Auxin triggered outgrowth of shoot primordia PIN1:GFP distribution - - PowerPoint PPT Presentation

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Auxin triggered outgrowth of shoot primordia PIN1:GFP distribution - - PowerPoint PPT Presentation

Oct 19, 2023 118 likes •542 views

2018 CDB Part IB Plant Development Lecture 4. Patterning of indeterminate growth Jim Haselo fg Department of Plant Sciences Auxin triggered outgrowth of shoot primordia PIN1:GFP distribution in the Arabidopsis shoot apical meristem

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2018 CDB Part IB

Plant Development

Jim Haselofg
 Department of Plant Sciences

Lecture 4. Patterning of indeterminate growth

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Auxin triggered outgrowth of shoot primordia

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PIN1:GFP distribution in the Arabidopsis shoot apical meristem

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Primordial outgrowths in the meristem are triggered by local influxes of auxin

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The meristem is self-organising and renews itself.

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The shoot meristem is divided into central, peripheral and rib zones. Central zone = undifferentiated cells Peripheral zone = formation of new lateral organs Rib zone = formation of new stem

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The meristem contains three different layers

  • f cells, L1, L2 & L3.

These generally maintain distinct lineages

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wt shootmeristemless (stm) wuschel (wus)

SHOOT MERISTEMLESS (STM) and WUSCHEL (WUS) are homeodomain genes that are required for formation and maintenance of the shoot apical meristem in Arabidopsis.

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WUSCHEL expression

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Ectopic expression of WUSCHEL induces stem cell proliferation

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Combined expression of STM and WUS triggers ectopic meristem formation and

  • rganogenesis
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WUS and STM initiate and maintain meristem growth

  • but how is the size of the apical

meristem constrained? the growth of the shoot meristem is negatively regulated by…. the CLAVATA genes

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Two other membrane proteins Clavata2 and Coryne associate to form a receptor kinase that functions on a parallel path.

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  • 1. Mutations in the genes, clavata1,

clavata2, coryne and clavata3, produce similar phenotypes - enlarged meristems.

  • 2. These genes function in the same

regulatory pathway.

  • 3. CLAVATA3 is a ligand for the CLAVATA1/

CLAVATA2/CORYNE receptors

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A glycopeptide regulating stem cell fate in Arabidopsis thaliana

Kentaro Ohyama, Hidefumi Shinohara, Mari Ogawa-Ohnishi & Yoshikatsu Matsubayashi

Nature Chemical Biology 5, 578 - 580 (2009) Published online: 7 June 2009 doi:10.1038/nchembio.182

Clavata3 forms a 13 amino acid arabinosylated glycopeptide

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CLV3 mRNA CLV1 mRNA

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Over expression of CLAVATA3 causes depletion of the central zone of the meristem.

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OC RZ

L1 L2 L3

(SC) PZ OP OP OP CZ

(a)

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CLAVATA3 acts as a signal across the meristem, repressing WUSCHEL activity in the central zone of the shoot meristem.

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Auxin regulated feedback initiates shoot

  • utgrowth.

The Clavata and Wus genes form part of a feedback regulated circuit, controlling cell proliferation within each meristem Wus activates a local cytokinin response in the meristem

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Cytokinin
 signalling

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Walls around tumours — why plants do not develop cancer John H. Doonan and Robert Sablowski, Nature Reviews Cancer, 10: 794 (2010)

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Lecture 5: Formation and specification of lateral organs