生长素作用机制

1. 生长素作用机制 Mechanism of Auxins Action

2. The developmental processes that are controlled by auxin flux

3. Control of leaf vein formation by polar auxin transport.

4. Queations 1.Discuss the evidence for the role of auxin in the following physiological phenomena: apical dominance, lateral and adventitious roots, leaf abscission, floral bud development, fruit development, and vascular differentiation. 2. What is ABP1? Which auxin responses does it seem to regulate? 3. What are early auxin-responsive genes? 4. Diagram and discuss the current model for the role of the AUX/IAA gene family in regulating the early auxin-responsive genes.

5. ABP1 and downstream auxin responses ABP1 located at the plasma membrane is involved in the control of early auxin electrophysiological responses. ABP1 is located both in the ER and at the outer face of the plasma membrane but the ABP1 in ER does not bind auxin.

6. 控制生长素的转录反应 • Aux/IAA 家族属于生长素快速诱导的半衰期很短的核蛋白，有4 个保守结构域. 其中结构域Ⅱ的13 个氨基酸特异序列是Aux / IAA 蛋白家族中共有的保守序列。 ARF生长素响应因子能与生长素早期反应基因启动子中的生长素应答元件（AuxRE）TGTCTC 序列特异性结合，由氨基酸的组成决定该蛋白具有调节生长素反应基因表达的转录激活或抑制作用.

7. ARF protein binds an AuxRE promoter element. • Under low-auxin conditions, Aux/IAA repressor binds ARF via heterodimerization between Aux/IAA and ARF domains III and IV. • (B) Auxin promotes Aux/IAA domain II-TIR1 association, bringing the Aux/IAA protein to the SCFTIR1 complex for ubiquitination and subsequent destruction by the 26S proteasome. • The activating ARF, with a Gln-rich (Q) middle domain, is then freed to promote auxin-induced gene expression. Woodward and Bartel, 2005 By interacting with specific substrates, the F-box proteins confer specificity to the degradation machinery.

8. Chaperone Mediated Protein Folding & Misfolding

9. Degradation of Misfolded Proteins • Lysosomal (extracellular) protein degradation • Protein degraded by lysosomal enzymes • Cytosolic (intracellular) protein degradation • The Ubiquitin Proteosome pathway

10. Cytosolic protein degradation • The Ubiquitin Proteosome Pathway www.ihf.de/forschung/ popup/ubiquitin.html

11. TIR1, a F-box protein, is an auxin receptor WT tir1 Rapid association and dissociation of TIR1–Aux/IAA complexes. Insensitive responses Interact with Aux/IAA domain II peptides in an auxin-dependent manner. Kepinski and Leyser, 2005

12. Crosslink of ABP1 and TIR1 signaling pathways • ATPase is rapidly stimulated by auxin ,ABP1 is the receptor relevant for this process. • Auxin induced de-novo synthesis of ATPase. Christian et al., 2006

13. Many of the proteins involved in plant hormone signalling pathways have been identified. • Strikingly, the ubiquitin–proteasome pathway plays a central part in most hormone-signalling pathways. • Hormone signalling is integrated at several levels during plant growth and development.

14. The Plant Cell, 2004,16, 3181–3195 The Ubiquitin-Proteasome Pathway and Plant Development The ubiquitin/26S proteasome (Ub/26S) pathway in Arabidopsis thaliana . COP1 Single subunit ring E3s SINAT5 The family of E3 ubiquitin ligases ARC1 ＳＣＦ Multisubunit ring E3s CUL3-BTB APC SCF 复合体主要由4 种蛋白组成：Skp1，Cullin （酵母中是Cdc53），Roc1 / Rbx1 / Hrt1 及F-box 蛋白.

15. 26S proteasome The Ubiquitination-Proteasome Pathway E1 SH E2 SH AMP ATP Ub E1 E2 S S E1 SH E3 substrate substrate E3 E2 S

16. Plant Sumoylation System

17. Model of auxin action SCFTIR1-Aux / IAA 复合体

18. A direct auxin-dependent interaction between the F-box protein TIR1 and several AUX/IAA proteins has been demonstrated, and two AUX/IAA proteins (IAA7 and IAA17) are stabilized in the tir1 mutant.

19. (Nature Chemical Biology,2009,5:301-307)

20. 黄少明介绍 • Auxin response factor 2 (ARF2) plays a major role in regulating auxin-mediated leaf longevity

21. Model depicting interactions between auxin function components and key genetic pathways controlling leaf development in Arabidopsis thaliana

22. Domain structures of the Aux/IAA and ARF families found in A. thaliana, S. moellendorffii and P. patens. BMC Evolutionary Biology 2009, 9:126

23. S. cerevisiae H. sapiens A. thaliana E1 Number in gene family 1 2 2 E2 E3 13  45  50 HECT RING/U-Box 50 7 5 APC Apc10 48 >500 600 SCF F-box 12 1 20 14 38 694 Evolutionary distribution of Ubiquitin processing enzymes

24. 赤霉素作用机制 Mechanism of Gibberellins Action

25. Gibberellins: Regulators of plant height • Gibberellins stimulate cell elongation and cell division • Gibberellins enhance cell wall extensibity without acidification • Gibberellins regulate the transcription of cell cycle kinases in intercalary meristem

26. Pea as a Model System to Study Hormonal Interaction Seeds Required for Pericarp Growth and Bioactive GA1 Production

27. GA Signaling Intermediates • GAI (a protein coded by GA-Insensitive gene ) • RGA ( a negative factor) • SPY ( a negative regulator of GA responses) SPY序列与动物的氧-乙酰-葡糖胺转移酶（O-GlaNAC transferase, OGT）高度相似 . 将UDP-GlcNAc的GlcNAc转移到目标蛋白Ser/Thr残基上, 促进RGA和GAI阻碍GA诱导基因的表达.

28. GRAS Proteins • The GRAS proteins are a family of plant specific proteins named afterGAI, RGA and SCR. • Their C-termini show considerable sequence homology. The N-terminal portion of each GRAS protein is highly divergent.

29. DELLA Proteins as Integrators of Multiple Signals GA反应转录因子,在高等植物中结构高度保守，属于GRAS蛋白家族. .

30. GID1-mediated gibberell in signaling in plants YAB1 GA-INSENSITIVE DWARF1

31. 李天丰介绍 • Characterization of the Molecular Mechanism Underlying Gibberellin Perception Complex Formation in Rice

33. Model for the Proteolysis-Independent Regulation of DELLA Repress or Activity.

34. GID1-mediated gibberellin signaling in plants (Hirano et al., 2009)

35. (Nature Chemical Biology,2009,5:301-307)

36. Gibberellin signal transduction:cereal aleurone layers • Gibberellic acid enhances the transcription of α-amylase mRNA • A GA-MYB transcription factor regulates α-amylase gene expression • Gibberellin receptors may interact with G-proteins on the plasma membrane • Signaling intermediates

37. 谢谢！