TITLE:
Characterization of randomly amplified polymorphic DNA (RAPD) fragments revealing clonal variability in cercariae of avian schistosome Trichobilharzia szidati (Trematoda: Schistosomatidae)
AUTHORS:
Anna Korsunenko, Galina Chrisanfova, Alexander Arifov, Alexey Ryskov, Seraphima Semyenova
KEYWORDS:
RAPD Variability; Cercariae Heterogeneity; Trichobilharzia szidati Repetitive DNA
JOURNAL NAME:
Open Journal of Genetics,
Vol.3 No.3,
August
28,
2013
ABSTRACT: Recently we applied randomly amplified
polymorphic DNA (RAPD) fingerprinting to detect clonal variability among
individual cercariae within daughter sporocysts and rediae of 10 digenean trematodes
(Platyhelminthes: Trematoda). The most variable RAPD patterns were obtained
for Schistosomatidae representative-avian schistosome Trichobilharzia szidati. In this
work, 50 polymorphic DNA fragments of approximately 300-1500 bp from RAPD
patterns of individual T. szidati cercariae
were cloned and sequenced. As a result genomic DNA sequences (total length of
approximately 41,000 bp) revealing clonal variability in T. szidati cercariae were obtained and analyzed. The analysis
indicated that these sequences contained tandem, inverted and dispersed repeats
as well as regions homological to retroelements of two human parasites, Schistosoma mansoni and S. japonicum. Tandem and inverted
repeats constituted 8.9% and 22.1% respectively, while the percentage of dispersed
repeats was 21.0%. The average content of these components was 41.7% with the average
AT content being 59.0%. About 40% of sequences included regions ranging in
length from 96 to 1005 bp which displayed amino acid homology with open reading
frame pol products of S. mansoni and S. japonicum retroelements: non-long terminal repeat retrotransposons
(nLTRs, 76%), long terminal repeat retrotransposons (LTRs, 14%), and
Penelope-like elements (PLEs, 10%). Most of these regions (86.4%) contained
frameshifts, gaps, and stop-codons. The largest portion of them was homological
to nLTRs of the RTE clade (67%). The
number of sequences homologous to the members of CR1 lineage was 7 times
smaller (9%). Homology with LTRs of Gypsy/Ty3 and BEL clades was revealed in 5%
and 9% of cases respectively. We assume that the repetitive elements
including retroelement-like sequences described in the current study may serve
as the source of clonal variability detected previously in T. szidati and other digenean trematodes. Such genome regions
rapidly accumulate mutations and thus may play an important functional role
in the life history of the species.