Oxidative Stress Poster Session
Discussion and Conclusion
The aim of this project has been to examine the genetic response to common environmental stresses in L. littorea.
I have been working with the question What, if any, genes are up-regulated in response to freezing and oxygen stresses in the foot muscle of L. littorea?. As shown by the results of northern blot analysis, I have obtained a partial answer - many genes show increased transcript abundance, but due to short sequences and/or the unique composition of these genes, I not yet unambiguously identified any of the clones presented here. Although this prevents me from making conclusions at this time, I have presented some interesting preliminary observations that indicate a positive outcome for this study.
In general, I am confident that all these clones represent real genes, despite sparse sequence homology data. All clones have: (1) polyA tails that are longer than the polyT primer used in reverse transcription; (2) a poly adenylation signal (AATAAA) within 25-100 bases of the polyA tail; and (3) a stop codon before the poly A signal.
As illustrated in table 1, clone sizes are smaller than the transcript size; perhaps when the missing sequence is obtained, more of the genes will be identified and/or an open reading frame will be present. This will allow for identification or possible protein structure predictions in the case of novel genes.
Below is some abbreviated analysis of the genes that have putative identities: a posible novel gene family and myosin heavy chain.
Anoxia treatment genesMany more genes were obtained from the anoxic library screen than the freezing library. Though I have not yet confirmed the identity and function of any of these genes, one group appears very interesting. Those in figure 1a, 1b, and 1c have very similar but not identical sequences, perhaps indicating a novel gene family. Although a BLAST search did not return any hits for these sequences, FASTA yielded a significant homology with glutenin from wheat (2.1e-44. In addition, the longest open reading frame in Clone EE gives an amino acid sequence that is very similar to glutenin both in terms of %composition and sequence. Since this protein is only found in plants, however, it is clearly not an identity for my group of clones. However, the similarity may indicate a novel protein that performs a similar function in L. littorea as glutenin does in wheat, namely that of energy storage.
LLFF15 - Freezing induced gene
This sequence appears to have some homology to myosin heavy chain. The BLAST alignment only shows a match of 105/150 bases, but in light of the fact that only 300 of LLFF 15's 1651 bases are in the reading frame, the match may actually be better than the numbers (expected value of 7.8e-35) indicate. In addition, the transcript size of LLFF 15 is similar to myosin, at roughly 6Kb. With such a small percentage of the complete gene, this match is quite significant.
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|English, T.E..; Storey, K.B..; (1998). Gene Up-regulation in Response to Anoxia or Freezing Stresses in the Marine Snail, Littorina littorea.. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Available at URL http://www.mcmaster.ca/inabis98/oxidative/english0445/index.html|
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