TY - JOUR
T1 - Ribosomal biosynthesis of α-amanitin in Galerina marginata
AU - Luo, Hong
AU - Hallen-Adams, Heather E.
AU - Scott-Craig, John S.
AU - Walton, Jonathan D.
N1 - Funding Information:
We thank Jeff Landgraf, Shari Tjugum-Holland, Christi Hemming, and Kevin Carr of the MSU Research Technology Support Facility (RTSF) for the 454 sequencing and bioinformatics assistance. This research was supported by Grant DE-FG02-91ER20021 to the Plant Research Laboratory from the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, Office of Science, US Department of Energy, and by Grant 1R01-GM088274 from the National Institutes of Health General Medical Sciences.
Funding Information:
Successful amplification of GmAMA1-1 and GmAMA1-2 by reverse transcriptase PCR with gene-specific primers indicated that both genes are transcribed in culture. This conclusion was supported by RNASeq performed at the DOE Joint Genome Institute (unpublished results). More than 50 million expression sequences were obtained from a culture of G. marginata grown on low carbon. Approximately equal numbers of gene-specific sequence reads were obtained from GmAMA1-1 and GmAMA1-2 .
PY - 2012/2
Y1 - 2012/2
N2 - Amatoxins, including α-amanitin, are bicyclic octapeptides found in mushrooms (Agaricomycetes, Agaricales) of certain species in the genera Amanita, Galerina, Lepiota, and Conocybe. Amatoxins and the chemically similar phallotoxins are synthesized on ribosomes in Amanita bisporigera, Amanita phalloides, and Amanita ocreata. In order to determine if amatoxins are synthesized by a similar mechanism in another, distantly related mushroom, we obtained genome survey sequence data from a monokaryotic isolate of Galerina marginata, which produces α-amanitin. The genome of G. marginata contains two copies of the α-amanitin gene (GmAMA1-1 and GmAMA1-2). The α-amanitin proprotein sequences of G. marginata (35 amino acids) are highly divergent from AMA1 of A. bisporigera except for the toxin region itself (IWGIGCNP in single-letter amino acid code) and the amino acids immediately upstream (N[A/S]TRLP). G. marginata does not contain any related toxin-encoding sequences besides GmAMA1-1 and GmAMA1-2. DNA from two other α-amanitin-producing isolates of Galerina (G. badipes and G. venenata) hybridized to GmAMA1, whereas DNA from the toxin non-producing species Galerina hybrida did not. Expression of the GmAMA1 genes was induced by growth on low carbon. RNASeq evidence indicates that both copies of GmAMA1 are expressed approximately equally. A prolyl oligopeptidase (POP) is strongly implicated in processing of the cyclic peptide toxins of A. bisporigera and Conocybe apala. G. marginata has two predicted POP genes; one, like AbPOPB of A. bisporigera, is present only in the toxin-producing isolates of Galerina and the other, like AbPOPA of A. bisporigera, is present in all species. Our results indicate that G. marginata biosynthesizes amatoxins on ribosomes by a pathway similar to Amanita species, involving a genetically encoded proprotein of 35 amino acids that is post-translationally processed by a POP. However, due to the high degree of divergence, the evolutionary relationship between AMA1 in the genera Amanita and Galerina is unclear.
AB - Amatoxins, including α-amanitin, are bicyclic octapeptides found in mushrooms (Agaricomycetes, Agaricales) of certain species in the genera Amanita, Galerina, Lepiota, and Conocybe. Amatoxins and the chemically similar phallotoxins are synthesized on ribosomes in Amanita bisporigera, Amanita phalloides, and Amanita ocreata. In order to determine if amatoxins are synthesized by a similar mechanism in another, distantly related mushroom, we obtained genome survey sequence data from a monokaryotic isolate of Galerina marginata, which produces α-amanitin. The genome of G. marginata contains two copies of the α-amanitin gene (GmAMA1-1 and GmAMA1-2). The α-amanitin proprotein sequences of G. marginata (35 amino acids) are highly divergent from AMA1 of A. bisporigera except for the toxin region itself (IWGIGCNP in single-letter amino acid code) and the amino acids immediately upstream (N[A/S]TRLP). G. marginata does not contain any related toxin-encoding sequences besides GmAMA1-1 and GmAMA1-2. DNA from two other α-amanitin-producing isolates of Galerina (G. badipes and G. venenata) hybridized to GmAMA1, whereas DNA from the toxin non-producing species Galerina hybrida did not. Expression of the GmAMA1 genes was induced by growth on low carbon. RNASeq evidence indicates that both copies of GmAMA1 are expressed approximately equally. A prolyl oligopeptidase (POP) is strongly implicated in processing of the cyclic peptide toxins of A. bisporigera and Conocybe apala. G. marginata has two predicted POP genes; one, like AbPOPB of A. bisporigera, is present only in the toxin-producing isolates of Galerina and the other, like AbPOPA of A. bisporigera, is present in all species. Our results indicate that G. marginata biosynthesizes amatoxins on ribosomes by a pathway similar to Amanita species, involving a genetically encoded proprotein of 35 amino acids that is post-translationally processed by a POP. However, due to the high degree of divergence, the evolutionary relationship between AMA1 in the genera Amanita and Galerina is unclear.
KW - Amanita
KW - Amatoxin
KW - Cyclic peptide
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U2 - 10.1016/j.fgb.2011.12.005
DO - 10.1016/j.fgb.2011.12.005
M3 - Article
C2 - 22202811
AN - SCOPUS:84856777045
SN - 1087-1845
VL - 49
SP - 123
EP - 129
JO - Fungal Genetics and Biology
JF - Fungal Genetics and Biology
IS - 2
ER -