Reduced Reproductive Success for a Conditioning Mutant in Experimental Populations of DROSOPHILA MELANOGASTER

Male Drosophila melanogaster that have courted newly-emerged males can modify their subsequent courtship behavior to avoid further courtship with immature males for up to 6 hr (previously reported). Here, it was hypothesized that such an experience-dependent modification would afford a mating advantage to normal males over males that carried a mutation that affects learning and memory. Coisogenic lines were constructed which varied at the dunce gene (dnc+ and dncM14 alleles) in order to test this hypothesis. Whether previously experienced with immature males or not, dnc+ and dncM14 males were indistinguishable in their response and mating efficiency when individually paired with virgin females. However, courtship performance of dnc+ and dncM14 males was different if they were first experienced with immature males and were then individually tested in an artificial population of nine immature males and one virgin female. In this situation, dnc+ males spent much less time in courtship with immature males and achieved copulation in one-third the time required for dncM14 males. As a control, the behavior and mating efficiency of courtship-naive dnc+ and dncM14 males in the artificial population was indistinguishable. In competition for a single virgin female, experienced dncM14 males showed a slight mating advantage over experienced dnc+ males. But when competition by experienced males for a single virgin female took place in the presence of nine immature males, dnc+ males were the successful maters in three-fourths of the trials.     

Genetic and biochemical aspects of sucrase from Drosophila melanogaster

Isoelectrofocusing of abdominal extracts of Drosophila melanogaster revealed the existence of two forms of sucrase (E.C. 3.2.1.26). One form exhibited an isoelectric point of 4.63 +/- 0.02 while the other form exhibited an isoelectric point of 4.83 +/- 0.02. The localization of the structural gene for sucrase is proposed on the basis of enzyme determinations in a series of duplication- and deletion-bearing aneuploids. We suggest that the sucrase structural gene lies between 31CD and 31EF on the left arm of chromosome 2 and that the two forms of abdominal sucrase derive from a common protein coded for by a single sucrase gene designated Sucr+.     

Cytogenetical analysis of the 2B3-4-2B11 region of the X chromosome of Drosophila melanogaster

Summary Of 13 ecs mutations, which affect female fertility, as revealed by complementation analysis, 7 are chromosome rearrangements involving the br complementation group. The other six show no cytologically detectable rearrangements and behave as completely or partially noncomplementing ecs alleles. All viable combinations of these 13 mutations were characterized by partial or complete female sterility. Viable heterozygotes carrying any of these mutations and the rearrangements Df(1)sta, T(1,3)sta, Df(1)St490, previously localized distal to the ecs locus, were also sterile. Using deletions and an electrophoretic mobility variant from the Staket strain, a minor chorion gene S70 has been mapped. It had been thought this gene was located in the 2B3-5 region, and corresponded to the ecs locus. However, in the present study, this gene was shown to map in the region removed by Df(1)sta (1E1-2-2B3-4) but outside that removed by Df(1)At127 (1E1-2-2A1-2), i.e. within the 2A1-2-2B3-4 region which is distal to the ecs locus. Rearrangements and point mutations at the ecs locus that result in female sterility had no effect on synthesis of the chorion protein s70. It may therefore be suggested that the chorion protein gene is not functionally associated with the ecs locus and that sterility is caused not by disruptions of the chorion protein gene but by lesions in the ecs gene itself. Thus, an ecs product, which controlls cell sensitivity to ecdysterone is also necessary for female fertility. Data on the locations of lesions affecting female fertility indicate that at least two elements at the ecs locus are essential for this function: a cis-acting distal zone with no effect on viability and a sequence within the essential part of the ecs locus. A defect in either of these zones or their separation by chromosomal rearrangement leads to female sterility.     

SSB, an antigen that selectively labels morphologically distinct synaptic boutons at the Drosophila larval neuromuscular junction.

In this report we describe the expression of Small Synaptic Bouton (SSB), an antigen that is selectively expressed in a specific subset of neuromuscular junction terminals in the body wall of Drosophila larva. The expression of SSB was studied with a polyclonal antibody raised against the cAMP phosphodiesterase of the Drosophila learning mutant dunce (Nighorn et al., 1991, Neuron 6:455-467); however, immunoreactivity was not abolished by the dunce (dnc) alleles dncM14 and dncM11 or deficiencies of the dnc gene, indicating that the antigen labelled could not be the dnc gene product, but another antigen that we termed SSB. Immunoreactivity was localized in the body wall muscles to a specific subset of neuromuscular junction terminals that have been implicated in activity-dependent plasticity. This demonstrates that these morphologically distinct terminals can be immunocytochemically distinguished and that they probably represent innervation by a distinct neuronal population. Confocal and electron microscopic examination demonstrated that staining was restricted to the synaptic boutons themselves, not to neurites or motor axons. Ultrastructural analysis showed label close to synaptic vesicles in the presynaptic terminal and in the surrounding subsynaptic reticulum. Central nervous system (CNS) staining was restricted to a segmentally repeated pattern of cell bodies in the ventral ganglion and to a few small groups of cells in the brain lobes.     

The effect of locus ecs in Drosophila melanogaster on fertility of females

A total of 13 ecs mutations affecting female fertility were isolated by complementation analysis. Seven of them were rearrangements with the br complementation group phenotype. Six other mutations had no cytologically detectable rearrangements and behaved as completely or partially non-complementing alleles of the ecs locus. All viable combinations of the above 13 mutations disturbed female fertility. Sterile were all fully viable compounds carrying any of these mutations and rearrangements Df (1) sta, T(1; 3)sta, Df(1)St490, previously localized on the molecular map distally to the ecs locus. According to data on location on molecular map of lesions affecting fertility, at least two elements at the ecs locus seem essential for this function: the most distal (left) cis-acting zone with no effect on viability and a sequence within the limits of the essential part of the ecs locus. Disturbance of any of these zones or their separation in the rearranged chromosomes lead to female sterility.     

Roles of the trkB and trkC gene products of Escherichia coli in K+ transport

Mutations at the trkB and trkC loci of Escherichia coli produce an abnormal efflux of K+. The mutations are partially dominant in diploids and revert frequently by what appears to be intragenic suppression to the null state. The mutations can be reverted by insertion of Tn10 into the mutated gene, and spontaneous revertants are fully recessive to the mutant allele in diploids. K+ efflux produced by NEM* and by DNP* persists in strains with presumed null mutations at either locus, indicating neither gene product is the primary target for the effect of these inhibitors on K+ efflux. The results are consistent with the view that trkB and trkC encode independent systems for K+ efflux. Mutations at these loci alter regulation of the process so that K+ efflux occurs inappropriately. A second mutation to the null state abolishes this abnormal K+ efflux. These genes may encode K+/H+ antiporters, an activity postulated to mediate K+ efflux and demonstrated to exist in E. coli and other bacteria.     

Genetic identification of a female partial-sterile mutant in soybean.

We report here the genetic identification of a female partial-sterile mutant derived from soybean mutant L67-3483. L67-3483, which originated from the cultivar Clark after X-ray irradiation, is male and female fertile. All F1 plants in reciprocal pollinations of L67-3483 with 'Clark', 'Minsoy', or 'BSR 101' were female partial sterile. Partial sterility is expressed in the heterozygous condition at a single locus and upon self-pollination this locus exhibits a 1:1 segregation pattern. This locus is located on the terminus of the soybean molecular linkage group D1b+W, between simple sequence repeat (SSR) markers Satt157 and Satt266, and is linked to each by 5.3 and 1.2 cM, respectively. This gene is transmitted through both female and male gametes and there was no segregation distortion of SSR markers linked to this gene. We concluded that this female partial-sterile gene is a new mutation class, and differs from the previously reported mutation classes in soybean, i.e., sporophytic mutation, gametophytic female-specific mutation, and general gametophytic mutation. Restriction of recombination around the mutant gene suggested that this gene is located near or within (a) small inversion(s) or adjacent to (a) chromosomal deletion(s).     

The host resistance locus Bcg is tightly linked to a group of cytoskeleton-associated protein genes that include villin and desmin.

In the mouse, innate resistance or susceptibility to infection with a group of unrelated intracellular parasites which includes, Mycobacteria, Salmonella, and Leishmania is determined by the expression of a single dominant autosomal gene designated Bcg located on the proximal portion of chromosome 1. The gene is expressed at the level of the mature tissue macrophage and influences its capacity to restrict intracellular proliferation of the parasites. We have used restriction fragment length polymorphism analysis in segregating populations of inter- and intraspecific backcross mice and in recombinant inbred strains to position four new marker genes, transition protein 1 (Tp-1), desmin (Des), the alpha subunit of inhibin (Inha), and retinal S-antigen (Sag), in the vicinity of the host resistance locus, Bcg. The gene order for Tp-1, Des, Inha, and Sag was established in an eight-point testcross with respect to anchor loci previously assigned to that portion of mouse chromosome 1 and was found to be centromere-Fn-1-Tp-1-(Vil,Bcg)-Des-Inha-Akp-3-Acrg+ ++-Sag. Two of these new marker genes were found very tightly linked to Bcg: Des was located 0.3 +/- 0.3 cM distal from (Vil,Bcg) and 0.3 +/- 0.3 cM proximal to Inha. Tp-1 mapped 0.8 +/- 0.8 cM proximal and Sag 12.8 +/- 1.7 cM distal to (Vil,Bcg). Tp-1, Des, Inha, and Sag all fall within a large mouse chromosome 1 segment homologous with the telomeric region of the long arm of human chromosome 2 (2q). Our findings indicate that the two closest markers to the host resistance locus, Bcg, encode cytoskeleton-associated proteins which are capable of interaction with actin filaments.     

Mapping of a wide compatibility locus in indica rice using SSR markers

Hybrid sterility between indica and japonica subspecies in rice is basically caused by partial abortion of gametes and hybrid fertility could be recovered by a single wide compatibility (WC) allele. In this study, a typical indica germplasm source of rice, UPRI 95-162, with strong wide compatibility in cross with japonica rice was studied for location of its WC locus. Bulked segregant analysis was performed and SSRs (simple sequence repeats) were conducted on a F₁ population derived from a three-way cross (UPRI 95-162/T8//Akihikari). The locus was located on chromosome 1 approximately 0.2 cM to SSR markers RM581 on one side and 1.5 cM to RM292 on another. This WC locus, tentatively designated as S-20 ⁿ (t), and its tight linkage markers, RM581 and RM292, would be very useful for efficient marker-assisted selection for breeding new WC varieties and for map-based cloning of the gene.     

Alloplasmic male sterile Brassica napus with Enarthrocarpus lyratus cytoplasm: introgression and molecular mapping of an E. lyratus chromosome segment carrying a fertility restoring gene.

A cytoplasmic male sterility (CMS) system for Brassica napus (2n = 38; AACC) was developed by backcross substitution of its nucleus into the cytoplasm of a wild crucifer, Enarthrocarpus lyratus. Male sterility was complete, stable, and expressed in small flowers with rudimentary anthers. Since the B. napus germplasm lines were complete or partial maintainers of male sterility, the required fertility restorer gene (Rfl) was introgressed from the cytoplasm donor species. Inheritance studies carried out on F1 and F2 populations derived from hybridizing cytoplasmic male sterile and male fertile near-isogenic (PNILs) lines of B. napus 'Westar', revealed a monogenic dominant control for fertility restoration. Bulked segregant analysis with 215 RAPD primers helped in the identification of putative primers associated with fertility restoration. Co-segregation analysis of eight such primers with Rfl gene revealed two markers, OPK 15700 and OPZ 061300, which flank the Rfl locus on either side at a distance of 8.2 and 2.5 cM, respectively. These DNA markers will be useful in marker-assisted selection for improving the commercial potential of this newly developed CMS-fertility-restorer system for hybrid seed production programs in rapeseed.     

Molecular analysis of two mouse dilute locus deletion mutations: spontaneous dilute lethal20J and radiation-induced dilute prenatal lethal Aa2 alleles.

The dilute (d) coat color locus of mouse chromosome 9 has been identified by more than 200 spontaneous and mutagen-induced recessive mutations. With the advent of molecular probes for this locus, the molecular lesion associated with different dilute alleles can be recognized and precisely defined. In this study, two dilute mutations, dilute-lethal20J (dl20J) and dilute prenatal lethal Aa2, have been examined. Using a dilute locus genomic probe in Southern blot analysis, we detected unique restriction fragments in dl20J and Aa2 DNA. Subsequent analysis of these fragments showed that they represented deletion breakpoint fusion fragments. DNA sequence analysis of each mutation-associated deletion breakpoint fusion fragment suggests that both genomic deletions were generated by nonhomologous recombination events. The spontaneous dl20J mutation is caused by an interstitial deletion that removes a single coding exon of the dilute gene. The correlation between this discrete deletion and the expression of all dilute-associated phenotypes in dl20J homozygotes defines the dl20J mutation as a functional null allele of the dilute gene. The radiation-induced Aa2 allele is a multilocus deletion that, by complementation analysis, affects both the dilute locus and the proximal prenatal lethal-3 (pl-3) functional unit. Molecular analysis of the Aa2 deletion breakpoint fusion fragment has provided access to a previously undefined gene proximal to d. Initial characterization of this new gene suggests that it may represent the genetically defined pl-3 functional unit.     

Genetic variation in alkaline phosphatase of the house mouse (Mus musculus) with emphasis on a manganese-requiring isozyme

Genetic variation among inbred strains is described for electrophoretic migration of alkaline phosphatase from intestine, kidney, blood plasma, and three isozymes of liver. A manganese-requiring isozyme of liver and kidney unaffected by neuraminidase is described, and the locus controlling variation in this isozyme is designated Akp-1. Data from recombinant inbred strains place the locus on chromosome 1 at a distance of 3.6 +/- 2.9 cM from the M1s locus on the side distal to the centromere. Test-cross data show the following gene order and recombination percentages: Dip-1 19.0 +/- 3.8% Lp 7.4 +/- 2.2% Akp-1.     

Dominant and Recessive Suppressors That Restore Glucose Transport in a Yeast Snf3 Mutant

The SNF3 gene of Saccharomyces cerevisiae encodes a high-affinity glucose transporter that is homologous to mammalian glucose transporters. To identify genes that are functionally related to SNF3, we selected for suppressors that remedy the growth defect of snf3 mutants on low concentrations of glucose or fructose. We recovered 38 recessive mutations that fall into a single complementation group, designated rgt1 (restores glucose transport). The rgt1 mutations suppress a snf3 null mutation and are not linked to snf3. A naturally occurring rgt1 allele was identified in a laboratory strain. We also selected five dominant suppressors. At least two are tightly linked to one another and are designated RGT2. The RGT2 locus was mapped 38 cM from SNF3 on chromosome IV. Kinetic analysis of glucose uptake showed that the rgt1 and RGT2 suppressors restore glucose-repressible high-affinity glucose transport in a snf3 mutant. These mutations identify genes that may regulate or encode additional glucose transport proteins.     

Fine mapping of a recessive genic male sterility gene (Bnms3) in rapeseed (Brassica napus) with AFLP- and Arabidopsis-derived PCR markers

9012AB, a recessive genic male sterility (RGMS) line developed from spontaneous mutation in Brassica napus (Chen et al. in Acta Agron Sin 24:431-438, 1998), has been playing an increasing role in hybrid cultivar development in China. The male sterility of 9012AB is controlled by two recessive genes (designated Bnms3 and Bnms4) interacting with one recessive epistatic suppressor gene (esp). Previous study has identified seven AFLP markers, six of which were co-segregated with the Bnms3 gene in a small population (Ke et al. in Plant Breed 124:367-370, 2005). By cloning these AFLP markers and their flanking sequences, five of the six co-segregated markers were successfully converted into sequence characterized amplified region (SCAR) markers. For fine mapping of the Bnms3 gene, these SCAR markers were analyzed in a NIL population of 4,136 individuals. The Bnms3 gene was then genetically mapped to a region of 0.56 cM, with 0.15 cM from marker SEP8 and 0.41 from marker SEP4, respectively. BLAST analysis with these SCAR marker sequences identified a collinear genomic region in Arabidopsis chromosome 5, from which two specific PCR markers further narrowed the Bnms3 locus from an interval of 0.56 to 0.14 cM. These results provide additional information for map-based cloning of the Bnms3 gene and will be helpful for marker-assisted selection (MAS) of elite RGMS lines and maintainers.     

Co-segregation of the gynomonoecious sex form1 gene (gsf1) of Tripsacum dactyloides (Poaceae) with molecular markers.

The only monogenic trait in Tripsacum to date was first identified in the prolific sex form variant Tripsacum dactyloides (L.) L. forma prolificum Dayton et Dewald. The expression of this trait is controlled by the presence of a single-gene, recessive pistillate mutation hereby designated the gynomonoecious sex form1 gene (gsf1), after the registered plant germplasm accession GSF-I (PI483447) from which it was first identified. This trait confers a high degree of feminization to the primarily male floral structure of the Tripsacum rachis. Two molecular markers were found to co-segregate with the gsf1 gene in a diploid (2n = 36) F2 population of Tripsacum dactyloides, where the female parent (GSF-I) had been previously determined to be homozygous recessive for the gene. Phenotypic scoring data were compared with restriction fragment length polymorphism data and linkage relationships were determined. The gsf1 gene is located ~7 cM from tda48, a Tripsacum-derived molecular marker, and ~9 cM from npi286, a maize-derived molecular marker. The marker npi286 also maps within ~5 cM of the tassel seed2 locus (ts2) of maize, which confers a similar change in the inflorescence of the maize tassel.     

The Drosophila sex determination gene daughterless has different functions in the germ line versus the soma

As a regulator of the female-specific gene Sxl, da+ provides an essential maternal component in the control of sex determination and dosage compensation; nevertheless, neither the maternal nor zygotic phenotypes of the original mutant da allele is sex-specific. Here we clarify the role of da+ in Drosophila development, finding: this sex determination gene is indeed pleiotropic; zygotic functioning of da+ is essential in both sexes for somatic cell development, but not for germ cell development; da female sterility results from a somatic, rather than germ-line, defect; and expression of da+ in the maternal germ line is required only for daughters in the subsequent generation, as expected for a specific regulator of Sxl+. These conclusions follow from the characterization of new da null alleles isolated by a selection for defects in maternally acting positive regulators of Sxl.