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At least 469 records · Page 26Linked to original sources
PubMed2000

Neuroepithelial defects of the inner ear in a new allele of the mouse mutation Ames waltzer.

This report presents new findings regarding a recessive insertional mutation in the transgenic line TgN2742Rpw that causes deafness and circling behavior in mice homozygous for the mutation. The mutant locus was mapped to a region on mouse chromosome 10 close to three spontaneous recessive mutations causing deafness: Ames waltzer (av), Waltzer (v), and Jackson circler (jc). Complementation testing revealed that the TgN2742Rpw mutation is allelic with av. Histological and auditory brainstem response (ABR) evaluation of animals that have the new allele balanced with the av(J) allele (called compound heterozygotes, TgN2742Rpw/av(J)) supports our genetic analysis. ABR evaluation shows complete absence of auditory response throughout the life span of TgN2742Rpw/av(J) compound heterozygotes. Scanning electron microscopy revealed abnormalities of inner and outer hair cell stereocilia in the cochleae of TgN2742Rpw mutants at 10 days after birth (DAB). The organ of Corti subsequently undergoes degeneration, leading to nearly complete loss of the cochlear neuroepithelium in older mutants by about 50 DAB. The vestibular neuroepithelia remain morphologically normal until at least 30 DAB. However, by 50 days, degenerative changes are evident in the saccular macula, which progresses to total loss of the saccular neuroepithelium in older animals. The new allele of av reported here will be designated av(TgN2742Rpw).

Alleles↗
PubMed2003

An Azospirillum brasilense Tn5 mutant with modified stress response and impaired in flocculation.

The analysis of an A. brasilense Tn5 mutant shows significant phenotypic differences compared to the wild type isogenic strain. The transposon was located disrupting an open reading frame of 840 bp (ORF280) which exhibits similarity to the universal stress protein (USP) family. The USP family encompasses proteins that are expressed as a response to cell growth arrest. The mutant revealed a pleiotrophic phenotype with respect to different stress conditions. The ORF mutation results in an increased sensitivity of cells to carbon starvation and heat-shock treatment. However, the mutant strain displays a higher tolerance to oxidative stress agents. In contrast to the isogenic parent strain, colonies of the mutant are weakly stained by Congo red added to solid media and are impaired in flocculation. Scanning electron micrographs revealed that the mutant lacks part of the surface material present as a thick layer of exopolysaccharides on the surface of the wild type cells. The pleiotrophic phenotype revealed for this mutant and the similarity of the C-terminal region of ORF280 to UspA from E. coli indicates that the A. brasilense ORF280 may be a Usp-like protein.

Azospirillum brasilense↗
PubMed2003

Characterization of Candida albicans colony-morphology mutants and their hybrids.

The collection wild-type strain of Candida albicans was used to obtain auxotrophic and colony-morphology mutants by 'nitrosoguanidine' treatment. Intraspecific protoplast fusion induced by Ca(2+)-poly(ethyleneglycol) was carried out in various pairings between the auxotrophic strain producing smooth colonies and containing blastospores and the colony-morphology mutants containing a mixture of blastospores and pseudohyphae or only hyphae. Hybrids exhibiting full or partial complementation were obtained when mutants producing smooth colonies and colony-morphology variants of different origins were fused. The mutation responsible for the colony-morphology character (if various types of colony morphomutants were crossed) proved to be recessive or semidominant. Representative hybrids exhibited elevated DNA contents as measured by flow cytometry. To illustrate various cell types, and especially the intermediate one (never observed in natural isolates), a preparation method was further developed for scanning electron microscopic studies.

Candida albicans↗
PubMed1986

A rehabilitation of the genetic map of the 84B-D region in Drosophila melanogaster.

A reanalysis of the 84B3 to 84D3,5 region of the polytene chromosomes of Drosophila melanogaster has led to the identification and localization of 16 genes. These genes include 11 vital loci, four genes exhibiting nonlethal visible mutant phenotypes and one gene encoding a nonessential enzyme. The identity of the gene products of two of the vital genes has been determined to be alpha-tubulin and glucose dehydrogenase (Gld). Three newly identified genes, sticking (stk), half out (hat) and trapped (ted), as well as Gld are required for eclosion. Among the nonessential genes are roughened eye (roe) and ruffed eye (rue), which affect eye texture. The roe phenotype is greatly enhanced by deletions that simultaneously remove roe and an unidentified locus in 84E. Mutations in another nonessential gene, rotund (rn), are characterized by pattern deletions of most adult appendages.

Animals↗
PubMed1981

Comparison of the mannan structure from the cell-wall mutant Candida sp. M-7002 and its wild type. I. Characterization of the proteo-mannan from the mutant and the wild-type cells.

The cell-wall mutant of a hydrocarbon-assimilating yeast, Candida sp. M-7002 and its wild type have shown a significant difference in mannose content. Each mannan was isolated from the mutant and the wild-type cells by fractionation with Cetavlon and copper reagent. Both mannans contain D-mannose, D-glucose and phosphate. The mutant mannan has a relatively high content of protein (18% in weight bases) whereas the wild-type mannan has a low protein content (5.1%) with a high amount of carbohydrate (greater than 90%). Structural analyses by enzymatic and chemical methods showed that both mannans had a mannosidic (alpha 1--6)-linked back bone substituted at O-2 by side chains of varying length. The side chains of the mutant mannan were shown to consist of single mannose units and disaccharide units whose linkages were predominantly alpha 1--2, while the wild-type mannan had two additional side chains of disaccharides. These additional side chains had alpha 1--3 linkages which were scarcely found in the mutant mannan. beta-Elimination reaction demonstrated that the mannans also contain mannosyl oligosaccharides linked to protein through O-glycosidic linkage. The chemical properties of the mannan of the Candida mutant indicates that the mutation might occur not only in the side chain structure but also in the (alpha 1--6)-linked mannan back bone.

Candida↗
PubMed1998

CLAVATA2, a regulator of meristem and organ development in Arabidopsis.

Mutations at the CLAVATA2 (CLV2) locus of Arabidopsis result in enlarged shoot and flower meristems, as well as alterations in the development of the gynoecia, flower pedicels, and stamens. The shoot and flower meristem phenotypes of clv2 mutants are similar to weak clv1 and clv3 mutants. We present genetic analysis that CLV2 may function in the same pathway as CLV1 and CLV3 in the regulation of meristem development, but function separately in the regulation of organ development. We also present evidence that clv2 phenotypes are altered when the mutants are grown under short-day light conditions. These alterations include flower-to-shoot transformations, as well as a nearly complete suppression of the flower phenotypes, indicating that the requirement for CLV2 changes in response to different physiological conditions. The stm-1 mutation dominantly suppresses clv2, and clv2 mutations suppress the strong stm-1 allele, but not the weak stm-2 allele.

Alleles↗
PubMedDate not supplied

Neonatal reductions in osteoclast number and function account for the transient nature of osteopetrosis in the rat mutation microphthalmia blanc (mib).

We have examined the general and skeletal manifestations of osteopetrosis in a new, mild osteopetrotic mutation in the rat, microphalmia blanc (mib). Newborn mutant (mib) rats exhibit the typical skeletal deformities and sclerosis of osteopetrosis at birth, which are reduced significantly during the first postnatal month but don't disappear entirely up to 8 months later. Osteoclast numbers, staining for TRAP and TraATPase, and bone resorption are reduced in mutants during the first 2 postnatal weeks but improve by 1 month. In mutants, serum concentrations of calcium and phosphorus are normal, but 1,25(OH)2 D levels are higher at 1 week than those in normal littermates. Neonatally, mutants exhibit extramedullary hemopoiesis in the spleen. These results are interpreted to mean that the transient perinatal skeletal sclerosis in mib rats is caused by reduced production and function of osteoclasts in this period. The recent description of transient, perinatal osteopetrosis in a child suggests that analyses of the early differences between mild and severe animal mutations might distinguish those children with osteopetrosis who need treatment from those who do not.

Aging↗
PubMed1994

Tetrad analysis possible in Arabidopsis with mutation of the QUARTET (QRT) genes.

Two Arabidopsis thaliana genes, QRT1 and QRT2, are required for pollen separation during normal development. In qrt mutants, the outer walls of the four meiotic products of the pollen mother cell are fused, and pollen grains are released in tetrads. Pollen is viable and fertile, and the cytoplasmic pollen contents are discrete. Pollination with a single tetrad usually yields four seeds, and genetic analysis confirmed that marker loci segregate in a 2:2 ratio within these tetrads. These mutations allow tetrad analysis to be performed in Arabidopsis and define steps in pollen cell wall development.

Arabidopsis↗
PubMed1991

Gastrulation in Drosophila: the formation of the ventral furrow and posterior midgut invaginations.

The ventral furrow and posterior midgut invaginations bring mesodermal and endodermal precursor cells into the interior of the Drosophila embryo during gastrulation. Both invaginations proceed through a similar sequence of rapid cell shape changes, which include apical flattening, constriction of the apical diameter, cell elongation and subsequent shortening. Based on the time course of apical constriction in the ventral furrow and posterior midgut, we identify two phases in this process: first, a slow stochastic phase in which some individual cells begin to constrict and, second, a rapid phase in which the remaining unconstricted cells constrict. Mutations in the concertina or folded gastrulation genes appear to block the transition to the second phase in both the ventral furrow and the posterior midgut invaginations.

Animals↗
PubMed1993

Promiscuous germination and growth of wildtype pollen from Arabidopsis and related species on the shoot of the Arabidopsis mutant, fiddlehead.

When pollen lands upon the stigmatic surface of a receptive flower, recognition events take place that permit germination, pollen tube growth, and tube penetration into the cell walls of the stigmatic papillae. Previously, we have described a mutant of Arabidopsis thaliana, named fiddlehead (fdh), where noncarpel organs of the shoot fuse late in ontogeny (Lolle et al., 1992). Here we demonstrate that wildtype Arabidopsis pollen grows on noncarpel organs of the fdh mutant. Pollen grains adhere, germinate, and emit pollen tubes when applied to vegetative and nonreproductive floral organs. Some of the emergent pollen tubes penetrate into the cell wall. Although pollen from a number of closely related species responds, tomato, tobacco, and snapdragon pollen does not. In addition, we show that organ fusion is not a prerequisite for pollen growth and that root epidermis does not express this activity. Based on these findings we propose that the fdh mutation identifies an important regulatory gene that controls the expression of an epidermis-specific developmental program normally expressed only during gynoecial ontogeny.

Arabidopsis↗
PubMed2003

Identification of functional similarities between proteins using directed evolution.

Protein sequences are often highly redundant and evolution can change them beyond recognition. It can therefore be difficult to identify proteins with functional or structural similarities by inspection of their sequences. Here we have used an experimental evolutionary approach to detect hidden similarities between the antisense RNA-binding protein Rop and other proteins. We created an envelope of functional Rop mutants by combinatorial mutagenesis, used the compilation of mutant sequences to search a database of protein structures, and thereby identified a segment of the enzyme valyl-tRNA-synthetase (ValRS). Further inspection revealed that the structures of the RNA-binding sites of both proteins are highly related, as indeed are the RNA ligands. From the known 3D structure of the ValRS in complex with tRNA, we were able to build a model of an RNA hairpin pair in complex with Rop that has proved to be consistent with the biochemical and NMR data for the interaction between Rop and RNA hairpins. We suggest that this approach (mutational envelope scanning), by generating sequence information de novo, can help uncover hidden similarities between proteins.

Amino Acids↗
PubMed1985

Clonal analysis of two mutations in the large subunit of RNA polymerase II of Drosophila.

Two mutations in the gene, RpII215, were analyzed to determine their effects on cell differentiation and proliferation. The mutations differ in that one, RpII215ts (ts), only displays a conditional recessive lethality, while the other, RpII215Ubl (Ubl), is a recessive lethal mutation that also displays a dominant mutant phenotype similar to that caused by the mutation Ultrabithorax (Ubx). Ubl causes a partial transformation of the haltere into a wing; however, this transformation is more complete in flies carrying both Ubl and Ubx. The present study shows that patches of Ubl/-tissue in gynandromorphs are morphologically normal. cuticle that has lost the wild-type copy of the RpII215 locus fails to show a haltere to wing transformation, nor does it show the synergistic enhancement of Ubx by Ubl. We conclude that an interaction between the two RpII215 alleles, Ubl and RpII215+, is responsible for the mutant phenotype. Gynandromorphs carrying the ts allele, when raised at permissive temperature, display larger patches of ts/-cuticle than expected, possibly indicating that the proliferation of ts/+ cells is reduced. This might result from an antagonistic interaction between different RpII215 alleles. Classical negative complementation does not appear to be the cause of the antagonistic interactions described above, as only one RpII215 subunit is thought to be present in an active multimeric polymerase enzyme. We have therefore coined the term 'negative heterosis' to describe the aforementioned interactions. We also observed that the effects of mutationally altered RNA polymerase II on somatic cells are different from its effects on germ cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Genetic characterization of cytological region 77A-D harboring the presenilin gene of Drosophila melanogaster.

We performed a systematic lethal mutagenesis of the genomic region uncovered by Df(3L)rdgC-co2 (cytological interval 77A-D) to isolate mutations in the single known Presenilin (Psn) gene of Drosophila melanogaster. Because this segment of chromosome III has not been systematically characterized before, inter se complementation testing of newly recovered mutants was carried out. A total of 79 lethal mutations were isolated, representing at least 17 lethal complementation groups, including one corresponding to the Psn gene. Fine structure mapping of the genomic region surrounding the Psn transcription unit by transgenic rescue experiments allowed us to localize two of the essential loci together with Psn within an approximately 12-kb genomic DNA region. One of these loci, located 3' to Psn, encodes a Drosophila protein related to the yeast 60S ribosomal protein L10 precursor. We also determined which of the newly recovered lethal mutant groups correspond to previously isolated lethal P-element insertions, lethal inversion breakpoints, and lethal polo gene mutants. Point mutations were identified in all five recovered Psn alleles, one of which results in a single amino acid substitution G-E at a conserved residue in the C-terminal cytoplasmic tail of the protein, suggesting an important functional role for this C-terminal domain of Presenilin. In addition, some viable mutations were recovered in the screen, including new alleles of the clipped and inturned loci.

Animals↗
PubMed1996

Self-sterility in Arabidopsis due to defective pollen tube guidance.

In flowering plants, a series of cell-cell interactions govern the delivery of sperm to the ovules through precise guidance of pollen tubes. Two Arabidopsis genes, POP2 and POP3, were found that mediate pollen tube guidance and are critical for self-fertility in diploid reproductive cells. The pop2 and pop3 mutations exhibited genetic redundancy: Self-sterility occurred only when male and female tissues were defective in both genes. This phenotype resembles that found in many self-incompatible species.

Arabidopsis↗
PubMed1985

Phage-mediated cloning of bldA, a region involved in Streptomyces coelicolor morphological development, and its analysis by genetic complementation.

Streptomyces coelicolor bald (bld) mutants form colonies of vegetative substrate mycelium, but do not develop aerial hyphae or spore chains. The bldA strains form none of the four antibiotics known to be produced by the parent strain. With a vector derived from the temperate bacteriophage phi C31, a 5.6-kilobase fragment of wildtype DNA was cloned which restored sporulation to five independent bldA mutants when lysogenized with the recombinant phage. The cloned gene(s) was dominant over the mutant alleles. Phage integration by recombination of the cloned bldA+ DNA with the bldA region of each mutant produced mainly sporulating colonies, presumably heterozygous bldA+/bldA partial diploids for the insert DNA. However, a minority of these primary transductants were bald and were apparently homozygous bldA/bldA mutant partial diploids, formed by some homogenetization process. The phages released from the bald lysogens carried bldA mutations and were used to show that bldA+ sequences had been cloned and that fine mapping of the region could be performed.

Alleles↗
PubMed1999

Ca(2+)-ATPase function is required for intracellular trafficking of the Notch receptor in Drosophila.

Maintaining high Ca(2+) concentrations in the lumen of the endoplasmic reticulum is important for protein synthesis and transport. We identified a lethal complementation group recovered in a screen for mutations that reduce Notch activity as loss-of-function alleles of the Drosophila Ca(2+)-ATPase gene Ca-P60A. Analysis of Ca-P60A mutants indicates that Ca(2+)-ATPase is essential for cell viability and tissue morphogenesis during development. Cultured cells treated with Ca(2+)-ATPase inhibitors exhibit impaired Notch cleavage and receptor trafficking to the cell surface, explaining the genetic interaction between Ca(2+)-ATPase and Notch. Notch and several other transmembrane proteins are mislocalized in tissue clones homozygous for Ca-P60A mutations, demonstrating a general effect on membrane protein trafficking caused by a deficiency in Ca(2+)-ATPase.

Animals↗
PubMed2004

The M1 matrix protein controls the filamentous phenotype of influenza A virus.

We show that most isolates of influenza A induce filamentous changes in infected cells in contrast to A/WSN/33 and A/PR8/34 strains which have undergone extensive laboratory passage and are mouse-adapted. Using reverse genetics, we created recombinant viruses in the naturally filamentous genetic background of A/Victoria/3/75 and established that this property is regulated by the M1 protein sequence, but that the phenotype is complex and several residues are involved. The filamentous phenotype was lost when the amino acid at position 41 was switched from A to V, at the same time, this recombinant virus also became insensitive to the antibody 14C2. On the other hand, the filamentous phenotype could be fully transferred to a virus containing RNA segment 7 of the A/WSN/33 virus by a combination of three mutations in both the amino and carboxy regions of the M1 protein. This observation suggests that an interaction among these regions of M1 may occur during assembly.

Amino Acid Substitution↗
PubMed1998

The parthenocarpic fruit (pat) mutant of tomato (Lycopersicon esculentum Mill.) sets seedless fruits and has aberrant anther and ovule development.

Among the different sources of genetic parthenocarpy described in tomato, the mutation referred to as parthenocarpic fruit (pat) is of particular interest because of its strong expressivity and because it confers earlier ripening, higher fruit set and enhanced fruit quality. As a pleiotropic effect, pat flowers have aberrantly developing androecia and reduced male and female fertility. In this work we extend the early description of the pat phenotype by investigating the expression of parthenocarpy in three different environments and by using light and scanning electron microscopy to analyse the development of male and female floral organs. The degree of parthenocarpy was high in the three experimental environments and was characterised by a precocious initiation of ovary growth to pre-anthesis floral stages. Aberrations in anther development were evident at flower bud stages and resulted in shorter, irregular and teratoid organs. Ectopic production of carpel-like structures bearing external ovules was evident in the most severely altered androecia. Analysis of ovule development revealed that a fraction of pat ovules becomes aberrant from very early stages, having defective integument growth. Meiosis was irregular in aberrant ovules and megaspore or gamete production was severely hampered. The described pat syndrome suggests that parthenocarpy in this mutant could be a secondary effect of a gene controlling, at early stages, organ identity and development.

Fruit↗