Chromosomal control of the aminopeptidases of wheat and its close relatives

Summary Isoelectric focussing was used to separate the isozymes of aminopeptidase of wheat and its relatives. Three distinct homoeoallelic sets of genes have been shown to be present. AMP-1, controlled by genes on the long arms of group 6, has previously been described, but two new systems, AMP-2 (group 4) and AMP-3 (group 7) are described here. The three systems are distinguished by their electrophoretic characteristics, by their genetic control and by their substrate specificity. Intervarietal, interspecific and intergeneric polymorphism has been observed at most of the loci. A further set of isozymes, AMP-4, was detected but the chromosomal control of these could not be determined.     

The genetical control and tissue-specificity of esterase isozymes in hexaploid wheat

A comparative genetic analysis of esterase (E.C.3.1.1.1) isozymes of wheat cultivar Chinese Spring in endosperm, embryo, coleoptile, leaf and root tissues revealed eight sets of isozymes characterised by different tissue specificities, pI ranges and the chromosomal locations of their controlling genes. This data was considered together with previously published work, resulting in a proposed rationalization of nine sets of wheat esterase isozymes. Although this classification included two sets of isozymes controlled by genes on the short arms of homoeologous group 3 chromosomes and three sets on the long arms of the same chromosomes, for which no recombination evidence of genetic distinctness has been obtained among either group, it is argued that the different characteristics of the various sets warrant retention of separate set nomenclatures. Previously unreported esterase genes includeEst-9, a low pI, monomeric, embryo-specific group with controlling genes on chromosomes 3BS and 3DS and two further members ofEs-1,Est-H1 inHordeum vulgare andEst-S ^l1 inAegilops longissima.     

Genetic and physical characterization of grain texture-related loci in diploid wheat

Endosperm texture, i.e. the hardness or softness of the grain, is an important quality criterion in cereals because it determines many grain end-use properties. Grain softness is the dominant trait and is mainly controlled by the Ha locus on the short arm of chromosome 5D in hexaploid bread wheat. Genes for puroindoline a (Pina-D1), puroindoline b (Pinb-D1), and grain softness related protein (Gsp-D1) have been shown to be linked to the Ha locus in different mapping populations and have been associated with the expression of grain softness. The study of the linkage relationships among these genes has been limited by the low level of polymorphism in the D genome of hexaploid Triticum aestivum. In the present study, a highly polymorphic Triticum monococcum mapping population was used to analyze linkage relationships among these three genes. Gsp-A ^m 1 and Pina-A ^m 1 were found to be completely linked and lie 0.14 cM distal to Pinb-A ^m 1 in the distal region of the short arm of chromosome 5A^m. The tight genetic linkage among these three genes was paralleled by their physical proximity within a single 105-kb clone isolated from a T. monococcum bacterial artificial chromosome (BAC) library. A restriction map of this BAC clone showed that Pina-A ^m 1 is located between Pinb-A ^m 1 and Gsp-A ^m 1. Partial sequences of the T. monococcum genes showed a high degree of similarity with their T. aestivum counterparts (≥ 94%). Marker-assisted selection strategies based on the tight linkage among Ha-related genes are discussed. Received: 27 June 1999 / Accepted: 18 August 1999     

Est-7, a set of genes controlling green tissue esterases in wheat and related species

Summary Analysis using isoelectric focusing of Chinese Spring wheat genetic stocks revealed a set of coleoptile and leaf esterase loci, designated Est-7, on the long arms of the group 2 chromosomes. A survey of 38 other hexaploid genotypes revealed onyl a single variant, at Est-D7. Homoeoloci were found on chromosome (arm) 2HL of Hordeum vulgare, 2RL of Secale cereale, 2R ^m of S. montanum, 2U of Aegilops umbellulata, 2E of Agropyron elongation and 2V of Dasypyrum villosa.     

The genetic control of grain esterases in hexaploid wheat

Summary Analysis of grain esterase isozymes in Chinese Spring aneuploid genotypes by IEF confirmed that genes on the long arms of chromosomes 3A, 3B and 3D (Est-5) control the production of 19 isozymes. Allelic variants have been found for the isozyme pattern controlled by each chromosome. Segregational data involving null alleles and complex phenotypic differences indicate that the wheat grain esterases are encoded by three compound and probably homoeoallelic loci, each capable of producing at least six different isozymes. In a sample of 138 hexaploid genotypes, seven alleles were distinguished.     

Genetics of two tissue esterase polymorphisms (Est-4 and Est-5) in the rabbit

Two polymorphic esterase systems were found after electrophoresis of rabbit tissue homogenates. Each of these systems is controlled by an autosomal locus with two alleles. Est-4 determines the absence (Est-4^a) or presence (Est-4^b) of two bands of esterase activity with intermediate anodal mobility and broad substrate specificity. This polymorphism was found to be present in liver, small intestine, and spleen but not in kidney, heart, and testis. Est-5 is coding for cathodally migrating esterases which differ in mobility (Est-5^a and Est-5^b). This polymorphism was found only in kidney and testis homogenates. Est-5 esterases are more active against -naphthyl acetate than against -naphthyl acetate and have no activity against -naphthyl butyrate. Linkage analysis indicated that Est-4 is localized on rabbit LG VI as part of a cluster of esterase loci, whereas Est-5 segregates independently. Rabbits from two inbred and nine partly inbred strains were tested for these polymorphisms.This investigation was supported in part by Public Health Service Research Grant RR-00251 from the Division of Research Resources and by funds from the University of Utrecht. The Jackson Laboratory is fully accredited by the American Association for Accreditation of Laboratory Animal Care.     

Genetics of a tissue esterase polymorphism (Est-6) in the rabbit (Oryctolagus cuniculus)

Genetic analysis of a polymorphic tissue esterase revealed a new locus (Est-6) with two alleles (Est-6 ^a andEst-6 ^b) on linkage group VI of the rabbit.Est-6 is closely linked to theEst-1,2,4 cluster. Esterase ofEst-6 is found in many organs, particularly in liver and small intestine, but not in erythrocytes and serum.Est-6 esterase hydrolyzes -naphthyl acetate and butyrate, naphthol AS-D acetate, indoxyl acetate, and butyrate as well as 5-bromoindoxyl acetate,N-acetyl-l-alanine--naphthyl ester but not 4-methylumbelliferyl acetate and fluorescein diacetate. The enzyme is inhibited by bis-p-nitrophenyl phosphate and eserine but not byp-chloromercuribenzoate. It was classified as a carboxylesterase (EC 3.1.1.1). Based on chromosomal localization, tissue distribution, substrate specificity, inhibitor sensitivity, and range ofpI's, rabbitEst-6 is assumed to be homologous with mouseEs-7.The contribution of Dr. O. von Deimling (No. 59) was supported by the Deutsche Forschungsgemeinschaft (De 315/2-2).     

The chromosomal location of a third set of malate dehydrogenase loci,Mdh-3, in wheat,barley and related species

Summary A third set of malate dehydrogenase loci have been identified and located on the short arms of homoeologous group 5 chromosomes in wheat. Allelic differences have been found at each of the three Mdh-3 loci. However, Mdh-D3 appears to be least variable, with a second allele found only in Sears' Synthetic among a survey of 42 varieties. Homoeoloci were identified on chromosome 7 (5H) of Hordeum vulgare, the short arm of 5E in Agropyron elongatum and 5U in Aegilops umbellulata.     

Genetic polymorphism at two linked loci,Sod and Est-6, in Drosophila melanogaster

We have examined the patterns of polymorphism at two linked loci, Sod and Est-6, separated by nearly 1000 kb on the left arm of chromosome 3 of Drosophila melanogaster. The evidence suggests that natural selection has been involved in shaping the polymorphisms. At the Sod locus, a fairly strong (s>0.01) selective sweep, started ≥2600 years ago, increased the frequency of a rare haplotype, F(A), to about 50% frequency in populations of Europe, Asia, and the Americas. More recently, an F(A) allele mutated to an S allele, which has increased to frequencies 5–15% in populations of Europe, Asia and North America. All S alleles are identical (or very nearly) in sequence and differ by one nucleotide substitution (which accounts for the F→S electrophoretic difference) from F(A) alleles. At the Est-6 locus, the evidence indicates both directional and balancing selection impacting separately the promoter and the coding regions of the gene, with linkage disequilibrium occurring within each region. Some linkage disequilibrium also exists between the two genes.     

Polymorphism of esterase 11 in Mus musculus,a further esterase locus on chromosome 8

A further esterase, esterase 11, which exhibits a polymorphism detectable by electrophoresis, has been observed in the house mouse, Mus musculus. In 15 inbred strains and two outbred strains, the ES-11A phenotype has been found, composed of two bands of enzyme activity of greater anodal electrophoretic mobility than the two bands of the ES-11B phenotype found in one inbred strain, one wild stock, and 101 wild mice. In F₁ hybrids (IS/Cam×C57 BL/Gr), the phenotype shown corresponds to a mixture of the two parental phenotypes. In backcrosses, ES-11 segregates as an autosomal gene, designated Es-11, closely linked to Es-2 and Es-5 on chromosome 8.This work was supported by the Medical Research Council.     

土壤肥力和施氮量对小麦氮素吸收运转及籽粒产量和蛋白质含量的影响

在不同土壤肥力条件下,研究了施氮量对小麦氮素吸收、转化及籽粒产量和蛋白质含量的影响。结果表明,增施氮肥可以提高小麦各生育阶段的吸氮强度,尤以生育后期提高的幅度为大认为是增施氮肥提高小麦籽粒产量和蛋白质含量的基础,增施氮肥虽提高了小麦植株的吸氮强度。吸氮量增加,但开花后营养器官氮素向籽粒中的转移率降低,增施氮肥不仅促进了小麦植株对肥料氮的吸收,而且也促进了对土壤氮的吸收,并讨论了在高、低土壤肥力条件下氮肥合理运筹的问题。     

Genetic control of dipeptidase in the Triticeae

Summary Isoelectric focusing has been employed to elucidate the genetic control of a series of dipeptidase isozymes in wheat and its relatives. The phenotype of wheat shows four bands, three of which are shown by aneuploid analysis to be controlled by the loci Dip-A1, Dip-B1 and Dip-D1 on chromosome arms 6AL, 6BL and 6DL, respectively. Varietal polymorphism for Dip-A1 and Dip-B1 was observed. Different homoeoloci were found in barley, Haynaldia villosa and Agropyron junceum.     

Effects of exogenous hormones on floret development and grain setin wheat

At specific stages during floret development, solutions of IAA,GA₃, zeatin and ABA were injected into the leaf sheath around theyoung spike of wheat (Triticum aestivum L.) to study theregulating effects of exogenous hormones on floret development. Zeatin promotedfloret development and significantly increased the number of fertile florets aswell as grain set, especially at the stage of anther-lobe formation. Zeatinalsoincreased the sugar concentrations in spikes at anthesis. In contrast, IAA,GA₃ and ABA inhibited floret development, with different patternsforeach of the hormones. IAA inhibited the development of the whole spike and allflorets in the spikelets such that grain loss occurred in all positions in thespikelets. GA₃ increased the number of fertile florets per spike,butdecreased grain set of the third floret in each spikelet, especially whenapplied at terminal spikelet formation. ABA inhibited floret development, anddecreased the number of fertile florets and grain set at almost all developmentstages, except at anther-lobe formation. The inhibitory effect of ABA wasmainlyon the first and third florets in each spikelet.     

Genetic dissection of grain yield in bread wheat. I. QTL analysis

Grain yield forms one of the key economic drivers behind a successful wheat (Triticum aestivum L.) cropping enterprise and is consequently a major target for wheat breeding programmes. However, due to its complex nature, little is known regarding the genetic control of grain yield. A doubled-haploid population, comprising 182 individuals, produced from a cross between two cultivars ‘Trident’ and ‘Molineux’, was used to construct a linkage map based largely on microsatellite molecular makers. ‘Trident’ represents a lineage of wheat varieties from southern Australia that has achieved consistently high relative grain yield across a range of environments. In comparison, ‘Molineux’ would be rated as a variety with low to moderate grain yield. The doubled-haploid population was grown from 2002 to 2005 in replicated field experiments at a range of environments across the southern Australian wheat belt. In total, grain yield data were recorded for the population at 18 site-year combinations. Grain yield components were also measured at three of these environments. Many loci previously found to be involved in the control of plant height, rust resistance and ear-emergence were found to influence grain yield and grain yield components in this population. An additional nine QTL, apparently unrelated to these traits, were also associated with grain yield. A QTL associated with grain yield on chromosome 1B, with no significant relationship with plant height, ear-emergence or rust resistance, was detected (LOD ≥2) at eight of the 18 environments. The mean yield, across 18 environments, of individuals carrying the ‘Molineux’ allele at the 1B locus was 4.8% higher than the mean grain yield of those lines carrying the ‘Trident’ allele at this locus. Another QTL identified on chromosome 4D was also associated with overall gain yield at six of the 18 environments. Of the nine grain yield QTL not shown to be associated with plant height, phenology or rust resistance, two were located near QTL associated with grain yield components. A third QTL, associated with grain yield components at each of the environments used for testing, was located on chromosome 7D. However, this QTL was not associated with grain yield at any of the environments. The implications of these findings on marker-assisted selection for grain yield are discussed.     

Es-6, a further polymorphic esterase in the rat

A further polymorphic rat esterase with broad tissue expression and restricted substrate specificity is described and tentatively called Es-6. Inbred rat strains have either fixed allele Es-6^F or fixed allele Es-6^S. Es-6 is not linked to the established esterase cluster consisting of the eight esterase loci Es-1, Es-2, Es-3M, Es-4M, Es-4W, Es-5 (=Es-3W), Es-7, and Es-8 in LG V of the rat or to RT1, Gc, c, a, and h. Esterases with apparently identical biochemical and genetical characteristics are Es-17 of the mouse and Es-A4 of humans.Supported by the Deutsche Forschungsgemeinschaft (Be 352/13 and Gu 105).     

The chromosomal locations of leaf peroxidase genes in hexaploid wheat,rye and barley

Summary Eight leaf peroxidase isozymes were distinguished by IEF in Chinese Spring. Two genes which control the production of three of these isozymes were located on chromosome arms 1BS and 1DS by nullisomic analysis. These loci probably form part of a homoeoallelic series and have been designated Per-B1 and Per-D1 respectively. Analysis of chromosome 1B short arm terminal deletion stocks indicated that the Per-B1 locus is located between the nucleolar organiser region and another isozyme marker, Hk-B1. Two variant leaf peroxidase phenotypes were distinguished in a small sample of hexaploid wheat varieties. Analysis of wheat-alien addition and substitution lines identified homoeologous loci in rye (Per-R1) and barley (Per-H1).     

基因型与生态环境对小麦籽粒品质与蛋白质组分的影响

通过2年3点试验,研究了40个小麦(Triticum aestivum)品种(品系)籽粒品质性状和蛋白质组分含量的变异。结果表明,籽粒品质和蛋白质组分在基因型间存在较大的差异;根据小麦籽粒品质的综合性状,可将40个小麦品种(品系)分为6组不同的品质类型,在本试验点的生态环境条件下。基本以中筋及弱筋小麦为主;生态环境对小麦籽粒的容重、沉降值、湿面筋含量、蛋白质含量、赖氨酸含量与蛋白质组分含量均有极显著的影响,而面筋指数、淀粉含量和直链淀粉含量对环境反应不敏感,适宜的生态环境条件有利于形成合理的谷蛋白／醇溶蛋白比。面粉面筋质量好,基因型与生态环境的互作对小麦籽粒品质。谷蛋白与醇溶蛋白及两者的比值有显著影响,对球蛋白影响不大,而面粉蛋白质含量、面筋含量、沉降值及千粒重主要受基因的表达和环境的独立影响,蛋白质组分含量在基因型间和环境间的变化与小麦籽粒烘烤品质密切相关。     

Gene networks in hexaploid wheat: interacting quantitative trait loci for grain protein content

In hexaploid wheat, single-locus and two-locus quantitative trait loci (QTL) analyses for grain protein content (GPC) were conducted using two different mapping populations (PI and PII). Main effect QTLs (M-QTLs), epistatic QTLs (E-QTLs) and QTL x environment interactions (QE, QQE) were detected using two-locus analyses in both the populations. Only a few QTLs were common in both the analyses, and the QTLs and the interactions detected in the two populations differed, suggesting the superiority of two-locus analysis and the need for using several mapping populations for QTL analysis. A sizable proportion of genetic variation for GPC was due to interactions (28.59% and 54.03%), rather than to M-QTL effects (7.24% and 7.22%), which are the only genetic effects often detected in the majority of QTL studies. Even E-QTLs made a marginal contribution to genetic variation (2.68% and 6.04%), thus suggesting that the major part of genetic variation is due to changes in gene networks rather than the presence or absence of specific genes. This is in sharp contrast to the genetic dissection of pre-harvest sprouting tolerance conducted by us earlier, where interaction effects were not substantial, suggesting that the nature of genetic variation also depends on the nature of the trait.     

Identification and chromosomal locations of aconitase gene loci in Triticeae species

Summary Two systems of monomeric aconitase (ACO) isozymes, designated ACO-1 and ACO-2, were identified in Triticum aestivum and in five diploid Triticeae species. The gene loci Aco-A1, Aco-B1, and Aco-D1 were located in T. aestivum cv. Chinese Spring chromosome arms 6Aq, 6Bq, and 6Dq, respectively, and the gene loci Aco-A2, Aco-B2, and Aco-D2 in 5 Aq, 5 Bq, and 5Dq, respectively. Aco-1 gene loci were also identified in 6E of Elytrigia elongata, 6HL of Hordeum vulgare cv. Betzes, 6RL of Secale cereale PI 252003, 6S¹ of T. longissimum, and CSU-31 of T. umbellulatum. Other Aco-2 gene loci were identified in 5RL of S. cereale cv. King II and 4EL of E. elongata. Conservation of synteny relationships is indicated among the species studied for the genes identified, with the exception of Aco-E2; the presence of this gene in 4EL suggests that E. elongata differs from Chinese Spring and King II by a translocation involving 4E and 5E.Adapted from a thesis submitted to the Graduate College, Texas A&M University, by K.J.C. in partial fulfillment of the requirements for the M.S. degree in Genetics