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dictyNews Volume 22 Number 01
Dicty News
Electronic Edition
Volume 22, number 1
January 23, 2004
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 Dicty-News, the Dicty Reference database and other
useful information is available at dictyBase - http://dictybase.org.
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Abstracts
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Analyses of cDNAs from growth and slug stages of Dictyostelium discoideum
Hideko Urushihara, Takahiro Morio, Tamao Saito, Yuji Kohara, Eiko Koriki,
Hiroshi Ochiai, Mineko Maeda, Jeffrey G. Williams, Ikuo Takeuchi, and
Yoshimasa Tanaka
Nuc. Acids Res., in press
Dictyostelium is a favored model for studying problems in cell and
developmental biology. To comprehend the genetic potential and networks that
direct growth and multicellular development, we are performing a large-scale
analysis of Dictyostelium cDNAs. Here, we newly determine 7,720 nucleotide
sequences of cDNAs from the multicellular, slug stage (S) and 10,439, from
the unicellular, vegetative stage (V). The combined 26,954 redundant ESTs
were computer assembled using the PHRAP pro-gram to yield 5,381 independent
sequences. These 5,381 predicted genes represent about half of the estimated
coding potential of the organism. One third of them were classified into 12
functional categories. Although the overall classification patterns of V
and S libraries were very similar, stage-specific genes exist in every
category. The majority of V-specific genes function in some aspect of protein
translation, while such genes are in a minority in the S-specific and common
populations. Instead, genes for signal transduction and multicellular
organization are enriched in the population of S-specific genes. Genes
encoding the enzymes of basic metabolism are mainly found in the common
gene population. These results therefore suggest major differences between
growing and developing Dictyostelium cells in the nature of the genes
transcribed.
Submitted by: HIDEKO URUSHIHARA [hideko@biol.tsukuba.ac.jp]
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Dictyostelium macroautophagy mutants vary in the severity of their
developmental defects.
Grant P. Otto, Mary Y. Wu, Nevzat Kazgan, O. Roger Anderson, and Richard H. Kessin
Journal of Biological Chemistry, in press
Macroautophagy is the major mechanism that eukaryotes use to recycle cellular
components during stressful conditions. We have previously shown that the
Atg12-Atg5 conjugation system, required for autophagosome formation in yeast,
is necessary for Dictyostelium development. A second conjugation reaction,
Aut7/Atg8 lipidation with phosphatidylethanolamine, as well as a protein kinase
complex and a phosphatidylinositol 3â-kinase complex, are also required for
macroautophagy in yeast. In this study, we characterize mutations in the
putative Dictyostelium discoideum orthologues of budding yeast genes that are
involved in one of each of these functions, ATG1, ATG6 and ATG8. All three
genes are required for macroautophagy in Dictyostelium. Mutant amoebae display
reduced survival during nitrogen starvation and reduced protein degradation
during development. Mutations in the three genes produceaberrant development
with defects of varying severity. As with other Dictyostelium macroautophagy
mutants, development of atg1-1, atg6- and atg8- is more aberrant in plaques on
bacterial lawns than on nitrocellulose filters. The most severe defect is
observed in the atg1-1 mutant, which does not aggregate on bacterial lawns and
arrests as loose mounds on nitrocellulose filters. The atg6- and atg8- mutants
display almost normal development on nitrocellulose filters, producing
multi-tipped aggregates that mature into small fruiting bodies. The
distribution of a green fluorescent protein fusion of the autophagosome marker,
Atg8, is aberrant in both atg1-1 and atg6- mutants.
Submitted by: Grant Otto [go25@columbia.edu]
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[End Dicty News, volume 22, number 1]
