Question 3. Intertidal mussels, Mxtihus.trassulus, collected from the same site

Question

Question 3. Intertidal mussels, Mxtihus.trassulus, collected from the same site in Washington, USA, in February and August were exposed for 2 h to different temperatures in the lab. Dissected gill tissue was then metabolically labeled at 13°C in the presence of 35S-labelled methione/cysteine before proteins were separated on 10 % SDS-polyacrylamide gels and imaged using standard fluorographic techniques. Individual lanes were loaded with equal counts of radioactivity (3.7'107 BQ), and the locations of molecular mass markers (not shown) are indicated on the right. Visible bands are indicative of protein expression; the darker the band, the more protein expressed. Heat-shock temperature (°C) 20 23 25 28 200 kDa 90 kDa 70 kDa> 40 kDa February August A. What is/are the independent and dependent variable(s) in this study? B. In response to thermal stress, many organisms increase their production of heat shock proteins, including Hsp70, a 70 ?Da molecular chaperone that functions to stabilize other proteins. What do the above results tell us about the relative stress experienced by mussels in the different treatment groups? C. Based on these results, when are mussels from this location most physiologically resistant to high temperature stress? When are they most likely to experience high temperature stress? D. Given that mussels can live for 10+ years, what is the likely biological mechanism underlying these results (i.e., this would be an example of what phenomenon)?

Explanation / Answer

In this study the independent variables are temperature provided in the lab, and the mussels collected in different months.Dependent variables: The expression of the 70Kda protein. Survival of the mussel is also dependent on the various temperatures. From the gel picture it can be seen that the mussels collected in the month of February express no chaperon 70Kda protein at 200C while at higher temperature they express the 70Kda protein very nicely. While in the mussels collected in the month of august have shown very less expression of 70Kda protein at 25 0C while at higher temperature 280C express large amount of this heat shock protein. As well as the expression of other proteins is also higher in the case where there is higher expression of Hsp70. This shows that the mussels collected in the month of august are facing more heat shock due to which the Hsp70 is expressed in higher amount and stabilizing the other proteins. From the gel picture it can be inferred that the mussels of august month ex[perience more heat stress and are more resistant to the heat stress due to more expression of the Hsp 70 chaperons due to which darker bands can be seen at higher temperature in the mussels of august month. The bicarbonate shell around them and the bivalve nature which let them hide themselves inside the sediments is the mechanism underlying their long survival. They are also called as freshwater Bivalve. They have tendency to form clumps together and this feature provide them strength to withstand in the tides and waves by preventing their flushing with water force.

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