细胞分裂素作用机制

1. 细胞分裂素作用机制 Mechanism of Cytokinin Action

2. Science,2007; 318: 68-69:

3. Cytokinins are perceived by histidine kinases and transduced by a two- component system (TCS) His phosphotransmitter proteins

4. The two-component and the multistep phosphorelay signaling systems

5. The Cytokinin Receptor Family: AHKs • CKI1 (cytokinin independent 1) • CRE1/AHK4/WOL (cytokinin response 1) • The WOODEN LEG Puzzle • AHK (Arabidopsis histidine kinase) AHK2 and AHK3 AHK1 and AHK5

6. 拟南芥CKI1基因编码的产物具有调控蛋白区域以及组氨酸激酶相似的序列; 组氨酸激酶中有5个保守位点(如His405）以及调控蛋白中包括磷酸化位点Asp1050高度保守氨基酸残基。

7. Cytokinin Premary Response Genes • Type-AARRs(Arabidopsis response regulator) 转录抑制剂 • Type-BARRs 转录激活子 • Type-CARRs (ARR22, ARR23)

8. Type-A promoter GUS fusions

9. Overexpression of a Type-A ARR Alters Rice Morphology and Cytokinin Metabolism (Naoya Hirose et al.,2007)

12. The Type-C RRs Represent the Most Ancient RR Group 藻类 水稻 杨树 The number of receptors remained fairly constant, while the other protein families expanded. Plant Physiology, 2009, 151, 782–791

13. AHP (Histidine-phosphotransfer Proteins)磷酸转运蛋白 Cyclases/histidine associated Sensory extracellar domain Hutchison et al, 2003

14. Newly identified components of cytokinin response • The CRF1–6 proteins have uniform localization throughout the cell; however, when treated with cytokinin they move rapidly into the nucleus. • This process is dependent on both the ck receptors and the AHPs but independent of the type-A or type-B ARRs. • GLABOROUS1 ENHANCER BINDING PROTEIN (GeBP) was identified through a yeast one hybrid screen as it bound to the promoter of the cytokinin-induced myb gene GLABOROUS1/

16. The triple mutant is less sensitive to exogenous cytokinins and has higher levels of type-A ARR transcripts. • Transcript levels of type-A ARRs are partially insensitive to exogenous cytokinins in the triple mutant. • 35S:VP16:GPL2 plants have reduced ARR transcript levels and display increased cytokinin sensitivity.

17. International Review of Cell and Molecular Biology, 2009, 276,

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

19. Functional analysis of AHK1/ATHK1 and cytokinin receptor histidine kinases in response to abscisic acid, drought, and salt stress in Arabidopsis ( PNAS 2007,104 :20623–20628)

20. Cytokinin signaling regulates cambial development in poplar (PNAS,2008,50:20032-20037)

21. 张小霞发言 • Anna Skylar et al., STIMPY mediates cytokinin signaling during shoot meristem establishment in Arabidopsis seedlings. Development. 2010, 137(4): 541–549

22. 脱落酸作用机制 Mechanism of Abscisic acid Action

23. ABA responses in Arabidopsis seed dormancy post-germinationgrowth stomatal closure inhibition of root growth ABA regulated gene expression

24. The sequence of measurable early ABA-signaling events in guard cell J Plant Growth Regul (2005) 24:1–12

25. Summary of guard cell signaling and ion channel regulation.

26. (Paul E Verslues1 and Jian-Kang Zhu,2007)

27. The RNA-binding protein FCA is anabscisic acid receptor Nature, 2006,439:19

28. The ABA receptors – we report you decide A number of potential abscisic-acid receptors have recently been described but some of these studies have been controversial. Peter McCourt and Robert Creelman (Current Opinion in Plant Biology 2008, 11:474–478)

29. The first ABA binding protein isolated (ABAP1) was identified in barley aleurone . ABAP1 and FCA differ in several fundamental aspects. • Magnesium protoporphyrin-IX chelatase H subunit (CHLH) ,also called GUN5in Arabidopsis (Shen et al.,2006). • A G-protein coupled receptor called GCR2 (Liu et al.,2007). • GTG1 and GTG2 act redundantly to mediate abscisic-acid responses (Risk et al.,2009). • a family of START proteins PYR/ PYL function as abscisic-acid receptors (Park etal.,2009;Ma et al.,2009).

30. Magnesium protoporphyrin-IX chelatase H subunit ABA binding by the H-subunit of the chloroplast CHLH.

31. Controversion • Barley chlorophyll-deficient mutants with mutations in the XanF gene (as the CHLH in Arabidopsis) showed no ABA-related phenotypes in seed germination, post-germination growth, and stomatal movement, and the ABA-binding activity of XanF was not detected using the system of the authors. (Muller and Hansson, 2009,Plant Physiol).

32. New Evidence in Arabidopsis Using a newly-developed ABA-affinity chromatographytechnique, we showed that the Mg-chelatase H subunit ABAR/CHLH specifically binds ABA through the C-terminal half. (Fu-Qing Wu et al.,Plant Physiol, 2009 )

35. Controversion • This is not clear that GCR2 has a trans -membrane domain. In addition, genetic analysis of the GCR2 family failed to detect an ABA related phenotype. At this point, GCR2 appears unlikely to function as an ABA receptor.

36. ( Science,2007,318:914c) 羊毛硫氨酸

37. Although we cannot rule out GCR2 as a lanthionine synthetase homolog, our data indicate that it may define a new type of nonclassical G protein–coupled receptor. (Science,2007,318:914d)

38. The Plant Journal (2007) 52, 1001–1013

39. Peter McCourt and Robert Creelman (Current Opinion in Plant Biology 2008, 11:474–478)

40. GPCR ( protein-coupled receptors)-type G protein :GTG1 and GTG2 • Arabidopsis mutants lacking both GTG1 and GTG2 exhibit ABA hyposensitivity. (Cell, 2009, 136:136–148)

42. GTG1 and GTG2 Interact with GPA1, and GTP-GPA1 Inhibits GTPase Activity of the GTGs

43. a classic ABA receptor involved in G protein signaling • receptor-like topology and membrane localization; • interaction with GPA1; • highly specific ABA binding; existence in two different conformations, GTP-bound and GDP-bound; • dependence of the efficiency of ABA binding on their conformation; • ABA hyposensitive phenotypes of mutants lacking GTGs; • no effect of ABA on expression of GTG transcripts, indicating that the role of GTG proteins in ABA signaling is posttranslational.

44. ABA signal transduction pathways are complex and involve a variety of small molecules and proteins 1.Two protein phosphatase 2C proteins (PP2Cs) called ABI1 and ABI2 have a central role in ABA response. 2.A variety of kinases, RNA-modifying enzymes and transcription factors have been proposed to function in ABA signaling (Aaron Santner et al., 2009)

45. The ubiquitin-proteasome pathway. Two RING E3 ligases, ABI3-interacting protein (AIP2) and Keep on Going (KEG), promote normal ABA signaling by regulating the abundance of ABA responsive transcription factors, namely ABA-insensitive 3 (ABI3) and ABI5.

47. Sumoylation of ABI5 by the Arabidopsis SUMO E3 ligase SIZ1 negatively regulates abscisicacid signaling • Loss-of-function T-DNA insertion siz1–2 and siz1–3 mutations caused ABA hyper-sensitivity. • abi5–4 suppressed ABA hypersensitivity caused by siz1 (siz1–2 abi5–4), demonstrating an epistatic genetic interaction between SIZ1 and ABI5. (PNAS,2009,106:5418-5423)

49. SUMO E3 ligase SIZ1 represses ABI5 signaling function independent of AFP1.

50. Genetic evidence indicates that at least six Arabidopsis PP2Cs, namely ABI1,ABI2, PP2CA/AHG3, AHG1, HAB1 and HAB2, act as negative regulatorsof ABA • hab1-1abi1-2abi2-2 and hab1-1abi1-2pp2ca-1 mutants showed an extreme response to exogenous ABA, impaired growth and partial constitutive response to endogenous ABA. (Silvia Rubio et al.,Plant Physiol 2009)