23. You have identified the receptor for a hormone in plants. This protein, whic

Question

23. You have identified the receptor for a hormone in plants. This protein, which consists ofa single polypeptide chain, is a receptor for a peptide hormone on the surface of cells. The gene appears to be expressed in all plant tissues, according to your analysis by real-time PCR which only detects the 3' of the mRNA. You have developed an antibody to detect the protein by western blot analysis. To your surprise by western blot analysis, in roots, the receptor is 120 kilodaltons in size, but in leaf tissue, the receptor is 100 kilodaltons. You know that only a single copy of this gene encodes for this protein, and there are no closely related proteins. Based on what you have learned up to this point, explain two different mechanisms that could result in these observations. Design an experiment to determine which possibility is more likely

Explanation / Answer

As there is only one copy of the gene, the the two varients of the receptors arise by post transcriptional or post translational modification.Post transcriptional modification is the processing of the precurser RNA into mRNA. In post transcriptional modifiaction, the two varients of receptors arise due to alternate splicing. In alternate splicing, some exons are included or excluded in the final product of mRNA. Thus resulting in multiple proteins. In root,some of the exons are included in whereas in leaf tissue it may be excluded. In post translational modifiaction, some groups are added or enzymatically modification of protein can happen.

To check whether it is post transcriptional or post translational modification, RNA from the leaf tissue and roots are isolated, then using the reverse transcriptase synthesise the cDNA of the isolated RNA. Using the primers of the gene, amplify the gene of the receptor specifiaclly from the whole RNA. Then run in an agarose gel electrophoresis, and compare the sizes of cDNA coresponding leaf tissue and root. If there is remarkable difference, then can conclude that it is post transcriptional modification.

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