Plant Cell, Development & Ultrastructure

Transcription

1 PCDU Lecture Plant Cell, Development & Ultrastructure Plant Cell Biology Labs Download at:

2 LHII: Light Harvesting Complex II Monomer Trimer Buchanan et al Chlorophylls 2 Carotinoids 36 Chlorophylls 6 Carotinoids

3 Light Harvesting Complexes LHCII 288 Chlorophylls 48 Carotinoids Buchanan et al. 2000

4 Regulation of Photosystem Activity Buchanan et al. 2000

5 Z-scheme of Electron Transport Ferredoxin FAD Phaeophytin Plastochinon Cytochrom b6/f Plastocyanin

6 Regulation of Photosystem Activity

7 Regulation of Photosystem Activity

8 Interplay Between Light- and Dark Reaction RubisCO Campbell Fig Photophosphorylation CO 2 -Fixation RubisCO = Ribulosebisphosphat Carboxylase/ Oxygenase

9 Calvin Cycle

10 Calvin Cycle

11 Fixing of CO 2 Under Normal Ambient Conditions Compartmentation of CO 2 Fixation C3 Plants Two Reactions Catalyzed by RubisCO Carboxylase Oxidative Splitting of R-1,5-bP under Stress Conditions: High Temperature Low CO 2 High O 2 Concentration Oxygenase Rescue Pathway Calvin Cycle

12 Compartmentation of CO 2 Fixation C3 Plants

13 Compartmentation of CO 2 Fixation C3 Plants

14 Compartmentation of CO 2 Fixation C3 Plants

15 Compartmentation of CO 2 Fixation C4 Plants

16 Compartmentation of CO 2 Fixation C4 Plants Raven et al Plastid Dimorphism in C4-Plants

17 Compartmentation of CO 2 Fixation C4 Plants RubisCO is Missing in Mesophyll Plastids. Photosystem II is Missing in Bundle Sheet Chloroplasts Carbon fixation takes place in the cytoplasm by PEP-carboxylase. Oxalic acid is formed, converted to malic acid, which gets imported into the bundle sheet cells. There, malic acid is converted back to CO 2 and pyruvate. Carbon gets fixed again, this time by RubisCO in the bundle sheet chloroplasts. Oxygen does not evolve in bundle sheet chloroplasts because photosystem II is missing. Raven: Biology of Plants Fig. 7-24

18 Compartmentation of CO 2 Fixation C4 Plants Aspartate C4 Photosynthesis

19 Compartmentation of CO 2 Fixation C4 Plants Malate C4 Photosynthesis

20 Compartmentation of CO 2 Fixation C4 Plants C4-/CAM-Plants Graham et al CAM = Crassulacean Acid Metabolism

21 Retrograde Signalling to the Nucleus EX: Executor proteins GUN: Genome uncoupling OGE: Organellar gene expression Tetpy: Tetrapyrrol STN: State transition (LHC-Kinase) ABA: Abscisic acid ROS: Reactive oxygen species

22 Import of Proteins into Chloroplasts Buchanan et al. 2000

23 Import of Proteins into Plastids

24 Import of Proteins into Plastids 1. Heterodimeric TOC-Receptor Discriminates Between.Fitting and Non-Fitting Transit Peptides 2. TOC-Receptor Binds to Fitting Transit Peptide 3. GTP Hydrolysis in both GTPases Opens TOC75 Channel.and Binding to Hsp70 Occurs 4. Transit to Inner Channel (TIC) and Hydrolysis of ATP β-barrel Protein β-barrel Protein Translocon in Outer Envelope Membrane of Chloroplasts β-barrel Protein Inaba & Schnell (2008) Biochem. J.413,

25 Import of Proteins into Plastids 5. TIC22 Couples Transport Between Outer and Inner Membrane 6. HSP93 Aids in Emergence of Preprotein at the Inner Surface 7. Stromal Processing Peptidase Cleaves Off Transit Peptide Inaba & Schnell (2008) Biochem. J.413, Translocon Inner envelope membrane of Chloroplasts)

26 Prokaryotic Cytoskeleton Proteins Actin-like distantly related proteins ParM Plasmid segregation

27 Bacterial FtsZ Proteins Screen of bacterial populations for Temperature-sensitive mutations affected in cell division FtsZ-Mutation Incomplete division leads to filament formation

28 Bacterial Fts-Proteins Margolin 2005

29 FtsZ Localization in Bacillus subtilis merge Chromosomal replication wall FtsZ Min-Proteins Margolin 2005

30 Phylogenetic Tree of FtsZ-Genes FtsZ2 (2-1 & 2-2) Chrysophyceae Cryptophyta Rhodophyta FtsZ1 FtsZ Does Not Occur in the Animal Kingdom

31 Expression of FtsZ GFP-Constructs Localization of FtsZ1 and FtsZ2-GFP in Equatorial Ring of Arabidopsis Chloroplasts

32 FtsZ Triple Mutant in Arabidopsis Schmitz et al FtsZ Triple Mutant of Arabidopsis is Viable Despite of Severe Chloroplast Phenotype

33 FtsZ-Proteins not more than 20% sequence homology! C-Terminus van den Ent et al FtsZ is Tubulin-Like GTPase with Mechanochemical Properties. FtsZ Forms Filaments, Tubes and Sheets. FtsT Polymer is Destabilized after Hydrolysis of GTP.

34 Polymer Structure of Dynamins and FtsZs

35 Contribution of Dynamins to PD rings Dynamin 100kDa GTP-hydrolyzing mechanochemical enzyme, peripheral membrane protein Pleckstrin-Domain PH = PIP2_binding Plekstrin-Homology Domain GED = GTPase regulatory Domain PRD = Prolin rich Domain Osteryoung 2001 Dnm Isoforms Dynamin cyt Phragmoplastin Cell plate Cell plate, chloroplast ADL2 (ARC5) outer PD ring + hgbp1 Mx Danino & Hinshaw 2001

36 Molecular Components of the PD Ring 5 Dynamin-like protein PDV1 PDV2 AtMinD1 AtMinE1 F1 F2 AtCDT1 3: Arc3... responsible for correct placement of Z-ring, protein with N-terminal FtsZ1-binding domain and C-terminal MORN-repeat (membrane binding) 5: Arc5...DLP, Dynamin-like 6: Arc6...cyanobacterial Ftn2 (ZipN), has a membrane anchor and a C-terminal J-domain binding to HSP70 chaperon, Arc6 also binds Cyclin-dependent kinase, possibly involved in temporal coordination of nuclear and plastidal division PDV1...plastid division protein, cytosolic partner of Arc5 PDV2...cytosolic partner of Arc5 AtMinDl...bacterial MinD-like, an ATPase, prevents Z-ring formation in unwanted sites AtMinEl...bacterial MinE-like, prevents Z-ring formation in unwanted sites GC1...cyanobacterial division inhibitor, SulA-like F1...AtFtsZ1can form heterodimers with AtFtsZ2 F2...AtFtsZ2 has a C-terminal CORE domain, binds Arc6 AtCDT1...cyclin-dependent kinase, forms part of the prereplication complex X...unidentified intermembrane space protein FtsZ1 in giant chloroplasts of MinE-overexpressing A. thaliana scale bar 5µm Fujiwara et al Min = mutants which produce minicell. Arc = mutants have defects in accumulation and replication of chloroplasts.

37 Division of Mitochondria Mitochondrial FtsZ and dynamin in eukaryotic lineages. Division of mitochondria does not require FtsZ in green plants, fungi and animals Arimura & Tsutsumi 2002 Mt = mitochondrial

38 Division of Mitochondria Kiefel et al. 2004

39 Division of Mitochondria Several Eukaryotic Lineages have Retained Copy of Mitochondrial FtsZ Haptophyta Chrysophyta Rhodophyta Glaucophyta Kiefel et al. 2004