Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSGenome-wide analysis of light responses in Mucor circinelloides. Victoriano Garre, Sergio López-García, Eusebio Navarro, Santiago Torres-Martínez.Departamento de Genética y Microbiología, Universidad de Murcia, 30100 Murcia, Spain.Light regulates developmental and physiological processes in a wide range of fungi. Particularly, Zygomycete fungi have developed complex mechanismsto control the responses to light that await detailed characterization at molecular level. The zygomycete Mucor circinelloides is a good model for thispurpose because its genome has been sequenced and several molecular tools are available. Mucor, like other Zygomycetes, has three white collar-1 genes(mcwc-1a, mcwc-1b and mcwc-1c) that code for proteins which present characteristics of photoreceptors. Each mcwc-1 gene controls a specific responseto light. Thus, mcwc-1a and mcwc-1c control phototropism and photocarotenogenesis, respectively, whereas the mcwc-1b function in regulation by lighthas not been proved. In order to deepen in the regulation by light in Mucor, a systematic approach using microarrays was followed to characterize whitelight-inducible transcriptional changes in wild-type and knockout mutants for each mcwc-1 gene. Analysis of microarray data revealed that light is mainly apositive signal for transcription in Mucor, as in other fungi, since 123 genes were up-regulated in the wild-type strain in response to light, whereas only 26were down-regulated, considering a threshold of threefold change. Genes strongly induced by light included genes known to be up-regulated by light, likethe carotenogenic gene carB (74-fold), cryptochrome (45-fold) and mcwc-1c (22-fold), supporting reliability of the microarray data. Although many of upregulatedgenes code for proteins implicated in protection against light-induced damage, several of them code for protein involved in signal transductionthat could be involved in light responses like phototropism. Transcriptomic analysis of mcwc-1 mutants showed that induction of around 60% of the genesis mediated by mcwc-1a, whereas only 1% is mediated by mcwc-1c and none is mediated by mcwc-1b, suggesting that mcwc-1a is the main photoreceptor.Searching for cis-acting regulatory motifs upstream of genes regulated by mcwc-1a identified consensus sequences similar to those found in lightregulated genes of Neurospora crassa. Moreover, the identification of a small group of genes regulated by the three mcwc-1 genes points out that thethree proteins form complexes to regulate gene expression. Funded by MINECO (BFU2012-32246), Spain.Shedding light on secondary metabolite cluster gene expression, sporulation, UV-damage repair and carotenogenesis in the rice pathogen Fusariumfujikuroi. Phillipp Wiemann, Bettina Tudzynski. Institut für Biologie und Biotechnologie der Pflanzen Westfälische Wilhelms-Universität MünsterSchlossplatz 8 48143 Münster Germany.The rice pathogen Fusarium fujikuroi produces economically important secondary metabolites like gibberellic acids and carotenoids as well asmycotoxins like bikaverin and fusarin C. Their production is activated in response to environmental stimuli such as light, pH or nutrient availability. In thisstudy, we evaluate the effects of light and different putative light receptors on growth and differentiation as well as secondary metabolism. Bimolecularfluorescence complementation proved that homologs of the Neurospora crassa White Collar proteins in F. fujikuroi (WcoA and WcoB) form a nuclearlocalized complex (WCC) that is needed for full functionality. Deletion and complementation of both genes revealed that the WCC represses bikaverin geneexpression in constant light conditions and induces immediate light-dependent carotenoid gene expression as shown by northern blot analyses.Additionally the WCC represses conidiogenesis in response to light. The effects observed regarding bikaverin and carotenoid gene expressions as well asconidiogenesis are antagonistically to the ones observed in the velvet mutant, making a connection between the WCC and the velvet complex feasible,similarly to the situation in Aspergillus nidulans. Since carotenoid production was maintained in both wcoA and wcoB single as well as in wcoA/B doublemutants in constant light conditions, we focused on characterization of additional putative light receptors in F. fujikuroi. Deletion of the phytochrome-likeencodinggene fph1 did not show any significant phenotype. Deletion of phl1, coding for a cryptochrome/photolyase demonstrated impaired carotenoidbiosynthesis gene expression upon exposure to light. Additionally, gene expression and HPLC analyses of these mutants demonstrated loss of fusarin Cgene expression and concomitant production formation compared to the wild type, suggesting a distinct transcriptional activity for this barelycharacterized class of enzymes. Finally UV mutagenesis experiments and qRT-PCR demonstrate that WcoA, WcoB and Phl1 are involved in UV-damagerepair most likely by transcriptionally activating phr1, encoding a CPD-photolyase. The data presented here allow us to draw a first model of how lightreceptors function in a signaling network in the rice pathogen F. fujikuroi.92