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Two linked genes encoding a secreted effector and a membrane protein are essential for Ustilago maydis ‐induced tumour formation
Author(s) -
Doehlemann Gunther,
Reissmann Stefanie,
Aßmann Daniela,
Fleckenstein Martin,
Kahmann Regine
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2011.07728.x
Subject(s) - ustilago , biology , effector , mutant , gene , microbiology and biotechnology , exocyst , transmembrane protein , phenotype , transmembrane domain , fungal protein , genetics , receptor , protein subunit
Summary Ustilago maydis is a biotrophic fungal pathogen that colonizes living tissue of its host plant maize. Based on transcriptional upregulation during biotrophic development we identified the pit ( p roteins i mportant for t umours) cluster, a novel gene cluster comprising four genes of which two are predicted to encode secreted effectors. Disruption of the gene cluster abolishes U. maydis ‐induced tumour formation and this phenotype can be caused by deleting either pit1 encoding a transmembrane protein or pit2 encoding a secreted protein. Pit1 localizes to the fungal plasma membrane at hyphal tips, endosomes and vacuoles while Pit2 is secreted to the biotrophic interface. Both Δ pit1 and Δ pit2 mutants are able to penetrate maize epidermis and grow intracellularly at sites of infection but fail to spread in the infected leaf. Microarray analysis shows an indistinguishable response of the plant to infection by Δ pit1 and Δ pit2 mutant strains. Transcriptional activation of maize defence genes in infections with Δ pit1 /2 mutant strains indicates that the mutants have a defect in suppressing plant immune responses. Our results suggest that the activity of Pit1 and Pit2 during tumour formation might be functionally linked and we discuss possibilities for a putative functional connection of the two proteins.