AtH SP23.6 mRNA Stained TRNA Stained rRNA 0 HEHEHE 1 2 4 6 8 10 12 24 Time (hrs)
ID: 253010 • Letter: A
Question
AtH SP23.6 mRNA Stained TRNA Stained rRNA 0 HEHEHE 1 2 4 6 8 10 12 24 Time (hrs) 42°C HS ?Above is an RNA blot (aka Northern Blot) that shows (top panel) the level of transcript (mRNA) for the AtHSP23.6 gene in leaves of 20 day old Arabidopsis plants at each of the indicated times after initiation of heat stress. ? The bottom panel shows the amount of RNA loaded in each lane of the gel- so shows that this was about the same for each of the samples. So, at what time point is the peak level of RNA accumulation for the time points analyzed in this experiment was? HSP23.6 PROTEIN 0 1 2 4 6 Time of 42-C heat stress (hrs) ? Above is PROTEIN blot (aka Western Blot) that shows the level of AtHSP23.6 PROTEIN in the mitochondria in cells of leaves of 20 day old Arabidopsis plants at each of the indicated times after initiation of heat stress. ? At what time point is the protein level at the peak? Exercise: using what was just presented regarding gene expression, formulate one or more testable hypotheses about the heat stress response of the AtHSP23.6 gene.Explanation / Answer
From the given gel diagrams, it is clear that the AtHSP23.6 gene is temperature sensitive. The RNA shows peak value at 2 hrs and 4 hr time point. This shows that elevated temperature induces transcription of the AtHSP23.6 gene. The concomitant increase in protein expression at 4 hrs is due to elevated mRNA levels.
To test that the given gene is indeed temperature sensitive (i.e. the elevated expression is not a background stochastic effect),
i. Since temperature induces the given gene transcription, try to check for any known temperature sensitive cis-elements in the promoter region of the gene. Identify specific sequences responsible for temperature sensitivity by deletion mapping.
ii. There must be a master regulator of temperature response. Check the expression of AtHSP23.6 in the mutant background of the master regulator. If the elevation of the gene expression is indeed due to temperature increase and not a stochastic response, we should not see an increase of gene expression in the mutant background of the master regulator.
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