dictyNews Electronic Edition Volume 40, number 28 November 07, 2014 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= Article for the ÒFree-living amoebae Special IssueÓ:Isolation and characterisation of various amoebophagous fungi and evaluation of their prey spectrum Rolf Michel, JuliaWalochnik, Patrick Scheid Experimental Parasitology This article gives an overview on the isolation and characterisation of endoparasitic fungi invading freeliving amoebae (FLA), including the ones forming thalli inside their hosts such as Cochlonema euryblastum and also the predatory fungi which capture amoebae by adhesive hyphae. They trap, intrude, and exploit amoebal trophozoites such as Acaulopage spp. and Stylopage spp. Previous phylogenetic studies proved Cochlonema to be a member of the Zoopagales. The genetic investigation of Acaulopage tetraceros demonstrated its close relationship to Cochlonema. Co-cultivation of A. tetraceros with a number of FLA revealed a great prey spectrum of this amoebophageous fungus. In addition it was shown that solitary amoebal stages of slime moulds such as Dictyostelium sp. and Physarum sp. are also suited as welcome prey amoebae. Submitted by Rolf Michel [r.michel1@gmx.de] ---------------------------------------------------------------------- The Social Amoeba Polysphondylium pallidum Loses Encystation and Sporulation, but Can Still Erect Fruiting Bodies in the Absence of Cellulose. Du Q, Schaap P. Protist. 2014 Jul 14;165(5):569-579. doi: 10.1016/j.protis.2014.07.003. Amoebas and other freely moving protists differentiate into walled cysts when exposed to stress. As cysts, amoeba pathogens are resistant to biocides, preventing treatment and eradication. Lack of gene modification procedures has left the mechanisms of encystation largely unexplored. Genetically tractable Dictyostelium discoideum amoebas require cellulose synthase for formation of multicellular fructifications with cellulose-rich stalk and spore cells. Amoebas of its distant relative Polysphondylium pallidum (Ppal), can additionally encyst individually in response to stress. Ppal has two cellulose synthase genes, DcsA and DcsB, which we deleted individually and in combination. Dcsa- mutants formed fruiting bodies with normal stalks, but their spore and cyst walls lacked cellulose, which obliterated stress-resistance of spores and rendered cysts entirely non-viable. A dcsa-/dcsb- mutant made no walled spores, stalk cells or cysts, although simple fruiting structures were formed with a droplet of amoeboid cells resting on an sheathed column of decaying cells. DcsB is expressed in prestalk and stalk cells, while DcsA is additionally expressed in spores and cysts. We conclude that cellulose is essential for encystation and that cellulose synthase may be a suitable target for drugs to prevent encystation and render amoeba pathogens susceptible to conventional antibiotics. Submitted by Qingyou Du [q.du@dundee.ac.uk] ---------------------------------------------------------------------- Deckstein, J., van Appeldorn, J., Tsangarides, M., Yiannakou, K., MŸller, R., Stumpf, M., Sukumaran, S. K., Eichinger, L., Noegel, A. A., Riyahi, T. Y. The Dictyostelium discoideum GPHR ortholog is an ER and Golgi protein with roles during development. Eukaryotic Cell, in press The Dictyostelium discoideum GPHR (Golgi pH regulator)/Gpr89 is a developmentally regulated transmembrane protein present on the endoplasmic reticulum (ER) and the Golgi apparatus. Transcript levels are low during growth and vary during development reaching high levels during aggregation and late developmental stages. The Arabidopsis ortholog was described as a G protein coupled receptor (GPCR) for abscisic acid present at the plasma membrane whereas the mammalian ortholog is a Golgi-associated anion channel functioning as Golgi pH regulator. To probe its role in D. discoideum we generated a strain lacking GPHR. The mutant had different growth characteristics compared to the AX2 parent strain and exhibited changes during late development and formed abnormally shaped small slugs and fruiting bodies. An analysis of development specific markers revealed that their expression was disturbed. The distribution of the endoplasmic reticulum and the Golgi was unaltered at the immunofluorescence level. Likewise, their function did not appear to be impaired since membrane proteins were properly processed and glycosylated. Also, changes in the external pH were sensed by the ER as indicated by a pH sensitive ER probe as in wild type. Submitted by Angelika Nšgel [noegel@uni-koeln.de] ---------------------------------------------------------------------- The Dictyostelium MAPK ERK1 is phosphorylated in a secondary response to early developmental signaling David J. Schwebs and Jeffrey A. Hadwiger* Department of Microbiology and Molecular Genetics, Oklahoma State University, 307 Life Sciences East, Stillwater, OK 74078 USA Cellular Signaling, in press Previous reports have suggested that the two mitogen-activated protein kinases (MAPKs) in Dictyostelium discoideum, ERK1 and ERK2, can be directly activated in response to external cAMP even though these MAPKs play different roles in the developmental life cycle. To better characterize MAPK regulation, the levels of phosphorylated MAPKs were analyzed in response to external signals. Only ERK2 was rapidly phosphorylated in response to the chemoattractants, cAMP and folate. In contrast, the phosphorylation of ERK1 occurred as a secondary or indirect response to these stimuli and this phosphorylation was enhanced by cell-cell interactions, suggesting that other external signals can activate ERK1. The phosphorylation of ERK1 or ERK2 did not require the function of the other MAPK in these responses. Folate stimulation of a chimeric population of erk1- and galpha4- cells revealed that the phosphorylation of ERK1 could be mediated through an intercellular signal other than folate. Loss of ERK1 function suppressed the developmental delay and the deficiency in anterior cell localization associated with galpha5- mutants suggesting that ERK1 function can be down regulated through Galpha5 subunit-mediated signaling. However, no major changes in the phosphorylation of ERK1 were observed in galpha5- cells suggesting that the Galpha5 subunit signaling pathway does not regulate the phosphorylation of ERK1. These findings suggest that the activation of ERK1 occurs as a secondary response to chemoattractants and that other cell-cell signaling mechanisms contribute to this activation. Galpha5 subunit signaling can down regulate ERK1 function to promote prestalk cell development but not through major changes to the level of phosphorylated ERK1. Submitted by Jeff Hadwiger [jeff.hadwiger@okstate.edu] ============================================================== [End dictyNews, volume 40, number 28]