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Apical Dominance is controlled by Interaction between Cytokinin biosynthesis/degradation and Auxin in Stem. Mori, H. Nagoya University.

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Presentation on theme: "Apical Dominance is controlled by Interaction between Cytokinin biosynthesis/degradation and Auxin in Stem. Mori, H. Nagoya University."— Presentation transcript:

1 Apical Dominance is controlled by Interaction between Cytokinin biosynthesis/degradation and Auxin in Stem. Mori, H. Nagoya University

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5 3days after decapitation intact

6 auxin axillary bud dormant decapitation Apical Dominance cytokinin outgrowth

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9 cdc2 CycD3;1 CycB1;2 histoneH4 PCNA Time after decapitation (hours) EtBr Northern Blot Analyses of Cell Cycle Related Genes

10 1cm 2cm 4cm 6cm

11 Expresson of PCNA mRNA

12 axillary bud dormant decapitation auxin cytokinin outgrowth ・ Auxin derived from terminal bud is transported basipetally. ・ When auxin applied to the cut stump after decapitation, Auxin can repress axillary bud outgrowth. ・ When auxin directly applied to axillary bud after decapitation, Auxin cannot repress axillary bud outgrowth.

13 Auxin is basipetally transported in stem. IAA axillary bud Scale leaf at 2nd node

14 The basipetal transport of auxin is essential for dormancy of axillary bud. Auxin acts at node or in stem, not in axillary bud.

15 The basipetal transport of IAA is essential for axillary buds dormancy intact IAA 0 hr decapitated IAA 1cm 1 hr 3 hr auxin transport rate: 1cm/hr

16 Subtracted cDNA clones 0hr-3hr 3hr-0hr Ps-IAA4/5, IAA7, Aux28, Aux22, GH3, F-box, cullin, auxin efflux carrier protein(PIN1 ), RD29B, LEA4, zeaxanthin epoxidase IAA-Ala hydrolase, GA2 oxidase, HMG-CoA synthase, squalene synthase, Isopentenyltransferase (IPT )

17 Current model of cytokinin metabolism in higher plants LOG (revised) LOG

18 1cm 2nd node

19 PsIPT1 PsIPT2 rRNA time after decapitation (hr) Expression of PsIPTs at the 2nd Node after Decapitation

20 excise the segments from intact seedlings IPT is NOT expressed incubate in MES buffer with or without IAA Is IPT expressed? excise the segments 3hr after decapitation IPT is expressed incubate in MES buffer with or without IAA Is IPT expression repressed ? 1cm

21 IAA Free M IAA PsIPT1 PsIPT2 rRNA incubation time (hr) PsIPTs Expression was Repressed by IAA

22 excise the segments from intact seedlings IPT is NOT expressed incubate in MES buffer with or without IAA Is IPT expressed? excise the segments after 3hr decapitation IPT is expressed incubate in MES buffer with or without IAA Is IPT expression repressed? 1cm

23 PsIPTs Expression was Induced in IAA Free Buffer IAA Free M IAA incubation time (hr) PsIPT1 PsIPT2 rRNA

24 excise the segments from intact seedlings Not IPT expression incubate in MES buffer with or without IAA IPT express? excise the segments after 3hr decapitation IPT is expressed incubate in MES buffer with or without IAA Repress IPT expression? 1cm IAA Free M IAA IAA Free10 -5 M IAA

25 PsIPTs Expression was Repressed by IAA Transported Basipetally in the Stem PsIPT1 PsIPT2 PsPIN1 + IAA Lanoline paste w or w/o IAA after decapitation 3hr Is IPT expression repressed? 1cm

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28 pPsIPT2::GUS in Arabidopsis

29 pPsIPT2::GUS (2,4-D treated for 1 week)

30 pPsIPT2::GUS (2,4-D free for 3 days)

31 IAA Free10 -5 M IAA incubation time (hr) GUS Transcripts Deceased by Auxin in Transformants harboring pPsIPT2::GUS

32 Cytokinin Levels in the Stems and Axillary Buds after Decapitation

33 Cytokinin Levels in the Excised Segments treated with/without IAA iPMPiPAiPt-ZMPt-ZRt-zeatin 0h 3h 6h -IAA (p mol/ gFW) iPMPiPAiPt-ZMPt-ZRt-zeatin 0h 3h 6h (p mol/ gFW) +IAA excised the segments put on the agar plate ± 1%(w/v) IAA treatment

34 Conclusion One role of auxin in apical dominance is to repress the PsIPTs expression; local cytokinin biosynthesis in the nodal stem is negatively regulated by auxin through the control of IPT expression. Cytokinin, which is thought to be derived from the roots so far, is locally biosynthesized in the stem rather than in the roots after decapitation.

35 PsIPTs Expression was Repressed by Basipetally Transported IAA in the Stem PsIPT1 PsIPT2 PsPIN1 + IAA 1% (w/v) IAA after decapitation 3hr Is IPT expression repressed? 1cm

36 Effect of IAA Applied to the Stump on PsPIN1 Expression PsPIN1 actin 012(hours)4 (cm) IAA

37 Can IAA from Axillary Buds induce PsPIN1? intact 0hr 9hr decapitated 3hr IAA Biosynthesis

38 Time after decapitation ( hours ) PsPIN1 actin IAA × Upper Stem IAA Lower Stem

39 PsIPT1 PsIPT2 rRNA time after decapitation (hr) Expression of PsIPTs at the 2nd Node after Decapitation

40 IAA CK 2.9 IAA CK 9.1 IAA CK IAA 20.8 CK IAA CK 3.6 IAA CK IAA CK 47.6 IAA CK 1.9 IAA CK 6.3 IAA CK IAA CK IAA CK IAA 39.9 CK 50.7 IAA CK IAA 72.2 CK (p mol/gFW) node upper stem lower stem

41 PsCKX1: was constantly expressed in stem before and after decapitation, was not induced by auxin. PsCKX2: was increased in stem after decapitation was induced by auxin. Cytokinin oxidase cDNAs were isolated from the stem 12 hr after decapitation.

42 Time after treatment (hr) decapitation TIBA treatment Relative amounts of mRNA Expression of PsCKX2 in Pea Stem

43 Time after treatment (hr) (x 10 3 ) 20 Relative amounts of mRNA +NAA -NAA PsCKX2 Expression in Excised Pea stem by Auxin

44 Time after treatment (hr) NAA PsCKX2 Expression in Pea stem Relative amounts of mRNA

45 Time after treatment (hr) (x 10 3 ) 20 Relative amounts of mRNA +NAA -NAA PsCKX2 Expression in Excised Pea stem by Auxin

46 IAA CK 2.9 IAA CK 9.1 IAA CK IAA 20.8 CK IAA CK 3.6 IAA CK IAA CK 47.6 IAA CK 1.9 IAA CK 6.3 IAA CK IAA CK IAA CK IAA 39.9 CK 50.7 IAA CK IAA 72.2 CK (p mol/gFW) node upper stem lower stem

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48 Time after decapitation (hr) PsCKX2 PsPIN1 PsIPT2 Relative amounts of mRNA Expression of PsCKX2, PsPIN1, PsIPT2 in stem

49 Model of Interaction Between Auxin and Cytokinin in Apical Dominance

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52 Effect of Striolactone GR24 on outgrowth of axillary bud after decapitation GR24control

53 Apical dominance Nagoya University ・ Mina TANAKA ・ Sae SATO-SHIMIZU ・ Aiko ISHIWATA ・ Yuka MADOKA RIKEN ・ Mikiko KOJIMA ・ Hitoshi SAKAKIBARA


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