Alternaria alternata can produce alternariol (AOH), alternariol monomethyl ether (AME), altenusin (ALN), and altenuene (ALT) on fruits and vegetables. Much is unknown about the biosynthetic gene clusters (BGCs) of secondary metabolites (SMs) including ALT in A. alternata isolated from strawberries. In the current study, we sequenced the whole genome of AOH- and AME-producing A. alternata KACC 411286 isolated from strawberry jam and carried out comparative analyses of the ALT BGC in its genome with those of other fungal strains after verification of its production of ALN and ALT. Our data showed that the assembled genome of A. alternata KACC 411286 is 34.2 Mb in size with 10 chromosomes. Gene Ontology analysis showed that genes involved in RNA transcription and protein synthesis and turnover are enriched in the genome of A. alternata KACC 411286. We identified a total of 40 SM BGCs, including the ALT BGC, in A. alternata KACC 411286. The comparative analysis showed that ALT BGCs are highly conserved between two A. alternata (KACC 411286 and ATCC 66981) and A. arborescens EGS 39–128. The functional conservation analyses of all six ALT biosynthetic genes also revealed that each gene in A. alternata KACC 411286 shares high amino acid and DNA sequence identity (above 78% identity) with its corresponding gene in four other Alternaria spp. except pksI in A. arborescens EGS 39–128 (55% identity at both the protein and DNA levels) and pksI in A. tenuissima BMP 0304 (53% at the DNA level). Our findings could provide a molecular basis for understanding the biosynthetic mechanisms of SMs, including ALT, in A. alternata KACC 411286 to reduce the contamination of fruits with multiple mycotoxins.
Sung-Yong Hong, Ji-Su Kim, Ae-Son Om· Journal of Fungi· 0 citations
Penitrem A is a toxic secondary metabolite (SM) produced by
Penicillium crustosum
(
P. crustosum
) on various foods such as nuts, dairy products, and fruits. However, the biosynthetic gene clusters (BGCs) responsible for SMs including penitrem A in
P. crustosum
isolated from pears is largely unexplored.
In the current study, we performed whole-genome sequencing of
P. crustosum
KACC 411287, which can produce penitrem A and roquefortine C, and identified its SM BGCs including BGCs of the toxins. Furthermore, we conducted a comparative analysis of the penitrem A and roquefortine C BGCs against those in other fungal strains. We also analyzed the carbohydrate-active enzyme-(CAZyme-) encoding genes in
P. crustosum
KACC 411287, and compared with those of other closely related fungal strains.
The
P. crustosum
KACC 411287 genome is composed of five chromosomes, totaling approximately 32.37 Mb in size. Gene Ontology analysis using 8,520 functionally annotated proteins exhibited that the genome of
P. crustosum
KACC 411287 contains a significant abundance of genes involved in degradation of organonitrogen compounds including amino acids or carbohydrates and fungal self-protective mechanisms including SM biosynthesis. Of the 8,520 functionally annotated proteins, 546 predicted CAZymes were identified in
P. crustosum
KACC 411287. We also detected 68 SM BGCs including penitrem A and roquefortine C BGCs in
P. crustosum
KACC 411287. Furthermore, the conserved functionality analyses exhibited that each gene within the penitrem A BGC in
P. crustosum
KACC 411287 is highly conserved with the corresponding gene in four other penitrem A-producing
Penicillium
strains (above 77% amino acid sequence identity) except for
ptmH
in
P. flavigenum
IBT 14082 (20%). In contrast, the sequence identity decreased significantly (0–69% identity) in two penitrem A non-producing
Penicillium
strains.
Our data strongly indicate that the penitrem A BGCs were highly conserved among
P. crustosum
KACC 411287 and three other penitrem A-producing
Pencillium
strains. Our findings expand our knowledge about the biosynthesis of SMs including penitrem A and roquefortine C in
P. crustosum
KACC 411287 that causes blue mold rot on pears. These results could provide new insight into the biosynthesis of penitrem A and roquefortine C in
P. crustosum
KACC 411287 to find potential approaches for alleviating penitrem A or roquefortine C contamination on pears.
