ISSN:0192-253X    

DOI:10.1002/dvg.1020100202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThree‐dimensional models were constructed utilizing the information gained from electron micrographs of serial sections of two clones of cystocytes undergoing their terminal divisions. In each clone a polyfusome connected all eight cystocytes together. Each of the spindles was oriented so that one pole touched the polyfusomes, while the other pointed away from it. This positioning of spindles ensures that one cell of each dividing pair retains all previously formed canals, while the other receives none. The two cells that eventually come to contain the maximum number of canals and fusomal material are the ones that differentiate as pro‐oocytes, while the others become nurse cells. The orientation of each spindle suggests that the polyfusome formed at one division determines the placement of the cytoskeletal fibers that anchor the spindles formed at the next division. There is a centripetal gathering together of new canals following each cycle of cystocyte division, which is thought to result from the subsequent contraction of the polyfusomal system. Females homozygous for theotu1mutation are characterized by ovarian tumors, which result when germarial cystocytes undergo supernumerary divisions and fail to differentiate into either nurse cells or oocytes. An analysis of electron micrographs taken of serially sectioned, mutant germaria showed that most germ cells were single or belonged to clusters of two or three interconnected cells. Thereforeotu1cystocytes are unable to undergo a sustained series of arrested cleavages. These cystocytes contain fusomal material that shows ultrastructural differences from normal polyfusomes. We conclude: (1) that a normal polyfusomal system is a necessary prerequisite for the production of a branched chain of cystocytes and for their subsequent differentiation into pro‐oocytes and nurse cells; and (2) that a product encoded by the otu+gene is essential for the construction of a functional polyf

ISSN:0192-253X    

DOI:10.1002/dvg.1020100203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractEight X‐linked recessive female sterile mutations, derived from a hybrid dysgenic screen ofDrosophila melanogasterand representing eight distinct loci, have been characterized by genetic and ultrastructural analysis. Four have abnormal respiratory appendages, three have essentially normal appendages but show moderate defects in the endochorion, and one mutant,fs(1)nela, exhibits major defects in both the endochorion and the respiratory appendages. Germ line clones of all eight mutants were generated using the dominant female sterile technique. Seven of the eight mutations are germ line specific, indicating that, although the eggshell is produced by the follicular cells, germ line functions play a significant role in its elaboration. The mutant that shows major defects,fs(1)nela, is somatic line specific, and exerts its effect in the ovar

ISSN:0192-253X    

DOI:10.1002/dvg.1020100204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper describes the flightless phenotype of thevestigial‐Depilatedeficiency ofDrosophila melanogaster.Recombination experiments and studies of revertants show that the dominant flightless and depilate phenotypes are inseparable from the deficiency and due to a single cause. Dosage studies on this region reveal that these phenotypes are due to antimorphic effects, probably on theSuppressor‐2 of zesteorPosteriorsexcombgenes which lie close to the distal breakpoint of the deficiency. The deficiency does not uncover a gene haplo‐insufficient for flight. A detailed phenotypic examination failed to reveal any effects of this mutation on the indirect flight muscles.Dr(2R)vgD/+ heterozygotes are unable to initiate flight or raise their wings, even during death by over etherisation. There is a close correlation between the dominant antimorphic flightlessness and patterned thoracic bristle loss which is revealed in interactions withDf(2R)vg62and the Su(z)2alleles. This is discussed in the light of the bnstle loss mutants of the Achaete‐scute complex. It is proposed that thevestigial‐Depilatedeficiency affects the development of thorac

ISSN:0192-253X    

DOI:10.1002/dvg.1020100205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractTwo modifiers ofbithorax1phenotypic expression are described. An X‐chromosome region is associated with sexual dimorphism inbx1penetrance. It is hypothesized that sexual dimorphism is in part due to a lack of dosage compensation of the modifier, in males. A third chromosome region that segregates with thepink peachallele is implicated in mediating temperature sensitivity. By appropriate combinations of modifiers, both sexual dimorphism and temperature sensitivity can be greatly reduce

ISSN:0192-253X    

DOI:10.1002/dvg.1020100206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

Abstractβ‐conglycinin, an abundant storage protein in soybean seeds, is comprised of three subunits: α', α, and β. Expression of genes encoding these subunits is tissue‐specific and temporally regulated in soybean plants. Both the α'‐and β‐subunit genes have been isolated and fully or partially characterized by DNA sequence analysis. Each has been transferred to transgenic plants and was found to be expressed in petunia and tobacco plants in a regulated manner as in soybean plants. Both the α'‐ and β‐subunit proteins were accumulated only in transgenic seeds during mid‐to‐late stages of seed development and assembled into multimeric forms with sedimentation coefficients of 7S and 9S. The α'‐ and β‐subunit genes were also introduced on the same plasmid into transgenic plants. When the promoters of the two genes were proximal to each other, there was an increase in the expression of the β‐subunit gene, suggesting that there is a strongcis‐acting sequence in the α'‐gene (promoter) that can affect expression of the α‐subunit gene.A series of deletion mutants was constructed in the α'‐gene promoter, and each was introduced into petunia plants. The DNA sequence approximately 250 bp upstream of the transcriptional initiation site contains sufficient regulatory information for expression of the α'‐subunit gene. The sequence about 200 bp upstream contains four 6‐bp repeats A (AGCCCA) that may play an important role in regulating expression of the α'‐gene. The function of this DNA sequence (‐78 to ‐257) was tested in a chimeric gene construct containing the CaMV 35S promoter, the CAT coding sequence, and the 3′ noncoding region of the α'‐gene. A dramatic enhancement of the CAT gene expression (at least 40‐fold) resulted when this DNA sequence was inserted into the 35S promoter at a position 90 bp upstream of the transcription start site, regardless of the orientation of the insert. There was a two‐ to threefold enhancement when the element was placed 3′ to the CAT coding region and no enhancement when placed downstream of the 3′ noncoding region. The enhancement was observed only in seeds during mid‐to‐late stages of seed development. This indicates that the 170‐bp DNA sequence can function as a strongcis‐acting element that controls seed‐specific and temporally regulated gene expression. This elem

ISSN:0192-253X    

DOI:10.1002/dvg.1020100207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0192-253X    

DOI:10.1002/dvg.1020100201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY