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this result is hardly surprising, given the fact that in multicellular metazoans,
including all deuterostomes, androglobin appears to be predominantly
expressed only in testis tissue (
Hoogewijs, Ebner, et al., 2012
), it suggests
that androglobin was present
in the ancestor
shared by metazoans
and choanoflagellates.
4.7. Fungi
Table 9.4
presents a summary of the globin subfamilies identified in about
240 available fungal genomes, representing an update of an earlier
census of fungal globins (
Hoogewijs, Dewilde, Vierstraete, Moens, &
Vinogradov, 2012
). The added fungal genomes have filled the lacunae
present in the earlier count, improving the representation of Doth-
ideomycetes and Basidiomycota. A detailed list of fungal globins is provided
by Supplementary Table S2 at
http://www.elsevierdirect.com/compan
ions/9780124076938
. The more complete coverage of fungal genomes
relative to the other microbial eukaryotes makes it clear that fungi are on
the average more globin rich than any other microbial eukaryote group.
However, the fungal globins encompass only two of the eight subfamilies,
the FHbs and SSDgbs. Furthermore, they are unique in the extensive pairing
of the two in most Ascomycota, except the Onygenales, which have only
SSDgbs, and in most of the Basidiomycota. This pairing is non-existent in
the bacterial genomes (
Vinogradov et al., 2013
). The Blastocladiomycota
and the Chytridiomycota appear to have only SSDgbs (
Table 9.4
). Many sac-
charomycete FHbs are incomplete, lacking the C-terminal moiety of the
reductase domain, the 1cqx3 domain comprising the NAD-binding site
(
Ilari & Boffi, 2008
). An important issue to resolve is whether the shortened
reductase domains are active and whether these incomplete FHbs have any
function. Such studies are woefully lacking.
5. PHYLOGENETIC RELATIONSHIPS
5.1. Methods of globin identification and alignment
Two approaches were used in the identification of putative globins and glo-
bin domains. In one, we employed the globin gene assignments, based on a
library of hidden Markov models (
Gough, Karplus, Hughey, & Chothia,
2001
), provided by the SUPERFAMILY website (
http://supfam.mrc-
lmb.cam.ac.uk
). In the other approach, we used known globin sequences
