dictyNews

Electronic Edition

Volume 48, number 17

August 26, 2022



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Abstracts

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An atypical MAPK regulates translocation of a GATA transcription

factor in response to chemoattractant stimulation



Jeffrey A. Hadwiger 1, * ,‡, Huaqing Cai 2, * ,‡, Ramee G. Aranda 1 

and Saher Fatima 1





Journal of Cell Science, published



The Dictyostelium atypical mitogen-activated protein kinase (MAPK)

Erk2 is required for chemotactic responses to cAMP as amoeba 

undergo multicellular development. In this study, Erk2 was found to 

be essential for the cAMP-stimulated translocation of the GATA 

transcription factor GtaC as indicated by the distribution of a GFP–

GtaC reporter. Erk2 was also found to be essential for the

translocation of GtaC in response to external folate, a foraging

signal that directs the chemotaxis of amoeba to bacteria. Erk1, the

only other Dictyostelium MAPK, was not required for the GtaC 

translocation to either chemoattractant, indicating that GFP–GtaC is 

akinase translocation reporter specific for atypical MAPKs. The

translocation of GFP–GtaC in response to folate was absent in mutants 

lacking the folate receptor Far1 or the coupled G-protein subunit 

G-alpha 4. Loss of GtaC function resulted in enhanced chemotactic  

movement to folate, suggesting that GtaC suppresses responses to 

folate. The alteration of four Erk2-preferred phosphorylation sites 

inGtaC impacted the translocation of GFP–GtaC in response to folate

and the GFP–GtaC-mediated rescue of aggregation and development 

of gtaC- cells. The ability of different chemoattractants to stimulate 

Erk2-regulated GtaC translocation suggests that atypical MAPK-

mediated regulation of transcription factors can contribute to 

differentcell fates.





Submitted by Jeff Hadwiger [[log in to unmask]]

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Generating polyketide diversity in Dictyostelium: a Steely hybrid 

polyketide synthase produces alternate products at different 

developmental stages



Tamao Saito1*, Tomoyuki Iijima2, Kohei Koyama2, Tomonori Shinagawa2, 

Ayaka Yamanaka2, Tsuyoshi Araki1, Noriyuki Suzuki1, Toyonobu Usuki1 

and Robert R Kay3*



1 Faculty of Science and Technology, Sophia University, Tokyo 

102-8554, JAPAN

2 Graduate School of Science and Technology, Sophia University, 

Tokyo 102-8554, JAPAN 

3 MRC laboratory of Molecular Biology, Cambridge CB2 0QH, UK



Corresponding authors: Tamao Saito and Robert R Kay





Proceedings of the Royal Society B, in press



Abstract: The soil is a rich ecosystem where many ecological 

interactions are mediated by small molecules, and in which amoebae 

are low-level predators and also prey. The social amoeba Dictyostelium 

discoideum has a high genomic potential for producing polyketides to 

mediate its ecological interactions, including the unique ‘Steely’ 

enzymes, consisting of a fusion between a fatty acid synthase and a 

chalcone synthase. We report here that D. discoideum further increases 

its polyketide potential by using the StlB Steely enzyme, and a 

downstream chlorinating enzyme, to make both a chlorinated signal 

molecule, DIF-1, during its multi-cellular development, and a set of 

abundant polyketides in terminally differentiated stalk cells. We 

identify one of these as a chlorinated dibenzofuran with potent anti-

bacterial activity. To do this, StlB switches expression from prespore 

to stalk cells in late development and is cleaved to release the 

chalcone synthase domain. Expression of this domain alone in StlB null 

cells allows synthesis of the stalk-associated, chlorinated polyketides. 

Thus, by altered expression and processing of StlB, cells make first a 

signal molecule, and then abundant secondary metabolites, which we 

speculate help to protect the mature spores from bacterial infection.





Submitted by Tamao Saito [[log in to unmask]]

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[End dictyNews, volume 48, number 17]