Abstract
More than 200 plants have been suffering from Verticillium wilt caused by Verticillium dahliae (V. dahliae) across the world. The target of rapamycin (TOR) is a lethal gene and controls cell growth and development in various eukaryotes, but little is known about TOR signaling in V. dahliae. Here, we found that V. dahliae strain is hypersensitive to rapamycin in the presence of rapamycin binding protein VdFKBP12 while the deletion mutant aaavdfkbp12 is insensitive to rapamycin. Heterologous expressing VdFKBP12 in Arabidopsis conferred rapamycin sensitivity, indicating that VdFKBP12 can bridge the interaction between rapamycin and TOR across species. The key across species of TOR complex 1 (TORC1) and TORC2 have been identified in V. dahliae, suggesting that TOR signaling pathway is evolutionarily conserved in eukaryotic species. Furthermore, the RNA-seq analysis showed that ribosomal biogenesis, RNA polymerase II transcription factors and many metabolic processes were significantly suppressed in rapamycin treated cells of V. dahliae. Importantly, transcript levels of genes associated with cell wall degrading enzymes (CWEDs) were dramatically down-regulated in TOR-inhibited cells. Further infection assay showed that the pathogenicity of V. dahliae and occurrence of Verticillium wilt can be blocked in the presence of rapamycin. These observations suggested that VdTOR is a key target of V. dahliae for controlling and preventing Verticillium wilt in plants.
Highlights
Verticillium dahliae (V. dahliae) is a soil-borne and hemibiotrophic fungus that causes over 200 plant species wilting including Brassicaceae, Rosaceae, and Solanaceae plants, resulting in tremendous economic losses every year (Pegg and Brady, 2002; Inderbitzin and Subbarao, 2014; Gomez-Lama Cabanas et al, 2015; Chen et al, 2017)
We found that the mycelial growth of V. dahliae was retarded by RAP, implying that VdFKBP12 may be functional in mediate RAP and VdTOR
V. dahliae is the main pathogen of Verticillium wilt, which is a devastating plant disease that causes a variety of economic crops wilting, including cotton, tomato, and eggplant (Pegg and Brady, 2002; Inderbitzin and Subbarao, 2014)
Summary
Verticillium dahliae (V. dahliae) is a soil-borne and hemibiotrophic fungus that causes over 200 plant species wilting including Brassicaceae, Rosaceae, and Solanaceae plants, resulting in tremendous economic losses every year (Pegg and Brady, 2002; Inderbitzin and Subbarao, 2014; Gomez-Lama Cabanas et al, 2015; Chen et al, 2017). The plant cell wall is an important interface for the interaction between host and phytopathogenic fungi, which plays a major barrier role in the process of phytopathogenic fungi invading the host. Most fungal pathogens secrete lots of cell wall degrading enzymes (CWDEs) including cellulases, xylanases, and pectinases to depolymerize the host cell wall (Tonukari, 2003; Quoc and Chau, 2017). V. dahliae have been reported to produce CWDEs for degrading plant cell wall (Cooper and Wood, 1980; Tzima et al, 2011; Chen et al, 2016). The EG-1 gene homolog VdEg-1 plays an important role in plant penetration and colonization. Pectinases play a critical role in pathogenesis and production levels correlated with pathogenicity in different Verticillium strains (Durrands and Cooper, 1988; Fradin and Thomma, 2006; Tzima et al, 2011; Chen et al, 2016)
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