线粒体基因组学习教案

1、会计学1第一页，共78页。Mitochondrial molecular genetics focus on mitochondria: brief overview of their function and structure mtDNA structure and replication:- animals- yeast- plants inheritance of mitochondria - petite mutants of yeast biogenesis of mitochondria by fission第1页/共78页第二页，共78页。MITOCHONDRIA essent

2、ial for cell life- ATP synthesis- many metabolic intermediates essential for cell death - unprogrammed death: necrosis( eg, due to loss of energy status) - programmed cell death(apoptosis - controlled cell destruction)第2页/共78页第三页，共78页。 Two membranes Inner membrane invaginated Numbers of mitochondria

3、 per cell vary but usually 100s/cellMatrix contains the TCA cycle (and other) soluble enzymesInner membrane contains metabolite transporters and the electron transport chainMitochondrial structure第3页/共78页第四页，共78页。The ribosomes can actually be visualized in some mitochondria. In these figures, they a

4、re seen in the matrix as small dark bodies. DNA can also be visualized in mitochondria. The DNA is circular and resembles that of a bacterium in its basic structure. Mitochondria also have their own ribosomes and tRNA: 22 tRNAs rRNAs (16S and 12S)第4页/共78页第五页，共78页。Mitochondria contain DNA molecules w

5、ith an assortment of genes.Mitochondrial genetic system consist of DNA and the molecular machinery needed to replicate and express the genes contained in this DNA. This machinery includes the macromolecules needed for transcription and translation. Mitochondria even possess their own ribosomes. Many

6、 of these macromolecules are encoded by mitochondrial genes, but some are encoded by nuclear genes and are therefore imported from the cytosol.第5页/共78页第六页，共78页。Mitochondria have their own DNA and RibosomesMitochondria have some of their own DNA, ribosomes, and can make many of their own proteins. Th

7、e DNA is circular and lies in the matrix in structures called nucleoids. Each nucleoid may contain 4-5 copies of the mitochondrial DNA (mtDNA).mitochondrialDNA第6页/共78页第七页，共78页。第7页/共78页第八页，共78页。第8页/共78页第九页，共78页。第9页/共78页第十页，共78页。第10页/共78页第十一页，共78页。第11页/共78页第十二页，共78页。Intramolecular recombination in the

8、 mtDNA of the Chinese cabbage, Brassica campestris油菜(yuci). Recombination between the repeated elements in the large circular DNA molecule partitions this molecule into two smaller ones. Alternatively, the repeated elements in the two small molecules may recombine with each other to produce a single

9、 large molecule.第12页/共78页第十三页，共78页。第13页/共78页第十四页，共78页。第14页/共78页第十五页，共78页。第15页/共78页第十六页，共78页。第16页/共78页第十七页，共78页。第17页/共78页第十八页，共78页。第18页/共78页第十九页，共78页。第19页/共78页第二十页，共78页。Expression of Mitochondrial genes第20页/共78页第二十一页，共78页。Expression of Mitochondrial genes第21页/共78页第二十二页，共78页。Expression of Mitochondria

10、l genes第22页/共78页第二十三页，共78页。Expression of Mitochondrial genes第23页/共78页第二十四页，共78页。Expression of Mitochondrial genes分子内(intramolecular) 剪接(jinji)(cis splicing) 以及分子间(intermolecular) 剪接(jinji)(trans splicing) 第24页/共78页第二十五页，共78页。第25页/共78页第二十六页，共78页。第26页/共78页第二十七页，共78页。第27页/共78页第二十八页，共78页。第28页/共78页第二十九页，

11、共78页。第29页/共78页第三十页，共78页。mt DNA and human disease第30页/共78页第三十一页，共78页。第31页/共78页第三十二页，共78页。第32页/共78页第三十三页，共78页。第33页/共78页第三十四页，共78页。Genetic organization of the chloroplast DNA in the liverwort Marchantia polymorpha. Symbols: rpo, RNA polymerase; rps, ribosomal proteins of small subunit; rpl and secX, ri

12、bosomal proteins of large subunit; 4.5S, 5S, 16S, 23S, rRNAs of the indicated size; rbs, ribulose bisphosphate carboxylse; psa, photosystem I; psb, photosystem II; pet, cytochrome b/f complex; atp, ATP synthesis; infA, initiation factor A; frx, iron-sulfur proteins; ndh, putative NADH reductase; mph

13、, chloroplast permease (?); tRNA genes are indicated by abbreviations for the amino acids.第34页/共78页第三十五页，共78页。第35页/共78页第三十六页，共78页。第36页/共78页第三十七页，共78页。 Chloroplast biogenesis. A mature chloroplast containing stacks (堆) of thylakoid类囊体 membranes (grana基粒) within its protoplasmic stroma (基质(j zh) devel

14、ops from a proplastid after exposure to light.第37页/共78页第三十八页，共78页。第38页/共78页第三十九页，共78页。Mitochondrial InheritanceYeast has been used extensively to study mitochondrial inheritance.There is a Yeast strain, called Petite小型小型(xioxng)菌聚落菌聚落 that have structurally abnormal mitochondria that are incapable o

15、f oxidative phosphorylation. These mitochondria have lost some or all of their DNA. Genetic crosses between petite and wt (wild-type) strains showed that inheritance of this trait did not segregate with any of the nuclear chromosomes. 第39页/共78页第四十页，共78页。Mitochondrial inheritance from yeast is bipare

16、ntal双亲(shungqn)的, and both parent cells contribute to the daughter cells when the haploid cells fuse. After meiosis and mitosis, there is random distribution of mitochondria to daughter cells. If the fusion is with yeast that are petite and yeast that are not, a certain percentage of the daughter ce

17、lls will be petite. Mitochondrial Inheritance第40页/共78页第四十一页，共78页。Mitochondrial Inheritance in Yeast第41页/共78页第四十二页，共78页。又称不均等的有丝分裂又称不均等的有丝分裂(yu s fn li)分离分离第42页/共78页第四十三页，共78页。在连续的细胞分裂过程中，异质性细胞中突变型在连续的细胞分裂过程中，异质性细胞中突变型mtDNAmtDNA和野生和野生型型mtDNAmtDNA的比例会发生漂变，向同质性的方向的比例会发生漂变，向同质性的方向(fngxing)(fngxing)发展。分裂

18、旺盛发展。分裂旺盛的细胞（如血细胞）往往有排斥突变的细胞（如血细胞）往往有排斥突变mtDNAmtDNA的趋势，经无数次的趋势，经无数次分裂后，细胞逐渐成为只有野生型分裂后，细胞逐渐成为只有野生型mtDNAmtDNA的同质性细胞。突变的同质性细胞。突变mtDNAmtDNA具有复制优势，在分裂不旺盛的细胞（如肌细胞）中逐具有复制优势，在分裂不旺盛的细胞（如肌细胞）中逐渐积累，形成只有突变型渐积累，形成只有突变型mtDNAmtDNA的同质性细胞。漂变的结果，的同质性细胞。漂变的结果，表型也随之发生改变。表型也随之发生改变。第43页/共78页第四十四页，共78页。This led to the sug

19、gestion that some genetic element existed in the cytoplasm and was inherited in a different manner from nuclear genes. This is called “non-Mendelian inheritance” or “cytoplasmic inheritance”.Mitochondrial InheritanceIn yeast and animals, this indicated inheritance of mitochondrial genes: in plants i

20、t also includes inheritance of chloroplast genes第44页/共78页第四十五页，共78页。Mitochondrial replication第45页/共78页第四十六页，共78页。Mitochondria replicate much like bacterial cells. When they get too large, they undergo fission. This involves a furrowing of the inner and then the outer membrane as if someone was pinch

21、ing the mitochondrion. Then the two daughter mitochondria split. Of course, the mitochondria must first replicate their DNA. An electron micrograph depicting the furrowing process is shown in these figures. Mitochondrial replicationcell division: random distribution of mitos between daughter cellsmi

22、tochondrialreplication第46页/共78页第四十七页，共78页。Sometimes new mitochondria are synthesized in centres that are rich in proteins and polyribosomes needed for their synthesis. The electron micrograph in the following figure shows such a centre. It appears that the cluster of mitochondria are sitting in a ma

23、trix of proteins and other materials needed for their production. 第47页/共78页第四十八页，共78页。Certain mitochondrial proteins are needed before the mitochondria can divide.They showed the result of the removal of an outer membrane protein from mitochondria called MDM10. This figure shows the results. The mit

24、ochondria are able to take in components and produce membranes and matrix enzymes. However, fission is not allowed and the result is a giant mitochondrion. giant mitochondrion第48页/共78页第四十九页，共78页。Human mtDNA small, double stranded circular chromosome 16,569 bp in total no non-coding DNA no introns po

25、lycistronic replication which is initiated from the D (displacement)- loop region followed by splicing of transcript to form messages.Organisation of the mitochondrial chromosome第49页/共78页第五十页，共78页。human mtDNAyeast mtDNAYeastmitochondrial chromosome第50页/共78页第五十一页，共78页。Human DNA 16,569 bp; no non-codi

26、ng DNA no introns polycistronic replication followed by splicing to form messages. Yeast mtDNA 68-75 kb, similar in structure to bacterial genome contains introns and non-regions between genes. Same proteins made as in animals genes transcribed separately第51页/共78页第五十二页，共78页。Despite having their own

27、genome, most mitochondrial proteins are encoded in the nucleus, made in the cytosol and imported into the mitochondria.第52页/共78页第五十三页，共78页。In all organisms, only a few of the proteins of the mitochondrion are encoded by mtDNA, but the precise number varies between organisms Subunits 1, 2, and 3 of c

28、ytochrome oxidase Subunits 6, 8, 9 of the Fo ATPase Apocytochrome b subunit of complexIII Seven NADH-CoQ reductase subunits (except in yeast)The nucleus encodes the remaining proteins which are made in the cytosol and imported into the mitochondrion. Synthesis of mitochondrial proteins第53页/共78页第五十四页

29、，共78页。Plant mtDNA chromosome size is much bigger but varies dramatically between species (200-2000 kb) arranged as different size circles, sometimes with plasmids. The plant mtDNA contains chloroplast sequences, indicating exchange of genetic information between organelles in plants. Much of the pla

30、nt mtDNA is non-coding, but coding regions are larger than animals and fungi. Number of proteins synthesised not known definitely but more than in animals and yeast (probably about 50)第54页/共78页第五十五页，共78页。Plant mitochondria have specialised functions in leaves they participate in photorespiration sit

31、es of vitamin synthesis (vit C, folic acid, biotin)第55页/共78页第五十六页，共78页。maize mitochondrial genome第56页/共78页第五十七页，共78页。In plants, respiration and photosynthesis operate simultaneously in the lightNIGHTDAY第57页/共78页第五十八页，共78页。Chloroplasts are the site of photosynthesis and belong to the plastid family o

32、f organelles - they develop from proplastids in the lightproplastidamyloplast (in storage organs)第58页/共78页第五十九页，共78页。Rice mitochondrial and chloroplast genomesPlant mitochondria contain chloroplast genes - suggesting that genetic transfer occurs between the two organelles第59页/共78页第六十页，共78页。Mitochond

33、rial DNA of animals and fungi uses a different genetic code than the “universal” code第60页/共78页第六十一页，共78页。RNA processing in mitochondriaPlant mitochondria “edit” their RNA transcripts. This was first noticed when comparing cDNA sequences with genomic DNA sequences.The most common change is to replace

34、 C with U, although in some instances other changes can occur. Matrix enzymes are thought to be responsible for this, but the reason for the editing is not known.Most of the DNA in plant mitochondria is non-coding, only some of which is transcribed. RNA editing occurs even in non-coding regions such

35、 as introns.第61页/共78页第六十二页，共78页。第62页/共78页第六十三页，共78页。第63页/共78页第六十四页，共78页。第64页/共78页第六十五页，共78页。Life on earth originated more than 3 billion years ago. The first cellular organisms were prokaryotic; they lacked true nuclei and cytoplasmic organelles and were heterotrophic.Eukaryotic organisms evolved 1

36、to 1.5 billions years ago. The first known eukaryotes were filamentous green algae, with nuclei and elaborate intracellular organization, including subcellular organelles.In the 1970 Lynn Margulis forcefully argued that both mitochondria and chloroplasts were once free-living organisms that became incorporated into primitive euk