A Tomato Peroxidase Involved in the Synthesis of Lignin and Suberin

Abstract

The last step in the synthesis of lignin and suberin has been proposed to be catalyzed by peroxidases, although other proteins may also be involved. To determine which peroxidases are involved in the synthesis of lignin and suberin, five peroxidases from tomato (Lycopersicon esculentum) roots, representing the majority of the peroxidase activity in this organ, have been partially purified and characterized kinetically. The purified peroxidases with isoelectric point (pI) values of 3.6 and 9.6 showed the highest catalytic efficiency when the substrate used was syringaldazine, an analog of lignin monomer. Using a combination of transgenic expression and antibody recognition, we now show that the peroxidase pI 9.6 is probably encoded by TPX1, a tomato peroxidase gene we have previously isolated. In situ RNA hybridization revealed that TPX1 expression is restricted to cells undergoing synthesis of lignin and suberin. Salt stress has been reported to induce the synthesis of lignin and/or suberin. This stress applied to tomato caused changes in the expression pattern of TPX1 and induced the TPX1 protein. We propose that the TPX1 product is involved in the synthesis of lignin and suberin.

The presence of Microlobius foetidus cause changes in the antioxidant defense of Urochloa decumbens?

“…This specie also has secondary enzymes such as peroxidases. The peroxidases may appear in several forms and are involved in several physiologic processes such as ionic or covalent interactions with polymers from the cellular wall, thus having a role at the biosynthetic pathway of lignin from the cellular wall (Passardi et al, 2005;Quiroga et al, 2000). In the other hand, GSH has no significant role in the elimination of H 2 O 2 in U. decumbens due its low level of activity when compared to other analyzed enzymes.…”

Impact of Phenolic Compounds and Related Enzymes in Sorghum Varieties for Resistance and Susceptibility to Biotic and Abiotic Stresses

“…After germination, POX activity appeared to be on average higher in varieties resistant to lodging than in susceptible ones. High activity of POX in varieties resistant to lodging could be related to the role of POX in the formation of physical polymeric barriers such as suberin and lignin (Cosgrove, 1997;Quiroga et al, 2000), which might confer the plant with high rigidity.…”

Responses of bioenergy sorghum cell wall metabolism to agronomic practices

“…Assays at constant o-dianisidine and variable hydrogen peroxide concentrations [19] showed that only 20% -30% of the isoenzymes displayed normal Michaelis-Menten kinetics while the majority displayed aberrant kinetics. In all the experiments, almost all the strongly acidic charge isomers were inactive, suggesting that they were some of the degradation products of the inactivated isoenzymes.…”

“…Purification and assay of peroxidase: Peroxidase was extracted from sorghum leaves (50 g) by high speed homogenization with 100 mL of ice-cold 50 mM Na 2 HPO 4 buffer pH 6.0 containing 25% polyvinylpyrrolidone (w/v) and 0.1% β-mercaptoethanol [19]. The homogenate was centrifuged (4000 g, 30 min, 4˚C) to pellet the cell debris.…”