Transcriptomics of the Rice Blast Fungus Magnaporthe oryzae in Response to the Bacterial Antagonist Lysobacter enzymogenes Reveals Candidate Fungal Defense Response Genes

Abstract

Plants and animals have evolved a first line of defense response to pathogens called innate or basal immunity. While basal defenses in these organisms are well studied, there is almost a complete lack of understanding of such systems in fungal species, and more specifically, how they are able to detect and mount a defense response upon pathogen attack. Hence, the goal of the present study was to understand how fungi respond to biotic stress by assessing the transcriptional profile of the rice blast pathogen, Magnaporthe oryzae, when challenged with the bacterial antagonist Lysobacter enzymogenes. Based on microscopic observations of interactions between M. oryzae and wild-type L. enzymogenes strain C3, we selected early and intermediate stages represented by time-points of 3 and 9 hours post-inoculation, respectively, to evaluate the fungal transcriptome using RNA-seq. For comparative purposes, we also challenged the fungus with L. enzymogenes mutant strain DCA, previously demonstrated to be devoid of antifungal activity. A comparison of transcriptional data from fungal interactions with the wild-type bacterial strain C3 and the mutant strain DCA revealed 463 fungal genes that were down-regulated during attack by C3; of these genes, 100 were also found to be up-regulated during the interaction with DCA. Functional categorization of genes in this suite included those with roles in carbohydrate metabolism, cellular transport and stress response. One gene in this suite belongs to the CFEM-domain class of fungal proteins. Another CFEM class protein called PTH11 has been previously characterized, and we found that a deletion in this gene caused advanced lesion development by C3 compared to its growth on the wild-type fungus. We discuss the characterization of this suite of 100 genes with respect to their role in the fungal defense response.

Transcriptomic responses of a simplified soil microcosm to a plant pathogen and its biocontrol agent reveal a complex reaction to harsh habitat

“…However, microbes have evolved strategies not only to fight each other, but in some cases relationships to adapt or support each other, increasing the overall fitness of the community [5]. Despite the widespread occurrence of interspecific microbial interactions in nature and their crucial relevance, there is a lack of understanding about how each species perceives and responds to interactions with other microbes within a complex community [7]. …”

“…Molecular interplay between soil microorganisms has mainly been studied in dual cultures of plant pathogens and biocontrol agents [2, 7–10]. Soil phytopathogenic fungi cause severe diseases in several crops, and Armillaria spp.…”

“…have been extensively studied using several approaches, including transcriptomics [17]. Most transcriptomic studies of microbial biocontrol mechanisms have focused on molecular responses of the biocontrol agent and the target plant pathogen in dual cultures [2, 7, 8, 10, 18]. However, microbial properties in complex consortia often differ from those of their single components [19].…”

Transcriptomic analysis reveals new regulatory roles of Clp signaling in secondary metabolite biosynthesis and surface motility in Lysobacter enzymogenes OH11

“…The antagonistic nature of this bacterium is thought to be due at least in part to the production of a large number of lytic enzymes capable for degrading the cell walls of pathogens (Christensen and Cook 1978; Kobayashi et al 2005) and to the antimicrobial metabolites HSAF (dihydromaltophilin; heat-stable and broad-spectrum antifungal compound with a novel mode of action) (Li et al 2006; Yu et al 2007) and the cyclic lipodepsipeptide WAP-8294A2, which also exhibits anti-MRSA (methicillin-resistant Staphylococcus aureus ) activity (Zhang et al 2011). In addition to its antagonism, L. enzymogenes directly attaches itself to the hypha of fungal pathogens and subsequently causes a pathogenic infection to the fungal host (Mathioni et al 2013; Patel et al 2011). The ability of L. enzymogenes to attach to fungal hypha was shown to be dependent on type IV pilus (T4P), which is a hair-like appendage found on the surface of a wide range of bacteria that is responsible for various roles such as surface motility, host attachment and pathogenesis (Burdman et al 2011; Mattick 2002; Patel et al 2011).…”

Characterization and Phylogenetic Analysis of Magnaporthe spp. strains on VariousHosts in Iran

“…Previously the possibility of biocontrol of Magnaporthe using antagonists was confirmed (3,(25)(26). The fungal and bacterial antagonists showed different reactions against different Magnaporthe strains.…”