Plant morphogenesis is dependent on a tight control of cell division and expansion. Cell elongation during post-embryonic hypocotyl growth is under the control of a light-regulated developmental switch. Light is generally believed to exert its effects on hypocotyl elongation through a phytochrome-and blue-light receptor-mediated inhibitory action on a so far unknown cell elongation mechanism. We describe here a new class of allelic mutants in Arabidopsis, at the locus PROCUSTE1 (prc1-1 to −4), which have a hypocotyl elongation defect specifically associated with the dark-grown development program. Normal hypocotyl elongation is restored in plants grown in white, blue or red light. In agreement with this, the constitutive photomorphogenic mutation cop1-6, which induces a de-etiolated phenotype in the dark, is epistatic to prc1-2 for the hypocotyl phenotype. Epistasis analyses in red and blue light respectively, indicate that phytochrome B but not the blue light receptor HY4, is required for the switch from PRC1-dependent to PRC1-independent elongation. The conditional hypocotyl growth defect is associated with a deformation of the hypocotyl surface due to an uncontrolled swelling of epidermal, cortical or endodermal cells, suggesting a defect in the structure of the expanding cell wall. A similar phenotype was observed in elongating roots, which was however, independent of the light conditions. The aerial part of mature mutant plants grown in the light was indistinguishable from the wild type. prc1 mutants provide a means of distinguishing, for the first time, two genetic pathways regulating hypocotyl cell elongation respectively in dark- and light-grown seedlings, whereby light not only inhibits hypocotyl growth, but also activates a PRC1-independent cell elongation program.

Reference

Reference
Aeschbacher
R. A.
,
Hauser
M. T.
,
Feldmann
K. A.
,
Benfey
P. N.
(
1995
)
The SABRE gene is required for normal cell expansion in Arabidopsis.
Genes Dev
9
,
330
340
Ahmad
M.
,
Cashmore
A. R.
(
1993
)
HY4 gene of A. thaliana encodes a protein with characteristics of a blue-light photoreceptor.
Nature
366
,
162
166
Baskin
T.
,
Herth
W.
,
Cork
A.
,
Birch
R.
,
Rolfe
B.
,
Redmond
J.
,
Williamson
R.
(
1995
)
Radial swelling mutants deficient in cellulose biosynthesis.
J. Cell. Bioch
21
,
440
–.
Chory
J.
,
Nagpal
P.
,
Peto
C. A.
(
1991
)
Phenotypic and genetic analysis of Det2 a new mutant that affects light-regulated seedling development in Arabidopsis.
Plant Cell
3
,
445
460
Chory
J.
,
Peto
C.
,
Feinbaum
R.
,
Pratt
L.
,
Ausubel
F.
(
1989
)
Arabidopsis thaliana mutant that develops as a light-grown plant in the absence of light.
Cell
58
,
991
999
Deng
X. W.
,
Caspar
T.
,
Quail
P. H.
(
1991
)
Cop1- A regulatory locus involved in light-controlled development and gene-expression in Arabidopsis.
Genes Dev
5
,
1172
1182
Ecker
J. R.
(
1995
)
The Ethylene Signal Transduction Pathway in Plants.
Science
268
,
667
675
Feldmann
K. A.
,
Marks
M. D.
,
Christianson
M. L.
,
Quatrano
R. S.
(
1989
)
A dwarf mutant of Arabidopsis generated by T-DNA insertion mutagenesis.
Science
243
,
13511354
–.
Fry
S. C.
(
1993
)
Loosening the ties.
Curr. Biol
3
,
355
357
Fry
S. C.
,
Smith
R. C.
,
Renwick
K. F.
,
Martin
D. J.
,
Hodge
S. K.
,
Matthews
K. J.
(
1992
)
Xyloglucan endotransglycosylase, a new wall-loosening enzyme activity from plants.
Biochem. J
282
,
821
828
Hauser
M. T.
,
Morikami
A.
,
Benfey
P. N.
(
1995
)
Conditional root expansion mutants of Arabidopsis.
Development
121
,
1237
1252
Konieczny
A.
,
Ausubel
F. M.
(
1993
)
A procedure for mapping Arabidopsis mutations using co-dominant ecotype-specific PCR-based markers.
Plant J
4
,
403
410
Lander
E. S.
,
Green
P.
,
Abrahamson
J.
,
Barlow
A.
,
Daly
M. J.
,
Lincoln
S. E.
,
Newburg
L.
(
1987
)
MAPMAKER: An interactive computer package for constructing primary genetic linkage maps of experimental and natural populations.
Genomics
1
,
174
181
Lin
C.
,
Robertson
D. E.
,
Ahmad
M.
,
Raibekas
A. A.
,
Schuman Jorns
M.
,
Dutton
P. L.
,
Cashmore
A. R.
(
1995
)
Association of flavin adenine dinucleotide with the Arabidopsis blue light receptor CRY1.
Science
269
,
968
970
Liscum
E.
,
Young
J. C.
,
Poff
K. L.
,
Hangarter
R. P.
(
1992
)
Genetic separation of phototropism and blue light inhibition of stem elongation.
Plant Physiol
100
,
267
271
Ludevid
D.
,
Höfte
H.
,
Himelblau
E.
,
Chrispeels
M. J.
(
1992
)
The expression pattern of the tonoplast intrinsic protein-TIP in Arabidopsis thaliana is correlated with cell enlargement.
Plant Physiol
100
,
1633
1639
McQueen-Mason
S.
,
Cosgrove
D. J.
(
1994
)
Disruption of hydrogen bonding between plant cell wall polymers by proteins that induce wall extension.
Proc. Natl. Acad. Sci. USA
91
,
6574
6578
McQueen-Mason
S. J.
,
Cosgrove
D. J.
(
1995
)
Expansin mode of action on cell walls- analysis of wall hydrolysis, stress relaxation and binding.
Plant Physiol
107
,
87
100
McQueen-Mason
S.
,
Durachko
D. M.
,
Cosgrove
D. J.
(
1992
)
Two endogenous proteins that induce cell wall extension in plant.
Plant Cell
4
,
1425
1433
Nishitani
K.
,
Tominaga
R.
(
1992
)
Endo-xyloglucan transferase, a novel class of glycosyltransferase that catalyzes transfer of a segment of xyloglucan molecule to another xyloglucan molecule.
J. Biol. Chem
267
,
21058
21064
Peters
J. L.
,
Schreuder
M. E. L.
,
Verduin
S. J. W.
,
Kendrik
R. E.
(
1992
)
Physiological characterization of a high-pigment mutant of tomato.
Photochem. Photobiol
56
,
75
82
Quail
P. H.
,
Boylan
M. T.
,
Parks
B. M.
,
Short
T. W.
,
Xu
Y.
,
Wagner
D.
(
1995
)
Phytochromes: photosensory perception and signal transduction.
Science
268
,
675
680
Reed
J. W.
,
Nagpal
P.
,
Pool
D. S.
,
Furuya
M.
,
Chory
J.
(
1993
)
Mutations in the gene for the red/far-red light receptor phytochrome b alter cell elongation and physiological responses throughout Arabidopsis development.
Plant Cell
5
,
147
157
Reiter
W.-D.
,
Chapple
C. C. S.
,
Somerville
C. R.
(
1993
)
Altered growth and cell walls in a fucose-deficient mutant of Arabidopsis.
Science
261
,
1032
1035
Roberts
K.
(
1994
)
The plant extracellular matrix in a new expansive mood.
Curr. Opin. Cell. Biol
6
,
688
694
Santoni
V.
,
Bellini
C.
,
Caboche
M.
(
1994
)
Use of two-dimensional protein-pattern analysis for the characterization of Arabidopsis thaliana mutants.
Planta
192
,
557
566
Takahashi
T.
,
Gasch
A.
,
Nishizawa
N.
,
Chua
N. H.
(
1995
)
The DIMINUTO gene of Arabidopsis is involved in regulating cell elongation.
Genes Dev
9
,
97
107
Wei
N.
,
Chamovitz
D. A.
,
Deng
X. W.
(
1994
)
Arabidopsis COP9 is a component of a novel signalling complex mediating light control of development.
Cell
78
,
117
124
Young
J. C.
,
Liscum
E.
,
Hangarter
R. P.
(
1992
)
Spectral-dependence of light-inhibited hypocotyl elongation in photomorphogenic mutants of Arabidopsis: evidence for a UV-A photosensor.
Planta
188
,
106
114
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