Genome-wide functional analysis reveals that infection-related fungal autophagy is necessary for rice blast disease

School of Biosciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, United Kingdom.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 09/2009; 106(37):15967-72. DOI: 10.1073/pnas.0901477106
Source: PubMed


To cause rice blast disease, the fungus Magnaporthe oryzae elaborates specialized infection structures called appressoria, which use enormous turgor to rupture the tough outer cuticle of a rice leaf. Here, we report the generation of a set of 22 isogenic M. oryzae mutants each differing by a single component of the predicted autophagic machinery of the fungus. Analysis of this set of targeted deletion mutants demonstrated that loss of any of the 16 genes necessary for nonselective macroautophagy renders the fungus unable to cause rice blast disease, due to impairment of both conidial programmed cell death and appressorium maturation. In contrast, genes necessary only for selective forms of autophagy, such as pexophagy and mitophagy, are dispensable for appressorium-mediated plant infection. A genome-wide analysis therefore demonstrates the importance of infection-associated, nonselective autophagy for the establishment of rice blast disease.

Download full-text


Available from: Nick Talbot, Oct 09, 2015
23 Reads
  • Source
    • "Interestingly, we found that Δfar1, Δfar2 and Δfar1Δfar2 double mutants were not impaired in lipid body mobilisation to the appressorium, or subsequent lipolysis during turgor generation in the appressorium. This study therefore provides evidence that lipid body mobilisation during appressorium development by M. oryzae, which occurs on the rice leaf surface in the absence of exogenous nutrients and is dependent on autophagy [4], [7], [9], [10], is regulated separately from lipid utilization and independently of Far1 and Far2. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The rice blast fungus Magnaporthe oryzae causes plant disease via specialised infection structures called appressoria. These dome-shaped cells are able to generate enormous internal pressure, which enables penetration of rice tissue by invasive hyphae. Previous studies have shown that mobilisation of lipid bodies and subsequent lipid metabolism are essential pre-requisites for successful appressorium-mediated plant infection, which requires autophagic recycling of the contents of germinated spores and germ tubes to the developing appressorium. Here, we set out to identify putative regulators of lipid metabolism in the rice blast fungus. We report the identification of FAR1 and FAR2, which encode highly conserved members of the Zn2-Cys6 family of transcriptional regulators. We generated Δfar1, Δfar2 and Δfar1Δfar2 double mutants in M. oryzae and show that these deletion mutants are deficient in growth on long chain fatty acids. In addition, Δfar2 mutants are also unable to grow on acetate and short chain fatty acids. FAR1 and FAR2 are necessary for differential expression of genes involved in fatty acid β-oxidation, acetyl-CoA translocation, peroxisomal biogenesis, and the glyoxylate cycle in response to the presence of lipids. Furthermore, FAR2 is necessary for expression of genes associated with acetyl-CoA synthesis. Interestingly, Δfar1, Δfar2 and Δfar1Δfar2 mutants show no observable delay or reduction in lipid body mobilisation during plant infection, suggesting that these transcriptional regulators control lipid substrate utilization by the fungus but not the mobilisation of intracellular lipid reserves during infection-related morphogenesis.
    PLoS ONE 06/2014; 9(6):e99760. DOI:10.1371/journal.pone.0099760 · 3.23 Impact Factor
  • Source
    • "However, we were unable to obtain LRG1 and PAX1 gene deletion mutants from Guy11 after examining more than three hundred transformants from various independent transformation experiments. We therefore used the isogenic Δku70 and Δku80 mutants of Guy11 as recipient strains for deletion of LRG1 and PAX1 because they show high rates of homologous recombination [43], [44]. Hereafter, both Δku70 (Ku70) and Δku80 (Ku80) are described as “wild type” strains due to their phenotypic similarity to Guy11 [43], [44]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: LIM domain proteins contain contiguous double-zinc finger domains and play important roles in cytoskeletal re-organisation and organ development in multi-cellular eukaryotes. Here, we report the characterization of four genes encoding LIM proteins in the rice blast fungus Magnaporthe oryzae. Targeted gene replacement of either the paxillin-encoding gene, PAX1, or LRG1 resulted in a significant reduction in hyphal growth and loss of pathogenicity, while deletion of RGA1 caused defects in conidiogenesis and appressorium development. A fourth LIM domain gene, LDP1, was not required for infection-associated development by M. oryzae. Live cell imaging revealed that Lrg1-GFP and Rga1-GFP both localize to septal pores, while Pax1-GFP is present in the cytoplasm. To explore the function of individual LIM domains, we carried out systematic deletion of each LIM domain, which revealed the importance of the Lrg1-LIM2 and Lrg1-RhoGAP domains for Lrg1 function and overlapping functions of the three LIM domains of Pax1. Interestingly, deletion of either PAX1 or LRG1 led to decreased sensitivity to cell wall-perturbing agents, such as Congo Red and SDS (sodium dodecyl sulfate). qRT-PCR analysis demonstrated the importance of both Lrg1 and Pax1 to regulation of genes associated with cell wall biogenesis. When considered together, our results indicate that LIM domain proteins are key regulators of infection-associated morphogenesis by the rice blast fungus.
    PLoS ONE 02/2014; 9(2):e88246. DOI:10.1371/journal.pone.0088246 · 3.23 Impact Factor
  • Source
    • "Atg26 was identified as a pathogenic factor in C. orbiculare [15], but does not appear to be important for pathogenesis in M. oryzae [19]. In our study, we showed that pexophagy was not dependent on Atg26 in M. oryzae, which may explain the dispensability of Atg26 for M. oryzae pathogenesis [19]. Furthermore, our findings clearly contrast to those reported for C. orbiculare [15,18], where pexophagy is essential for host invasion. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Pexophagy, the degradation of peroxisomes via selective autophagy, depends on Atg20/Snx42 function in Saccharomyces cerevisiae. Besides its role in selective autophagy, Atg20/Snx42 is also involved in an autophagy-independent endosomal retrieval trafficking, in cooperation with two other sorting nexins, Snx41 and Snx4. Recently, we reported that the sorting nexin MoSnx41, which showed high sequence similarity to yeast Snx41 and Snx42/Atg20 proteins, regulates the gamma-glutamyl cycle and GSH production and is essential for conidiation and pathogenicity in Magnaporthe oryzae. Pexophagy was also found to be defective in Mosnx41Δ mutant. These findings indicate that MoSnx41 likely serves combined functions of Snx42/Atg20 and Snx41 in M. oryzae.. In this study, we performed complementation analyses and demonstrate that MoSnx41 alone serves the dual function of protein sorting (ScSnx41) and pexophagy (ScSnx42/Atg20). To study the potential biological function of pexophagy in fungal pathogenic life cycle, we created deletion mutants of potential pexophagy-specific genes, and characterized them in terms of pexophagy, conidiation and pathogenesis. We identified Pex14 as an essential protein for pexophagy in M. oryzae. Overall, our results show that pexophagy per se is not essential for asexual development or virulence in M. oryzae.
    PLoS ONE 11/2013; 8(11):e79128. DOI:10.1371/journal.pone.0079128 · 3.23 Impact Factor
Show more