Poster: Cell walls

Abs # 602: Regulations of maize cell wall glucanase activities by two types of acidic wall proteins during cell elongation

Presenter:	Inouhe, Masahiro , inouhe@sci.ehime-u.ac.jp
Authors	Inouhe, Masahiro  (A)   Maruoka, Hirokazu  (A)   Thomas, Bruce R (B)   Nevins, Donald J (B)
Affiliations:	(A): Ehime University (B): University of California Davis

Exo- and endoglucanases present in cereal cell walls participate in the autonomous hydrolysis of cell wall polysaccharides in growing tissues such as coleoptile, root, mesocotyl, and expanding true leaves. These hydrolytic enzymes are expressed in the cell walls at the younger stages of development and mediate the structural changes in the matrix b-glucans to facilitate cell elongation and expansion of the tissues. We have focused our current attention on the regulation of the cell wall metabolism and identified several factors that stimulate glucanase activity and the cell wall auto-hydrolysis in maize. Several types of acidic wall proteins (AWPs) with or without chitinase activity were isolated from maize cell walls. They functioned as potent glucanase activators in vitro. The activation of glucanases by chitinases was further characterized under several experimental conditions including different substrates, pH, and temperatures. Chitinases were shown to be less effective on the other polysaccharide hydrolases than on glucanases. Positive interactions between AWPs and glucanases in situ were also disclosed by their associated changes during development of maize seedlings. AWP lacking chitinase activity appeared more effective in enhancement of the degradation of b-(1,3)(1,4)-glucan than AWP's capable of chitinase activity.