Allelism Tests between the Rust Resistance Gene Present in Common Bean Cultivar Ouro Negro and Genes Ur-5 and Ur-11

The pathogenic variability of the fungus Uromyces appendiculatus is an obstacle for the creation of rust‐resistant common bean (Phaseolus vulgaris L.) varieties. Gene pyramiding is an alternative strategy for the development of varieties with durable resistance. However, to reach this goal it is important to identify different genes with ample resistance spectra. Cultivars Ouro Negro, Mexico 309 and Belmidak RR‐3 have been shown to be resistant to several rust races identified in the state of Minas Gerais, Brazil. Ouro Negro is the only rust resistance source being used in the BIOAGRO/Universidade Federal de Viçosa (UFV) breeding programme, which aims at pyramiding resistance genes in the ‘carioca‐type’ cultivar Rudá. It would be also interesting to use Mexico 309 (Ur‐5) and Belmidak RR‐3 (Ur‐11) in the breeding programme. However, there is no available information on the possible allelic relationships between the Ouro Negro resistance gene and Ur‐5 and Ur‐11. This work aimed at: (1) determining the allelic relationship between the Ouro Negro resistance gene and Ur‐5 and Ur‐11; and (2) evaluating a random amplified polymorphic DNA (RAPD) marker previously reported as being linked to Ur‐11, in populations from crosses between Belmidak RR‐3 and Rudá. The allelism tests confirmed that the Ouro Negro rust resistance gene is distinct from Ur‐5 and Ur‐11 and the molecular analyses confirmed that the RAPD marker can be used in our breeding programme to develop ‘carioca‐type’ cultivars with the Ur‐11 gene.     

Allelism of pleiotropic drug resistance in Saccharomyces cerevisiae

Allelism of pleiotropic drug resistant (pdr) mutants was evaluated by complementation tests, linkage to chromosome-VII centromere markers and response to a partial suppressor (sur). Complementation tests were confounded by incomplete dominance and somatic segregation. Phenotypic suppression by sur was observed for all mutant and wild type alleles and thus could not be used to distinguish alleles. Five different alleles were tentatively identified by their close linkage to leul; 88 tetrads from three factor crosses produced the following linkages--leul (4.7) pdrl (17.0) trp5. Resistance of DRI 9/T7, a [cir o] strain of French origin, was not inherited as an allele of pdr but was controlled by a different pleiotropic centromere linked gene. An evaluation of published data suggest that antl, AMYl, till, cyh3, BOR2, and axe1 may be alleles of pdr. Thus pdr appears to be an allele that influences permeability to many inhibitors.     

Allelism within the DEX and STA gene families in Saccharomyces diastaticus

Summary Saccharomyces diastaticus produces an extracellular glucoamylase and is therefore capable of hydrolyzing and fermenting starch. Tamaki (1978) studied starch utilization in S. diastaticus and found three polymeric genes controlling this function: STA1, STA2 and STA3. Independently, Erratt and Stewart (1978) studied dextrin utilization by the yeast S. diastaticus and designated the gene, which they identified, DEX1. Erratt and Stewart (1981a, b) later described two other genes which controlled glucoamylase production in S. diastaticus: DEX2 and a third which was allelic to STA3. At that time STA1 and STA2 were not available to test for allelism in the DEX gene family. In this study strains containing the remaining 4 genes have been examined to determine if further allelism exists between the two gene families. It was ascertained that DEX1 is allelic to STA2 and DEX2 is allelic to STA1. Therefore, no new gene controlling starch utilization has been identified and these two nomenclatures can now be consolidated into one. Based on the fact that the glucoamylase from S. diastaticus can hydrolyze both dextrin and starch, dextrin being the term used to described partially hydrolyzed starch, and the more wide use of the nomenclature STA, we propose to retain STA as the designation for genes coding for glucoamylase production in S. diastaticus.     

Allelism of IMP1 and GAL2 genes of Saccharomyces cerevisiae.

Cloning and characterization of the previously described Saccharomyces cerevisiae IMP1 gene, which was assumed to be a nuclear determinant involved in the nucleomitochondrial control of the utilization of galactose, demonstrate allelism to the GAL2 gene. Galactose metabolism does not necessarily involve the induction of the specific transport system coded by GAL2/IMP1, because a null mutant takes up galactose and grows on it. Data on galactose uptake are presented, and the dependence on ATP for constitutive and inducible galactose transport is discussed. These results can account for the inability of imp1/gal2 mutants to grow on galactose in a respiration-deficient background. Under these conditions, uptake was affected at the functional level but not at the biosynthetic level.     

陆地棉枯萎病抗性基因的等位性测定及连锁分析

1995-1996年,对我国育成的有代表性的5个抗病品种进行抗枯萎病基因的等位性测定。结果表明:在所选用的5个抗病品种中至少存在两个不同的抗病基因(暂定名为Fwl和Fw2)。连锁分析显示:Fwl与T586的8个标志性状间、Fw2与T582、T586的13个标志性状间无连锁关系。 Abstract:Allelism in vestigation of genes resistante to Fusarium wilt in cotton suggested that there were 2 genes(assigned symbols Fw1 and Fw2)in 5 cultivars used.No linkage was found between Fw1 and the marker genes in T586 and between Fw2 and those marker genes in T582 and T586.     

Multiple Allelism of the net Gene in Drosophila melanogaster and Drosophila simulans

Thenetgene mutations are known to cause abnormal pattern of veining in all wing regions except for the first posterior cells. In natural populations of Drosophila melanogaster, the net alleles were identified, which differ in phenotypic expression from standard mutations. The mutants net-extra-analis from a population Belokurikha-2000 have only a single additional vein in the third posterior cell. A line from Chernobyl-1986 population have another nontypical allele net ^Ch86 and shows a lower degree of abnormalities than that usually observed. About 10% of these flies have an additional vein fragment in the first posterior cell. In both males and females ofD. simulans population Tashkent -2001, which exhibit net ^ST91 mutation, a net of additional veins is formed as a specific additional fragment in the first posterior cell. The pattern of veining conferred by alleles net-extra-analis and net ^Ch86 is altered to a lesser extent; these alleles are dominant with respect to alleles net ^2-45 and net ^ST91, which cause more abnormalities. The heterozygotes for alleles net ^ST9 and net ^Ch86 and for Df(2) net ⁶² deletion have an additional fragment in the first posterior cell and show similarly strong deviations from normal wing vein pattern. The naturalnet alleles correspond, presumably, to different molecular gene defects involved into uncertain local interactions with numerous modifying factors and other genes that specify the wing vein pattern.     

Fertility Genes in Natural Populations of DROSOPHILA MELANOGASTER. I. Frequency, Allelism and Persistence of Sterility Genes

Three or four percent of the wild flies in natural populations of D. melanogaster have been found to be sterile. An analysis of sterility associated with the second chromosome revealed a much lower frequency of genetically sterile flies. The accumulation of sterility genes in a cage population was proportional to that of lethal genes, as were their equilibrium frequencies in several natural populations. Many sterile chromosomes were associated with low viability due to pleiotropic effects. The number of chromosomes leading to sterility in both sexes was larger than the expectation based on random combination of male and female sterility genes. This suggests that there is some linkage disequilibrium between male and female sterility genes, as well as a pleiotropic effect of single sterility genes. Some sterility genes were maintained in natural and cage populations, and the patterns of persistence of the sterility genes were very similar to those of lethal genes.     

基因网络中基因关系图谱的构建及其应用

尽快破解基因组所包含基因的功能是一项费力但又很重要的工作。一个基因功能的实现依赖于该基因与其它基因间的相互作用。基因网络是一组基因的集合体,这些基因通过相互协作来控制生物体重要的生命过程。通过基因敲除、RNA干扰或其它方法改变基因网络中某个基因的表达水平,将会引起该网络中其它基因表达水平的变化。而这种变化可以方便地通过基因表达差异显示技术检测相应mRNA含量变化来反映。因此,将这两类方法组合在一起,可以在基因组水平上有效地检测出基因网络中的基因关系。这种策略对基因功能研究方法是一个重要补充。     

Intrachromosomal Gene Conversion and the Maintenance of Sequence Homogeneity among Repeated Genes

Intrachromosomal gene conversion is the non-reciprocal transfer of information between a pair of repeated genes on a single chromosome. This process produces eventual sequence homogeneity within a family of repeated genes. An evolutionary model for a single chromosome lineage was formulated and analyzed. Expressions were derived for the fixation probability, mean time to fixation or loss, and mean conditional fixation time for a variant repeat with an arbitrary initial frequency. It was shown that a small conversional advantage or disadvantage for the variant repeat (higher or lower probability of producing two variant genes by conversion than two wild-type genes) can have a dramatic effect on the probability of fixation. The results imply that intrachromosomal gene conversion can act sufficiently rapidly to be an important mechanism for maintaining sequence homogeneity among repeated genes.     

Allelism relationships between diuron-resistant, antimycin-resistant and funiculosin-resistant loci of the mitochondrial map in Saccharomyces cerevisiae.

Summary Using allelism tests, two diuron (DIU1, DIU2), one funiculosin (FUN1), and two antimycin (ANA1, ANA2) resistance loci are resolved into two mitochondrial drug-resistant genetic loci. DIU1 is allelic to ANA2 and FUN1. DIU2 is allelic to ANA1.Chercheur qualifié du Fonds National de la Recherche Scientifique     

Interspecific Tests of Allelism Reveal the Evolutionary Timing and Pattern of Accumulation of Reproductive Isolation Mutations

Despite extensive theory, little is known about the empirical accumulation and evolutionary timing of mutations that contribute to speciation. Here we combined QTL (Quantitative Trait Loci) analyses of reproductive isolation, with information on species evolutionary relationships, to reconstruct the order and timing of mutations contributing to reproductive isolation between three plant (Solanum) species. To evaluate whether reproductive isolation QTL that appear to coincide in more than one species pair are homologous, we used cross-specific tests of allelism and found evidence for both homologous and lineage-specific (non-homologous) alleles at these co-localized loci. These data, along with isolation QTL unique to single species pairs, indicate that >85% of isolation-causing mutations arose later in the history of divergence between species. Phylogenetically explicit analyses of these data support non-linear models of accumulation of hybrid incompatibility, although the specific best-fit model differs between seed (pairwise interactions) and pollen (multi-locus interactions) sterility traits. Our findings corroborate theory that predicts an acceleration (‘snowballing’) in the accumulation of isolation loci as lineages progressively diverge, and suggest different underlying genetic bases for pollen versus seed sterility. Pollen sterility in particular appears to be due to complex genetic interactions, and we show this is consistent with a snowball model where later arising mutations are more likely to be involved in pairwise or multi-locus interactions that specifically involve ancestral alleles, compared to earlier arising mutations.     

A Gene with Specific and Global Effects on Recombination of Sequences from Tandemly Repeated Genes in Saccharomyces Cerevisiae

The preservation of sequence homogeneity and copy number of tandemly repeated genes may require specific mechanisms or regulation of recombination. We have identified mutations that specifically affect recombination among natural repetitions in the yeast Saccharomyces cerevisiae. The rrm3 mutation stimulates mitotic recombination in the naturally occurring tandem repeats of the rDNA and copper chelatin (CUP1) genes. This mutation does not affect recombination of several other types of repeated genes tested including Ty elements, mating type information and duplications created by transformation. In addition to stimulating exchange among the multiple CUP1 repeats at their natural chromosomal location, rrm3 also increases recombination of a duplication of CUP1 units present at his4. This suggests that the RRM3 gene may encode a sequence-specific factor that contributes to a global suppression of mitotic exchange in sequences that can be maintained as tandem arrays.