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Identification and characterization of secreted and pathogenesis-related proteins in Ustilago maydis.

ABSTRACT: Interactions between plants and fungal pathogens require a complex interplay at the plant-fungus interface. Extracellular effector proteins are thought to play a crucial role in establishing a successful infection. To identify pathogenesis-related proteins in Ustilago maydis we combined the isolation of secreted proteins using a signal sequence trap approach with bioinformatic analyses and the subsequent characterization of knock-out mutants. We identified 29 secreted proteins including hydrophobins and proteins with a repetitive structure similar to the repellent protein Rep1. Hum3, a protein containing both, a hydrophobin domain and a repetitive Rep1-like region, is shown to be processed during passage through the secretory pathway. While single knock-outs of hydrophobin or repellent-like genes did not affect pathogenicity, we found a strong effect of a double knock-out of hum3 and the repetitive rsp1. Yeast-like growth, mating, aerial hyphae formation and surface hydrophobicity were unaffected in this double mutant. However, pathogenic development in planta stops early after penetration leading to a complete loss of pathogenicity. This indicates that Hum3 and Rsp1 are pathogenicity proteins that share an essential function in early stages of the infection. Our results demonstrate that focusing on secreted proteins is a promising way to discover novel pathogenicity proteins that might be broadly applied to a variety of fungal pathogens.

SUBMITTER: Muller O

PROVIDER: S-EPMC2757621 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

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Identification and characterization of secreted and pathogenesis-related proteins in Ustilago maydis.

Müller Olaf O Schreier Peter H PH Uhrig Joachim F JF

Molecular genetics and genomics : MGG 20071005 1

Interactions between plants and fungal pathogens require a complex interplay at the plant-fungus interface. Extracellular effector proteins are thought to play a crucial role in establishing a successful infection. To identify pathogenesis-related proteins in Ustilago maydis we combined the isolation of secreted proteins using a signal sequence trap approach with bioinformatic analyses and the subsequent characterization of knock-out mutants. We identified 29 secreted proteins including hydropho ...[more]

PMID: 17917743

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Project description:Analyzing culture supernatants of yeast and hyphal cells of Candida albicans by mass spectrometry, we found two close homologues of pathogenesis-related (PR-) 1 proteins, Rbe1p and Rbt4p, in the secretome of this human pathogen. By sequence homology, we assigned three yet not characterized open reading frames, ORF19.6200, ORF19.2787 and ORF19.2336, in addition to Rbe1p and Rbt4p to a novel family of proteins. Correspondent with our secretome analysis RBE1 was expressed in blastospores and opaque cells, whereas transcription was down-regulated in hyphae. On the contrary, RBT4 was up-regulated in hyphae and down-regulated in opaque cells. Remarkably, transcription of RBT4 and RBE1 was each up-regulated in blastospores of M-bM-^HM-^Frbe1 or hyphae of M-bM-^HM-^Frbt4 deletion strains, respectively, indicating a compensatory function of both proteins. In a M-bM-^HM-^Frbe1/M-bM-^HM-^Frbt4 double deletion strain, genome-wide transcriptional analysis showed differential transcription of a limited set of genes that are also implicated in virulence and oxidative stress response. In this context, deletion of RBE1 or RBT4 in a clinical C. albicans isolate resulted in a moderate but significant attenuation in virulence in a mouse model for disseminated candidiasis. However, a synergistic effect was observed in the M-bM-^HM-^Frbe1/M-bM-^HM-^Frbt4 double deletion strain, where virulence was strongly affected. Furthermore, the double deletion strain showed increased sensitivity to attack by polymorphonuclear leukocytes (neutrophils). Therfore, our data suggest that the crucial contribution of both C. albicans pathogenesis-related proteins for in vivo virulence results at least partially from reduced survival in phagocytes. Experiments were performed under blastospore (YPD) as well as hyphae (alpha-MEM)-inducing conditions. In total, three biological replicates were performed for each condition. All experiments were performed as dye swaps. Thus, in total six arrays have been hybridzed for each comparison (alpha-MEM and YPD, respectively). Hybridization experiments included a reference strain (C. albicans SC5314) and a double deletion strain (C. albicans MRC27). The array included one technical replicate of each probe.

Dataset Information

Identification and characterization of secreted and pathogenesis-related proteins in Ustilago maydis.

Publications

Identification and characterization of secreted and pathogenesis-related proteins in Ustilago maydis.

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