Hydrogen peroxide generation and lignification by peroxidases from Acacia eburneainfected with Ravenelia esculenta

Abstract

Ravenelia esculenta Naras. and Thirum. is a rust fungus which infects Acacia eburnea Willd. producing hypertrophy in the infected organs. We analysed the changes in the reaction patterns of peroxidase from the tissues at progressive disease stages. Peroxidases (POX) from the tissues were analysed for oxidation of reduced nicotinamine adenine dinucleotide (NADH), NADH-dependent hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) generation and polymerization of cinnamyl alcohol, a lignin precursor in plants. The effect of cofactors like Mn<sup>2+</sup> and dichlorophenol (DCP) was also studied. Effect of externally added H<sub>2</sub>O<sub>2</sub> on NADH oxidation and cinnamyl alcohol polymerization was analyzed. NADH oxidation and H<sub>2</sub>O<sub>2</sub> generation are accelerated by supplement of cofactors. The cofactor requirements of the two reactions are different. The amount of H<sub>2</sub>O<sub>2</sub> generated varies with disease stages, but the rate of NADH oxidation is comparable. Externally added H<sub>2</sub>O<sub>2</sub> has an accelerating effect on NADH oxidation. Cinnamyl alcohol polymerizing activity of POX increased with disease progression and was strongly inhibited by H<sub>2</sub>O<sub>2</sub>. Stimulation of these reactions by cofactors has a physiological significance in terms of susceptibility of the host.

Peroxidase and polyphenol oxidase activities in compatible host–pathogen interaction inJasminum officinaleandUromyces hobsoni: Insights into susceptibility of host

“…However, the host in this study was found to be highly susceptible to rust infection. In addition to the increase in POX activity during disease development in our study, the enzyme also generates hydrogen peroxide during polymerization of monolignols (Kuvalekar & Gandhe, 2010).…”