A Tomato Peroxidase Involved in the Synthesis of Lignin and Suberin1

• Published in: Plant physiology (Bethesda) Vol. 122; no. 4; pp. 1119 - 1128
• Main Authors: Quiroga, Mónica, Guerrero, Consuelo, Botella, Miguel A., Barceló, Araceli, Amaya, Iraida, Medina, María I., Alonso, Francisco J., de Forchetti, Silvia Milrad, Tigier, Horacio, Valpuesta, Victoriano
• Format: Journal Article
• Language: English
• Published: American Society of Plant Physiologists 01-04-2000
• ISSN: 0032-0889; 1532-2548

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.