E class genes

FLORAL IDENTITY GENES1.Transcription factors2.Control the expression of other genes

CADASTRAL GENES1.Spatial regulators2.By setting the boundaries for their expression

MERISTEM IDENTITY GENES1.Transcription factors2.Belongs to MADS box gene family3.Initial induction of organ identity genes4.Positive regulators

http://www.adonline.id.au/flowers/floral-identity/

Elliott Meyerowitz, Enrico Coen and colleagues


APETELA 1*APETELA 2

APETELA 3*PISTILLATA*

AGAMOUS*

Those marked * are MADS Box genes

The ABC and SEP genes specify floral organ identity.The three SEP genes function redundantly and are necessary for petal, stamen and carpel development, in the absence of SEP genes the inner whorls of flower develops as sepals.SEP genes are AGL homologWhen the SEPALLATA genes are expressed together with the ABC genes, both vegetative and cauline leaves are converted to floral organsSEP triple mutant exhibits floral indeterminacy. Phenotype resembles to the BC double mutant.

Fig: Conversion of leaves to petals and stamens.(a)Wild-type seedling. Cotyledons and rosette leaves are indicated. (b) 35S::AP3 35S::PI 35S::SEP3 seedling. Rosette leaves are converted to petal-like organs, but cotyledons are normal.(c) 35S::AP3 35S::PI 35S::SEP3 35S::AP1 seedling. Compared with (b), rosette leaves are more completely converted to petals.(d) 35S::AP3 35S::PI 35S::SEP3 35S::AG inflorescence. Cauline leaves are converted to stamen-like organs. Flowers also consist primarily of stamen-like organs.Abbreviations: CL, cauline leaves; Ct, cotyledons; F, flowers; RL, rosette leaves.

TRENDS in Plant Science Vol.6 No.7 July 2001

(a) Wild-type flower consisting of four sepals, four petals, six stamens and two fused carpels.(b) sep1 sep2 sep3 triple mutant flower in which petals and stamens are replaced by sepaloid organs and carpelsare replaced by a new flower that repeats this same phenotype. In addition, there is internode elongation between internal flowers, presumably because of a functional ERECTA gene.(c) Dissected sep1 sep2 sep3 triple mutant flower with 1st-whorl sepals (top), second and third whorl sepaloidorgans (middle), and a new flower (bottom) that replaces the carpels.(d) pi ag (bc) double mutant that reiterates the same sepal, sepal, sepal phenotype

NATURE |VOL 405 | 11 MAY 2000

NATURE REVIEWS | GENETICS VOLUME 6 | SEPTEMBER 2005

A revised version of the ABC model postulates that, in whorl 1, A-class activity specifies sepals; in whorl 2, A + B + SEP activities specify petals; in whorl 3, B + C + SEP activities specify stamens; and, in whorl 4, C + SEP activities specify carpals.


Two Dimers of MADS proteins combine to form tetramersBind to two CArg( CCCA/T6GG) sites in promoters of target genes


RNA transcripts are expressed as spatially restricted patterns that are consistent with their site of actionSEP genes and ABC genes exhibits different temporal expression profile

Developmental Cell 16, 711–722, May 19, 2009

Dotted lines or arrows indicate abolished regulation. The thickness of lines or arrows represents the strength of regulation. IM, inflorescence meristem.

Figure . Putative protein–protein interactions among SEP (black) and AP1/FUL (blue), B-class (red), C/D class (green), AGL6-like (orange) and SOC1-like (purple) proteins in different floral whorls of Arabidopsis thaliana based on yeast two- and three-hybrid assays and RNA expression. The different proteins are indicated by different colored rectangular borders: yellow-SEP3; green-SEP1/2; blue-SEP4

TRENDS in Plant Science Vol.10 No.9 September 2005

Thomas Jack ‘Molecular and GeneticMechanisms of Floral Control’ The Plant Cell, Vol. 16, S1–S17, Supplement 2004

Beth A. Krizek And Jennifer C. Fletcher ‘Molecular Mechanisms Of Flower Development: An Armchair Guide’ Nature Publishing Group, September 2005, Volume 6 688-698

Yaron Y. Levy and Caroline Dean ‘The Transition to Flowering’ The Plant Cell, Vol. 10, 1973–1989, December 1998

Soraya Pelaz, Rosalinda Tapia-Lo´ pez, Elena R. Alvarez-Buylla and Martin F. Yanofsky, Conversion of leaves into petals in Arabidopsis,Current Biology 2001, 11:182–184.

Soraya Pelaz, Gary S. Ditta, Elvira Baumann, Ellen Wisman and Martin F. Yanofsky, B and C floral organ identity functions require SEPALLATA MADS-box genes, NATURE |VOL 405 | 11 MAY 2000

Simon T. Malcomber and Elizabeth A. Kellogg, SEPALLATA gene diversification: brave new whorls, TRENDS in Plant Science Vol.10 No.9 September 2005

Chang Liu, Wanyan Xi,Lisha Shen, Caiping Tan and Hao Yu, Regulation of Floral Patterning by Flowering Time Genes, Developmental Cell 16, 711–722, May 19, 2009

Gary Ditta, Anusak Pinyopich, Pedro Robles, Soraya Pelaz, and Martin F. Yanofsky, The SEP4 Gene of Arabidopsis thaliana Functions in Floral Organ and Meristem Identity, Current Biology, Vol. 14, 1935–1940, November 9, 2004

Thomas Jack, Relearning our ABCs: new twists on an old model, TRENDS in Plant Science Vol.6 No.7 July 2001

E class genes

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