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Lecture 5 Plant hormones and Signal transduction

Lecture 5 Plant hormones and Signal transduction. PLSC 452/552 1/23/14 Department of Plant Sciences Neal Stewart Lab. Brain teaser .

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Lecture 5 Plant hormones and Signal transduction

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  1. Lecture 5Plant hormonesandSignal transduction PLSC 452/552 1/23/14 Department of Plant Sciences Neal Stewart Lab

  2. Brain 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 be when Little Johnny returns as Big Johnny in 15 years?

  3. 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: introduction

  4. What is a hormone? • 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 responsive

  5. Major plant hormones • Auxin – Greek: auxein; to grow 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.

  6. Finding plant hormones Observational: Darwin stumbles on auxin • Noticed grass tips grow toward light • With tip growth responded to light • Without tip growth had no response Mutation screening: (aka forward genetics) • Dwarf plants are can be hormone deficient

  7. ABRC teaching tools website

  8. General hormone biochemistry • Present in all cells at various levels • Classes of hormones work in signal cascades • Hormone-receptor interactions • Respond to a host of factors and biological needs • Abiotic • Water stress • Light • Nutrient deficiency • Biotic • Growth • Development • Herbivore stress

  9. Hormone biosynthesis Made from four biosynthetic pathways: • Terpenoids • AMP + IPP (cytokinins) • Carotenoid breakdown (abscisic acid) • Diterpene (gibberellic acid) • Triterpene (brassinosteroids) • Fatty acids (jasmonic acid) • Tryptophan (auxins) • Methionine (ethylene)

  10. KEGG database: http://www.genome.jp/kegg/

  11. Auxins • Greek: auxein; to grow or increase • Apical dominance growth • Cell elongation • Hormone level very important 2, 4-dichlorophenoxyacetic Acid http://pubchem.ncbi.nlm.nih.gov/

  12. http://www.nsf.gov/news/news_images.jsp?cntn_id=104205

  13. Taiz and Zeiger. 2002. Plant Physiology, 3rd Ed.

  14. Auxin: Apical dominance http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Auxin.html

  15. Cytokinin • Cytokinesis (cell division) • Accidently added degraded DNA to medium • Organization and development of xylem tissue • Response to light • Lateral growth of shoots • Open stomata Kinetin http://pubchem.ncbi.nlm.nih.gov/

  16. Application: cotton spraying • Adding cytokinins to young cotton increase drought-resistance • Arizona – 31% US cotton, highest yield acre-1

  17. Auxin 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 = Shoot growth • >Auxin = Cytokinin = Root growth

  18. Auxin Cytokinin http://users.ugent.be/~pdebergh/pri/pri4ez04.jpg

  19. Abscisic 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 http://pubchem.ncbi.nlm.nih.gov/

  20. http://www.rikenresearch.riken.jp/eng/research/6121

  21. Jasmonic acid • First identified in jasmine oil • Response to biotic stress • Wounding induces JA biosynthesis • Microbial and fungal invasion • Plant growth effects similar to auxin • Specialty growth structures http://pubchem.ncbi.nlm.nih.gov/

  22. Jasmonic acid: Plant-insect co-evolution Tri-trophic interactions Degenhardt(2009) Plant Physiology 149:96-102

  23. Jasmonic acid: Pathogen response http://park.itc.u-tokyo.ac.jp/biotec-res-ctr/kampo/eng/research_plant.html

  24. Gibberellic acid • Originally found in Gibberella (rice pathogen) • Responsible for ‘foolish seedling’ phenomenon • Uninhibited growth until breaking • Involved in cell elongation • Flowering and seed germination http://pubchem.ncbi.nlm.nih.gov/

  25. Modification of GA in rice Miyako Ueguchi-Tanaka 2005 Nature437, 693-698

  26. Spraying GA for increased fruit yield GA induces fruiting in absence of seed http://www.extension.org/pages/31607/using-plant-growth-regulators-to-increase-the-size-of-table-grape-berries#.Ut9EYbROmM8

  27. Ethylene: the cell phone of PGRs • A hydrocarbon gas • Involved in fruit ripening, stress response • Inhibition of growth in dark conditions • Excess ethylene inhibits callus growth

  28. Conversational Plants? • Ethylene production increases during stress • Drought • Heat • Perceived by neighboring plants • Unstressed plants induce stress pathways

  29. Brassinosteroids • Stress responses • Switchgrass suspension cells have minor amounts of lignin (small amounts of H monolignols) • Addition of brassinolide induces normal lignin formation and composition • Stem elongation • Seed germination • Pollen tube growth • Cell differentiation control Brassinolide http://pubchem.ncbi.nlm.nih.gov/

  30. Overview of hormone mutants Cytokinin mutant Brassinosteroid mutant Cytokinin mutant closer look Ethylene mutant grown in dark Abscisic acid mutant Bishopp A et al. Development 2006;133:1857-1869

  31. Hormones (PGR) pathways • PGRs work in complex cascades to produce signals • Synergistic • Anatognistic • Variety of actions in cell • Gene transcription • Protein degradation http://chriscarterart.wordpress.com/2010/05/09/mothers-day-2/mikado-plant-watercolor-sketch-chris-carter-050910/

  32. Arabidopsis histidine kinase sensing and signaling; 2) A histidine phosphotransferase protein nuclear translocation; 3) A response regulation transcription activation; and 4) a negative feedback loop through cytokinin-inducible ARR gene products. http://molbio.mgh.harvard.edu/sheenweb/cytokinin_signaling.html

  33. 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 induction

  34. Lecture summary • Hormones are biochemicals that regulate plant growth based on biological and environmental cues • Auxin and cytokinin are key for plant growth • Abiotic and biotic stress response is regulated by hormones • Cell signaling is regulated by specific receptors on cell membranes

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