Abstract
BackgroundThe Ambrosia Fusarium Clade phytopathogenic Fusarium fungi species have a symbiotic relationship with ambrosia beetles in the genus Euwallacea (Coleoptera: Curculionidae). Related beetle species referred to as Euwallacea sp. near fornicatus have been spread in California, USA and are recognized as the causal agents of Fusarium dieback, a disease that causes mortality of many plant species. Despite the importance of this fungi, no transcriptomic resources have been generated. The datasets described here represent the first ever transcripts available for these species. We focused our study on the isolated species of Fusarium that is associated with one of the cryptic species referred to as Kuroshio Shot Hole Borer (KSHB) Euwallacea sp. near fornicatus.ResultsHydrogen concentration is a critical signal in fungi for growth and host colonization, the aim of this study was to evaluate the effect of different pH conditions on growth and gene expression of the fungus Fusarium sp. associated with KSHB. An RNA-seq approach was used to compare the gene expression of the fungus grown for 2 weeks in liquid medium at three different pH levels (5.0, 6.0, and 7.0). An unbuffered treatment was included to evaluate the capability of the fungus to change the pH of its environment and the impact in gene expression. The results showed that the fungus can grow and modulate its genetic expression at different pH conditions; however, growth was stunted in acidic pH in comparison with neutral pH. The results showed a differential expression pattern in each pH condition even when acidic conditions prevailed at the end of the experiment. After comparing transcriptomics data from the three treatments, we found a total of 4,943 unique transcripts that were differentially expressed.ConclusionsWe identified transcripts related to pH signaling such as the conserved PAL/RIM pathway, some transcripts related to secondary metabolism and other transcripts that were differentially expressed. Our analysis suggests possible mechanisms involved in pathogenicity in this novel Fusarium species. This is the first report that shows transcriptomic data of this pathogen as well as the first report of genes and proteins involved in their metabolism identifying potential virulence factors.
Highlights
The Ambrosia Fusarium Clade phytopathogenic Fusarium fungi species have a symbiotic relationship with ambrosia beetles in the genus Euwallacea (Coleoptera: Curculionidae)
Considering that for Fusarium sp. associated with KSBH some of these polyketide synthases (PKS) are represented by partial OFRs, we looked for their complete coding sequences in the genome of Fusarium sp. associated with KSBH which has been recently announced [70] and was generated from the same strain used in this study
Identity of the strain used in this study Based on the phylogenetic analysis, the strain HFEW16-IV-019 used in this study is grouped with isolates corresponding to Fusarium sp. associated with KSBH that were collected in the locations of El Cajon, Fallbrook, Bonsall and Escondido, CA
Summary
The Ambrosia Fusarium Clade phytopathogenic Fusarium fungi species have a symbiotic relationship with ambrosia beetles in the genus Euwallacea (Coleoptera: Curculionidae). Hydrogen ion concentration (pH) is a critical host environment variable which can limit or enhance the growth of the phytopathogenic fungi and its ability to compromise the host defense response through the secretion of pathogenicity factors such as hydrolytic enzymes [1,2,3] and the production of toxins [4, 5]. It has been reported that fusaric acid, through nitric oxide signaling, induces programmed cell death in their plant hosts [9] These studies show that some pathogens have the ability to modulate environmental pH [10]
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