Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Botanik 1 • Föreläsning 080513 • Johan Edqvist • [email protected] Gibberelliner (GA) Fler än 125 olika gibbereliner har identifierats Tetracykliska terpenoider Gibberelliner (GA) Upptäcktes av japanska forskare på 1920-talet Risplantor som blev tokigt långa ”bakanae eller foolish seedling disease” efter infektion av svampen Giberella fujikoroi. 1958 isolerades GA från rosenbönan Phaseolus coccineus. GA GA syntetiseras via Terpenoid pathway. Innehåller syntessteg i plastider, ER och cytosol. Gibberelliner (GA) Syntes av GA sker i många olika vävnader Gibberelliner (GA) Fenotyper hos Arabidopsis plantor med mutationer vid olika steg av GA syntesen. Gibberelliner (GA) Stimulerar tillväxt GA stimulerar både celldelning och cellelongering Dvärgmutant Gröna revolutionen 60- o 70-talet Ris, vete Dvärgmutanter +Gibberellin Gibberelliner (GA) GA stimulerar både celldelning och cellelongering Tillsats av GA påverkar dvärgmutant men inte vildtyp. Gibberelliner (GA) GA3 kan inducera bolting och blomning i kål Gibberelliner (GA) Påverkar fruktutveckling Thompson Seedless +Gibberelin (GA3) Gibberelliner (GA) Reglerar frövila och frögroning GA 100 pp miljard GA 1 pp miljard Vatten Gibberelliner (GA) Reglerar frövila och frögroning korn GA verkar i aleuronelagret Samspel mellan GA och ABA Tobak Brassica Styr frövila och frögroning Samspel mellan GA och ABA Styr frövila och frögroning Gibberelliner (GA) Gibberelliner (GA) Gibberelliner (GA) A tropism is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. Types of tropisms Chemotropism: in response to chemicals Geotropism or Gravitropism: in response to gravity Hydrotropism: in response to moisture or water Heliotropism: in response to sunlight Phototropism: response to light Thermotropism: to temperature Thigmotropism: in response to touch or contact Phototropism Phototropism Phototropism Blue-light 400-500 nm Phototropism Expression of the DR5::GUS reporter in hypocotyl of untreated (a) or auxin efflux inhibitor (NPA)-treated (b) wild-type seedlings upon stimulation by light (a, b) Friml et al (2002) Nature 415: 806-809 Phototropin Ingen phototropism i nph-mutanter nph: non-phototrophic hypcotyl NPH= photoreceptor phototropin (Phot1) Liscum & Briggs (1995) Plant Cell 7, 473-485 Phototropin Nph1(Phot1) undergoes autophosphorylation and functions as a photoreceptor for phototropism NPH photoreceptorn phototropin är ett plasmamembran associerat phosphoprotein med massan 120kD. Phototropins are blue-light receptors controlling a range of responses that serve to optimize the photosynthetic efficiency of plants. Liscum & Briggs (1995) Plant Cell 7, 473-485 Phototropin Phot1 & Phot2 har överlappande funktioner Annual Reviews Phototropin Light drives the formation of a covalent adduct between the FMN chromophore and a conserved cysteine residue within the LOV domain. In darkness, the FMN chromophore is noncovalently bound within the LOV domain, forming a species that absorbs maximally at 447 nm (LOV447). Light drives the production of a highly reactive triplet-state flavin (LOV660) that leads to formation of a covalent bond between the C(4a) carbon of the FMN chromophore and a conserved cysteine residue within the LOV domain (LOV390). Annual Reviews Phototropin Expression of the phot1-GFP Fusion Protein in 3-DayOld Etiolated Seedlings. Sakamoto & Briggs (2002) Plant Cell 14: 1723-1735 Gravitropism Root gravitropism Perception of gravity is correlated with sedimentation of amyloplasts Root cap Columella cells from root cap Amyloplast: Starch-containing non-pigmented plastids Columella cells Amyloplasts and gravity Starch-statholith hypothesis: amyloplasts=gravity sensors Gravitropism Starch-statholith hypothesis: amyloplasts=gravity sensors Protoplast pressure hypothesis: The weight of the entire protoplast changes the gravity perception of the plant. Tensegrity model (tensegrity = tensional integrity): The interaction of falling amyloplasts with the structural integrity of the cell is responsible for gravitropism. Actin filaments form a structural meshwork anchored to the plasma membrane. The amyloplasts create tension which leads to disruption of the actin meshwork. Because actin tension affects calcium channels on the plasma membrane, we expect a transient increase in cytosolic Ca2+ level. Auxin and root gravitropism Assymetric distribution of auxin Growth inhibition on lower side of root Gravistimulation results in asymmetric auxin accumulation in lateral root cells Auxin and root gravitropism PIN3-auxin efflux carrier Efflux: something that flows out b, c, pin3 hypocotyls are defective in gravitropic (b) as well as phototropic (c) responses. Scale bars, 500 m. d, pin3 mutants are defective in root gravitropism. Each gravistimulated root was assigned to one of twelve 30° sectors. The length of each bar represents the percentage of seedlings showing direction of root growth within that sector. Friml et al (2002) Nature 415: 806-809 Gravitropism Cytokinin and root gravitropism GUS reporter gene Symmetrical distribution of cytokinin Asymmetrical distribution of cytokinin Circadian rythms Regular rhythms of growth and activity, which occur in an approximately 24-hour cycle day night Diurnal movements Controlled internally-the biological clock Circadian rythms Fig. 1. The circadian system has a regulatory role in nearly all aspects of a plant's life. (A) Germination, (B) hypocotyl elongation, (C) leaf movements, (D) circumnutations, (E) shade avoidance, (F) flowering time, (G) flower opening, (H) scent production, (I) tuberization, (J) winter dormancy, (K) stomatal opening, (L) photosynthesis, (M) photoprotection, and (N) protection from temperature extremes. Environmental signals: zeitgeibers Free-running Suspension of circadian rhytm Restart PHY (phytochromes) red-light-sensing CRY (cryptochromes) blue-light-sensing Figure 1 Schematic representation of circadian clock structures PHY (phytochromes) red-light-sensing CRY (cryptochromes) blue-light-sensing Biochemical Journal www.biochemj.org Biochem. J. (2006) 397, 15-24 Circadian oscillator Light at dawn activates LHY and CCA1 LHY and CCA activates LHCB and other morning genes LHY and CCA repress TOC1 and other evening genes Circadian oscillator Reduction of LHY and CCA1 during the day allows increase in TOC1-levels TOC1 stimulates expression of LHY and CCA1 The circadian clock of Arabidopsis has an intrinsic period of between 22 and 29 h, depending on plant accession and growth conditions. Consequently, the clock mechanism is reset each dawn and/or dusk to prevent the clock becoming increasingly desynchronized with the external light/dark cycles. CCG: circadian clock genes Figure 4 Model of the Arabidopsis circadian clock PHY (phytochromes) red-light-sensing CRY (cryptochromes) blue-light-sensing Biochemical Journal www.biochemj.org The circle around the model indicates time of day, with 0 representing dawn. Components are positioned within the circle according to their approximate maximal transcript abundance in continuous light, with the exception of LKP2 and ZTL which are not transcribed in a circadian-dependent manner [105,108] and thus are represented by hexagons. Biochem. J. (2006) 397, 15-24 CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) Wang and Tobin (1999) Cell 93: 1207-1217 CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) Wang and Tobin (1999) Cell 93: 1207-1217 Correct circadian period enhances growth and survival. Dodd et al (2005) Science 309: 630 - 633 ztl-1 [= 27.1 hours–32.5 hours] toc1-1 [= 20.7 hours] Correct circadian period enhances growth and survival. ztl-1 [= 27.1 hours–32.5 hours] toc1-1 [= 20.7 hours] Dodd et al (2005) Science 309: 630 - 633 Photoperiodism Daylength and flowering Photoperiodism LDP: Blommar när daglängden överskrider en viss kritisk längd SDP: Blommar när daglängden är kortare än en viss kritisk längd. Photoperiodism Gullfrö Light period shorter than a critical length Bolmört Light period longer than a critical length 22,5C: 10h 20min Photoperiodism Short-day Long-day Chrysantemum Short-day plant Short-day Long-day Spinach Long-day plant Photoperiodism Photoperiodism Red light Red light Red light Far-red light Red light Far-red light Red light Far-red light Red light Far-red light Phytochromes: red-light receptors Red light induces germination Far-red light prevents germination Phytochromes: red-light receptors Pfr=Biologically active Present in two forms (Pr (r=red) and Pfr (fr=far-red)) with different absorption spectra Phytochrome Pfr=Biologically active Phytochrome Phytochrome chromophore (Pr form) Phytochrome Phytochrome Phytochrome Phytochrome Fotomorfogenes Thigmotropism Growth in response to touch Thigma is the Greek word for touch Thigmonastic movements Mimosa pudica Touch response Nastic movement: Movement that is caused by an external stimulus, such as light or temperature, but is directionally independent of its source, unlike tropisms. Nastic movement: Movement that is caused by an external stimulus, such as light or temperature, but is directionally independent of its source, unlike tropisms. Thigmonastic movements – mechanical stimulation Nyctinastic movements - sleep movements Changes in turgor pressure Turgor pressure or turgidity is the pressure of the cell contents against the cell wall, in plant cells, determined by the water content of the vacuole, resulting from osmotic pressure. Nastic leaf movements Changes in size of the parenchyma cells in the pulvinus Changes in turgor pressure On receiving the action potential signal, the cells in the lower half of the pulvinus respond by expelling potassium and chlorine ions and taking up of calcium ions. This results in an osmotic gradient that draws water out of the affected cells. The lower pulvinus cells temporarily shrink due to water loss. This forces the entire structure to curve down in the manner of a fan. In this contracted position, the pulvinus no longer functions as a support and the petiole droops. Thigmonastic movements Thigmonastic movements Nastic movement: Movement that is caused by an external stimulus, such as light or temperature, but is directionally independent of its source, unlike tropisms. Thigmomorphogenesis Untouched Touched