dictyNews
Electronic Edition
Volume 41, number 15
July 18, 2015

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=========
Abstracts
=========


Absence of catalytic domain in a putative protein kinase C (PkcA) 
suppresses tip dominance in Dictyostelium discoideum 

Wasima Mohamed a, Sibnath Ray b, Derrick Brazill b, Ramamurthy Baskar a,

a Department of Biotechnology, Bhupat and Jyoti Mehta School of 
Biosciences, Indian Institute of Technology Madras, Chennai, 600036, 
India
b Department of Biological Sciences, Center for Translational and Basic 
Research, Hunter College and The Graduate Center of the City University 
of New York, New York, NY 10065


Developmental Biology, in press

A number of organisms possess several isoforms of protein kinase C but 
little is known about the significance of any specific isoform during 
embryogenesis and development. To address this we characterized a PKC 
ortholog (PkcA; DDB_G0288147) in Dictyostelium discoideum. pkcA expression 
switches from prestalk in mound to prespore in slug, indicating a dynamic 
expression pattern. Mutants lacking the catalytic domain of PkcA (pkcA-) 
did not exhibit tip dominance. A striking phenotype of pkcA- was the 
formation of an aggregate with a central hollow, and aggregates later 
fragmented to form small mounds, each becoming a fruiting body. Optical 
density wave patterns of cAMP in the late aggregates showed several cAMP 
wave generation centers. We attribute these defects in pkcA- to impaired 
cAMP signaling, altered cell motility and decreased expression of the cell 
adhesion molecules- CadA and CsaA. pkcA- slugs showed ectopic expression 
of ecmA in the prespore region. Further, the use of a PKC-specific inhibitor, 
GF109203X that inhibits the activity of catalytic domain phenocopied pkcA-.


Submitted by Ramamurthy Baskar [[log in to unmask]] 
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The GATA transcription factor GtaC regulates early developmental gene 
expression dynamics in Dictyostelium

Balaji Santhanam1,2,4, Huaqing Cai3, Peter N. Devreotes3, Gad Shaulsky2,5 
and Mariko Katoh-Kurasawa2,4,5


1 Graduate Program in Structural Computational Biology and Molecular 
Biophysics, Baylor College of Medicine, Houston, TX 77030
2 Department of Molecular and Human Genetics, Baylor College of Medicine, 
Houston, TX 77030
3 Department of Cell Biology, School of Medicine, Johns Hopkins University, 
Baltimore, MD 21205

4 These authors contributed equally to this work. 
5 Corresponding authors


Nature Communications, Article number:7551| doi:10.1038/ncomms8551

In many systems, including the social amoeba Dictyostelium discoideum, 
development is often marked by dynamic morphological and transcriptional 
changes orchestrated by key transcription factors. However, efforts to 
examine sequential genome-wide changes of gene regulation in developmental 
processes have been fairly limited. Here we report the developmental 
regulatory dynamics of GtaC, a GATA-type zinc-finger transcription factor, 
through the analyses of serial ChIP- and RNA-sequencing data. GtaC is 
essential for developmental progression, decoding extracellular cAMP 
pulses during early development and may play a role in mediating cell-type 
differentiation at later stages. We find that GtaC exhibits temporally 
distinctive DNA-binding patterns concordant with each developmental stage. 
We identify direct GtaC targets and observe cotemporaneous GtaC-binding 
and developmental expression regulation. Our results suggest that GtaC 
regulates multiple physiological processes as Dictyostelium transitions 
from a group of unicellular amoebae to an integrated multicellular 
organism.


Submitted by Mariko Katoh-Kurasawa[[log in to unmask]] 
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[End dictyNews, volume 41, number 15]