Reproductive relationships between annual species ofCalendula (Compositae)

Breeding experiments were carried out inCalendula species. In the annuals, which are selfers, rarely some outcrossing was observed only in the most peripheral flowers. In experimental crosses fruit was produced in all combinations. Fertile F₁ and F₂ hybrids could be grown from crosses between parents with similar chromosome numbers:C. palaestina ×C. pachysperma and crosses of different morphological forms ofC. arvensis. In crosses of species with different chromosome numbers at least partly fertile F₁ hybrids were obtained fromC. tripterocarpa ×C. stellata andC. tripterocarpa ×C. arvensis and crosses of the latter withC. palaestina. Fertile F₂ plants were grown from the combination ofC. arvensis ×C. tripterocarpa. Considering this information and previously obtained data, a scheme is proposed for explaining speciation in the genusCalendula.     

Restriction fragment length polymorphism and chromosome mapping of a mouse homeo box gene,Hox-2.1

Restriction endonuclease fragment length polymorphisms (RFLPs) were found using the cDNA probe Hox-2.1 for the homeo box-2.1 gene in the mouse. Polymorphism was detected in restriction patterns generated by fragments fromHindIII digestion. The great majority of laboratory strains of mice carries theHox-2.1 ^a allele. Only two laboratory strains carry theHox-2.1 ^b allele. Among strains of wild origin, the European subspecies (Mus m. domesticus, M. m. brevirostris, andM. m. musculus) and some Asian subspecies (M. m. castaneus) carry theHox-2.1 ^a allele. The subspecies from Far Eastern countries (M. m. molossinus, Chinese mice of wild origin, andM. m. yamashinai) carry theHox-2.1 ^ballele. Using the RFLP, theHox-2.1 gene was mapped on chromosome 11. Three-point cross test data showed that the recombination frequency is 29.6% between theHba and theHox-2.1 genes and 23.5% between theHox-2.1 and theEs-3 genes. The gene order ofHba-Hox-2.1-Es-3 has been confirmed.     

The HLE hybrid dysgenesis syndrome in the midgeChironomus thummi: Differences in the dysgenic potential between strains

After crossing experiments between twoChironomus subspecies the HLE hybrid dysgenesis syndrome occurs non-reciprocally in the F1 hybrids if the males of each of the fourCh. th. thummi strains (HL, So, G, Kr) are crossed to females ofCh. th. piger, strain E. In hybrid egg masses, differences in the strength of the abnormal trait reduced egg hatch were found between the differentpiger E ×thummi interstrain crosses. From the results it is concluded that eachthummi strain has a specific hybrid dysgenesis potential which determines the severity of the HLE syndrome in the hybrids. The HLE syndrome occurs also in the hybrids of crosses of differentCh. th. thummi strains. In these hybrids the syndrome is only obtained if the male parent descends from a strain which has a higher HLE hybrid dysgenesis potential than that strain from which the female parent is derived. These results demonstrate that the HLE syndrome is not restricted to the hybrids of thethummi × piger subspecies cross. In theCh. th. thummi interstrain crosses the hybrids of that cross direction are normal, which is reciprocal to the cross direction affected by the HLE syndrome. This is in contrast to thethummi × piger subspecies crosses, where the hybrids of one cross direction always show the HLE syndrome and the hybrids of the reciprocal cross direction the Rud syndrome. Thus, the present study also demonstrates that the HLE and Rud hybrid dysgenesis syndrome inChironomus are independent from one another.     

Dikaryotic fruiting body development in a single dikaryon of <Emphasis Type="Italic">Agrocybe aegerita</Emphasis> and the spectrum of monokaryotic fruiting types in its monokaryotic progeny

Using monokaryotic offspring from several dikaryotic parental strains, the phenomenon of monokaryotic fruiting has been previously analysed in the commercially cultivated high-quality edible mushroom Agrocybe aegerita, revealing a variety of monokaryotic fruiting types. Here, we report a single dikaryotic A. aegerita strain, A. aegerita AAE-3, and 40 monokaryons derived from it, which exhibit a wide spectrum of monokaryotic fruiting types, including a rare, previously unknown type. Advantageously, the selected parental strain A. aegerita AAE-3 completes its life cycle within three weeks by the formation of dikaryotic fruiting bodies of typical agaric morphology on malt extract agar plates. In order to morphologically compare normal dikaryotic fruiting to monokaryotic fruiting, histology was performed from all dikaryotic fruiting body development stages and all fruiting types of monokaryotic origin. No clamp connections or dikaryotic hyphae were observed within the plectenchyma of monokaryotic fruiting stages. Among the monokaryotic fruiting types of the A. aegerita AAE-3-derived monokaryons, we also characterised the rare ‘stipe type’ here described as ‘elongated initials type’ as no differentiation into a future cap and stipe was seen. The two mating-compatible monokaryotic strains representing the extremes of the fruiting type spectrum observed, A. aegerita AAE-3-13 (‘mycelium type’) and A. aegerita AAE-3-32 (‘abortive?+?true homokaryotic fruiting fruiter type, AHF?+?THF fruiter type’), were also found to readily produce oidia (arthrospores). In order to obtain a set of mating-compatible monokaryons covering the whole observed spectrum of monokaryotic fruiting, the two monokaryons A. aegerita AAE-3-40 (‘initials type’) and A. aegerita AAE-3-37 (‘elongated initials type’) have been selected for their mating compatibility with A. aegerita AAE-3-32 and A. aegerita AAE-3-13, respectively. Together with the parental dikaryotic strain A. aegerita AAE-3, this set of standard monokaryons could prove useful for studies exploring the factors regulating monokaryotic fruiting in comparison to dikaryotic mushroom formation.     

Analysis ofH-2 mutants: Evidence for multiple CML target specificities controlled by theH-2K b gene

C57BL/6 (H-2 ^b ) mice and two mutants derived from this strain, B6.C-H-2 ^ba (Hz1) andE6-H-2 ^bd (M505), were studied in a number of functional tests, in vitro and in vivo, that assay for differences at theH-2 complex. All three strains give rise to reciprocal mixed lymphocyte reactivity (MLR) and cell-mediated lympholysis (CML) in vitro as well as graft-host reactivity (GVHR) and skin graft rejection in vivo. Analysis for cross-reactivity between these strains in CML revealed that the gained antigens in each mutant do not cross-react, and that Hz1 has lost an antigen shared by C57BL/6 and M505 strains. In addition, spleen cells from B10.A(4R) mice, which differ from theH-2 ^b haplotype only at theK end of theH-2 complex, recognize a common antigen shared by all three strains tested. Provided that the mutations occurred in theH-2K ^b gene, these data indicate that a) there are at least three antigenic specificities coded for by theH-2K ^b gene(s) that serve as targets for receptors on thymus-derived (T) cells in CML; b) since C57BL/6 strain mice and the mutants are serologically indistinguishable on a qualitative basis, the antigens recognized by the receptors on T cells and by humoral H-2 antibody are nonidentical; and c) mutation in theH-2K ^b locus itself can give rise to allogeneic recognition phenomena such as MLR and GVHR.     

Mating reaction inSaccharomyces cerevisiae VIII. Mating-type-specific substances responsible for sexual cell agglutination

The agglutination factors ofa and α mating types ofSaccharomyces cerevisiae were solubilized from isolated cell-wall fractions by treatment with snail enzyme (Glusulase) and shown to be adsorbed specifically by cells of the opposite mating type, resulting in the loss of agglutinability of these cells. The agglutination factors ofa and α types adsorbed by cells of the opposite mating type at pH 5.5 were eluted at pH 9.0. These factors were further purified on Sepharose 4B. From the elution pattern on Sepharose 4B, the molecular weights of the solubilized agglutination factors are estimated to be about one million. Thus purified agglutination factors contained carbohydrate and protein and were considerably resistant to heat treatment. Neutral protease ofBacillus subtilis inactivated botha and α type agglutination factors. Trypsin inactivated the α type agglutination factor only.     

Localization and phenotypic expression of a Tol marker in Citrobacter freundii

Among colicin-A-tolerant mutants of Citrobacter freundii we characterized some as Tol-2 mutants. The Tol-2 mutation results in insensitivity to bacteriocin S6 and an enhanced sensitivity to deoxycholate (DOC), ethylenediaminetetraacetic acid (EDTA) and to ampicillin. The Tol-2 mutation was mapped close near gal and the gene order pro-tol-gal was established in crosses between C. freundii Hfr tol ⁺ donor strains and C. freundii tol ^- acceptor strains. In these crosses a difference was observed in phenotypic expression of the pleiotropic properties of this tol ⁺ gene. Expression of resistance to DOC is substantially slower than the expression of EDTA-resistance. This phenomenon may play a disturbing role in those studies on cell envelope mutants, in which resistance to DOC is used as a selected marker. The differences in expression of DOC-and EDTA-resistance are discussed.     

Cleft palate susceptibility linked to histocompatibility-2 (H-2) in the mouse

Data have been obtained indicating that cortisone-induced cleft palate in the mouse is linked to theH-2 ^a complex. Cortisone (2.5 mg) was administered to pregnant females on days 11 through 14 of pregnancy. On day 17 of pregnancy, the fetuses were inspected for cleft palates. Sham experiments were done by injecting sterile saline instead of cortisone. The inbred strains, A/J and C57BL/6, and the congenic strains C57BL/10ScSn and B10.A were tested for susceptibility to cleft palate. The clefting frequency was also observed in hybrids of the congenic strains. The A/J and B10.A strains showed a characteristic high susceptibility to cleft palate (i.e., 99% and 81% incidence of cleft palate, respectively) after teratogenic treatment. The C57BL/6 and C57BL/ 10ScSn demonstrated a significant resistance to the teratogen (i.e., 25% and 21 % incidence of clefting, respectively). The teratogenic treatment of congenic hybrids indicated that maternal influences significantly affected the incidence of cleft palate formation. The maternal influence appeared to depend upon the specificH-2 haplotype of the mother.     

The effect of Sa and MiniSa plasmids on the induction of plant crown galls and hairy roots byAgrobacterium tumefaciens andAgrobacterium rhizogenes

The Inc-W group plasmid Sa or its derivative MiniSa were introduced into two strains ofAgrobacterium tumefaciens with Ti plasmids, one strain ofA. tumefaciens with the Ri plasmid and oneA. rhizogenes strain with the Ri plasmid. The effect was similar in allAgrobacterium strains. The pSa suppressed fully the virulence ofAgrobacterium strains (i.e. their ability to induce tumor growths - crown galls or hairj⁷ roots) inKalanchoe plants and carrot root slices. The MiniSa plasmid caused only a slight decrease of the frequency and size of tumor growths induced. The mechanism of suppression of virulence by the Sa plasmid inAgrobacterium tumefaciens andAgrobacterium rhizogenes seems to be similar.     

Multigenic control of immune responses of inbred mice against the terpolymers poly(Glu57Lys38Ala5) and poly(Glu54Lys36Ala10) and linkage withH-2 haplotype

Results of immunizations of recombinant inbred and congenic strains of mice with the random polymers poly(glu⁵⁷ lys³⁸ala⁵) or GLA⁵ and poly(glu⁵⁴lys³⁶ala¹⁰) or GLA¹⁰ indicate that there is an association of the responsiveness with theH-2 haplotype. Although the C57BL/6J mice (H-2 ^b haplotype) are “non responders”, the C57BL/6By originally derived from mice of the same haplotype are responders. The immune response pattern of recombinant strains carrying haplotypes derived by crossing over within theH-2 complex indicate that the responsiveness is under control of anIr gene which maps to the left of theIB subregion. Studies with the backcross mice indicated multigenic control of the responsiveness, with one locus beingH-2 linked and another locus segregating independently ofH-2.     

Immune response of mice to the Thy-1.1 antigen: Effect of theIr-5 alleles studied in 129/J and B10.129 (6M) mice

The primary immune response to the Thy-1.1 antigen was measured by a plaque assay that detected cells producing antibodies lytic for AKR thymocytes. B10.129(6M) mice carrying theH-2 complex of an intermediate responder (129) on a low-responder (B10) background, were low responders. Studies employing different F₁ hybrids and segregating generations of 129/J and 6M mice indicated that differences in responsiveness of those two strains depend on alleles at a single locus, loosely linked to theH-2 complex. These results lend further support to the previously advanced concept that the expression of theIr-Thy-1 allcles controlling the response to the Thy-1.1 antigen is influenced by the alleles at theIr-5 locus. In addition, studies employing F₁ hybrids produced through matings of 129/J, 6M, C3H.B10 and C57BL/6J mice to a panel of inbred strains suggested that in regard to the responsiveness to the Thy-1.1 antigen, 129/J and 6M mice are phenotypically, and presumably genotypically, similar to C3H.B10 and C57BL/6J mice, respectively.     

Genomic organization of multiple genes coding for rhodotorucine A,a lipopeptide mating pheromone of the basidiomycetous yeast Rhodosporidium toruloides

Rhodotorucine A, a lipopeptide mating pheromone, is secreted from mating type A cells of Rhodosporidium toruloides and induces sexual differentiation of the opposite mating type a cells. Genome of A-type cells contains three homologous genes (RHA1, RHA2, and RHA3) encoding rhodotorucine A. Genomic Southern blot analysis using RHA1 DNA as a probe showed that RHA1 strongly hybridize with A-type genomic DNA but weakly with a-type, suggesting that the sequences of RHA genes were dissimilar in the opposite a-type genome. The range of dissimilar regions in a-type genome was searched using RHA-flanking DNA segments as probes. The result suggests that a-type genome lacks sequences coding for rhodotorucine A and its 5 upstream but contains its 3 non-coding sequences. The absence of mating pheromone genes in the opposite mating type genome suggests that the expression of mating-type-specific genes in R. toruloides is not controlled trans-criptionally, as shown in the yeast Saccharomyces cerevisiae.     

Graphiolales: Basidiomycetes parasitic on palms

Graphiola phoenicis was restudied by light microscopy and investigated in detail with the scanning and the transmission electron microscopes. Hyphae of the fruitbody are mainly dikaryotic. Karyogamy occurs in cells which are interpreted as meiosporangia (basidia), and which develop in chains. Shortly after karyogamy, meiosis takes place in these basidia. Primary, sessile meiospores are then formed which later divide and produce thick-walled diaspores. The latter germinate either by hyphae or by yeast-like budding. The nutritional requirements of pure cultures of the yeast stage were also investigated. Life cycle, karyological criteria, ultrastructural details, and chemical tests clearly show thatGraphiola belongs in theBasidiomycetes. The taxonomic position within theHeterobasidiomycetes is discussed and the orderGraphiolales is validated.     

A New Mating Compatibility Locus in PHYSARUM POLYCEPHALUM

The rate and extent of plasmodium formation were studied in mating tests involving pairs of largely isogenic amoebal strains compatible for mating-type (mt) alleles. A systematic variability was observed: plasmodia formed either rapidly and extensively or slowly and inefficiently. Plasmodium formation was found to be 10³- to 10⁴-fold more extensive in "rapid" crosses than in "slow" crosses. A genetic analysis revealed that the variability reflects the influence of a multiallelic compatibility locus that determines mating efficiency. This compatibility locus (designated matB), together with the original mating type locus, mt (in this work designated matA), constitute a tetrapolar mating specificity system in Physarum polycephalum.     

Morphological and Mutational Analysis of Mating in Ustilago hordei

Martinez-Espinoza, A. D., Gerhardt, S. A., and Sherwood, J. E. 1993. Morphological and mutational analysis of mating in Ustilago hordei. Experimental Mycology 17, 200-214. Ustilago hordei is a basidiomycete that causes covered smut on barley. Mating in U. hordei, which is controlled by a single locus with two alleles, results in the conversion of haploid, nonpathogenic yeast-like sporidia to dikaryotic, pathogenic mycelia. When sporidia of the opposite mating type were mixed and placed on water agar, both cell types produced conjugation tubes within 2 h at 21°C. Growth of conjugation tubes was directed toward the tip of tubes arising from cells of the opposite mating type. These tubes fused and the dikaryotic mycelium emerged from the conjugation bridge. Sporidia separated by a dialysis membrane were still capable of inducing conjugation tube formation by cells of the opposite mating type, indicating the involvement of diffusible small-molecular-weight mating factors (pheromones). Numerous nutritional and environmental variables were examined in order to optimize conjugation tube induction. Twenty-six mutants that fail to form dikaryotic mycelium have been isolated and characterized. These mutants were arranged into classes based on their ability to form conjugation tubes, the ability to induce conjugation tube formation by opposite mating-type cells, and cell morphology. These mutants provide an indication of the genetic complexity involved in this critical phase of the U. hordei life cycle.     

High Mutability in Male Hybrids of DROSOPHILA MELANOGASTER

The frequencies of sex-linked lethal mutations arising in hybrid male offspring from various crosses and in nonhybrid controls were determined. The hybrids were produced by crossing representative strains of the P-M system of hybrid dysgenesis in all possible combinations. Males from the cross of P males x M females had a mutation rate about 15 times higher than that of nonhybrid males from the P strain. Genetically identical males from the reciprocal cross had a mutation rate 3 to 4 times that of the nonhybrids. For crosses involving a Q strain, a significant increase in the mutation rate was detected in males produced by matings of Q males with M females. No increase was observed in genetically identical males from the reciprocal mating. Crosses between P and Q strains gave male hybrids with mutation rates not different from those of nonhybrids. Many of the lethals that occurred in hybrids from the cross of P males x M females appeared to be unstable; fewer lethals that arose in hybrids from the cross of Q males x M females were unstable. The relationship between P and Q strains is discussed with respect to a model of mutation induction in dysgenic hybrids.     

Sexual reproduction and sex determination in green algae

The sexual reproductive processes of some representative freshwater green algae are reviewed. Chlamydomonas reinhardtii is a unicellular volvocine alga having two mating types: mating type plus (mt⁺) and mating type minus (mt^?), which are controlled by a single, complex mating-type locus. Sexual adhesion between the gametes is mediated by sex-specific agglutinin molecules on their flagellar membranes. Cell fusion is initiated by an adhesive interaction between the mt⁺ and mt^? mating structures, followed by localized membrane fusion. The loci of sex-limited genes and the conformation of sex-determining regions have been rearranged during the evolution of volvocine algae; however, the essential function of the sex-determining genes of the isogamous unicellular Chlamydomonas reinhardtii is conserved in the multicellular oogamous Volvox carteri. The sexual reproduction of the unicellular charophycean alga, Closterium peracerosum-strigosum-littorale complex, is also focused on here. The sexual reproductive processes of heterothallic strains are controlled by two multifunctional sex pheromones, PR-IP and PR-IP Inducer, which independently promote multiple steps in conjugation at the appropriate times through different induction mechanisms. The molecules involved in sexual reproduction and sex determination have also been characterized.     

Analysis of theilv-linked genes that determine the morphology ofEscherichia coli Cells

The genetic location ofwee relative tocya was measured by cotransduction with a Tn5 insertion inilv. These experiments locatedwee at 84.8 min in the standardEscherichia coli map. Mutations incya andwee give rise to morphological changes, coccal morphology incya and short rods inwee, suggesting that both may be involved in the pathways of cell elongation. Addition of cAMP to the cultures reverted thecya but not thewee phenotype. Cells ofE. coli in the absence of thewee gene product were, contrary to what has been described forcya cells, as sensitive to mecillinam as in its presence. These results suggested that the action of Wee on elongation is exerted at a level different from that of adenyl cyclase.