Peanut scab caused by
Elsinoë arachidis
is found throughout China’s peanut-growing areas. Elsinochrome produced by
E
.
arachidis
is a perylenequinone photosensitive mycotoxin vital to the pathogenic process of the pathogen. In this study, the complex mechanism underlying the regulation of elsinochrome biosynthesis by
E
.
arachidis
was investigated based on various nutritional and environmental factors. The initiation of elsinochrome biosynthesis depends on light.
E
.
arachidis
produced substantially more quantities of elsinochrome when grown on a semi-synthetic medium (PDA) than when grown on synthetic media with defined ingredients in the presence of light. Elsinochrome accumulation decreased when adjusted with either citrate or phosphate buffers and changing pH suppressed the radical growth. At temperatures ranging from 10°C to 25°C, the production of elsinochrome increased, peaking at 28°C, and it decreased slightly at 30°C. 63 field-collected isolates from China were assessed for the level of elsinochrome production, and pathogenicity analysis was conducted by selecting 12 strains from each 3 of the 4 groups with different levels of elsinochrome production. A direct correlation was observed between elsinochrome production and pathogenicity among the isolates. The results showed elsinochrome biosynthesis to be controlled by
E
.
arachidis
and showed elsinochrome to be a vital virulence factor of
E
.
arachidis
, required for disease severity.
Elsinochromes (ESCs) are virulence factors produced by Elsinoë arachidis which is the cause of peanut scab. However, the biosynthesis pathway of ESCs in E. arachidis has not been elucidated and the potential pathogenic mechanism of E. arachidis is poorly understood. In this study, we report a high-quality genome sequence of E. arachidis. The size of the E. arachidis genome is 33.18Mb, which is comparable to the Ascomycota genome (average 36.91 Mb), encoding 9174 predicted genes. The self-detoxification family including transporters and cytochrome P450 enzymes were analysis, candidate effectors and cell wall degrading enzymes were investigated as the pathogenicity genes by using PHI and CAZy databases. Additionally, the E. arachidis genome contains 24 secondary metabolism gene clusters, in which ESCB1 was identified as the core gene of ESC biosynthesis. Taken together, the genome sequence of E. arachidis provides a new route to explore its potential pathogenic mechanism and the biosynthesis pathway of ESCs.
Background: Elsinoë arachidis, an important peanut pathogenic fungus that distributes widely and leads to large-scale losses in peanut producing regions in China, produce elsinochromes (ESCs) as the vital toxin through pathogenic process. However, the biosynthesis of elsinochromes have not been investigated and the transcriptional response of the light on synthesis of elsinochrome in Elsinoë is poorly understood. Results: In this paper, high-quality genome of E. arachidis by PacBio RS II sequencing method was reported. The 33.18Mb genome encodes 9056 predicted genes, of which the proportion of genes encoding secreted proteins 8.0% (734 secreted proteins), 124 transporter-related genes, 949 signal peptides, 1,829 transmembrane protein-coding genes, 127 non-coding RNAs and 13 pseudogenes. Mapped the E. arachidis assembly to 16 scaffold that contain 86 secondary metabolites gene clusters, including six polyketide synthase gene clusters encoding two melanin, one elsinochromes and three T-toxin were also identified in the genome. Additionally, ESC biosynthesis-related gene cluster predicted to contain ESCB1 which was high expression under light condition. Conclusion: Analysis of genomic information of E. arachidis lays a solid molecular data foundation for further exploration of pathogenic mechanisms and toxin biosynthesis pathways. Taken together, we provide a valuable foundation in the biosynthesis of elsinochrome and essential information for further comprehend its virulence mechanism.
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