The product of the maize homeobox gene, knotted1 (kn1), localizes to the nuclei of cells in shoot meristems, but is absent from portions of the meristem where leaf primordia or floral organs initiate. Recessive mutant alleles of kn1 were obtained by screening for loss of the dominant leaf phenotype in maize. Mutant kn1 alleles carrying nonsense, splicing and frame shift mutations cause severe inflorescence and floral defects. Mutant tassels produce fewer branches and spikelets. Ears are often absent, and when present, are small with few spikelets. In addition, extra carpels form in female florets and ovule tissue proliferates abnormally. Less frequently, extra leaves form in the axils of vegetative leaves. These mutations reveal a role for kn1 in meristem maintenance, particularly as it affects branching and lateral organ formation.

REFERENCES

REFERENCES
Barton
M. K.
,
Poethig
R. S.
(
1993
)
Formation of the shoot apical meristem in Arabidopsis thaliana -an analysis of development in the wild type and in the shootmeristemless mutant.
Development
119
,
823
831
Cheng
P.-C.
,
Greyson
R. I.
,
Walden
D. B.
(
1983
)
Organ initiation and the development of unisexual flowers in the tassel and ear of Zea mays.
Am. J. of Bot
70
,
450
462
Chuck
G.
,
Lincoln
C.
,
Hake
S.
(
1996
)
KNAT1 induces lobed leaves with ectopic meristems when overexpressed in Arabidopsis.
Plant Cell
8
,
1277
1289
Clark
S. E.
,
Jacobsen
S. E.
,
Levin
J. Z.
,
Meyerowitz
E. M.
(
1996
)
The CLAVATA and SHOOT MERISTEMLESS loci competitively regulate meristem activity in Arabidopsis.
Development
122
,
1567
1575
Colbert
J. T.
,
Costigan
S. A.
,
Zhao
Z.
(
1990
)
Photoregulation of-tubulin mRNA abundance in etiolated oat and barley seedlings.
Plant Phys
93
,
1196
1202
Dellaporta
S. L.
,
Calderon-Urrea
A.
(
1993
)
Sex determination in flowering plants.
Plant Cell
5
,
1241
1251
DeLong
A.
,
Calderon-Urrea
A.
,
Dellaporta
S. L.
(
1993
)
Sex determination gene TASSELSEED2 of maize encodes a short-chain alcohol dehydrogenase required for stage-specific floral organ abortion.
Cell
74
,
757
768
Endrizzi
K.
,
Moussian
B.
,
Haecker
A.
,
Levin
J. Z.
,
Laux
T.
(
1996
)
The SHOOT MERISTEMLESS gene is required for maintenance of undifferentiated cells in Arabidopsis shoot and floral meristems and acts at a different regulatory level than the meristem genes WUSCHEL and ZWILLE.
Plant J
10
,
967
979
Gelinas
D.
,
Postlethwaite
S. N.
,
Nelson
O. E.
(
1969
)
Characterization of development in maize through the use of mutants. II. The abnormal growth conditioned by the Knotted mutant.
Am. J. of Bot
56
,
671
678
Hake
S.
(
1992
)
Unraveling the knots in plant development.
Trends Genet
8
,
109
114
Hake
S.
,
Vollbrecht
E.
,
Freeling
M.
(
1989
)
Cloning Knotted, the dominant morphological mutant in maize using Ds2 as a transposon tag.
EMBO J
8
,
15
22
Hareven
D.
,
Gutfinger
T.
,
Parnis
A.
,
Eshed
Y.
,
Lifschitz
E.
(
1996
)
The making of a compound leaf: Genetic manipulation of leaf architecture in tomato.
Cell
84
,
735
744
Herskowitz
I.
(
1989
)
A regulatory heirarchy for cell specialization in yeast.
Nature
342
,
749
757
Irish
E. E.
,
Nelson
T. M.
(
1993
)
Development of tassel seed 2 inflorescences in maize.
Am. J. of Bot
80
,
292
299
Jackson
D.
,
Veit
B.
,
Hake
S.
(
1994
)
Expression of maize KNOTTED1 related homeobox genes in the shoot apical meristem predicts patterns of morphogenesis in the vegetative shoot.
Development
120
,
405
413
Kano-Murakami
Y.
,
Yanai
T.
,
Tagiri
A.
,
Matsuoka
M.
(
1993
)
A rice homeotic gene, OSH1, causes unusual phenotypes in transgenic tobacco.
FEBS Letters
334
,
365
368
Karu
A. E.
,
Miller
P. L.
,
Chase
C.
,
Cornutt
W.
(
1985
)
A point-addressable transfer system for automated sampling, feeding, and expansion of hybridoma cultures.
J. f Immunol. Methods
76
,
145
156
Kerstetter
R.
,
Vollbrecht
E.
,
Lowe
B.
,
Veit
B.
,
Yamaguchi
J.
,
Hake
S.
(
1994
)
Sequence analysis and expression patterns divide the maize knotted1 -like homeobox genes into two classes.
Plant Cell
6
,
1877
1887
Lincoln
C.
,
Long
J.
,
Yamaguchi
J.
,
Serikawa
K.
,
Hake
S.
(
1994
)
A knotted1 -like homeobox gene in Arabidopsis is expressed in the vegetative meristem and dramatically alters leaf morphology when overexpressed in transgenic plants.
Plant Cell
6
,
1859
1876
Long
J. A.
,
Moan
E. I.
,
Medford
J. I.
,
Barton
M. K.
(
1996
)
A member of the KNOTTED class of homeodomain proteins encoded by the STM gene of Arabidopsis.
Nature
379
,
66
69
Ma
H.
,
McMullen
M. D.
,
Finer
J. J.
(
1994
).
Identification of a homeobox-containing gene with enhanced expression during soybean (Glycine max L.) somatic embryo development.
Plant Mol. Biol
24
,
465
473
Mena
M.
,
Ambrose
B.
,
Meeley
R. B.
,
Briggs
S. P.
,
Yanofsky
M. F.
,
Schmidt
R. J.
(
1996
)
Diversification of C-function activity in maize flower development.
Science
274
,
1537
1540
Mizukami
Y.
,
Ma
H.
(
1995
)
Separation of AG function in floral meristem determinacy from that in reproductive organ identity by expressing antisense AG RNA.
Plant Mol. Biol
28
,
767
784
Muller
K.
,
Romano
N.
,
Gerstner
O.
,
Garcia-Maroto
F.
,
Pozzi
C.
,
Salamini
F.
,
Rohde
W.
(
1995
)
The barley Hooded mutation caused by a duplication in a homeobox gene intron.
Nature
374
,
727
730
Mushegian
A. R.
,
Koonin
E. V.
(
1996
)
Sequence analysis of eukaryotic developmental proteins: ancient and novel domains.
Genetics
144
,
817
828
Nickerson
N. H.
(
1954
)
Morphological analysis of the maize ear.
Am. J. of Bot
41
,
87
92
Peltz
S. W.
,
Brown
A. H.
,
Jacobson
A.
(
1993
)
mRNA destabilization triggered by premature translational termination depends on at least three cis -acting sequence elements and one trans -acting factor.
Genes Dev
7
,
1737
1754
Rogers
S.
,
Wells
R.
,
Rechsteiner
M.
(
1986
)
Amino acid sequences common to rapidly degraded proteins: The PEST hypothesis.
Science
234
,
364
368
Schneeberger
R. G.
,
Becraft
P. W.
,
Hake
S.
,
Freeling
M.
(
1995
)
Ectopic expression of the knox homeo box gene roughsheath1 alters cell fate in the maize leaf.
Genes Dev
9
,
2292
2304
Sinha
N.
,
Hake
S.
(
1994
)
The Knotted leaf blade is a mosaic of blade, sheath, and auricle identities.
Dev. Genet
15
,
401
414
Sinha
N. R.
,
Williams
R. E.
,
Hake
S.
(
1993
)
Overexpression of the maize homeo box gene, KNOTTED-1, causes a switch from determinate to indeterminate cell fates.
Genes Dev
7
,
787
795
Smith
L. G.
,
Greene
B.
,
Veit
B.
,
Hake
S.
(
1992
)
A dominant mutation in the maize homeobox gene, Knotted-1, causes its ectopic expression in leaf cells with altered fates.
Development
116
,
21
30
Smith
L. G.
,
Jackson
D.
,
Hake
S.
(
1995
)
Expression of knotted1 marks shoot meristem formation during maize embryogenesis.
Dev. Genet
16
,
344
348
Urlaub
G.
,
Mitchell
P. J.
,
Ciudad
C. J.
,
Chasin
L. A.
(
1989
)
Nonsense mutations in the dihydrofolate reductase gene affect RNA processing.
Mol. Cell. Biol
9
,
2868
2880
Veit
B.
,
Schmidt
R. J.
,
Hake
S.
,
Yanofsky
M. F.
(
1993
)
Maize floral development: New genes and old mutants.
Plant Cell
5
,
1205
1215
Vollbrecht
E.
,
Veit
B.
,
Sinha
N.
,
Hake
S.
(
1991
)
The developmental gene Knotted-1 is a member of a maize homeobox gene family.
Nature
350
,
241
243
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
39
This content is only available via PDF.