Aluminum tolerance genes on the short arm of chromosome 3R are linked to organic acid release in triticale.
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Triticale, a hybrid between wheat and rye, shows a high degree of Al tolerance that is inherited from rye, but the mechanisms of high Al tolerance in both rye and triticale are unknown. We found that the short arm of chromosome 3R carries genes necessary for Al tolerance in triticale (x Triticosecale Wittmark cv Currency). Detailed comparative studies with a 3DS.3RL translocation line (ST22) and a non-substitution line (ST2) were conducted. Root elongation was similarly inhibited by Al in ST2 and ST22 during the first 12 h of Al treatment, but more strongly in ST22 than in ST2 at 18 h and thereafter. The root inhibition induced by other metals (Cu, Cd, and La) was similar between ST2 and ST22, suggesting that the action of the genes for Al tolerance on the short arm of triticale chromosome 3R is highly specific to Al. A 2-fold larger amount of malate and citrate was released from the roots of ST2 than from ST22 at 12 and 18 h after Al treatment, respectively. The marked lag phase in the inhibition of root elongation and the release of organic acids implies that the expression of genes on the short arm of triticale chromosome 3R is induced by Al, and that these genes are necessary for the release of organic acids. (+info)
Intake of umami-tasting solutions by mice: a genetic analysis.
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In two-bottle preference tests with water and solutions of monosodium glutamate (MSG) and inosine-5'-monophosphate (IMP), mice from the C57BL/6ByJ inbred strain consumed more and had higher preferences for these solutions compared with mice from the 129/J strain. The C57BL/6ByJ mice consumed 300 mmol/L MSG in large amounts, which were comparable to intakes of highly preferred solutions of sweeteners. The strain differences in voluntary consumption of 300 mmol/L MSG depended at least in part on postingestive effects because prior experience with MSG influenced the expression of the strain difference in MSG acceptance. The strain difference in MSG acceptance was in the opposite direction to the strain difference in NaCl acceptance and was not affected by previous consumption of saccharin. Although the C57BL/6ByJ mice had higher avidity for both MSG and sweeteners than did the 129/J mice, there was no correlation between preferences for these solutions in the second hybrid generation (F(2)) derived from these two strains. Thus, the strain differences in MSG acceptance are not related to the strain differences in salty or sweet taste responsiveness and most likely represent specific umami taste responsiveness. High acceptance of MSG solutions by the C57BL/6ByJ mice was inherited as a recessive trait in the F(2) generation. Further genetic linkage analyses using the F(2) hybrids are being conducted to map chromosomal locations of genes determining the strain difference in MSG acceptance. (+info)
Inheritance of unique fruit and foliage color mutation in NuMex pinata.
(35/2497)
The inheritance of mature fruit color in peppers (Capsicum spp.) is controlled by several genes. However, the inheritance of the transition of colors the fruit undergo during ripening has not been described extensively. The authors describe the inheritance of a unique gene which affects foliage color and fruit color transition occurring in the jalapeno cultivar NuMex Pinata. The gene responsible is designated the tra gene. (+info)
Single-locus inheritance in the allotetraploid Coffea arabica L. and interspecific hybrid C. arabica x C. canephora.
(36/2497)
Molecular cytogenetic analysis has indicated that Coffea arabica is an amphidiploid formed from the hybridization between two closely related diploid progenitor species, C. canephora and C. eugenioides. Our aim was to determine the mode of inheritance in C. arabica and in a tetraploid interspecific hybrid (called arabusta) between C. arabica and C. canephora as revealed by segregation analyses of restriction fragment length polymorphism (RFLP) loci markers. The observed RFLP allele segregations in an F(2) progeny of C. arabica conform to disomic inheritance as expected, with regular bivalent pairing of homologous chromosomes in the F1 hybrid. In contrast, RFLP loci followed tetrasomic inheritance in the arabusta interspecific hybrid, although bivalents have been reported to predominate greatly at meiosis in its hybrid. These results suggest that homologous chromosomes do not pair in C. arabica, not as a consequence of structural differentiation, but because of the functioning of pairing regulating factors. Moreover, the arabusta hybrid seems to offer the possibility of gene exchange between the homologous genomes. (+info)
Dominance, epistasis and the genetics of postzygotic isolation.
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The sterility and inviability of species hybrids can be explained by between-locus "Dobzhansky-Muller" incompatibilities: alleles that are fit on their "normal" genetic backgrounds sometimes lower fitness when brought together in hybrids. We present a model of two-locus incompatibilities that distinguishes among three types of hybrid interactions: those between heterozygous loci (H(0)), those between a heterozygous and a homozygous (or hemizygous) locus (H(1)), and those between homozygous loci (H(2)). We predict the relative fitnesses of hybrid genotypes by calculating the expected numbers of each type of incompatibility. We use this model to study Haldane's rule and the large effect of X chromosomes on postzygotic isolation. We show that the severity of H(0) vs. H(1) incompatibilities is key to understanding Haldane's rule, while the severity of H(1) vs. H(2) incompatibilities must also be considered to explain large X effects. Large X effects are not inevitable in backcross analyses but rather-like Haldane's rule-may often reflect the recessivity of alleles causing postzygotic isolation. We also consider incompatibilities involving the Y (or W) chromosome and maternal effects. Such incompatibilities are common in Drosophila species crosses, and their consequences in male- vs. female-heterogametic taxa may explain the pattern of exceptions to Haldane's rule. (+info)
The Drosophila melanogaster hybrid male rescue gene causes inviability in male and female species hybrids.
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The Drosophila melanogaster mutation Hmr rescues inviable hybrid sons from the cross of D. melanogaster females to males of its sibling species D. mauritiana, D. simulans, and D. sechellia. We have extended previous observations that hybrid daughters from this cross are poorly viable at high temperatures and have shown that this female lethality is suppressed by Hmr and the rescue mutations In(1)AB and D. simulans Lhr. Deficiencies defined here as Hmr(-) also suppressed lethality, demonstrating that reducing Hmr(+) activity can rescue otherwise inviable hybrids. An Hmr(+) duplication had the opposite effect of reducing the viability of female and sibling X-male hybrid progeny. Similar dose-dependent viability effects of Hmr were observed in the reciprocal cross of D. simulans females to D. melanogaster males. Finally, Lhr and Hmr(+) were shown to have mutually antagonistic effects on hybrid viability. These data suggest a model where the interaction of sibling species Lhr(+) and D. melanogaster Hmr(+) causes lethality in both sexes of species hybrids and in both directions of crossing. Our results further suggest that a twofold difference in Hmr(+) dosage accounts in part for the differential viability of male and female hybrid progeny, but also that additional, unidentified genes must be invoked to account for the invariant lethality of hybrid sons of D. melanogaster mothers. Implications of our findings for understanding Haldane's rule-the observation that hybrid breakdown is often specific to the heterogametic sex-are also discussed. (+info)
Estimation of parameters of deleterious mutations in partial selfing or partial outcrossing populations and in nonequilibrium populations.
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The Deng-Lynch method was developed to estimate the rate and effects of deleterious genomic mutations (DGM) in natural populations under the assumption that populations are either completely outcrossing or completely selfing and that populations are at mutation-selection (M-S) balance. However, in many plant and animal populations, selfing or outcrossing is often incomplete in that a proportion of populations undergo inbreeding while the rest are outcrossing. In addition, the degrees of deviation of populations from M-S balance are often not known. Through computer simulations, we investigated the robustness and the applicability of the Deng-Lynch method under different degrees of partial selfing or partial outcrossing and for nonequilibrium populations approaching M-S balance at different stages. The investigation was implemented under constant, variable, and epistatic mutation effects. We found that, generally, the estimation by the Deng-Lynch method is fairly robust if the selfing rate (S) is <0.10 in outcrossing populations and if S > 0.8 in selfing populations. The estimation may be unbiased under partial selfing with variable and epistatic mutation effects in predominantly outcrossing populations. The estimation is fairly robust in nonequilibrium populations at different stages approaching M-S balance. The dynamics of populations approaching M-S balance under various parameters are also studied. Under mutation and selection, populations approach balance at a rapid pace. Generally, it takes 400-2000 generations to reach M-S balance even when starting from homogeneous individuals free of DGM. Our investigation here provides a basis for characterizing DGM in partial selfing or outcrossing populations and for nonequilibrium populations. (+info)
Extractable nuclear antigen effect on the DNA anti-DNA reaction and NZB/NZW mouse nephritis.
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Extractable nuclear antigen (ENA) is composed of at least two components, one a ribonucleo-protein sensitive to ribonuclease or heat and the other a protein. Antibodies to ENA are associated with a relatively benign clinical course in patients with systemic lupus erythematosus (SLE) in which DNA anti DNA complexes are thought pathogenic. The effect of ENA and anti-ENA on DNA anti-DNA reactions in vitro was studied. ENA effectively inhibited an anti-DNA hemagglutination reaction but no effect was found on binding of radioactive DNA or on the anti-hemocyanin hemagglutination reaction. The inhibitory effect was not abolished by yeast ribonuclease (RNase), heating, or DNase. Anti-ENA HAD NO EFFECT ON ANTI-DNA hemagglutination. In vivo, ENA altered the NZB/NZW mouse nephritis thought to be a model for human SLE nephritis. These results suggest the possiblity of a role for ENA in alteration of diseases due to pathogenic DNA anti-DNA complexes. (+info)