TABLE CONTENTS

Distinctive Mitochondrial Genome Features of the Heteroderid Nematodes:
Multipartite Structure and Extensive Poly(T) Variation within Protein-
Coding Genes
Dowton, M. (1), V.C. Blok (2), T. Gibson (1), A.H. Riepsamen (1), J. Rowe (3),
M. Phillips (2), J. Barrett (1), & K. Meiklejohn (1)
(1) School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia; (2)
Department of Nematology, Scottish Crop Research Institute, Dundee DD2 D5A, Scotland; (3) Entomology and
Nematology Department, IACR-Rothamsted,
Harpenden, Hertfordshire AL5 2JQ, United Kingdom
In virtually all animal mitochondrial genomes characterized to date, all mitochondrial genes
are found on a single, circular molecule. However, in Globodera pallida, the mitochondrial
genes are distributed on multiple circles, with individual circles having overlapping subsets
of these mitochondrial genes. We are currently investigating the evolutionary origin of
multipartism in the heteroderid nematodes. G. rostochiensis is very similar to G. pallida,
with mitochondrial genes distributed on multiple circles, each about 8 kb in size. We have
made initial investigations of the structure of the mitochondrial genome of Heterodera
glycines and H. cynodontis. Although we lack complete data, we find no evidence for
multipartism in Heterodera nematodes. This suggests that multipartism arose during the
evolution of the Punctoderinae. We are currently investigating the mitochondrial genome of
Betulodera to narrow down the origin of this unusual mitochondrial feature. During these
investigations, we have noticed another novel mitochondrial feature, one that is similarly very
rare amongst animals. Many protein-coding genes in Globodera have long poly(T) stretches,
as many as 20 bases long. Further, when multiple copies of these genes are sequenced from
the same cyst, we see variation in the number of Ts, with some representing frame-shift
mutations that would result in the production of highly divergent proteins. The most
common form is usually not a frameshift mutation, but frameshift versions can represent a
significant proportion of the versions present. cDNA analyses and examination of EST
databases indicate that these versions are not necessarily corrected, as cDNA and EST copies
retain the frameshifts. This mitochondrial feature appears most pronounced in the Globodera
mitochondrial genome, but also in the Heterodera. We also have preliminary evidence of T-
variation in the mitochondrial ND4 gene of Meloidogyne javanica. Thus poly(T) variation is
present in a broader evolutionary range of nematodes than is multipartism.
5 th International Congress of Nematology, 2008 148