Copy Link
Add to Bookmark
Report
dictyNews Volume 21 Number 01
Dicty News
Electronic Edition
Volume 21, number 1
July 11, 2003
Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to dicty@northwestern.edu.
Back issues of Dicty-News, the Dicty Reference database and other
useful information is available at dictyBase - http://dictybase.org.
===========================================
Special Note to the Dictyostelium community
===========================================
Dear Dicty People,
The following paper is now in press at Biomed Central Genetics
(http://www.biomedcentral.com/bmcgenet/). We are preparing to send axenic
diploid strains and the appropriate haploids to various labs around the world.
Could you please get in touch in the next week or two if you need them?
This will diminish the workload a bit.
Thanks,
Robert Insall
=============
Abstracts
=============
Parasexual Genetics of Dictyostelium Gene Disruptions: Identification of a
Ras Pathway Using Diploids
Jason King and Robert H. Insall*
School of Biosciences
University of Birmingham
Birmingham B15 2TT
UK
Biomed Central Genetics, in press
The relative ease of targeted gene disruption in the social amoeba Dictyostelium
has stimulated its widespread use as an experimental organism for cell and
developmental biology. However, the field has been hamstrung by the lack of
techniques to recombine disrupted genes. Here we describe new techniques for
parasexual fusion of strains in liquid medium, selection and maintenance of
the resulting stable diploid strains, and segregation to make recombined
haploids. We have used these techniques to isolate rasS/gefB double nulls.
The phenotypes of these mutants are no more severe than either parent, with
movement, phagocytosis and fluid-phase endocytosis affected to the same degree
as in rasS or gefB single nulls. This suggests that the RasS and GefB proteins
lie on the same linear pathway. In addition, we have produced diploids from one
AX2- and one AX3- derived parent, providing an axenic strain with fewer secondary
phenotypes than has been previously available.
Submitted by: Robert Insall [R.H.Insall@bham.ac.uk]
-----------------------------------------------------------------------------
Construction of a gamete-enriched gene pool and RNAi-mediated functional
analysis in Dictyostelium discoideum
Tetsuya Muramoto1, Katsuya Suzuki1, Hajime Shimizu**1, Yuji Kohara2, Eiko
Kohriki1, Shinji Obara1, Yoshimasa Tanaka1, and Hideko Urushihara*1
1Institute of Biological Sciences, University of Tsukuba, Tsukuba-shi
305-8572, Japan; 2Center for Genetic Resource Information, National
Institute of Genetics, Mishima-shi 411-8540, Japan
Mechanisms of Development, in press
Macrocysts in Dictyostelium discoideum possess prototypic features of sexual
reproduction and are useful for understanding the basic mechanisms of the
reproductive process. Here, we randomly analyzed 1,071 gamete cDNAs, and
then constructed a gamete-specific subtraction library, FC-IC. Nucleotide
sequences of all 903 FC-IC clones were determined and clustered into 272
independent genes. Expression analysis based on real-time RT-PCR revealed 67
gamete-enriched genes, among which those involved in 'signal transduction'
and 'multicellular organization' are prevalent. One of them, FC-IC0003,
ap-peared also to be mating-type specific, and was named gmsA. RNAi-mediated
silencing as well as disruption of gmsA reduced the cellular competency for
sexual cell fusion, indicating the involvement of this gene in the sexual
devel-opment of D. discoideum.
Submitted by: Hideko Urushihara [hideko@biol.tsukuba.ac.jp]
-----------------------------------------------------------------------------
Mutation of the Dictyostelium discoideum fbxA gene affects cell-fate decisions
and spatial patterning.
Herbert L. Ennis, Dee N. Dao, MaryY. Wu and Richard H. Kessin
Department of Anatomy and Cell Biology, Columbia University, College of
Physicians and Surgeons, New York, NY 10032
Protist, In Press
Cell-fate decisions and spatial patterning in Dictyostelium are regulated by
a number of genes. Our studies have implicated a gene called fbxA, which
codes for an F-box protein, in these pathways. The FbxA protein is one of
the controls on a cAMP phosphodiesterase called RegA, mediating its
degradation via ubiquitin-linked proteolysis. Using marked strains, we
showed that the fbxA mutant has defective cell-type proportioning, with a
dearth of prestalk cells compared to prespore cells. In this work, we show
that this effect occurs earlier during the 24 hour developmental cycle than
previously thought. The normal sorting of the prestalk and prespore cells
in aggregates and mounds is not affected by the mutation. The mutant cells
sort abnormally at the tipped mound stage, when prespore and prestalk cells
normally distribute into their proper compartments. The fbxA mutant forms
prestalk cells in low numbers when not in chimeras, but in the presence of
wild-type amoebae the mutant preferentially forms viable spores, driving the
wild type to form non-viable stalk cells. In an attempt to identify the signal
transduction pathway that mediates proportionality in prestalk and prespore
cells, we asked whether certain signal transduction mutants were immune to the
effects of the fbxA cells and formed spores in chimeras.
Submitted by: Herb Ennis [he28@columbia.edu]
===============================================================================
[End Dicty News, volume 21, number 1]
