Talk at VIII Biennial Conference of Society of Spanish Evolutionary Biology (SESBE).
MATB. Previous studies have revealed that species of the genus
Trichaptum (Hymenochaetales, Basidiomycota) possess a tetrapolar mating system,
with multiple inferred alleles for MATA and MATB. We characterized the
chromosomal location of MAT loci, the molecular structure of MAT regions and their
allelic richness. We found multiple MAT alleles segregating in both multiple
Trichaptum specimens and non-Trichaptum species. Phylogenetic analyses and
various nucleotide statistics suggested that long-term balancing selection have
generated trans-species polymorphisms. Mating sequences were classified in
different allelic classes based on an identity threshold of higher than 86%. The
observed alleles could potentially generate 14,560 different mating types. The
inferred allelic information mirrored the outcome of in vitro crosses, thus allowing
us to estimate the degree of allelic divergence needed for successful mating. Even
with the high amount of divergence, key amino acids in functional domains are
conserved. We conclude that the genetic diversity of mating in Trichaptum loci is
due to long-term balancing selection that likely promote sexual outcrossing, with
limited recombination and duplication activity. Our large number of sequenced
specimens highlighted the importance of sequencing multiple individuals from
different species to clarify the mechanisms generating diversity and the
evolutionary forces maintaining them.
1. Long-term balancing selection in a white-rot
fungi
David Peris
Department of Biosciences, UiO
Department of Health, VIU
VIII Biennial Conference SESBE
2nd February 2022
@DPerisN
@FungiaLab
8. Running hypotheses
(H1): The tetrapolar character of Trichaptum must be
determined by two unlinked loci.
(H2): The high number of alleles is maintained by balancing
selection
18. A pair of the complex interacts with the other pair from a different allele
Trichaptum spp.
aHD2.9 aHD1.22
aHD.4
Homeodomain 1 (HD1)
Homeodomain 2 (HD2)
Casselton and Olesnicky 1998
Chr 2
Basidiomycetes
MATA-122
aHD2.12 aHD1.5 bHD2.7
bHD.8
aHD.30 bHD.5
bHD2.5 bHD1.7
Chr 2
MATA-21
MATA
alpha beta
Tetrapolar
19. Pairs from the same chromosome cannot interact
Trichaptum spp.
aHD2.9 aHD1.22
aHD.4
Homeodomain 1 (HD1)
Homeodomain 2 (HD2)
Casselton and Olesnicky 1998
Chr 2
Basidiomycetes
MATA-122
aHD2.12 aHD1.5 bHD2.7
bHD.8
aHD.30 bHD.5
bHD2.5 bHD1.7
Chr 2
MATA-21
alpha beta
MATA
Tetrapolar
20. Pairs from different complexes does not interact
Trichaptum spp.
aHD2.9 aHD1.22
aHD.4
Homeodomain 1 (HD1)
Homeodomain 2 (HD2)
Casselton and Olesnicky 1998
Chr 2
Basidiomycetes
MATA-122
aHD2.12 aHD1.5 bHD2.7
bHD.8
aHD.30 bHD.5
bHD2.5 bHD1.7
Chr 2
MATA-21
alpha beta
MATA
Tetrapolar
21. Trichaptum spp.
Casselton and Olesnicky 1998
Basidiomycetes
A pheromone interacts with the pheromone receptor from a different allele
Pheromone receptor (STE3)
Pheromone precursor (Ph)
Chr 9
MATB-7
P/R3.2.1
Chr 9
MATB-11
STE3.2.1 STE3.4.12
STE3.2.1 STE3.4.8
P/R3.2.1
P/R3.4.12
P/R3.4.8
Ph3.2.1
Ph3.2.1
Ph3.4.12
Ph3.4.8
P/R 3.2 P/R 3.4
MATB
Tetrapolar
27. bHD proteins are older than aHD and were segregating for long time
28.
29. Trichaptum life cycle: inbreeding reduced to 25%
Monokaryons
(n)
Dikaryons
(n+n)
Diploid (2n) < karyogamy
Haploid spores < meiosis
(n)
Haploid spores
(n)
Mating type 12
MATA-21 MATB-7
Mating type 26
MATA-122 MATB-11
Plasmogamy
A21B7
A21B21
A27B21
A27B7
30. 50% chance of inbreeding
Homeodomain 1
Homeodomain 2
HMG-domain transcription activator
Hsueh & Heitman 2008
Jackson et al 2013
MAT/MATa
Diploid (2n)
a
a
Tetrad
Spore
Saccharomyces cerevisiae
2 1
a1
Chr III
MAT
MATa
Bipolar
32. Take home messages
Trichaptum species are tetrapolar due to the presence of unlinked MATA and MATB loci.
Trichaptum mating genes is an example of long-term balancing selection generating trans-
species polymorphisms.
33. Take home messages
Trichaptum species are tetrapolar due to the presence of unlinked MATA and MATB loci.
Trichaptum mating genes is an example of long-term balancing selection generating trans-
species polymorphisms.
We inferred 17,550 Trichaptum mating types that reduced inbreeding and facilitate outbreeding
34. Take home messages
Trichaptum species are tetrapolar due to the presence of unlinked MATA and MATB loci.
Trichaptum mating genes is an example of long-term balancing selection generating trans-
species polymorphisms.
We inferred 17,550 Trichaptum mating types that reduced inbreeding and facilitate outbreeding
A new fantastic organism to study the evolution of sex in fungi
35. Inger Skrede
Dabao Sun Lu
Vilde Bruhn Kinneberg
Ine-Susanne Methlie
Malin Dahl
Ingvild Myhre Ekeberg
Håvard Kauserud
UiO@Speciomics
Thank you
Timothy James
Collaborations
Acknowledgements
Sebastián Ramos Onsins (CRAG)
Georgina May