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Transcript 
Mechanical stimuli and
vascular tissue differentiation
Pia Stieger
University of Neuchâtel
Switzerland
VASCULAR TISSUES
CONNECTORS OF PLANT ORGANS
Fukuda (2004) Mol. Cell. Biol. 5
Nelson and Dengler (1997) Plant Cell 9
DEVELOPMENT
I. Patterning
Recruitment of
cambium cells
Scarpella and Meijer
(2004) New Phytol
Arrangement of
xylem and phloem
II. Differentiation
Formation of
xylem and phloem
Fukuda (2004)
Mol. Cell. Biol. 5
Secondary
growth
PATTERNING-AUXIN
Reinhardt et al. (2003) Nature
Scarpella et al. (2006) Genes&Development
PATTERNING
AD-& ABAXIAL TRANSCRIPTION FACTORS
Emery et al. (2003) Curr.Biol.
DIFFERENTIATION
Sieve elements,
companion cells, parenchyma Tracheary elements, fibers, parenchyma
elongation
division
secondary cell
wall formation
programmed
cell death
•cellulose synth.
•lignin synth.
•wall degrading enzymes
•transcription factors
•lignin synthesis
•cell cycle control
•PCD-genes
•primary cell wall synth.
SECONDARY GROWTH & WOOD FORMATION
Arabidopsis
annuals
Poplar
perennials
Chaffey et al. (2002)
RESEARCH FOCUS
INTERPLAY OF AUXIN, KANADI
AND HD-ZIPIII
IN VASCULAR DEVELOPMENT
MECHANICAL SIGNALS
IN VASCULAR DEVELOPMENT
MECHANICAL
SIGNALS
MECHANICAL CONTROL OF DIVISION PLANE
Compressive forces in a cell culture induce spatial ordering
of division and cambium-like growth
Lintilhac et al. (1984) Nature
Cambium formation from callus in grafts depends
on mechanical pressure
Barnett et al (2000) Cell and molecular biology of wood formation
Cell differentiation in Zinnia depends on cell culture density
McCann et al.(2001) Plant Physiol
PLANT GROWTH IN
MICRO- AND HYPERGRAVITY
Microgravity:
Hypergravity:
Increase of
•hypocotyl growth
•cell wall extensibility
•xyloclucan degrading enzymes
Increase of
•cell wall thickening
•lignins
•cell wall polysaccharides
Decrease of
Cell wall polysaccharides
Decrease of
•hypocotyl growth
•cell wall extensibility
•xyloclucan breakdown
Soga et al. (2002) Planta
Soga et al. (2004) Planta
Hoson et al. (1996) J Exp. Bot
REACTION WOOD
Timell (1984)
Kwon et al.(2001) Phytochemistry
THE EXPERIMENTAL SYSTEM
11 ms-2 = 1.123g
Centrifugal force
az = r ( 2Π f)2
Effects of mechanostimulation on stem growth
Stem growth 14d
50
45
Centrifugation
40
35
Vibration
40
stem growth (cm )
stem growth (cm)
30
35
30
25
20
25
20
15
15
10
10
5
5
0
0
Control
Centrifugation/vibration
STEM DIFFERENTIATION
Control 14d
Centrifugation 14d
CELLULOSE SYNTHESIS GENES
5h
C M
24h
48h
C M C M
72h
C M
IRX1
IRX3
IRX5
Actin2
LIGNIN BIOSYNTHESIS
LIGNIN BIOSYNTHESIS GENES
5h
C M
24h
C M
PAL3
PAL4
CCR1
CAD6
HCT
COMT
Effects of mechanostimulation on free phenols
Free phenol content after 10d
(methanol extraction, Ciocalteu reaction)
3
Centrifugation
2.5
2
1.5
1
0.5
3.5
caffeic acid (m g gFW -1)
caffeic acid (mg gFW-1)
3.5
3
Vibration
2.5
2
1.5
1
0.5
0
0
Control
Centrifugation/vibration
Effects of mechanostimulation on monolignols
Monolignol content after 10d
(saponification, HPLC)
0.8
0.6
1
0.8
0.6
0.4
0.4
0.2
0.2
0
0
Control
Centrifugation/vibration
vaniline
ferulic acid
syringic acid
syringaldehyde
1.2
coumaric acid
1.4
benzaldehyde
1.6
benzoic acid
vaniline
1.8
ng/mg plant FW
1
Vibration
2
ferulic acid
1.2
syringic acid
1.4
syringaldehyde
ng/mg plant FW
1.6
coumaric acid
1.8
benzoic acid
2
benzaldehyde
Centrifugation
ETHYLENE-RELATED GENE EXPRESSION
5h
C M
24h
48h
C M C M
72h
C M
ACC-oxidase
EIN2
ACTIN2
Effects of mechanostimulation on stem growth
in ein2 mutants
Stem growth 14d
40
35
Stem growth (cm)
30
25
20
15
10
5
0
Control
Centrifugation
STEM DIFFERENTIATION IN ein2
Control 10d
Centrifugation 10d
Effects of mechanostimulation on free phenols
in ein2 mutants
Free phenol content after 10d of centrifugation
(methanol extraction, Ciocalteu reaction)
3.5
caffeic acid (mg gFW-1)
3
2.5
2
1.5
1
0.5
0
Control
Centrifugation
Effects of mechanostimulation on monolignols
in ein2 mutants
Monolignol content after 10d of centrifugation
ng/m g plant FW
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Control
Centrifugation
vaniline
ferulic acid
syringic acid
syringaldehyde
1.6
coumaric acid
1.8
benzaldehyde
2
benzoic acid
(saponification)
SUMMARY and CONCLUSIONS
•Mechanical stimulation decreased stem growth
•Secondary growth was induced, when plants were mechanically
stimulated.
•Mechanical stimulation induced new phloem poles.
•Lignin biosynthesis genes were induced by mechanical stimulation,
as well as contents of free phenols and monolignols
•Decreased stem growth, secondary growth and enhanced lignin
production did not occur in the ethylene insensitive mutant
ein2 after mechanical stimulation.
Ethylene involved in the signal transduction from mechanical
stimulation to secondary growth?
Pia Stieger
Marlyse Meylan-Bettex
Eliane Abou-Mansour
Mustafa Tiouabi
Institute of Botany
University of Neuchâtel
Institute of Chemistry
University of Neuchâtel
Funding: COST E28 GENOSILVA
COST E50 CEMARE
Pro Techno Foundation
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