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Cell wall mechanics and growth control in plants: the role of pectins revisited.

Peaucelle A, Braybrook S, Höfte H - Front Plant Sci (2012)

Bottom Line: How is the extensibility of growing plant cell walls regulated?In the past, most studies have focused on the role of the cellulose/xyloglucan network and the enigmatic wall-loosening agents expansins.Here we review first how in the closest relatives of the land plants, the Charophycean algae, cell wall synthesis is coupled to cell wall extensibility by a chemical Ca(2+)-exchange mechanism between Ca(2+)-pectate complexes.

View Article: PubMed Central - PubMed

Affiliation: Institut Jean-Pierre Bourgin, UMR1318 INRA/AgroParisTech, Saclay Plant Sciences, INRA Centre de Versailles, Versailles, France.

ABSTRACT
How is the extensibility of growing plant cell walls regulated? In the past, most studies have focused on the role of the cellulose/xyloglucan network and the enigmatic wall-loosening agents expansins. Here we review first how in the closest relatives of the land plants, the Charophycean algae, cell wall synthesis is coupled to cell wall extensibility by a chemical Ca(2+)-exchange mechanism between Ca(2+)-pectate complexes. We next discuss evidence for the existence in terrestrial plants of a similar "primitive" Ca(2+)-pectate-based growth control mechanism in parallel to the more recent, land plant-specific, expansin-dependent process.

No MeSH data available.


Related in: MedlinePlus

Cartoon summarizing Ca 2+–pectate-dependent growth control in the alga Chara corallina. (A) In this species, cellulose microfibrils are parallel and oriented transversely to the elongation axis. Ca2+ (red ovals)-pectate complexes are load-bearing. One stretched and two relaxed Ca2+–pectate complexes are shown. Newly deposited pectate will chelate Ca2+ preferentially out of the stretched complexes, thus leading to wall relaxation and turgor-driven mechanical deformation until other complexes become load-bearing. (B) Cartoon of an “eggbox” consisting of two antiparallel poly-galacturonic acid chains complexed by Ca2+.
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Figure 2: Cartoon summarizing Ca 2+–pectate-dependent growth control in the alga Chara corallina. (A) In this species, cellulose microfibrils are parallel and oriented transversely to the elongation axis. Ca2+ (red ovals)-pectate complexes are load-bearing. One stretched and two relaxed Ca2+–pectate complexes are shown. Newly deposited pectate will chelate Ca2+ preferentially out of the stretched complexes, thus leading to wall relaxation and turgor-driven mechanical deformation until other complexes become load-bearing. (B) Cartoon of an “eggbox” consisting of two antiparallel poly-galacturonic acid chains complexed by Ca2+.

Mentions: Within this view, pectins form a matrix around the cellulose–XG network but are thought not to have a major load-bearing role (Cosgrove, 1999). Pectins are block co-polymers; homogalacturonan (HG), a main pectic polymer, consists of a-1,4-linked galacturonic acids. HG is secreted in a highly methylesterified form and selectively de-methylesterified by pectin methylesterases (PME; Pelloux et al., 2007). After de-methylesterification, pectate can form Ca2+–pectate cross-linked complexes, referred to as “eggboxes” (Figure 2B; Grant et al., 1973). These cross-links, together with rhamnogalacturonan II (RGII)-boron diester bonds, are thought to indirectly affect the cellulose–XG network by influencing the wall porosity and hence the accessibility of primary wall relaxation proteins to their substrate (Cosgrove, 1999). The more Ca2+–pectate present, the denser the gel and the more inextensible the cell wall is expected to be.


Cell wall mechanics and growth control in plants: the role of pectins revisited.

Peaucelle A, Braybrook S, Höfte H - Front Plant Sci (2012)

Cartoon summarizing Ca 2+–pectate-dependent growth control in the alga Chara corallina. (A) In this species, cellulose microfibrils are parallel and oriented transversely to the elongation axis. Ca2+ (red ovals)-pectate complexes are load-bearing. One stretched and two relaxed Ca2+–pectate complexes are shown. Newly deposited pectate will chelate Ca2+ preferentially out of the stretched complexes, thus leading to wall relaxation and turgor-driven mechanical deformation until other complexes become load-bearing. (B) Cartoon of an “eggbox” consisting of two antiparallel poly-galacturonic acid chains complexed by Ca2+.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3368173&req=5

Figure 2: Cartoon summarizing Ca 2+–pectate-dependent growth control in the alga Chara corallina. (A) In this species, cellulose microfibrils are parallel and oriented transversely to the elongation axis. Ca2+ (red ovals)-pectate complexes are load-bearing. One stretched and two relaxed Ca2+–pectate complexes are shown. Newly deposited pectate will chelate Ca2+ preferentially out of the stretched complexes, thus leading to wall relaxation and turgor-driven mechanical deformation until other complexes become load-bearing. (B) Cartoon of an “eggbox” consisting of two antiparallel poly-galacturonic acid chains complexed by Ca2+.
Mentions: Within this view, pectins form a matrix around the cellulose–XG network but are thought not to have a major load-bearing role (Cosgrove, 1999). Pectins are block co-polymers; homogalacturonan (HG), a main pectic polymer, consists of a-1,4-linked galacturonic acids. HG is secreted in a highly methylesterified form and selectively de-methylesterified by pectin methylesterases (PME; Pelloux et al., 2007). After de-methylesterification, pectate can form Ca2+–pectate cross-linked complexes, referred to as “eggboxes” (Figure 2B; Grant et al., 1973). These cross-links, together with rhamnogalacturonan II (RGII)-boron diester bonds, are thought to indirectly affect the cellulose–XG network by influencing the wall porosity and hence the accessibility of primary wall relaxation proteins to their substrate (Cosgrove, 1999). The more Ca2+–pectate present, the denser the gel and the more inextensible the cell wall is expected to be.

Bottom Line: How is the extensibility of growing plant cell walls regulated?In the past, most studies have focused on the role of the cellulose/xyloglucan network and the enigmatic wall-loosening agents expansins.Here we review first how in the closest relatives of the land plants, the Charophycean algae, cell wall synthesis is coupled to cell wall extensibility by a chemical Ca(2+)-exchange mechanism between Ca(2+)-pectate complexes.

View Article: PubMed Central - PubMed

Affiliation: Institut Jean-Pierre Bourgin, UMR1318 INRA/AgroParisTech, Saclay Plant Sciences, INRA Centre de Versailles, Versailles, France.

ABSTRACT
How is the extensibility of growing plant cell walls regulated? In the past, most studies have focused on the role of the cellulose/xyloglucan network and the enigmatic wall-loosening agents expansins. Here we review first how in the closest relatives of the land plants, the Charophycean algae, cell wall synthesis is coupled to cell wall extensibility by a chemical Ca(2+)-exchange mechanism between Ca(2+)-pectate complexes. We next discuss evidence for the existence in terrestrial plants of a similar "primitive" Ca(2+)-pectate-based growth control mechanism in parallel to the more recent, land plant-specific, expansin-dependent process.

No MeSH data available.


Related in: MedlinePlus