Differential expression of Paragonimus westermani eggshell proteins during the developmental stages.
Eggs of trematode parasites are comprised of numerous vitelline cells and one fertilized ovum, and are encapsulated within a protein shell provided by the vitellocytes. In this study, we isolated two full-length cDNA clones that showed substantial levels of sequence identity with trematode-specific eggshell precursor proteins from the human lung fluke, Paragonimus westermani. These cDNAs, designated Pw-Vit20 (868-bp-long) and Pw-Vit36 (883-bp-long), shared a 76% identity with one another at the nucleotide level, and each encoded a 261-amino acid (aa) polypeptide. The deduced aa sequences contained a N-terminal hydrophobic segment, as well as a sequence motif of Gly-Gly-Gly-Tyr-Asp-Asn/Thr-Tyr-Gly-Lys/Gln, which is highly homologous with the eggshell proteins of Fasciola hepatica. With the high frequencies of tyrosine, glycine and lysine, the positions occupied by tyrosine, which has been proved to be converted into dihydroxyphenylalanine, were well preserved. Pw-Vit20 and Pw-Vit36 were found to be monoexonic genes with variably diverged variants scattered into multiple genomic loci. Their protein products were localized in the vitelline follicles and eggshells. Expression of Pw-Vit20 was restricted to the egg and adult stages, thus suggesting a critical involvement of Pw-Vit20 in the parasite's fecundity activity. Conversely, Pw-Vit36 was constitutively expressed in the metacercariae and juvenile stages in the vitelline follicles and ducts, which suggested that the prepositioning of stem or primordial vitelline cells within the juveniles prior to sexual maturation. Pw-Vit36 might acquire a unique or additional function relevant to the maturation and/or development of the vitelline cells/follicles during the evolutionary period of P. westermani. Differential biological implications of multiple eggshell precursor proteins may provide insight into the molecular mechanism of eggshell formation and the developmental process of the vitelline follicles in the parasitic trematode.
Bae
Young-An
YA
Department of Molecular Parasitology and Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, 300 Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi-do 440-746, Republic of Korea.
Kim
Seon-Hee
SH
Cai
Guo-Bin
GB
Lee
Eung-Goo
EG
Kim
Tong-Soo
TS
Agatsuma
Takeshi
T
Kong
Yoon
Y
D000595:Amino Acid Sequence; D000818:Animals; D018076:DNA, Complementary / Q000235:genetics; D018509:DNA, Helminth / Q000235:genetics; D004527:Egg Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D020224:Expressed Sequence Tags; D005260:Female; D018507:Gene Expression Regulation, Developmental; D017238:Genes, Helminth; D016678:Genome; D015801:Helminth Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D048492:Paragonimus westermani / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D016415:Sequence Alignment
D018076:DNA, Complementary; D018509:DNA, Helminth; D004527:Egg Proteins; D015801:Helminth Proteins; C015753:chorion proteins