Driouich, Azeddine

Kiefer-Meyer, Marie-Christine

Lehner, Arnaud

Lerouge, Patrice

Leroux, Christelle

Mollet, Jean-Claude

Pelloux, Jérôme

English

Archive Ouverte en Sciences de l'Information et de la Communication

HAL Id: hal-02082428
https://hal-normandie-univ.archives-ouvertes.fr/hal-02082428
Submitted on 28 Mar 2019
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Involvement of Pectin methylesterases in Arabidopsis
pollen imbibitions and germination
Christelle Leroux, Arnaud Lehner, Marie-Christine Kiefer-Meyer, Jérôme
Pelloux, Azeddine Driouich, Patrice Lerouge, Jean-Claude Mollet
To cite this version:
Christelle Leroux, Arnaud Lehner, Marie-Christine Kiefer-Meyer, Jérôme Pelloux, Azeddine Driouich,
et al.. Involvement of Pectin methylesterases in Arabidopsis pollen imbibitions and germination.
1ere journée de l’Institut de Recherche et d’Innovation Biomédicale, Jun 2012, Rouen, France. ￿hal-
02082428￿
: Demethylesterified HG : Methylesterified HG :Calcium
Involvement of pectin methylesterases in Arabidopsis pollen 
imbibition and germination.
Leroux Ca, Lehner Aa, Kiefer-Meyer MCa, Pelloux Jb, Driouich Aa, Lerouge Pa & Mollet JCa
a Laboratoire Glycobiologie et Matrice Extracellulaire Végétale, UPRES-EA 4358, PRIMACEN IBiSA, IRIB, 
Université de Rouen, 76821 Mont Saint-Aignan Cedex, France. 
b Biologie des Plantes et contrôle des Insectes ravageurs, UPRES-EA 3900,
Université de Picardie-Jules Verne, 80039 Amiens, France.
 The intine is composed of complex
polysaccharides including homogalacturonans
(HGs) which are secreted in the cell wall in a
highly methyesterified form.
Demethylesterification of HGs is catalyzed in
the cell wall by pectin methylesterases (PMEs).
Interestingly, more than 20% of Arabidopsis
PMEs (14 among 66) are specifically expressed
in pollen grain and pollen tube. Their
expression is gene- and time- dependent (Fig.
3).
Figure 3: RT-PCR detection of PMEs transcripts in wild type
pollen grains, imbibed pollen grains and pollen tubes. Gene
identities of RT-PCR products are indicated on the left. An
equal amount of cDNA was amplified in each sample. ACT12
and TUB4 have been used as positive controls.
Two knock-out mutants impaired in two homologous PME
(ppme1 and pme48; Fig. 3) present a strong delay in pollen
germination (not shown) and a remarkable phenotype with
multiple pollen tube tips emerging from the grain (Fig. 4D).
Figure 1: in-vivo pollen tube growth in the pistil
stained by Aniline blue. Green zone: Pollen
grains on stigma. Red zone: Pollen tubes in the
transmitting tract. Blue zone: Ovary.
Enzymatic activity of PME appears to be essential during pollen germination by facilitating the rupture of the 
pollen grain wall and then the emergence of the pollen tube
Konrad et al; (2011).  Calcium regulation of tip growth: new genes for old mechanisms Current opinion in plant biology 14:1-10.
(a)
1
2
2 3
4
5
Figure 2: Schematic
representation of dry (a),
imbibed (b) and germinated
(c) pollen grain.
1, Vegetative cell; 2, Sperm
cells; 3, Plasma membrane;
4, Intine; 5, Exine
Blue arrow: H₂0 influx; Black
arrow: Calcium influx; (Konrad
et al., 2011) .
At1g69940 PPME 1, Group I
At5g07410 PME 48, Group I
At5g07420 PME 49, Group I
At5g07430 PME 50, Group I
At3g17060 PME 67, Group I
At2g26450 PME 13, Group II
At2g47030 PME 04, Group II
At2g47040 PME 05, Group II
At3g05610 PME 21, Group II
At3g06830 PME 23, Group II
At3g62170 PME 37, Group II
At4g15980 PME 43, Group II
At4g33230 PME 45, Group II
At5g27870 PME 28, Group II
At3g46520 ACT12
At5g44340 TUB4
Locus Name (UniProt)
200 µm
 The possible implication of PMEs, HGs, calcium ions and polygalacturonases during pollen
germination is presented Figure 4. It is based on the phenotypes of WT (A, B) or mutant (C, D)
pollen grains observed during imbibition and pollen tube growth.
i) Random action of PME : The partially de-methylesterified HGs may become a target for
pectin-degrading enzymes, such as polygalacturonases.
-> Enzymatic degradation of the intine and mechanical rupture of the
exine due to turgor pressure.
ii) Block-wize action of the PME : The blocks of de-methylesterified HGs can interact with Ca²⁺ promoting the
formation of the “egg-box” structure and thus rigidifying the intine.
-> Mechanical rupture of the intine and exine due to turgor pressure.
WT: methylesterified HGs are hydrophobic. Upon the action of PME they
become more hydrophilic.
->the imbibition is fast in WT (A).
-> PMEs are present, structure or mechanical properties of the
intine are modified, the tube can emerge from the grain(B).
Mutants: methylesterified HGs are hydrophobic. De-
methylesterification is perturbed.
->the imbibition is slow (C).
-> PME actions are reduced. Germination is perturbed : No
germination (D, left grain) or abnormal germination with a
first tube that fails to emerge and a second tube that takes
over to ensure future fertilization (D, right grain)
A
10 µm
C
10 µm
B
10 µm
t + 20 min
D
10 µm
t + 80 min
Fig 4: Theoretical model presenting the possible involvement
of PME during pollen grain germination
(b)
1
2
2
3
4
5
Ca2+Ca2+Ca
2+
H2O
H2O
1. HGs of the intine are 
highly methylesterified
PME
2. Imbibition and secretion of 
PME in the intine
PME
PME
PME
3. Calcium influx
i) Random action i) Block-wise action
3. Polygalacturonases
4. Rigidification of the 
intine and mechanical
rupture due to turgor
pressure
4. Enzymatic digestion leads
to intine degradation
PME PME
Intine
Plasma membrane
Exine
Pollen tube with new cell wall
First tube
Second tube
 During sexual plant reproduction, pollen germination and pollen tube elongation in the pistil are
essential for delivering sperm cells to the ovule (Fig. 1).
Pollen grain contains two sperm cells and a vegetative cell limited from the outside to the inside, by
the exine, the intine and the plasma membrane. The water influx permit the imbibition (Fig. 2a),
before a calcium influx (Fig. 2b) which is localized at the future site of emergence of the tube (Fig. 2c).
(c)
4
5
1
2
2
Pollen tube cell wall


Involvement of Pectin methylesterases in Arabidopsis pollen imbibitions and germination

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Involvement of Pectin methylesterases in Arabidopsis pollen imbibitions and germination

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