Role of extensin peroxidase in tomato ( Lycopersicon esculentum Mill.) seedling growth

Abstract

It is proposed that inhibition of extensin peroxidase activity leads to a less rigid cell wall and thus promotes cell expansion and plant growth. A low-molecular-weight inhibitor derived from the cell walls of suspension-cultured tomato cells was found to completely inhibit extensin peroxidase-mediated extensin cross-linking in vitro at a concentration of 260 microg/ml. The inhibitor had no effect upon guaiacol oxidation catalyzed by extensin peroxidase or horseradish peroxidase. We have demonstrated that the light-irradiated inhibition of plant growth may be partially offset by inhibition of endogenous extensin peroxidase activity. Overall plant growth was enhanced by up to 15% in the presence of inhibitor relative to control plants. Inhibitor-treated and illuminated tomato hypocotyls grew up to 15% taller than untreated controls. The inhibitor had no effect upon etiolated plants over a 15-d period, suggesting that only low levels of peroxidase-mediated cross-linking can be found in the cell walls of etiolated plants. SDS-PAGE/Western blots of ionically bound protein from both etiolated and illuminated hypocotyls identified a doublet at 57/58.5 kDa which is immunoreactive with antibodies raised to tomato extensin peroxidase. Levels of the 58.5-kDa protein, determined by SDS-PAGE, were at least threefold higher in illuminated tomato hypocotyls than in etiolated hypocotyls. Three fold higher levels of extensin peroxidase, elevated in-vitro extensin cross-linking activity and 15% higher levels of cross-linked, non-extractable extensin were observed in illuminated tomato hypocotyls compared with etiolated tomato hypocotyls. This suggests that white-light inhibition of tomato hypocotyl growth appears to be mediated, at least partially, by deposition of cell wall extensin, a process regulated by Mr-58,500 extensin peroxidase. Our results indicate that the contribution of peroxidase-mediated extensin deposition to plant cell wall architecture may have an important role in plant growth.

The association of peroxisomes with the developing cell plate in dividing onion root cells depends on actin microfilaments and myosin

“…Peroxide crosslinks pectin side chains (Schopfer 1996) and catalyses the polymerisation of extensin monomers into an insoluble, cross-linked network (Cooper and Varner 1984). Consistent with this, inhibition of extensin peroxidase, the enzyme that uses peroxide to cross-link extensin monomers, also results in increased cell elongation in tomato (Brownleader et al 2000). Although hydrogen peroxide production is not currently known in dividing cells, were the hardening of the cell plate to involve peroxide-based cross-linking of pectins or extensins, then peroxisomes adjacent to the cell plate would play two roles.…”

Growth regulators and guaiacol peroxidase activity during the induction phase of somatic embryogenesis in Picea species

“…In plant cells, peroxidase isoenzymes are located in the cell wall and vacuole (Carpin et al 1999). They participate in the antioxidant system, protecting cells from excessive accumulation of hydrogen peroxide and pathogen attack (Sutherland 1991) as well as in plant cell development (Brownleader et al 2000;Cordewener et al 1991), e.g. in somatic embryos of coniferous tree species (Mo et al 1996;Kormuták et al 2003).…”

Genome-Wide Identification of Genes Expressed in Arabidopsis Pistils Specifically along the Path of Pollen Tube Growth

“…For example, cell walllocalized peroxidases can cause an increase in wall extensibility by generating hydroxyl radicals that degrade cell wall polysaccharides (Schopfer, 2001) or they can increase wall rigidity by mediating rapid cross-linking (insolubilization) of the structural cell wall Pro-rich extensins, as occurs upon physical damage, treatment with fungal elicitors, and pathogen infection (Bradley et al, 1992;Brownleader et al, 2000;Jackson et al, 2001). The presence of stigma surface peroxidases has been used as an indication of stigma receptivity for pollination in several species (e.g.…”