|Department:||The Faculty of Bio Sciences|
|Full text PDF:||http://www.ub.uni-heidelberg.de/archiv/18287|
This study was originally designed to investigate the role of global cellular processes like the cell cycle in mediating signal from the circadian clock to rhythmic growth and development in Neurospora crassa. In a first attempt clock control over growth and cell cycle related genes was tested by real-time monitoring of gene expression with a luciferase based assay. It was observed that under conditions, which restrict growth and conidiation, the target genes showed no or poor rhythmicity. In contrast, under native growth conditions or in cultures which overcome growth repression by aging rhythmic gene expression could be observed in any of the target genes. Surprisingly, this included also typical “housekeeping” genes like tubulin, histoneH1 or actin for example. A further hallmark of these rhythms was that they were equal in phase even in genes which had previously been reported to be expressed antiphasic (Sancar et al., 2011). These observations suggest that the luciferase assay may interfere with clock controlled processes which are related to native growth. With a further project the role of clock control over metabolism for rhythmic growth should be analyzed. For this purpose a mutant was characterized which had been shown to be defective in the trehalose synthase clock controlled gene 9 (ccg-9RIP) (Shinohara et al., 2002). The mutant displays the loss of clock control over conidiation and a severe defect in vegetative growth and asexual development. These observations strongly suggested a link between clock control over carbohydrate metabolism and circadian growth. Changes in the transcriptome during conidiation were analyzed in ccg-9RIP. The majority of misregulated genes are related to metabolic functions. However, genotype and phenotype of ccg-9RIP did not cosegregate during backcrossing. A knockout of ccg-9 by gene replacement grew rhythmic and did not show any defect during vegetative growth and asexual development under several conditions. These results demonstrate that ccg-9 does not have any role in circadian growth. Furthermore, the phenotype of ccg-9RIP must be caused by disruption of other genes than ccg-9.