Salicylic acid is a modulator of catalase isozymes in chickpea plants infected with Fusarium oxysporum f. sp. ciceri

Abstract

The relationship between salicylic acid level catalases isoforms chickpea cv. ICCV-10 infected with Fusarium oxysporum f. sp. ciceri was investigated. Pathogen-treated chickpea plants showed high levels of SA compared with the control. Two isoforms of catalases in shoot extract (CAT-IS and CAT-IIS) and single isoform in root extract (CAT-R) were detected in chickpea. CAT-IS and CAT-R activities were inhibited in respective extracts treated with pathogen whereas, CAT-IIS activity was not inhibited. These isoforms were purified and their kinetic properties studied in the presence or absence of SA. The molecular mass determined by SDS-PAGE of CAT-IS, CAT-IIS and CAT-R was found to be 97, 40 and 66kDa respectively. Kinetic studies indicated that Km and Vmax of CAT-IS were 0.2mM and 300 U/mg, 0.53mM and 180 U/mg for CAT-IIS and 0.25mM and 280 U/mg for CAT-R, respectively. CAT-IS and CAT-R were found to be more sensitive to SA and 50% of their activities were inhibited at 6 and 4?M respectively, whereas CAT-IIS was insensitive to SA up to 100?M. Quenching of the intrinsic tryptophan fluorescence of purified catalases were used to quantitate SA binding; the estimated Kd value for CAT-IS, CAT-IIS and CAT-R found to be 2.3?M, 3.1mM and 2.8?M respectively. SA is a modulator of catalase isozymes activity, supports its role in establishment of SAR in chickpea plants infected with the pathogen. © 2011 Elsevier Masson SAS.