Plant Hormones and Signal Transduction植物激素与信号转导

1、Lecture 5Plant hormonesandSignal transductionPLSC 452/5521/23/14Department of Plant SciencesNeal Stewart LabBrain teaser Little Johnny nails a sign 90 cm off the ground to a tree outside of his clubhouse that says “no girls allowed.” If the tree grows 12 cm every year, at what height will the sign b

2、e when Little Johnny returns as Big Johnny in 15 years?Overview Define “hormone” as a functional compound. What is the function and importance of hormones? Know the major plant hormones Understand real-world application of hormones Importance of hormones for tissue culture: introductionWhat is a hor

3、mone? Biochemical which regulates growth based on biological and environmental influences Synonyms: Plant hormones, plant growth regulators (PGRs), phytohormones Regulate growth and development Mobile throughout plant Environment and stress responsiveMajor plant hormones Auxin Greek: auxein; to grow

4、 or increase Cytokinin cytokinesis (cell division) Abscisic acid abscission Jasmonic acid found in jasmine oil Gibberellic acid pathogen Gibberella Ethylene chemical brother to ethanol Brassinosteroids derived from Brassica spp.Finding plant hormonesObservational:Darwin stumbles on auxin Noticed gra

5、ss tips grow toward light With tip growth responded to light Without tip growth had no responseMutation screening: (aka forward genetics) Dwarf plants are can be hormone deficientABRC teaching tools websiteGeneral hormone biochemistry Present in all cells at various levels Classes of hormones work i

6、n signal cascades Hormone-receptor interactions Respond to a host of factors and biological needs Abiotic Water stress Light Nutrient deficiency Biotic Growth Development Herbivore stressHormone biosynthesisMade from four biosynthetic pathways: Terpenoids AMP + IPP (cytokinins) Carotenoid breakdown

7、(abscisic acid) Diterpene (gibberellic acid) Triterpene (brassinosteroids) Fatty acids (jasmonic acid) Tryptophan (auxins) Methionine (ethylene)KEGG database: :/Auxins Greek: auxein; to grow or increase Apical dominance growth Cell elongation Hormone level very important2, 4-dichlorophenoxyacetic Ac

8、id :/ :/=104205Taiz and Zeiger. 2002. Plant Physiology, 3rd Ed.Auxin: Apical dominanceCytokinin Cytokinesis (cell division) Accidently added degraded DNA to medium Organization and development of xylem tissue Response to light Lateral growth of shoots Open stomata :/KinetinApplication: cotton sprayi

9、ng Adding cytokinins to young cotton increase drought-resistance Arizona 31% US cotton, highest yield acre-1Auxin and cytokinin ratio importance Auxin alone = Large cells (no division) Cytokinin alone = Cells have no change Auxin + Cytokinin = Normal cell growth and division Auxin + Cytokinin = Shoo

10、t growth Auxin = Cytokinin = Root growthAuxinCytokininAbscisic acid (ABA) Originally implicated in leaf and fruit abscission Involved in leaf senescence Maintains seed dormancy (opposed to GA) Involved in stomata regulation (closes) Single hormone unit :/Jasmonic acid First identified in jasmine oil

11、 Response to biotic stress Wounding induces JA biosynthesis Microbial and fungal invasion Plant growth effects similar to auxin Specialty growth structures :/Jasmonic acid: Plant-insect co-evolutionTri-trophic interactionsDegenhardt (2009) Plant Physiology 149:96-102Jasmonic acid: Pathogen responseG

12、ibberellic acid Originally found in Gibberella (rice pathogen) Responsible for foolish seedling phenomenon Uninhibited growth until breaking Involved in cell elongation Flowering and seed germination :/Modification of GA in riceMiyako Ueguchi-Tanaka 2005 Nature 437, 693-698Spraying GA for increased

13、fruit yieldGA induces fruiting in absence of seed :/ /pages/31607/using-plant-growth-regulators-to-increase-the-size-of-table-grape-berries#.Ut9EYbROmM8Ethylene: the cell phone of PGRs A hydrocarbon gas Involved in fruit ripening, stress response Inhibition of growth in dark conditions

14、Excess ethylene inhibits callus growthConversational Plants? Ethylene production increases during stress Drought Heat Perceived by neighboring plants Unstressed plants induce stress pathwaysBrassinosteroids Stress responses Switchgrass suspension cells have minor amounts of lignin (small amounts of

15、H monolignols) Addition of brassinolide induces normal lignin formation and composition Stem elongation Seed germination Pollen tube growth Cell differentiation controlBrassinolide :/BrassinosteroidmutantBishopp A et al. Development 2006;133:1857-1869Overview of hormone mutantsEthylenemutantgrown in

16、 darkCytokininmutantCytokininmutantcloser lookAbscisic acidmutantHormones (PGR) pathways PGRs work in complex cascades to produce signals Synergistic Anatognistic Variety of actions in cell Gene transcription Protein degradation :/Arabidopsis histidine kinase sensing and signaling; 2) A histidine ph

17、osphotransferase protein nuclear translocation; 3) A response regulation transcription activation; and 4) a negative feedback loop through cytokinin-inducible ARR gene products. Introduction: the importance of manipulation of hormones for tissue culture Auxins and cytokinins are very important Higher auxin induces root growth Equal ratio induces callus and cell enlargement Lower auxin induces shoot growth Gibberellic acid germinates difficult seeds Add brassinosteroids for cell wall inductionLectu