Abstract
Developmental mutants with defects in fruiting body formation are excellent resources for the identification of genetic components that control cellular differentiation processes in filamentous fungi. The mutant pro4 of the ascomycete Sordaria macrospora is characterized by a developmental arrest during the sexual life cycle. This mutant generates only pre-fruiting bodies (protoperithecia), and is unable to form ascospores. Besides being sterile, pro4 is auxotrophic for leucine. Ascospore analysis revealed that the two phenotypes are genetically linked. After isolation of the wild-type leu1 gene from S. macrospora, complementation experiments demonstrated that the gene was able to restore both prototrophy and fertility in pro4. To investigate the control of leu1 expression, other genes involved in leucine biosynthesis specifically and in the general control of amino acid biosynthesis (“cross-pathway control”) have been analysed using Northern hybridization and quantitative RT-PCR. These analyses demonstrated that genes of leucine biosynthesis are transcribed at higher levels under conditions of amino acid starvation. In addition, the expression data for the cpc1 and cpc2 genes indicate that cross-pathway control is superimposed on leucine-specific regulation of fruiting body development in the leu1 mutant. This was further substantiated by growth experiments in which the wild-type strain was found to show a sterile phenotype when grown on a medium containing the amino acid analogue 5-methyl-tryptophan. Taken together, these data show that pro4 represents a novel mutant type in S. macrospora, in which amino acid starvation acts as a signal that interrupts the development of the fruiting body.
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Acknowledgements
I thank Ingeborg Godehardt and Susanne Schlewinski for their excellent technical assistance, Edda Jung for her help in preparing the manuscript, Dr. S. Masloff for generating mutant pro4, Prof. G. Marzluf for providing the leu1 gene from N. crassa, Prof. G. Braus for his advice on analysing the transcriptional expression of cross-pathway-specific genes, Dr. M. Nowrousian for her advice and help in performing qRT-PCR experiments, and Dr. S. Pöggeler for her comments on the manuscript. We are grateful to an anonymous reviewer, who suggested the use of 5-methyl-tryptophan as an alternative amino acid analogue to induce the general control of amino acid biosynthesis. This work is supported by Deutsche Forschungsgemeinschaft (SFB 480, project A1).
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Communicated by C.P. Hollenberg
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Kück, U. A Sordaria macrospora mutant lacking the leu1 gene shows a developmental arrest during fruiting body formation. Mol Genet Genomics 274, 307–315 (2005). https://doi.org/10.1007/s00438-005-0021-8
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DOI: https://doi.org/10.1007/s00438-005-0021-8