Female Sterility Phenotype Research Articles

Two Drosophila learning mutants, dunce and rutabaga, provide evidence of a maternal role for cAMP on embryogenesis

The dunce gene of Drosophila melanogaster encodes a cAMP-specific phosphodiesterase (form II). Mutant dunce flies have elevated levels of cAMP and exhibit a number of defects including learning deficiencies and female sterility. Two partial suppressors of the female sterility phenotype have been selected in an X chromosome containing a dunce null mutation. Both suppressors are associated with reduced AC 2 2 Abbreviations: PDE, cAMP-specific phosphodiesterase (form II); EMS, ethyl methanesulfonate; AC, adenylate cyclase. activity. Complementation analyses suggest that both are alleles of the learning mutant rutabaga. Females homozygous for dunce null mutations that abolish PDE activity do not deposit eggs. The suppressors exhibit differential effects on egg deposition and production of progeny; double-mutant females deposit many eggs that fail to hatch, but some develop to adults. These adult progeny exhibit morphological defects that are confined mostly to the second and third thoracic segments or to the first five abdominal segments. These observations demonstrate that the dunce gene is required in adult females for egg laying and that the dunce gene provides an essential maternal function required for normal development of the zygote. Clonal analysis, employing the dominant female-sterile mutation ovo D1 , demonstrates that the former requirement for PDE activity resides in somatic cells and that the latter requirement resides in germ line cells. Female germ line cells homozygous for a dunce null mutation produce oocytes that fail to develop. Thus, homozygous dunce null-mutant zygotes develop to adults solely because of the enzyme or mRNA present in the oocytes of heterozygous mothers. Mutant alleles of rutabaga act in the germ line cells to partially suppress the developmental defects caused by dunce mutations. Thus the rutabaga gene, as well as the dunce gene, functions in both somatic and germ line cells.

GENETIC ANALYSIS OF CHROMOMERE 3D4 IN DROSOPHILA MELANOGASTER . II. REGULATORY SITES FOR THE DUNCE GENE

Chromomere 3D4 of the X chromosome of D. melanogaster contains two genes, dunce (dnc) and sperm amotile (sam). Mutations in dnc cause defects in memory formation and female fertility and reduce or eliminate the activity of a cAMP-specific phosphodiesterase designated form II. A fine structure map of this region has been constructed showing the locations of two sam mutations, five dnc mutations and a newly identified locus designated control of fertility (cf) that acts in cis to regulate the female sterility phenotype of dnc. The two sam mutations are separated by 0.02 +/- 0.01 cM, the rightmost being located 0.08 +/- 0.02 cM to the left of the null mutation dncM11. A cluster of null and form II-defective dnc mutations is located 0.04 +/- 0.01 cM to the right of dncM11. The cf locus is 0.06 +/- 0.02 cM to the right of this cluster. The location of the dnc and cf sites identify a region of approximately 0.10 cM that is required for proper expression of dnc+. The dncCK mutation, associated with a reciprocal translocation between 3L and the X, exhibits reduced form II activity and female sterility. This translocation breakpoint has been mapped to the left of the dnc+ gene and is near the breakpoint of Df(1)N64j15 which also reduces expression of dnc+. The effect of these independent chromosomal breaks on the dnc+ gene suggests the existence of a site to the left of dnc+ that is also required for proper expression of the gene.

Genetic analysis of mutations at the Glued locus and interacting loci in Drosophila melanogaster.

A genetic analysis of the dominant mutation Glued that perturbs the development of the normal axonal architecture of the fly's visual system was undertaken. Ten new alleles at this locus were identified and characterized. Two complementation groups that were identified failed to complement the original allele, suggesting that it is a double mutant or that it resides at a complex locus. Several of the new alleles display visual-system abnormalities similar to those of the original mutation. Seven of the eight members of one complementation group are embryonic/early larval lethals, like the original mutation. The other allele in this group is temperature sensitive. Homozygous mutant adults exhibit a temperature-sensitive female sterile phenotype. Unsuccessful attempts to recover genetic mosaics carrying clones of cells homozygous for some of these mutations revealed that they are either essential for the viability of individual cells or that they affect some other fundamental cellular function, such as mitosis or the ability to participate in tissue level organization, which prevents them from being recovered in adult mosaics. This also indicates that these mutations do not specifically affect neural cells. A number of X-ray- and EMS-induced partial and complete phenotypic "revertants" of the original allele have also been isolated as material for comparative analysis of visual system development. All "revertants" that alter the abnormal eye phenotype towards the wild type have similar impact on the organization of the optic lobe.

The genetics of dopa decarboxylase in Drosophila melanogaster. III. Effects of a temperature sensitive dopa decarboxylase deficient mutation on female fertility

AbstractThe mutation Ddcts1 effects female sterility when homozygous, hemizygous, or heterozygous over a series of Ddc null alleles (Ddcx) indicating that some aspect of Ddc gene function is necessary for female fertility. Ovary transplant experiments demonstrate that the female sterility phenotype is ovary autonomous. Two to 3% of the total DDC activity measurable in newly hatched females is localized in their previtellogenic ovaries. The degree to which females heterozygous for Ddcts1 over different Ddc null alleles are fertile at 22°C reflects a continuous spectrum of allelic complementation similar to that observed for the effects of these genotypes on viability at 30°C. Fertility of all the Ddcts1/Ddcx females tested is significantly depressed at 30 vis‐a‐vis 22°C providing evidence that it is the DDC enzyme activity itself which is required for female fertility. Ddcts1/Ddcts1 homozygous and Ddcts1/Df hemizygous females are nonconditionally, completely sterile at 18, 20, 22, 25, and 30°C. Although all homo‐ and hemizygous females do lay some eggs, no evidence of embryogenesis or fertilization has ever been detected. The absolute, nonconditional sterility of Ddcts1 homo‐ and hemizygous females stands in stark contrast to the conventional temperature dependent effects of these same genotypes on viability and to the temperature sensitive effects of Ddcts1/Ddcx heterozygous females on both fertility and viability. Reasons for these tissue‐specific and genotypic differences are discussed.

ISOLATION AND CHARACTERIZATION OF PERITHECIAL DEVELOPMENT MUTANTS IN NEUROSPORA

The isolation and characterization of mutants that block perithecial development in Neurospora crassa are described. Several classes of mutants have been isolated after UV mutagenesis, and those that block perithecial development when used as the female (protoperithecial) component of a cross have been further characterized. These mutants fall into 29 complementation groups. Twelve of the 33 mutants block development at the protoperithecial stage; no other clustering of block points is observed. Many of the mutants show an altered vegetative growth rate as well; in several mutants this lower growth rate cosegregates with the female sterile phenotype. Only one mutant also blocks development of the perithecium when used as the conidial parent. None of the mutants are temperature sensitive; two can be suppressed by growth on a complete crossing medium. There is no indication that the mutants are at or in the mating-type locus, nor are any of the mutants mating-type specific. Genetic mosaics have been formed using mixtures of mutant and marked wild-type nuclei; no mutants are cell autonomous by this criterion. The significance of these results in terms of "developmental" mutants isolated in other organisms and in relation to models of eukaryotic development is discussed.