dictyNews
Electronic Edition
Volume 35, number 10
October 15, 2010
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Abstracts
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Development of twelve polymorphic microsatellite markers from the
social amoeba Dictyostelium giganteum suitable for genetic diversity
studies on cellular slime moulds.
Santosh Sathe1*, Albert Lalremruata2, Ramesh K Aggarwal2
1Centre for Ecological Sciences, Indian Institute of Science,
Bangalore 560012, India.
2Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
(*E-mail: [log in to unmask])
Molecular Ecology Resources, in press
Knowledge of the genetic structure of social groups formed by cellular
slime mould amoebae is essential for understanding the importance
of genetic relatedness in the evolution of their social behaviour.
Only a few studies have examined genetic heterogeneity in
naturally-occurring cellular slime mould groups, and they have
been restricted to Dictyostelium discoideum, D. giganteum and
D. purpureum. Part of the reason for this state of affairs is the
paucity of genetic markers. We have developed twelve new
microsatellite DNA markers from a partial genomic DNA library of
D. giganteum. We studied the utility of these markers by genotyping
the DNA isolated from 57 strains of cellular slime moulds. Most of
the strains belonged to D. giganteum; the rest were
D. macrocephalum, D. discoideum, D. purpureum, D. mucoroides,
D. rosarium and Polysphondylium pallidum. The markers
successfully amplified DNA from all the species listed above and
yielded 2 to 9 alleles per marker. The high levels of polymorphism
seen and the fact that DNA from several species could be
amplified show that the markers are well-suited for addressing
questions related to species relationships, genetic diversity and
kinship in the cellular slime moulds.
Submitted by Santosh Sathe [[log in to unmask]]
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Prolyl hydroxylation- and glycosylation-dependent functions of Skp1
in O2-regulated development of Dictyostelium
Zhuo A. Wang, Divyendu Singha, Hanke van der Wel, and
Christopher M. West
Department of Biochemistry and Molecular Biology, Oklahoma
Center for Medical Glycobiology, University of Oklahoma Health
Sciences Center, Oklahoma City, OK 73104 USA
Devel. Biol., in press
O2 regulates multicellular development of the social amoeba
Dictyostelium, suggesting it may serve as an important cue in its
native soil environment. Dictyostelium expresses an HIFalpha-type
prolyl 4-hydroxylase (P4H1) whose levels affect the O2-threshold
for culmination implicating it as a direct O2-sensor, as in animals.
But Dictyostelium lacks HIFalpha, a mediator of animal prolyl
4-hydroxylase signaling, and P4H1 can hydroxylate Pro143 of Skp1,
a subunit of E3SCFubiquitin-ligases. Skp1 hydroxyproline then
becomes the target of five sequential glycosyltransferase reactions
that modulate the O2-signal. Here we show that genetically induced
changes in Skp1 levels also affect the O2-threshold, in opposite
direction to that of the modification enzymes suggesting that the
latter reduce Skp1 activity. Consistent with this, overexpressed
Skp1 is poorly hydroxylated and Skp1 is the only P4H1 substrate
detectable in extracts. Effects of Pro143 mutations, and of
combinations of Skp1 and enzyme level perturbations, are
consistent with pathway modulation of Skp1 activity. However,
some effects were not mirrored by changes in modification of
the bulk Skp1 pool, implicating a Skp1 subpopulation and possibly
additional unknown factors. Altered Skp1 levels also affected other
developmental transitions in modification-dependent fashion.
Whereas hydroxylation of animal HIFalpha results in its
polyubiquitination and proteasomal degradation, Dictyostelium
Skp1 levels were little affected by its modification status. These
data indicate that Skp1 and possibly E3SCFubiquitin-ligase activity
modulate O2-dependent culmination and other developmental
processes, and at least partially mediate the action of the
hydroxylation/glycosylation pathway in O2-sensing.
Submitted by Chris West [[log in to unmask]]
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[End dictyNews, volume 35, number 10]
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