Use of Nystatin-Resistant Mutations in Parasexual Genetic Analysis in DICTYOSTELIUM DISCOIDEUM

Nystatin-resistant mutations exhibit extreme sensitivity to 1.3 mm coumarin. The mutations fall into three complementation groups so it is possible to select for nonallelic mutations conferring sensitivity to coumarin by selection on nystatin-containing nutrient agar plates. Complementation between such coumarin-sensitive mutations allows the selection of diploids on coumarin-containing nutrient agar. Two of the nystatin resistance genes, nysB and nysC, have been mapped tentatively to the previously unmarked linkage group V.     

Parasexual Genetic Analysis of Cell Proportioning Mutants of DICTYOSTELIUM DISCOIDEUM

Eight independently isolated mutants of Dictyostelium discoideum that differentiate exclusively into stalk cells make up one complementation group and carry single recessive mutations at the stalky locus, stkA, located on linkage group II. KY19, a previously described strain that differentiates into spores, but not stalk cells, was found to possess a recessive mutation defining the stalkless locus, stlA, located on linkage group VI. An analysis of the properties of these mutants, together with the phenotype of a haploid double mutant carrying stkA and stlA indicates that stlA results in poorly organized stalk tubes and incomplete stalk cell differentiation, while stkA causes all of the cells to differentiate into stalk cells, even when not enclosed in the stalk tube. The significance of these results is discussed in relation to current theories of pattern formation in D. discoideum.     

Parasexual Genetic Analysis of the Cellular Slime Mold DICTYOSTELIUM DISCOIDEUM A3

Haploid strain A3 of the cellular slime mold Dictyostelium discoideum is valuable for biochemical studies because it is capable of axenic growth. Mutants of A3 temperature-sensitive for growth and resistant to the drugs cycloheximide, acriflavin, or methanol were isolated.--Heterozygous diploid recombinants, formed at low frequency by cell and nuclear fusion, were isolated by selecting temperature-resistant progeny of mixed cultures of two nonallelic temperature-sensitive haploids (LOOMIS 1969). Each drug-resistant mutation was found to be recessive. Two independently isolated methanol-resistant mutants were in one complementation group.--Diploids of A3 heterozygous for drug resistance formed drug-resistant segregants with a frequency of approximately 10(-4). Segregants selected for resistance to a single drug were either haploid or diploid; the fraction which was haploid varied from 0.11 to 0.86, depending on the selected marker. Segregants selected for resistance to two or three drugs were almost all haploid.--Using this parasexual cycle of diploid formation and haploidization, linkage of these temperature-sensitive and drug-resistance mutations to each other and to mutations studied by KATZ and SUSSMAN (1972) and by WILLIAMS, KESSIN and Newell (1974b) was analyzed. The methanol-resistant mutants were found to be partially resistant to acriflavin, and unlinked to the mutant selected for acriflavin resistance, which was methanol-sensitive. Of the expected seven linkage groups in D. discoideum, five, and a possible sixth, have been marked.--Linkage analysis of a mutant abnormal in morphogenesis showed that its phenotype results from two unlinked chromosomal mutations.     

Characterization of Dominant Resistance to Cobalt Chloride in DICTYOSTELIUM DISCOIDEUM and Its Use in Parasexual Genetic Analysis

Strains of Dictyostelium discoideum resistant to cobaltous chloride have been isolated at a frequency of approximately 10^-6. The resistant strains have one of three phenotypes, recessive to wild type, dominant to wild type and dominant to wild type but requiring the presence of cobaltous chloride to maintain resistance. Strains carrying a dominant cobaltous chloride resistance mutation and a recessive growth temperature-sensitive mutation can be mixed with wild-type haploid lines and then subjected to selection so that only diploid lines survive. Differential sensitivity to cycloheximide has also been observed. Hypersensitivity to cycloheximide in combination with dominant cobaltous chloride resistance provides a means of selecting diploids without the use of temperature-sensitive mutations.     

Genetic Analysis of the Gene for N-Acetylglucosaminidase in DICTYOSTELIUM DISCOIDEUM

Three independent mutations affecting N-acetylglucosaminidase in Dictyostelium discoideum were mapped by the parasexual system and found to lie on linkage group IV. These mutations as well as two others were found to be recessive and noncomplementing in heterozygous diploids. Thus they all appear to affect the nagA locus. Since two of the mutations give rise to thermolabile enzyme, this defines the structural gene for N-acetylglucosaminidase. The enzyme is a homodimer of a 68,000 dalton subunit and thus would be expected to be determined by a single locus. The expression of this gene is regulated by the stages of development; however, it should be mentioned that none of the mutations fell in a separate locus that might determine a specific positive regulatory proteins.     

A Genetic Map of DICTYOSTELIUM DISCOIDEUM Based on Mitotic Recombination

A genetic map of the cellular slime mold Dictyostelium discoideum is presented in which 42 loci are ordered on five of the seven linkage groups. Although most of the loci were ordered using standing mitotic crossing-over techniques in which recessive selective markers were employed, use was also made of unselected recombined haploid strains. Consistent with cytological studies in which the chromosomes appear to be acrocentric, only a single arm has been found for each of the five linkage groups studied. The mating-type locus, matA, has been located in the tsgE-sprA interval on linkage group I on the basis of studies on diploids formed between strains of opposite mating type that have escaped from vegetative incompatibility.     

Linkage Analysis of Nystatin Resistance Mutations in DICTYOSTELIUM DISCOIDEUM

Earlier linkage analyses of nystatin resistance loci in Dictyostelium discoideum tentatively mapped the nysB and nysC loci to the previously unmarked linkage group V. The data presented here establishes that nysB maps to linkage group VI and that nysC maps to linkage group IV. The third nystatin resistance locus, nysA, maps to linkage group II.     

The Characteristics of Primary Hybrids Obtained in Crosses between Common Wheat from China and Cultivated Rye

Russian Journal of Genetics - The gene pool of winter common wheat from China maintained in the VIR collection is unique in the variety of alleles of the genes of selection-valuable traits and...     

小麦背景中黑麦1R染色体的遗传变异

运用细胞遗传学方法鉴定了来源于中国春×Ｍ２７（１Ｒ／１Ｄ代换系）的花粉植株和Ｆ２单株染色体组成。发现７个花粉植株中出现７种染色体组成变异类型,每株呈现一类变异;而２７个Ｆ２单株中,存在１１种染色体组成变异类型,变异频率仅为３７．０％,低于花粉植株。花粉植株群体中,观察到一个能稳定向后代传递的小麦／１Ｒ小片段易位,但Ｆ２群体中未检测到小麦／黑麦易位。表明常规染色体工程结合花药培养是有计划、有目的实现异源染色体小片段向小麦转移的简便、高效、快速途径。     

Genetic Analyses of the Polarity Alleles in Recombinants from Mitochondrial Genetic Crosses

A number of minority recombinant and parental types from a heterosexual cross were analyzed for the omega allele they carry. It was found that recombinant progeny can be omega(-), that minority parental types among the progeny can be omega(+) rather than omega(-), and, finally, that certain of the results suggest that the omega locus may not be at the proximal end of the mitochondrial genetic map (Bolotin et al., 1971; Grivell et al., 1973) but rather may lie between the [cap1-r/cap-s] and [ery1-r/ery-s] loci.     

Nature of Lactose-fermenting Salmonella Strains Obtained from Clinical Sources

Six of seven lactose-fermenting (lac(+)) Salmonella strains obtained from clinical sources were found to be capable of transferring the lac(+) property by conjugation to Salmonella typhosa WR4204. All of the six S. typhosa strains which received the lac(+) property transferred it in turn to S. typhimurium WR5000 at the high frequencies typical of extrachromosomal F-merogenotes. These six lac elements were also transmissible from S. typhosa WR4204 to Proteus mirabilis and to some strains of Escherichia coli K-12; moreover, they were capable of promoting low frequency transfer of chromosomal genes from S. typhimurium WR5000 to S. typhosa WR4204. One of these lac elements was shown also to be capable of promoting low frequency chromosome transfer in E. coli K-12. E. coli K-12 strains harboring these lac elements exhibited sensitivity to the male specific phage R-17. Sensitivity to R-17 was not detected in Salmonella strains containing the elements. Examination of the lac elements in P. mirabilis by cesium chloride density gradient centrifugation showed that each element had a guanine plus cytosine content of 50%. The sizes of the elements varied from 0.8 to 3% of the total Proteus deoxyribonucleic acid. The amount of beta-galactosidase produced by induced and uninduced cultures of S. typhimurium WR5000 and S. typhosa WR4204 containing the lac elements was lower than that produced by these strains with the F-lac episome. The heat sensitivity of beta-galactosidase produced by the lac elements in their original Salmonella hosts indicated that the enzyme made by these strains differs from E. coli beta-galactosidase.     

结球甘蓝二、四倍体间杂交三倍体的获得及细胞学鉴定

在对结球甘蓝4x×2x和2x×4x的授粉受精及胚胎发育观察的基础上,结合幼胚离体培养技术,成功地获得了结球甘蓝三倍体材料,并对其减数分裂行为、染色体在后期Ⅰ的分离及雌雄配子的传递率进行了观察研究,这为创建结球甘蓝"初级三体系"等遗传研究奠定了基础.     

Genetic Control of Embryo Lethality in Crosses between Common Wheat and Rye

The phenotypic manifestation and genetic control of embryo lethality observed in crosses between common wheat and rye were studied. It was found that crosses between common wheat and inbred self-fertile rye lines L2 and 535 gave rise to ungerminating grains, in which the development and differentiation of the hybrid embryo are arrested. Study of the degree of embryo development in the hybrid grains obtained by crossing common wheat varieties with inbred rye lines L2 and 535 showed that genotypes of the parents affected the ratio between undifferentiated embryos of various sizes. Analysis of this trait was performed by test crosses according to a novel pedigree program with the use of interlinear hybrids and a set of fourth-generation hybrid recombinant inbred lines. Rye line L2 was shown to bear the Eml (Embryo lethality) gene, which terminates the development of the hybrid embryo in amphihaploids. The suggestion of complementary interaction between wheat and rye genes during formation of a “new” character in wheat-rye F₁ hybrids is discussed. A method of detecting an allele not complementary to the rye Eml allele in wheat is proposed. The proposed test program allows appropriate study of the system of wheat and rye genes involved in complementary interaction in the genotype of a distant hybrid.__________Translated from Genetika, Vol. 41, No. 8, 2005, pp. 1075–1083.Original Russian Text Copyright © 2005 by Tikhenko, Tsvetkova, Voylokov.     

自花授粉作物杂交育种组合潜势的预测和比较

在黄花烟草Nicotiana russica中,开花期这一性状用V_5作亲本可能产生较大变异,无论是选择早开花的还是选择迟开花的,都有较大机会得到理想目标株系;对于株高这一性状,含有V(?)的组合可望有较大机会产生高于标准品种的株系。通过组合间育种潜势的比较,能了解各亲本中基因分布的基本情况,进而进行客观评价并对杂交组合做出取舍。试验证明,用一个组合的早期世代的参数m和D来预测高世代或纯系的育种潜势是可行的。     

携带大片段BIBAC克隆在不同农杆菌中的遗传稳定性研究

大片段克隆在农杆菌中的稳定性是利用可转化大片段载体进行农杆菌介导遗传转化的关键问题.选用插入片段分子质量分别为150kb和50kb的BIBAC克隆,测定了在3种农杆菌AGL-1,EHA105和LBA4404中的遗传稳定性.从第1、3、5次继代培养的农杆菌中抽提的质粒及酶切结果显示,由于农杆菌背景质粒的干扰,难以判断质粒的降解与否.将农杆菌质粒再转化到大肠杆菌宿主中,发现来自农杆菌AGL-1和EHA105的质粒出现了明显的降解,片段变小,而来自农杆菌LBA4404的质粒没有变化.结果表明,大片段BIBAC质粒在不同农杆菌菌株中的稳定性不同,在农杆菌LBA4404中比较稳定,适合用于遗传转化.     

小麦背景中簇毛麦6V染色体的遗传稳定性及其在配子中的传递

小麦－簇毛麦６Ｖ二体附加系,６Ａ（６Ｖ）二体代换系,６Ａ＾Ｌ．６Ｖ＾ｓ二体易位系在细胞学上是基本稳定的６Ｖ,６Ａ＾Ｌ．６Ｖ＾ｓ染色体能够通过配子稳定地传递给后代,在杂合状态下,带有６Ｖ的配子传递率普遍显著下降,在单体附加系（２１”Ｗ＋６Ｖ）中,６Ｖ通过雌配子的传递率（１１．３％）高于通过雄配子的传递率（５．９％）,在单体代换系（２０”Ｗ＋６Ａ－６Ｖ）中,６Ｖ通过雌配子的传递率（１０．４％）低于通过