Special Interest Group Meeting

Gene regulation mediated through a red- and blue-light sensing protein complex in Aspergillus nidulans

Julio Rodriguez-Romero, Maren Hedtke and Reinhard Fischer, Department of Microbiology. Karlsruhe Institute of Technolgy (KIT), Karlsruhe, Germany

A. nidulans develops mainly asexually in the light and mainly sexually in the dark. We have discovered phytochrome (FphA) as a red-light sensor (3), and found that the blue-light receptor system proteins LreA (WC-1) and LreB (WC-2) along with VeA form a light-regulator complex (LRC)(2). We propose a functional relationship and a cross-talk between both photoreceptors.

In order to identify light-regulated genes, we used a two-colour microarray system. After 30 minutes of illumination about 260 genes (approx. 2.5% of the whole genome) were differentially regulated. 209 genes were up- and 51 down-regulated. Some of those genes display homology to other photo-inducible genes identified previously in N. crassa like ccg-1, con-10, con-6.

The regulation of conJ^con-10 and ccgA^ccg-1 has been studied in detail. Differential expression of conJ and ccgA was confirmed by real time PCR. Blue- and red- light induced the transcription of both genes, although to a lower extent than the combination of blue and red light. Surprisingly, we found that the induction by blue light required FphA and red light induction was partially dependent on LreA. Thus, we propose a functional interconnection between both photoreceptors. Furthermore using chromatin IP (ChIP), we found that the LRC binds directly to the promoters of conJ and ccgA. We do have evidence that not only the WC homologues are able to bind DNA but also the phytochrome FphA. Phytochrome-DNA interaction occurs probably through the response regulator domain at the carboxy terminus of FphA.

References

1. C. H. Chen, et al., EMBO J 28, 1029-42 (2009).
2. J. Purschwitz, et al., Mol Genet Genomics (2008).
3. A. Blumenstein, et al., Curr Biol 15, 1833-8 (2005).