Studies of plants with mutations in the CRABS CLAW gene indicate that it is involved in suppressing early radial growth of the gynoecium and in promoting its later elongation. It is also required for the initiation of nectary development. To gain further insight, the gene was cloned by chromosome walking. CRABS CLAW encodes a putative transcription factor containing a zinc finger and a helix-loop-helix domain. The latter resembles the first two helices of the HMG box, known to bind DNA. At least five other genes of Arabidopsis carry the same combination of domains, and we have named them the yabby family. The new helix-loop-helix domain itself we call the yabby domain. Consistent with the mutant phenotype, CRABS CLAW expression is mostly limited to carpels and nectaries. It is expressed in gynoecial primordia from their inception, firstly in lateral sectors where it may inhibit radial growth, and later in the epidermis and in four internal strips. The internal expression may be sufficient to support longitudinal growth, as carpels are longer in a crabs claw promoter mutant where expression is now confined to these regions. The patterns of expression of CRABS CLAW in ectopic carpels of floral homeotic mutants suggest that it is negatively regulated by the A and B organ identity functions, but largely independent of C function. CRABS CLAW expression occurs in nectaries throughout their growth and maturation. It is also expressed in their presumptive anlagen so it may specify cells that will later develop as nectaries. Nectaries arise from the floral receptacle at normal positions in all A, B and C organ identity mutants examined, and CRABS CLAW is always expressed within them. Thus CRABS CLAW expression is regulated independently in carpels and nectaries.

Reference

Alvarez
J.
,
Smyth
D. R.
(
1999
)
CRABS CLAW and SPATULA, two Arabidopsis genes that control carpel development in parallel with AGAMOUS.
Development,
126
,
2377
2386
Baxevanis
A. D.
,
Landsman
D.
(
1995
)
The HMG-1 box protein family: classification and functional relationships.
Nucl. Acids Res
23
,
1604
1613
Bowman
J. L.
,
Smyth
D. R.
,
Meyerowitz
E. M.
(
1989
)
Genes directing flower development in Arabidopsis.
Plant Cell
1
,
37
52
Bowman
J. L.
,
Smyth
D. R.
,
Meyerowitz
E. M.
(
1991
)
Genetic interactions among floral homeotic genes of Arabidopsis.
Development
112
,
1
20
Coen
E. S.
,
Meyerowitz
E. M.
(
1991
)
The war of the whorls: genetic interactions controlling flower development.
Nature
353
,
31
37
Drews
G. N.
,
Bowman
J. L.
,
Meyerowitz
E. M.
(
1991
)
Negative regulation of the Arabidopsis homeotic gene AGAMOUS by the APETALA2 product.
Cell
65
,
991
1002
Elliott
R. C.
,
Betzner
A. S.
,
Huttner
E.
,
Oakes
M. P.
,
Tucker
W. Q. J.
,
Gerentes
D.
,
Perez
P.
,
Smyth
D. R.
(
1996
)
AINTEGUMENTA, an APETALA2 -like gene of Arabidopsis with pleiotropic roles in ovule development and floral organ growth.
Plant Cell
8
,
155
168
Goto
K.
,
Meyerowitz
E. M.
(
1994
)
Function and regulation of the Arabidopsis floral homeotic gene PISTILLATA.
Genes Dev
8
,
1548
1560
Hill
J. P.
,
Lord
E. M.
(
1989
)
Floral development in Arabidopsis thaliana: a comparison of the wild type and the homeotic pistillata mutant.
Can. J. Bot
67
,
2922
2936
Jack
T.
,
Brockman
L. L.
,
Meyerowitz
E. M.
(
1992
)
The homeotic gene APETALA3 of Arabidopsis thaliana encodes a MADS-box and is expressed in petals and stamens.
Cell
68
,
683
697
Klug
A.
,
Schwabe
J. W. R.
(
1995
)
Zinc fingers.
FASEB J
9
,
597
604
Liu
Z.
,
Meyerowitz
E. M.
(
1995
)
LEUNIG regulates AGAMOUS expression in Arabidopsis flowers.
Development
121
,
975
991
Mackay
J. P.
,
Crossley
M.
(
1998
)
Zinc fingers are sticking together.
Trends Biochem. Sci
23
,
1
4
Mandel
M. A.
,
Gustafson-Brown
C.
,
Savidge
B.
,
Yanofsky
M. F.
(
1992
)
Molecular characterization of the Arabidopsis floral homeotic gene APETALA1.
Nature
360
,
273
277
Mitchell
P. J.
,
Tjian
R.
(
1989
)
Transcriptional regulation in mammalian cells by sequence-specific DNA binding proteins.
Science
245
,
371
378
Mizukami
Y.
,
Ma
H.
(
1992
)
Ectopic expression of the floral homeotic gene AGAMOUS in transgenic Arabidopsis plants alters floral organ identity.
Cell
71
,
119
131
Olszewski
N. E.
,
Martin
F. B.
,
Ausubel
F.M.
(
1988
)
Specialized binary vector for plant transformation: expression of the Arabidopsis thaliana AHAS gene in Nicotiana tabacum.
Nucl. Acids Res
16
,
10765
10782
Raikhel
N.
(
1992
)
Nuclear targeting in plants.
Plant Physiol
100
,
1627
1632
Roe
J. L.
,
Nemhauser
J. L.
,
Zambryski
P. C.
(
1997
)
TOUSLED participates in apical tissue formation during gynoecium development in Arabidopsis.
Plant Cell
9
,
335
353
Rost
B.
(
1996
)
PHD: predicting one-dimensional protein structure by profile based neural networks.
Meth. Enzymol
266
,
525
539
Stemmer
C.
,
Ritt
C.
,
Igloi
G.L.
,
Grimm
R.
,
Grasser
K.D.
(
1997
)
Variability in Arabidopsis thaliana chromosomal high-mobility-group-1-like proteins.
Eur. J. Biochem
250
,
646
652
Vijayraghavan
U.
,
Siddiqi
I.
,
Meyerowitz
E. M.
(
1995
).
Isolation of an 800kb contiguous DNA fragment encompassing a 3.5 cM region of chromosome 1 in Arabidopsis using YAC clones.
Genome
38
,
817
823
Weigel
D.
,
Alvarez
J.
,
Smyth
D. R.
,
Yanofsky
M. F.
,
Meyerowitz
E. M.
(
1992
)
LEAFY controls floral meristem identity in Arabidopsis.
Cell
69
,
843
859
Weigel
D.
,
Meyerowitz
E. M.
(
1993
)
Activation of floral homeotic genes in Arabidopsis.
Science
261
,
1723
1726
Weigel
D.
,
Meyerowitz
E. M.
(
1994
)
The ABCs of floral homeotic genes.
Cell,
78
,
203
209
Werner
M. H.
,
Huth
J. R.
,
Gronenborn
A. M.
,
Clore
G. M.
(
1995
)
Molecular basis of human 46X, Y sex reversal revealed from the three-dimensional solution structure of the human SRY-DNA complex.
Cell
81
,
705
714
Yanofsky
M. F.
,
Ma
H.
,
Bowman
J. L.
,
Drews
G. N.
,
Feldmann
K. A.
,
Meyerowitz
E. M.
(
1990
)
The protein encoded by the Arabidopsis homeotic gene agamous resembles transcription factors.
Nature
346
,
35
40
This content is only available via PDF.