Data from: Expansion and diversification of the MSDIN family of cyclic peptide genes in the poisonous agarics Amanita phalloides and A. bisporigera

Background: The cyclic peptide toxins of Amanita mushrooms, such as
α-amanitin and phalloidin, are encoded by the “MSDIN” gene family and
ribosomally biosynthesized. Based on partial genome sequence and PCR
analysis, some members of the MSDIN family were previously identified in
Amanita bisporigera, and several other members are known from other
species of Amanita. However, the complete complement in any one species,
and hence the genetic capacity for these fungi to make cyclic peptides,
remains unknown. Results: Draft genome sequences of two cyclic
peptide-producing mushrooms, the “Death Cap” A. phalloides and the
“Destroying Angel” A. bisporigera, were obtained. Each species has ~30
MSDIN genes, most of which are predicted to encode unknown cyclic
peptides. Some MSDIN genes were duplicated in one or the other species,
but only three were common to both species. A gene encoding cycloamanide
B, a previously described nontoxic cyclic heptapeptide, was also present
in A. phalloides, but genes for antamanide and cycloamanides A, C, and D
were not. In A. bisporigera, RNA expression was observed for 20 of the
MSDIN family members. Based on their predicted sequences, novel cyclic
peptides were searched for by LC/MS/MS in extracts of A. phalloides. The
presence of two cyclic peptides, named cycloamanides E and F with
structures cyclo(SFFFPVP) and cyclo(IVGILGLP), was thereby demonstrated.
Of the MSDIN genes reported earlier from another specimen of A.
bisporigera, 9 of 14 were not found in the current genome assembly.
Differences between previous and current results for the complement of
MSDIN genes and cyclic peptides in the two fungi probably represents
natural variation among geographically dispersed isolates of A. phalloides
and among the members of the poorly defined A. bisporigera species
complex. Both A. phalloides and A. bisporigera contain two prolyl
oligopeptidase genes, one of which (POPB) is probably dedicated to cyclic
peptide biosynthesis as it is in Galerina marginata. Conclusion: The MSDIN
gene family has expanded and diverged rapidly in Amanita section
Phalloideae. Together, A. bisporigera and A. phalloides are predicted to
have the capacity to make more than 50 cyclic hexa-, hepta-, octa-, nona-
and decapeptides.

背景：鹅膏属（Amanita）蘑菇中的环肽毒素，如α-鹅膏毒肽（α-amanitin）与鬼笔毒肽（phalloidin），由‘MSDIN’基因家族编码并经核糖体途径完成生物合成。此前基于部分基因组序列与聚合酶链式反应（PCR）分析，研究者已在双孢鹅膏（Amanita bisporigera）中鉴定出MSDIN家族的部分成员，且从其他鹅膏属物种中获知该家族另有若干成员。但截至目前，任一物种中MSDIN家族的完整基因集合，即这类真菌合成环肽的遗传潜力，仍未明确。
结果：本研究获取了两种产环肽蘑菇——‘死亡帽’毒鹅膏（A. phalloides）与‘毁灭天使’双孢鹅膏（Amanita bisporigera）的草图基因组序列。两个物种各携带约30个MSDIN基因，其中多数预测可编码未知功能的环肽。部分MSDIN基因在其中一个物种中发生了复制，但仅有3个基因在两个物种中均存在。毒鹅膏中还存在编码环酰胺B（cycloamanide B，此前已报道的非毒性环七肽）的基因，而编码蚂蚁毒素（antamanide）、环酰胺A、C及D的基因并未检出。在双孢鹅膏中，20个MSDIN家族成员可检测到RNA表达。基于其预测序列，本研究通过液相色谱-串联质谱（LC/MS/MS）对毒鹅膏提取物中的新型环肽进行了靶向检索，最终确认了两种环肽的存在，分别命名为环酰胺E（cyclo(SFFFPVP)）与环酰胺F（cyclo(IVGILGLP)）。此前从另一株双孢鹅膏标本中报道的14个MSDIN基因中，有9个未在本次基因组组装结果中被检出。两次研究（此前与本次）在两种真菌的MSDIN基因集合与环肽组成上的差异，大概率源于地理分布不同的毒鹅膏分离株之间的自然变异，以及界定模糊的双孢鹅膏物种复合群内成员间的遗传差异。毒鹅膏与双孢鹅膏均携带两个脯氨酸寡肽酶基因，其中一个（POPB）与边缘盔孢伞（Galerina marginata）的情况类似，可能专门负责环肽的生物合成。
结论：MSDIN基因家族在鹅膏属鹅膏组（section Phalloideae）中发生了快速扩张与分化。综合来看，双孢鹅膏与毒鹅膏预计可合成超过50种六肽、七肽、八肽、九肽及十肽环肽。