleles associated with resistance to diseases are represented only by the BoLA-DRB3.2 allele *7 (1.2%). Thus, the Mongolian and Kalmyk cattle breeds are characterized by a wide diversity of alleles and genotypes for the BoLA-DRB3 gene. In contrast, the population of Yakut cattle from the Verkhoyanskii region of the Republic of Sakha has a poor diversity of alleles and genotypes for the BoLA-DRB3 gene and a very low level of heterozygosity, suggesting an unfavorable state of the population that is probably caused by inbreeding depression due to a long-term isolation and a small number of animals.