Richard Owen, 1843 defined concept of homologous organs

Homeotic transformations of organs in plants…

“Metamorphosis of Plants”

Published by Johan Goethe, 1790

Wild type.                APETALA1:    PISTILLATA :   AGAMOUS:                                  "A" class           "B" class          "C" class

Wild type.                APETALA1:    PISTILLATA :   AGAMOUS:                                  "A" class           "B" class          "C" class

AP1 mRNA AG1 mRNA AP1 in AG1 mutant

~550 MYA

AGclade

Plena clade

plena

Shp1/2

AgFar

adaxial abaxial

apical

basal

Central zone

phyllotaxy

Abaxialdomain

Adaxialdomain

adaxial

abaxial

Lateral primordia formation/polarity:

abaxial identity:

crabsclaw, YABBY, KANADI - arabidopsis

adaxial identity:

phantastica - Antirrhinumroughsheath - maizephabulosa - arabidopsis

1. Ad/ab polarity is needed for lateral expansion

2. Adaxial cells determine initiation of the axial meristem

McConnell and Barton. 1998. Development 125:2935

PhbWild type

Wild Type phabulosa

STARTSterolbindingdomain

HomeoBox-ZipperDNA bindingdomain

Dominant Phabulosa/Phavulota mutations

WT

Phb

Emery et al. 2003. Current Biology, Vol. 13, 1768–1774,

Dominant Phb phenotype

Triple knockout phenotype:

Abaxialdomain

Adaxialdomain

Boundary required for Later growth of leaf blade

Development 126, 4117-4128 (1999)Members of the YABBYgene family specify abaxial cell fate in ArabidopsisKellee R. Siegfried1,*, Yuval Eshed1, Stuart F. Baum1, Denichiro Otsuga2, Gary N. Drews2and John L. Bowman1,‡

KANADI regulates organ polarityin ArabidopsisRandall A. Kerstetter, Krista Bollman, R. Alexandra Taylor,Kirsten Bomblies & R. Scott Poethig

2001 Nature 411:706-8

Abaxial determinants:

STARTSterolbindingdomain

HomeoBox-ZipperDNA bindingdomain

Dominant Phabulosa/Phavulota mutations

Carrington and Ambros 2003, Science 301:337

PTGS pathway in eukaryotes

Adapted from Williams and Rubin 2001, PNAS

Carpel Factory (DCL1)

Jacobsen et al. 1998. Development 126:5231

Argonaut phenotypes

AGO is a component of the RISC RNA induced silencing complex

Kidner and Martienssen, Nature. 2004 Mar 4;428(6978):81-4

miR165 WT

miR165 ago

PHB WT

PHBago

Abaxialdomain

Adaxialdomain

Boundary required for Later growth of leaf blade

Asymmetric expression of YAB3 requiresKANADI function

PHABULOSA expression in the radialized(adaxialized) KANADI triple mutant

In tomato, YABBY is restricted to cytoplasmic dense cells at the margins of the ad/ab boundary

Emery et al. 2003. Current Biology, Vol. 13, 1768–1774,

Bohmert et al EMBO J 17:170-180

Meristem initiation/maintenance:

Meristem size:

Lateral organ polarity:

clavata1clavata2clavata3

Abaxial genes:crabsclaw, YABBYKanadi

Adaxial genes:phabulosaPhavolutaRevoluta

Knotted -maizeshoot apical meristemless -arabidopsis

Organ number and polarity:Carpel FactoryArgonaute

STARTSterolbindingdomain

HomeoBox-ZipperDNA bindingdomain

Dominant Phabulosa/Phavulota mutations

Bohmert et al EMBO J 17:170-180

adaxial

abaxial

Lateral primordia formation/polarity:

abaxial identity:

crabsclaw, YABBY, KANADI - arabidopsis

adaxial identity:

phantastica - Antirrhinumroughsheath - maizephabulosa - arabidopsis

Carrington and Ambros 2003, Science 301:337

Wild type.                APETALA1:    PISTILLATA :   AGAMOUS:                                  "A" class           "B" class          "C" class

AP1 mRNA AG1 mRNA AP1 in AG1 mutant

STARTSterolbindingdomain

HomeoBox-ZipperDNA bindingdomain

Dominant Phabulosa/Phavulota mutations

PhvAdaxial domain

Domain boundary Required for lateralgrowth

WT clv3 clv3

Fletcher et al. 1999. Science 283:1911-14

KANADI expression in the abaxial domain

Development 126, 4117-4128 (1999)Members of the YABBYgene family specify abaxial cell fate in ArabidopsisKellee R. Siegfried1,*, Yuval Eshed1, Stuart F. Baum1, Denichiro Otsuga2, Gary N. Drews2and John L. Bowman1,‡

Development 126, 4117-4128 (1999)Members of the YABBYgene family specify abaxial cell fate in ArabidopsisKellee R. Siegfried1,*, Yuval Eshed1, Stuart F. Baum1, Denichiro Otsuga2, Gary N. Drews2and John L. Bowman1,‡

Establishment of polarity in lateral organs of plantsYuval Eshed*, Stuart F. Baum, John V. Perea and John L. Bowman

Current Biology 2001, 11:1251–1260