Date of Award

5-8-2009

Document Type

Thesis

Degree Name

Bachelor of Arts

First Advisor

Gillen, Christopher M.

Abstract

Previous studies in freshwater crayfish have used the molting cycle to correlate Ca2+ flux with the upregulation of Ca2+ transport and binding proteins. In an effort to better understand the regulation of genes encoding sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), calmodulin (CaM) and sarcoplasmic Ca2+ binding protein (SCP), cold exposure of Procambarus clarkii (4 degrees C for 7 days compared with 23 degrees C) was used to disrupt intracellular Ca2+ homeostasis. Real-time PCR results indicated that both SERCA and CaM mRNA expression did not significantly change after cold exposure. We have identified three pcSCP variants (pcSCP1a, pcSCP1b, pcSCP1c) that differ in a 123 bp region but are otherwise identical. SCP1a was 222,000 times more highly expressed in the axial muscle than in the hepatopancreas, consistent with its hypothesized identity as an invertebrate analog of vertebrate parvalbumin. While expression of SCP did not vary in axial muscle after cold exposure, it was significantly downregulated in cardiac muscle where mRNA levels were undetectable after cold exposure. This decreased calcium buffering activity could help crayfish maintain heart contractions in times of cold stress. SCP expression was evaluated in fast-twitch and slow-twitch muscles, and mRNA expression was highest in the deep flexor fast-twitch muscle for all three variants. The increased mRNA expression of the calcium-buffering SCP was expected in fast-twitch muscle tissues to promote relaxation. SCP1a was 100 fold higher in the deep flexor than the slow-twitch superficial flexor muscle, a larger increase than the other variants, and a possible indicator of variant-specific expression.

Comments

Includes bibliographical references: pages 32-37

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