1. HORMONE PHYSIOLOGY AND SIGNAL TRANSDUCTION Huseyin Tombuloglu, Phd. GBE 304 Spring 2015

2. ABSCISIC ACID A Seed Maturation and Antistress Signal

3. Brassicas in the field

4. Poppies in the field Controlling of timing How they know the blooming time?

5. Figure 23.3 Precocious germination in the ABA- deficient vivipary 14 mutant of maize

6. Abscisic Acid (ABA) For many years, plant physiologists suspected that the phenomena of seed and bud dormancy were caused by inhibitory compounds, and they attempted to extract and isolate such compounds from a variety of plant tissues, especially dormant buds.

7. Abscisic Acid (ABA) Natural inhibitory compound. Affects bud and seed dormancy. Affects leaf abscission. Controls stomatal closure in drought-stressed plants. Promotion of flowering in short-day plants….plants that flower when the day- length is shorter than some critical period. May also influence cold-hardiness.

8. Functions of ABA Additions if ABA, or natural production in plants will: Promote seed dormancy. Promote bud dormancy. Accelerate leaf abscission. The dormancy response caused by ABA in plants may result from suppression of RNA and protein synthesis.

9. Positive ABA-activated regulators (top, in green) and negative ABA- signalling regulators (bottom, in red) in guard cells are shown. http://www.nature.com/nat ure/journal/v410/n6826/fu ll/410327a0.html http://biology.ucsd.edu/l abs/schroeder/clickable gc.html

13. Two more hormones… There are two more hormones to discuss...

14. Brassinolide (Br) It is a sterol, much like estrogen and testosterone (which function as sex hormones in animals). Critical for normal plant growth and development. Plays roles in stem elongation, leaf development, pollen tube growth, vascular differentiation, seed germination, photomorphogenesis, and stress responses.

15. Jasmonic Acid (JA) JA is a fatty-acid-derived plant hormone that is similar in overall structure to physiologically active small molecules from animals called prostaglandins. In plants, jasmonic acid is firmly associated with pathogen defense pathways.

16. Jasmonic Acid (JA) The physical stimuli of certain insects can trigger the synthesis of JA, which then functions to increase expression of genes involved in defending the plant. Microbial and viral pathogens can also trigger JA synthesis. The study of JA-mediated events in the plant cell are of interest to plant pathologists who wish to engineer transgenic plants that are disease-resistant.

17. Signal Transduction Signals from outside a cell can be perceived, sometimes by receptors that span the plasma membrane. After stimulation of such receptors, information can be relayed by a series of small molecules or proteins to the cell nucleus, where activation of specific transcription factors can stimulate new gene expression programs. The resulting gene expression results in the production of new proteins that can function in the final biological responses to the signal.

18. Signal Transduction

19. Summary Hormones elicit a multitude of growth & development responses in plants. Identified the major plant hormones. Identified modes of action/practical applications. Identified signal transduction mechanisms. Play vital roles in sensing endogenous/exogenous signals…and causing a plant response.