Recombination DNA Technology (Nucleic Acid Hybridization )
E class genes
1.
2. FLORAL IDENTITY GENES
1.Transcription factors
2.Control the expression of other genes
CADASTRAL GENES
1.Spatial regulators
2.By setting the boundaries for their expression
MERISTEM IDENTITY GENES
1.Transcription factors
2.Belongs to MADS box gene family
3.Initial induction of organ identity genes
4.Positive regulators
7. 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 homolog
When the SEPALLATA genes are expressed together with the ABC
genes, both vegetative and cauline leaves are converted to floral
organs
SEP triple mutant exhibits floral indeterminacy. Phenotype
resembles to the BC double mutant.
8. 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
9. (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 carpels
are 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 sepaloid
organs (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
10. 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.
NATURE REVIEWS | GENETICS VOLUME 6 | SEPTEMBER 2005
11. Two Dimers of MADS proteins combine to form tetramers
Bind to two CArg( CCCA/T6GG) sites in promoters of target genes
NATURE REVIEWS | GENETICS VOLUME 6 | SEPTEMBER 2005
12. RNA transcripts are expressed as spatially restricted patterns that
are consistent with their site of action
SEP genes and ABC genes exhibits different temporal expression
profile
NATURE REVIEWS | GENETICS VOLUME 6 | SEPTEMBER 2005
13. Dotted lines or arrows indicate abolished regulation.
The thickness of lines or arrows represents the strength of
regulation. IM, inflorescence meristem.
Developmental Cell 16, 711–722, May 19, 2009
14. 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
15. 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
16. 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
Editor's Notes
new class of floral organ identity MADS-box genes, SEP1, SEP2, and SEP3, was recently described
This trio of largely redundant genes is required for the development of petals, stamens, and carpels since triple
mutants lacking all three SEP activities produce flowers that consist only of sepals helps B ancd C genes
Protein-protein interaction data, together with the fact that sep1 sep2 sep3 triple mutants closely resemble BC double mutants (ap3 ag or pi ag), indicate that the SEP proteins interact with the products of the B and C organ identity genes to direct petal, stamen, and carpel development
Regulation of floral organ identity genes a model was praposed.
A genetic model shows that activation of floral homeotic gene expression requires the orchestrated regulation of SEP3 by SVP, SOC1, and AGL24 in emerging floral meristems. In floral anlagen and stage 1 and 2 floral meristems, class B and C homeotic genes are not activated by LFY alone, because its coregulator, SEP3, is repressed by SVP, SOC1, and AGL24, whose expression is directly mediated by AP1. To repress SEP3, SVP interacts with TFL2 to modulate H3K27me3, while SOC1 and AGL24 interact with SAP18 to modulate H3 acetylation. In early stage 3 (e3) floral meristem, strong repression of SVP, SOC1, and AGL24 by AP1 derepresses SEP3, which in turn functions with LFY to activate class B and C genes. The asterisk indicates the region where high SEP3 expression coincides with initial expression of class B and C genes. Dotted lines or arrows indicate abolished regulation. The thickness of lines or arrows represents the strength of regulation. IM, inflorescence meristem.
