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Lecture 15 Cytokinins Regulators of cell division

Lecture 15 Cytokinins Regulators of cell division. Outline. Discovery & Structure Biosynthesis & Metabolism Biological Roles of Cytokinins Mode of Action. Discovery. G. Haberlandt ( 德国植物学家， 1913) 将打碎的植物 韧皮 组织放在马铃薯块茎 的伤口上，发现伤口附近薄壁细胞分裂。. Conclusion:

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Lecture 15 Cytokinins Regulators of cell division

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  1. Lecture 15 Cytokinins Regulators of cell division Outline Discovery & Structure Biosynthesis & Metabolism Biological Roles of Cytokinins Mode of Action

  2. Discovery • G. Haberlandt(德国植物学家，1913) 将打碎的植物韧皮组织放在马铃薯块茎 的伤口上，发现伤口附近薄壁细胞分裂。 Conclusion: Substance in the phloem could induce division of parenchyma cells(薄壁细胞) of potato.

  3. Discovery • 1954年，F. Skoog（USA）等 重复Haberlandt工作，结果相同。 假设：某种物质=生长素？ 验证：向培养基中加生长素 结果：细胞体积变大，但不分裂。 结论：促进细胞分裂的物质不是生长素。

  4. Discovery • F. Skoog等重新假设 细胞分裂需要合成DNA， 那么，促进分裂的物质是DNA 或与DNA代谢产物有关？

  5. Aged herring spermDNA Cell division (鲱鱼) Herring Cell division Fresh DNA Discovery • C. Miller (Skoog’s graduate, 1955)

  6. 高压 灭菌 Fresh DNA Cell Division Discovery • C. Miller (Skoog’s graduate, 1955) 结论： 促进细胞分裂的不是DNA本身， 而是DNA的降解产物。

  7. NH CH2 O N6—呋喃甲基腺嘌呤（化学名） 6 5 1 N 7 N 8 9 2 4 N H N Discovery • Kinetin from herring spermDNA (1955) 激动素（KT）

  8. Discovery • 1964年，首次从植物组织分离得到细胞分裂素——玉米素 Zeatin 广泛存在于植物和细菌

  9. Structure • Natural CKs in plant cell 共同结构 ——嘌呤

  10. 6 Structure • Synthesized CK——嘌呤类 6 -苄氨基嘌呤 6 - BA

  11. Structure • Synthesized CK——苯脲类 生物活性比 腺嘌呤类的高 CPPU: N-（2-chloro-4-pyridy)-N’-phenylurea 氯 吡啶 苯脲 应用 果实：葡萄、草莓、西瓜、猕猴桃等 块根 茎类

  12. 膨大剂使用不当造成西瓜爆裂 CPPU俗称： KT30 膨大剂 膨大素 大果灵

  13. Biosynthesis • 从头合成：甲瓦龙酸→玉米素

  14. 甲瓦龙酸→GA12

  15. Biosynthesis • tRNA降解 虽然tRNA可降解释放iP, 但这种方式似乎不能满足 植物对CK的需要。 故此途径不是CK合成的主要途径。 ——武维华（第一版） 异戊烯 基腺苷 酵母丝氨酸tRNA

  16. Biosynthesis • Sites • Primarily in root tip CK from root tip are transported to shoots via thexylem.

  17. Biosynthesis • Sites • in shoot meristem tissues CK produced in young leaves transports in phloem. G. Haberlandt (德国，1913) F. Skoog（美国,1954）等证实： 韧皮细胞中有促进细胞分裂的物质

  18. Biosynthesis • Sites • in shoot meristem tissues CK is produced incrown gall. 冠瘿组织

  19. Metabolism CKs in plant cells Free CK Bound CK Active Active or Inactive?

  20. Metabolism Free CK • 被高浓度自由态CK所诱导 • 不可逆 细胞分裂素氧化酶

  21. Bound CKs • 嘌呤环上不可逆结合 N3-G，有活性 N7-G，无活性 N9-G，无活性 N9-Ala 羽扇豆酸(无活性)

  22. Bound CKs • 侧链羟基与单糖结合 CK-O-xyloside(木糖基)，无活性 CK-O-glucoside，无活性 葡糖葡糖苷酶可催化其释放出自由态CK 因此，CK-O-glucoside 可能是CK在植物细胞的储存形式。

  23. Metabolism • 植物组织调节活性CK浓度途径的多样性 Free CK: Active Bound CK • 不可逆结合 • 侧链羟基与单糖结合 N3-G，有活性 N7-G，无活性 N9-G，无活性 N9-Ala CK-O-木糖(无) CK-O-G(无) ≒CK +G

  24. Lecture 15 Cytokinins Regulators of cell division Outline Discovery & Structure Biosynthesis & Metabolism Biological Roles of Cytokinins Mode of Action

  25. Biological Roles of CK - Regulation of Cell Division - Deetiolation 去黄化 - Apical Dominance - Leaf Senesence (衰老) - Development of fruit and seed

  26. Biological Roles of CK • Regulation of Cell Divisionin vivo • 真核细胞周期 • 由周期素和依赖周期素的蛋白激酶共同调节。 • CyclinCyclin-Dependent Protein Kinase CDK-Cyclin CK诱导 基因表达 IAA诱导基因表达

  27. 调节细胞分裂的激素：IAA, GA, CK • 启动细胞从G1期进入S期 IAA诱导CDK表达 CK诱导Cyclin表达 • 缩短G1期，提前进入S期 GAs

  28. Biological Roles of CK • Regulation of Cell Divisionin vitro

  29. Etiolated seedling黄化苗 Biological Roles of CK • Deetiolation (去黄化) • 叶绿体未形成 • 子叶未打开 • 顶端弯钩

  30. CK promotes Chloroplast development From Chory et al. 1994 A. Etioplasts in dark B. Thylakoid formation in dark-grown seedling treated with CK.

  31. CK promotes cell expansion in cotyledons 子叶 光下还是黑暗CK都能促进子叶伸展 子叶面积增大，干重不变 • 不涉及质子外流 • IAA和GA无此作用 in water T3 - Incubation for 3 days

  32. 促进细胞生长的激素 IAA、GA、 CK In discussion IAA促进细胞壁伸展 促进新微纤丝沉积

  33. 高 低 IAA 低 高 CK Biological Roles of CK • Apical Dominance顶端优势 地上部分CK/IAA的相对含量调控着顶端优势。 CK与IAA相互拮抗： - CK促进侧芽生长，抑制顶芽生长； - IAA促进顶芽生长，抑制侧芽生长。

  34. Biological Roles of CK • Leaf Senescence (衰老) CK 与 ABA和乙烯的拮抗作用调节叶片衰老 - CK 延缓衰老 - ABA 和乙烯促进衰老 Ipt: CK合成基因

  35. 氨基异丁酸 黄瓜幼苗 Biological Roles of CK • Development of fruit and seed Cell division and growth Accumulation of nutrients

  36. Lecture 15 Cytokinins Regulators of cell division Outline Discovery & Structure Biosynthesis & Metabolism Biological Roles of CK Mode of Action

  37. Mode of Action Learn by yourself

  38. Christchurch, New Zealand Pupils played on the lawn in their school.

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