Deising, Holger B.

Heilmann, Jessica

Lange, Mario

Raschke, Anja

English

JKI Open Journal Systems (Julius Kühn-Institut)

11th Young Scientists Meeting 2018, Braunschweig, Germany, November 14-16 Raschke et al. Transcriptional regulation of iron homeosta-sis of the hemibiotrophic phytopathogen Colletotrichum graminicola Anja Raschke1,2, Jessica Heilmann1, Mario Lange1,2 and Holger B. Deising1,2 1 Martin Luther University Halle-Wittenberg, Department of Phytopathology and Plant Protection, Halle (Saale) 2 Martin Luther University Halle-Wittenberg, Interdisciplinary Center for Crop Plant Research, Halle (Saale) E-mail of corresponding author: anja.raschke@landw.uni-halle.deIron is an essential microelement for all organisms. Due to its low solubility com-bined with the potential to produce dam-aging highly reactive oxygen species, a tight regulation of iron uptake and stor-age is essential for all living cells. Pathogenic fungi employ several strate-gies for iron uptake from the host tissue: (i) reductive iron assimilation (RIA), (ii) si-derophore-mediated Fe3+ acquisition(SIA), (iii) heme uptake, and (iv) low affin-ity iron uptake. As free heme is rare inmaize - the host plant of Colletotrichumgraminicola - this hemibiotrophic fungusmainly applies RIA and SIA. Saprophytichyphae growth under iron starvationleads to an up-regulation of both RIA andSIA pathways. During the biotrophicstage of infection RIA is highly active,while SIA is specifically suppressed. Thesubsequent necrotrophic stage is charac-terized by a reversal in the iron uptakespecificity. Maize leaves pretreated withthe C. graminicola siderophore Coprogenrespond with an increased defense reac-tion including respiratory burst whenthese leaves were infected later on.In contrast, Coprogen alone did not in-duce a defense response. This revealsthat C. graminicola specifically repressesthe SIA pathway, possibly to evade plantrecognition. During the necrotrophicphase such hiding is no longer required.This strategy resembles the specific re-pression of the synthesis of β-1,3-Glu-cane, a pathogen associated molecular pattern (PAMP), during biotrophy.  In other fungal species the tight regula-tion of the SIA und RIA pathways occurs on transcriptional level mediated by two transcription factors SreA and HapX, re-spectively. However, the so far studied Aspergillus spp. were either necrotrophs or saprophytes. Here we report on the identification of sreA and hapX homologs from the hemibiotrophic fungus C. gram-inicola that were denominated as CgSRE1 and CgHAP10. We showed that both genes are iron-dependent regulated on transcriptional level in saprophytic hy-phae. Targeted deletions of these loci led to delayed growth in response to iron availability. Remarkably, the Δsre1 strain showed altered hyphal morphology re-sembling cell wall-deficient mutants. Cell wall deficiency, therefore, could be re-sponsible for the reduced virulence of ΔCgsre1.  Detailed functional characterization of the putative transcription factors CgSre1 and CgHap10 during biotrophic and ne-crotrophic stages will gain further knowledge of iron acquisition and regula-tion of iron homeostasis in fungal viru-lence and provide valuable data to de-velop novel plant protection strategies.  52 Berichte aus dem Julius Kühn-Institut 200

Transcriptional regulation of iron homeostasis of the hemibiotrophic phytopathogen Colletotrichum graminicola

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Transcriptional regulation of iron homeostasis of the hemibiotrophic phytopathogen Colletotrichum graminicola

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