Biology Reference
In-Depth Information
transcripts. Five flp genes have been characterized from second (infective)
stage larval Globodera pallida (potato cyst nematode) including Gp-flp-1,
Gp-flp-6, Gp-flp-12, Gp-flp-14, and Gp-flp-18.
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Another four flp genes were
characterized from the root knot nematode Meloidogyne incognita (Mi-flp-1,
Mi-flp-7, Mi-flp-12, Mi-flp-14); Mm-flp-12 was also identified from Meloi-
dogyne minor.
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While these efforts yielded novel information on neuro-
peptide genes in parasites, they did not allow meaningful comparisons
between the neuropeptide complements of parasites and C. elegans.
Broader guidance on the diversity of flp genes in nematode parasites was
provided from a bioinformatics screen for flp transcripts from expressed
sequence tag (EST) data for 32 nematode parasites. These efforts identi-
fied 31 flp genes in parasites, 29 of which had orthologs in C. elegans.
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While the flp gene complement recorded for any one parasite was
markedly smaller than C. elegans, the vast majority of C. elegans flp genes
had orthologs that occurred in some nematode parasite species.
More recently, genome-wide neuropeptide gene surveys have been
completed for M. incognita and the migratory endoparasite Bursaphelen-
chus xylophilus which causes pine wilt disease.
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The former reported
the Mi-flp and Mi-ins gene complements whereas the latter reported the
Bx-flp, Bx-ins, and Bx-nlp gene complements. Both of these plant parasitic
nematodes display constricted flp gene diversity with 19 (M. incognita)
and 21 (B. xylophilus) flp genes compared to the 29 flp genes in C. elegans.
While no NLPs have been structurally characterized from parasites
other than Ascaris, a screen of parasite transcriptomic data uncovered
orthologs of 26 of the 46 C. elegans nlp genes.
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The Tc -nlp-12 transcript has
been characterized from the sheep parasite Trichostrongylus colubriformis,
with expression identified in the tail and appearing to match that for the
C. elegans ortholog.
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Genomic screens of M. incognita and B. xylophilus
recovered sequence homologs for 21 and 17 of the C. elegans nlp genes,
respectively. While these datasets reveal complexity in the parasitic
nematode flp and nlp gene complements, they are similarly reduced in
comparison to C. elegans. Data on parasitic nematode ins genes is
restricted to the genomic survey of B. xylophilus which identified seven
ins gene orthologs, dramatically fewer than the 40 genes (39 ins genes
and daf-28) identified in C. elegans and suggesting even more profound
constriction of ins family genes or structural divergence that prevented
discovery using C. elegans-derived search strings.
The Role of Neuropeptides in Other Parasites
As with Ascaris, most data on neuropeptide function in other parasites
relate to FLPs. Two flp-18 peptides (AF3, AVPGVLRFamide, and AF4,
GDVPGVLRFamide) increased spontaneous phasic activity, induced
body wall muscle contractions and decreased cyclic AMP levels in A. galli,
effects that were independent of cholinergic signaling.
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Spontaneous and
