ISSN 10227954, Russian Journal of Genetics, 2015, Vol. 51, No. 1, pp. 39–45. © Pleiades Publishing, Inc., 2015.
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1
INTRODUCTION
The Myxogastria (also known as Myxomycetes) are
plasmodial slime molds, eukaryotic microorganisms
that occur in terrestrial ecosystems and aquatic habi
tats [1]. Their life cycle includes two trophic stages:
one consists of uninucleate amoeboid or flagellate
cells, and the other is a complex macroscopic multi
nucleate form (plasmodium) that can achieve macro
scopic dimensions. Under favorable conditions, the
plasmodium is mobile, giving rise to one or more fruit
ing bodies that contain spores. However, under unfa
vorable conditions, a plasmodium can change into a
hardened, resistant structure called a microcyst or
sclerotium, to survive until conditions improve [2].
DNA sequence analysis supported the view that Myx
ogastria belong in supergroup Amoebozoa of the Pro
tist Kingdom [3, 4].
Class Myxogastria has traditionally included five
orders: Liceida, Trichiida, Echinostelida, Physarida,
and Stemonitida [5]. The ordinallevel phylogeny has
long been controversial, with scholars proposing dif
ferent phylogenies based on morphological features.
Martin and Alexopoulos [5] placed the order Echinos
telida in a central position within Myxogastria, further
splitting it into Liceida, Trichiida, and Physarida,
clustered in three parallel clades, with Stemonitida
forming a separated clade. Ross [6] observed that the
development of sporophoresis was epihypothallic in
Stemonitida, with the hypothallus formed on the
1
The article is published in the original.
lower surface of the plasmodium, while Liceida, Tri
chiida, Echinostelida, and Physarida were subhypo
thallic. Collins [7] based the characteristic of plasmo
dia suggested the Physarida was the most primitive,
possessing phaneroplasmodia, it was further divided
into Echinostelida which has a protoplasmodium,
Stemonitida with a phaneroplasmodium, Liceida with
a protoplasmodium or phaneroplasmodium, and
finally Trichiida, which has an intermediate between a
aphaneroplasmodium and phaneroplasmodium.
Several efforts are now underway to develop a
molecular phylogeny for Myxogastria. The phylogenic
studies undertaken to date have been based mainly on
small subunit ribosomal RNA (SSU rRNA) and elon
gation factor 1alpha (
EF1
α
) sequences, and the
results have indicated that the two types of genes can
better reflect the myxogastrian phylogenetic relation
ship at different levels. An initial phylogenetic study
based on molecular data suggested that Echinostelida,
whose members produce sporocarps with a simple
structure, represent the most basal clade of myxogas
tria [8]. The existence of two more advanced groups
has also been proposed, one characterized by bright
color spores and consisting of Trichiida and Liceida,
and the other characterized by dark spores and com
prising Physarida and Stemonitida [8, 9]. More recent
analyses based on the SSU rRNA gene [4, 10, 11] have
defined the primary phylogenetic bifurcation within
Class Myxogastria as a split between the darkspored
superorder Columellidia (orders Trichiida and
Liceida) and the brightspored superorder Lucispo
ridia (orders Physarida and Stemonitida). In addition,
Further Resolving the Phylogeny of Myxogastria (Slime Molds)
Based on COI and SSU rRNA Genes
1
Q. Sh. Liu, Sh. Zh. Yan, and Sh. L. Chen
College of Life Sciences, Nanjing Normal University, no. 1 Wenyuan Road, Qixia District, Nanjing 210046, China
email: liuqisha2006@163.com, yanshuzhen@njnu.edu.cn, chenshuanglin@njnu.edu.cn
Received April 30, 2014
Abstract
—To date, molecular systematics of Myxogastria has been based primarily on small subunit riboso
mal RNA (SSU rRNA) and elongation factor 1alpha (EF1
α
) genes. To establish a natural classification sys
tem for the organisms, we examined phylogenetic relationships among myxogastrian species using cyto
chrome c oxidase subunit I (COI) and SSU rRNA genes. Twenty new sequences were obtained, including
10 COI and 10 SSU rRNA sequences, were compared with sequences of related species from GenBank in
order to construct phylogenic trees. The analysis of the two data sets supported the modern phylogeny of
myxogastria: orders Liceida and Trichiida formed a sister group at the most basal clade, while orders Ste
monitida and Physarida formed a close group, and order Echinostelida was a sister group to Stemonitida and
Physarida. However, the partial COI sequences were too conserved to resolve of the branches in Stemonitida
and Physarida. In addition, we also deemed the specific edited mRNA events of COI sequences in myxogas
trian species.
DOI: 10.1134/S1022795414110076
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