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Molecular Insights into Nuclear and Mitochondrial Genes in Marine Organisms

This article explores the intricate world of molecules, focusing on nuclear genes such as ribosomal internal transcribed spacer (ITS) and mitochondrial genes like cytochrome c oxidase subunit III (CO3). We examine the role of ITS in coding for ribosomal RNA, the variability of spacer regions across species, and the significance of polyphenolic adhesive proteins like Mefp-1 in mussels. Additionally, we highlight the importance of mitochondrial DNA in evolutionary studies and the distinctive features of adhesive proteins used in various biomedical applications.

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Molecular Insights into Nuclear and Mitochondrial Genes in Marine Organisms

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  1. S3: “Meet the Molecules” • Nuclear genes • ITS = ribosomal internal transcribed spacer • Glu = Polyphenolic adhesive protein • Mitochondrial gene • CO3 = Cytochrome c oxidase subunit III

  2. DNA RNA Ribosome (RNA + proteins) The molecules • ITS = the internal transcribed spacer of the nuclear ribosomal genes • Ribosomal genes code for rRNA • Spacer regions are transcribed but then removed • Region has restriction site polymorphism between species http://fp.bio.utk.edu/mycology/Techniques/mt-what_dna.htm

  3. DNA RNA Ribosome (RNA + proteins) ITS http://fp.bio.utk.edu/mycology/Techniques/mt-what_dna.htm

  4. ITS (1781-1799) (303-321) (1809 bp total) (1341 bp total) ITS Multiple copies in genome = many targets for PCR http://fp.bio.utk.edu/mycology/Techniques/mt-what_dna.htm

  5. ITS PCR product M. galloprovincialis (~959 bp) | 442 | 156 | 172 | 189 | M. trossulus (~951 bp) | 197 | 240 | 156 | 169 | 189 | • Restriction sites and fragment lengths for the Mytilus ITS locus using Hha I restriction enzyme • ITS is under less selection  more variable! • Reference: Braby & Somero, 2005, Marine Biology

  6. ITS M. galloprovincialis (~959 bp) | 442 | 156 | 172 | 189 | M. trossulus (~951 bp) | 197 | 240 | 156 | 169 | 189 | 442 240 197

  7. The molecules • Glu =Polyphenolic adhesive protein - nuclear • Mefp-1 protein • One of the glues that attaches byssal threads to rocks • Number of repeats (and therefore gene length) varies between species = repeat protein

  8. Glu • Adhesive proteins anchor byssal treads to hard surface • At least five different proteins • Many variants of each • Most studied foot protein is Mefp-1 • The Mefp-1 gene codes for the polyphenolic adhesive protein http://biomaterials.bme.northwestern.edu/mussel.asp

  9. Glu Collagen-like threads with adhesive proteins http://biomaterials.bme.northwestern.edu/mussel.asp

  10. Glu DOPA groups (hydroxylated tyrosines) chelate metal ions on surface http://biomaterials.bme.northwestern.edu/mussel.asp

  11. Novel uses for mussel adhesives • Safe, natural glue for surgeries • Coating for medical implants • Tooth coating for decay prevention • Anti-biofouling for boats • But synthesis is difficult • Sticky • Post-translational modification

  12. Mefp-1 protein ~110 kDa • Decapeptide repeats contain multiple • Lys = Lysine = electrostatic • Hyp = Hydroxyproline = “sticky” • DOPA = hydroxylated tyrosine = chelator • Repeats vary in number with ≤ 80/protein

  13. Mefp-1 gene 160 2502 bp 474 654 • Glu primers amplify • 2 products in invader M. galloprovincialis • ~ 300 and 500 bp (shown above) • 1 product in native M. trossulus • ~ 240 bp • Number of repeats (and therefore gene length) varies between species

  14. The molecules 3. CO3 = Cytochrome c oxidase subunit III - mitochondrial • One subunit of a large protein in the electron transport chain • Species level differences are observed after DNA sequencing

  15. Mitochondria • Organelles involved in oxidative respiration to produce ATP • Derived from bacterial endosymbionts (about 1.2 billion years ago) • Have genome, a circular DNA molecule (as in modern bacteria) http://www.bioeng.auckland.ac.nz/images/database/bioinformatics/mitochondria.gif

  16. Mitochondrial DNA (mtDNA) • Most ancestral genes lost or explanted to nucleus • Remaining genes: • Proteins for respiration • Ribosomal genes • Mitochondrial DNA qualities: • A haploid genome • Non-Mendelian inheritance • Little or no repair, therefore, evolves ~ 4 x faster than nuclear DNA • Useful for evolutionary studies of closely related species http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Endosymbiosis.html

  17. http://pages.slu.edu/faculty/kennellj/ Cellular respiration

  18. 3D structure of cytochromes http://dec4.ucdavis.edu/website/Bioenergetics/

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