GENOMAS DEL CLOROPLASTO Y LA MITOCONDRIA. prof. Jorge Hernández T., Ph.D.

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1 GENOMAS DEL CLOROPLASTO Y LA MITOCONDRIA prof. Jorge Hernández T., Ph.D.

2 La Teoría Endosimbiótica prof. Jorge Hernández T., Ph.D.

5 Evidence for Endosymbiotic Theory Mitochondria have very similar characteristics to purple-aerobic bacteria. They both use oxygen in the production of ATP, and they both do this by using the Kreb s Cycle and oxidative phosphorylation. Similarly, chloroplasts are very similar to photosynthetic bacteria in that they both have similar chlorophyll that harnesses light energy that is converted into chemical energy. Mitochondria and chloroplasts are similar in size to bacteria, 1 to 10 µm. Mitochondria and chloroplasts DNA (circular), RNA, ribosomes, chlorophyll (for chloroplasts), and protein synthesis is similar to that for bacteria. It was also determined that mitochondria and chloroplasts divide independently of the cell they live in. Both mitochondria and chloroplasts have double phospholipid bilayers. This appears to have arisen by mitochondria and chloroplasts entering eukaryotic cells via endocytosis. Strong phylogenetic evidence No histones prof. Jorge Hernández T., Ph.D.

7 Gram (-) Gram (-) prof. Jorge Hernández T., Ph.D.

8 Horizontal gene transfer prof. Jorge Hernández T., Ph.D.

10 Mechanisms of DNA transfer from chloroplast and mitochondrial DNA to the nucleus Bulk DNA recombination between escaped organelle DNA and nuclear DNA Experimental DNA transfer in yeast Non-coding sequence frequently transferred Whole organelle sequences transferred Degradation of the organelle genomes in pollen could make DNA fragments available for uptake (MUST HAPPEN) cdna intermediates Nuclear copies of organelle genes often lack organelle-specific introns and edited sites (MAY HAPPEN) prof. Jorge Hernández T., Ph.D.

13 Reproducción in vivo de la Transferencia prof. Jorge Hernández T., Ph.D.

17 Chloroplast Gene Transfer Rate estimates from tobacco chloroplasts 1 transfer in 5 million leaf cells 1 transfer in pollen grains Higher rates of transfer in the pollen? Degradation of the organelle genomes in pollen could make DNA fragments available for uptake prof. Jorge Hernández T., Ph.D.

18 Transferencia y adaptación al genoma nuclear prof. Jorge Hernández T., Ph.D.

20 Why are the organelle genomes maintained? Hydrophobicity -hydrophobic proteins are poorly imported (excess of membrane embedded proteins) Fitness advantage if coding sequence and regulation are in same location Other constraints (e.g. RNA editing, genetic code) prof. Jorge Hernández T., Ph.D.

21 Genoma cloroplásticos secuenciados prof. Jorge Hernández T., Ph.D.

26 El genoma cloroplástico prof. Jorge Hernández T., Ph.D.

27 Chloroplast DNA (cpdna) General features: 1. double-stranded, circular molecule 2. no histones, but have bound proteins (e.g., Hu), organized into nucleoids 3. G-C content typically less than nuclear DNA 4. multiple copies (~30-100) per plastid (i.e., all cp genes are multi-copy) 5. can be 10-20% of the total DNA in leaves prof. Jorge Hernández T., Ph.D.

30 Major protein complexes of the chloroplast thylakoid membrane of Arabidopsis thaliana Polypeptide subunits encoded in the chloroplast Polypeptide subunits encoded in the nucleus Allen et al., 2011 prof. Jorge Hernández T., Ph.D.

32 Volvox carteri Dunaliella salina Chlamydomonas reinhardtii prof. Jorge Hernández T., Ph.D.

38 Genes cloroplásticos prof. Jorge Hernández T., Ph.D.

chloroplast SS gene (rbcs) in the nucleus Extremely abundant, because inefficient Pyrenoid in algae is mostly RuBPCase

41 Ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBPCase (Rubisco) Catalyzes carboxylation of ribulose-1,5 bisphosphate: CO 2 + RuBP 3PGA (x 2) 2 subunits, large (LS) and small (SS) 8 copies of each per holoenzyme LS gene (rbcl) in the chloroplast SS gene (rbcs) in the nucleus Extremely abundant, because inefficient Pyrenoid in algae is mostly RuBPCase Regulated during light-dark cycles enzyme more active in the light also synthesized mainly in the light prof. Jorge Hernández T., Ph.D.

42 Translational regulation of RuBPCase LS by SS Incoming SS somehow promotes translation of rbcl mrna Buchanan et al. There also seems to be autoregulation of rbcl translation: Cohen et al. (2006) Plant Physiol. 141, 1089; Wostrikoff and Stern (2007) PNAS 104, 6466 prof. Jorge Hernández T., Ph.D.

Retrograde Signaling & Regulation Retrograde Regulation - Regulation of nuclear genes by the chloroplast - Nuclear genes typically encode chloroplast proteins - Signaled by: (1) Developmental state

43 Retrograde Signaling & Regulation Retrograde Regulation - Regulation of nuclear genes by the chloroplast - Nuclear genes typically encode chloroplast proteins - Signaled by: (1) Developmental state of the plastid/gene expression (2) Photo-oxidative stress Retrograde regulation Anterograde Regulation - Regulation of chloroplast genes by nuclear gene products - Occurs at most levels of expression Anterograde regulation prof. Jorge Hernández T., Ph.D.

49 Translational regulation of RuBPCase LS by SS Incoming SS somehow promotes translation of rbcl mrna! Bogorad lab There also seems to be autoregulation of rbcl translation: Fig in Buchanan et al. Cohen et al. (2006) Plant Physiol. 141, 1089; Wostrikoff and Stern (2007) PNAS 104, 6466 prof. Jorge Hernández T., Ph.D.

51 The Protein Import Machinery of Chloroplast prof. Jorge Hernández T., Ph.D.

54 El genoma mitocondrial prof. Jorge Hernández T., Ph.D.

55 Human Mitochondrial DNA (mtdna) The human mitochondrion contains 5-10 identical, circular molecules of DNA. Each consists of 16,569 base pairs carrying the information for 37 genes which encode: 2 different molecules of ribosomal RNA (rrna) 22 different molecules of transfer RNA (trna) (at least one for each amino acid) 13 polypeptides The rrna and trna molecules are used in the machinery that synthesizes the 13 polypeptides. The 13 polypeptides are subunits of the protein complexes in the inner mitochondrial membrane, including subunits of NADH dehydrogenase, cytochrome c oxidase, and ATP synthase. However, each of these protein complexes also requires subunits that are encoded by nuclear genes, synthesized in the cytosol, and imported from the cytosol into the mitochondrion. prof. Jorge Hernández T., Ph.D.

58 Complete mitochondrial genome maps for Dunaliella salina, Chlamydomonas reinhardtii Volvox carteri prof. Jorge Hernández T., Ph.D.

60 The Protein Import Machinery of Mitochondria prof. Jorge Hernández T., Ph.D.

61 El genoma cloroplástico vs el mitocondrial prof. Jorge Hernández T., Ph.D.

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