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Comp Biochem Physiol B Biochem Mol Biol. 2016 Feb;192:38-48. doi: 10.1016/j.cbpb.2015.11.008. Epub 2015 Nov 25.

Three cDNAs encoding vitellogenin homologs from Antarctic copepod, Tigriopus kingsejongensis: Cloning and transcriptional analysis in different maturation stages, temperatures, and putative reproductive hormones.

Author information

1
Interdisciplinary program of Biomedical Mechanical & Electrical Engineering, Pukyong National University, Busan, 608-737, South Korea.
2
Korea Polar Research Institute, Korea Ocean Research and Development Institute, Incheon 406-840, South Korea.
3
Department of Marine Biology, Pukyong National University, Busan 608-737, South Korea.
4
Interdisciplinary program of Biomedical Mechanical & Electrical Engineering, Pukyong National University, Busan, 608-737, South Korea; Department of Marine Biology, Pukyong National University, Busan 608-737, South Korea. Electronic address: kimhw@pknu.ac.kr.

Abstract

Three full-length cDNAs encoding lipoprotein homologs were identified in Tigriopus kingsejongensis, a newly identified copepod from Antarctica. Structural and transcriptional analyses revealed homology with two vitellogenin-like proteins, Tik-Vg1 and Tik-Vg2, which were 1855 and 1795 amino acids in length, respectively, along with a third protein, Tik-MEP, which produced a 1517-residue protein with similarity to a melanin engaging protein (MEP) in insects Phylogenetic analysis showed that Vgs in Maxillopods including two Tik-Vgs belong to the arthropod vitellogenin-like clade, which includes clottable proteins (CPs) in decapod crustaceans and vitellogenins in insects. Tik-MEP clustered together with insect MEPs, which appear to have evolved before the apoB-like and arthropod Vg-like clades. Interestingly, no genes orthologous to those found in the apoB clade were identified in Maxillopoda, suggesting that functions of large lipid transfer proteins (LLTPs) in reproduction and lipid metabolism may be different from those in insect and decapod crustaceans. As suggested by phylogenetic analyses, the two Tik-Vgs belonging to the arthropod Vg-like clade appear to play major roles in oocyte maturation, while Vgs belonging to the apoB clade function primarily in the reproduction of decapod crustaceans. Transcriptional analysis of Tik-Vg expression revealed a 24-fold increase in mature and ovigerous females compared with immature female, whereas expression of Tik-MEP remained low through all reproductive stages. Acute temperature changes did not affect the transcription of Tik-Vg genes, whereas Tik-MEP appeared to be affected by temperature change. Among the three hormones thought to be involved in molting and reproduction in arthropods, only farnesoic acid (FA) induced transcription of the two Tik-Vg genes. Regardless of developmental stage and hormone treatment, Tik-Vg1 and Tik-Vg2 exhibited a strong positive correlation in expression, suggesting that expression of these genes may be regulated by the same transcriptional machinery.

KEYWORDS:

Antarctic; Copepod; Ecdysone; Farnesoic acid; Vitellogenin

PMID:
26627129
DOI:
10.1016/j.cbpb.2015.11.008
[Indexed for MEDLINE]

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