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Characterization and expression of the multicatalytic proteasesubunit(26S proteasome) during the reproductive cycle of the Shrimp (Metapenaeus ensis)

by Shek, Wing-kit

Abstract (Summary)
(Uncorrected OCR) Abstract of thesis entitled CHARACTERIZATION AND EXPRESSION OF THE MULTICATALYTIC PROTEASE SUBUNIT (26S PROTEASOME) DURING THE REPRODUCTIVE CYCLE OF THE SHRIMP (Metapenaeus ensis) Submitted by Shek Wing Kit for the degree of Master of Philosophy at The University of Hong Kong in November 2004 The 26S proteasome is a multicatalytic complex (MCP) in the ubiquitin-proteasome degradation pathway. MCP is responsible for the degradation of intracellular proteins (i.e. cyclin) that control mitosis and meiosis during ovary maturation and larval development. In cloning the vitellogenin gene of the shrimp, several partial cDNAs encoding a homologue of the proteasome subunit have been isolated from the ovary. To study the possible involvements of proteasome in the female shrimp maturation and in the larvae development, the proteasome cDNAs have been cloned and characterized. The full-length cDNA of MeC8 is 1,362 bp and consists of the longest open reading frame (ORF) encoded for a protein of 255 amino acid residues. The deduced amino acid sequence of MeC8 is most similar to that of the proteasome of the African claw frog, with similarity over 80%. MeC8 was ubiquitously expressed in the ovary, but the mRNA expression level in the larvae was decreased when they were transformed from nauplius to zoea. On the contrary, the protein level of MeC8 was increased when the larvae were transformed from nauplius to zoea. These results suggest that the proteasome was maternally deposited in the oocytes for larval development. Besides the ovary, proteasome transcripts can also be detected in the eyestalk, muscle, testis, gut and ventral nerve cord. The wide spread expression of proteasome in shrimp was similar to that of other organisms. However, the localization of proteasome in the ovary was quite different from that in other tissues. In maturing oocytes, proteasome was localized in the nucleus while in other tissues such as in muscle, proteasome was detected in the bundle of muscle fibers. In the ventral nerve cord, proteasome was mainly concentrated in the cytoplasm of neurosecretory cells; and in the midgut, proteasome was localized in the cilia of cells in the internal wall lining of the gut. In summary, the presence of proteasome in the ovary indicates its importance in oocyte maturation, during which meiosis takes place. It also shows from immunohistochemical results that there is no or only little change of subunit expression or modification during maturation of ovary.
Bibliographical Information:

Advisor:

School:The University of Hong Kong

School Location:China - Hong Kong SAR

Source Type:Master's Thesis

Keywords:proteinase shrimps reproduction genetics

ISBN:

Date of Publication:01/01/2005

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