Expansins cell expansion

Figure 6. The potential sites for modification of Type I primary cell walls by enzymes and/or expansins. The activities of the enzymes/expansins are associated with numerous aspects of plant growth and development including cell expansion, fruit ripening, and organ abscission.

In addition, a new class of proteins (a-expansins) has been discovered in plants that appear to disrupt the interactions between cellulose chains, without hydrolytic activity, to allow cell wall expansion [18]. A different, but related, set of molecules (P-expansins) has been found in pollen [19]. These molecules appear to help the growing pollen tube penetrate through the cell walls in the ovule allowing fertihzation. There is prehminary evidence that the addition of expansin to cellulases stimulates crystalhne cellulose hydrolysis [20]. 

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