dictyNews
Electronic Edition
Volume 36, number 6
Feb 25, 2011
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Abstracts
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Protein Kinase B Homologue pkbR1 Performs One of Its Roles at First Finger
Stage of Dictyostelium
Hiroshi Ochiai,a,b,c,1 Kosuke Takeda,a† Masashi Fukuzawa,d Atsushi Kato,a,e,f
Shigeharu Takiya,c,e,f Tetsuo Ohmachi, b
a Division of Biological Sciences, Graduate School of Science, Hokkaido University,
Sapporo 060-0810, Japan;
b Department of Biochemistry and Molecular Biology, Faculty of Agriculture & Life
Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki 036-8561, Japan;
c Division of Genome Dynamics, Creative Research Initiative ”Sousei”, Hokkaido
University, Sapporo 060-0810, Japan;
d Department of Biology, Faculty of Agriculture & Life Science, Hirosaki University,
3 Bunkyo-cho, Hirosaki 036-8561, Japan;
e Division of Functional Genome Science, Department of Biological Sciences,
Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan;
f Department of Biological Sciences, Faculty of Science, Hokkaido University, S
apporo 060-0810, Japan
† The present address: Section of Cell and Developmental Biology, Division of
Biological Sciences and Center for Molecular Genetics, University of California,
San Diego, La Jolla, California 92093-0380.
1 Corresponding author
Eukaryotic Cell, in press
Dictyostelium discoideum has protein kinases AKT/PKBA and PKBR1 that belong
to the AGC family of kinases. The protein kinase B related kinase (PKBR1) has
been studied with emphasis on its role in chemotaxis, but its roles in late
development remained so far obscure. The pkbR1 null mutant stays in the first
finger stage for about 16 hr and longer. Only a few aggregates continue to the
migrating slugs stage, however, the slugs immediately go back probably to the
previous first finger stage, and stay there for approximately 37 hr. Finally the
mutant fingers diversify into various multicellular bodies. Expression of the pkbR1
finger protein is probably required for development to the slug stage and to
express ecmB which is first observed in migrating slugs. The mutant also showed
no ST-lacZ expression, which is of the earliest step in differentiation to one of the
stalk cell sub-types. The pkbR1 null mutant forms a small number of aberrant
fruiting bodies but in the presence of 10% of wild-type amoebae the mutant
preferentially forms viable spores, driving the wild type to form non-viable stalk
cells. These results suggest that the mutant has defects in a system that changes
the physiological dynamics in the prestalk cell region of a finger. We suggest that
the arrest of its development is due to loss of the second wave of expression of
a protein kinase A catalytic subunit gene (pkaC) only in the prestalk region of the
pkbR1 null mutant.
Submitted by Hiroshi Ochiai [[log in to unmask]]
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Kin discrimination and possible cryptic species in the social amoeba
Polysphondylium violaceum
Sara E Kalla, David C Queller, Andrea Lasagni, and Joan E Strassmann
BMC Evolutionary Biology 2011, 11:31
Background
The genetic diversity of many protists is unknown. The differences that result
from this diversity can be important in interactions among individuals. The
social amoeba Polysphondylium violaceum, which is a member of the
Dictyostelia, has a social stage where individual amoebae aggregate together
to form a multicellular fruiting body with dead stalk cells and live spores.
Individuals can either cooperate with amoebae from the same clone, or sort
to form clonal fruiting bodies. In this study we look at genetic diversity in
P. violaceum and at how this diversity impacts social behavior.
Results
The phylogeny of the ribosomal DNA sequence (17S to 5.8S region) shows
that P. violaceum is made up of at least two groups. Mating compatibility is
more common between clones from the same phylogenetic group, though
matings between clones from different phylogenetic groups sometimes occurred.
P. violaceum clones are more likely to form clonal fruiting bodies when they are
mixed with clones from a different group than when they are mixed with a clone
of the same group.
Conclusion
Both the phylogenetic and mating analyses suggest the possibility of cryptic
species in P. violaceum. The level of divergence found within P. violaceum is
comparable to the divergence between sibling species in other dictyostelids.
Both major groups A/B and C/D/E/F show kin discrimination, which elevates
relatedness within fruiting bodies but not to the level of clonality. The diminished
cooperation in mixes between groups suggests that the level of genetic
variation between individuals influences the extent of their cooperation.
Submitted by: Sara Kalla [[log in to unmask]]
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[End dictyNews, volume 36, number 6]
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