Elicitation of Lignin Biosynthesis and Isoperoxidase Activity by Pectic Fragments in Suspension Cultures of Castor Bean

Abstract

Suspension cultures of castor bean (Ricinus communis L.) which have been treated with pectic fragment elicitor rapidly accumulate lignin as measured by derivatization with thioglycolic acid. The responsiveness of cultured cells to elicitor is dependent on the stage of culture growth. In 6-day (maximally responsive) cultures, increases in lignin are first evident 3 hours after addition of pectic fragment elicitor with maximal rates of lignin synthesis between 4 and 10 hours. The abundance of lignin in cultures after 12 hours of elicitor treatment is 10-to 20-fold higher than in untreated control cultures and can thereby account for as much as 2% of the dry cell weight. Only intermediate sizes of pectic oligomer are active as elicitors of lignin. Half-maximal accumulation of lignin occurs at 250 to 300 micrograms per milliliter of an optimal elicitor preparation with an average degree of polymerization of seven. We consider the synthesis of lignin in elicited cultures to be a mechanism of plant disease resistance which is induced by the elicitor. Plant peroxidases have been proposed to catalyze the last enzymatic steps in the biosynthesis of both lignin and hydrogen peroxide. Six extracellular isoenzymes of peroxidase (two anionic, designated Al and A2, and four cationic, designated C2, C3, C4, and C7) are detectable in healthy suspension cultures of castor bean by native gel electrophoresis. Treatment of cultures with elicitor causes substantial changes in the activity of four of these species (Al, C2, C3, and C7). Elicitor treatment also results in the appearance of three new peroxidase isoenzymes that are not readily detectable in healthy cultures (Cl, C5, and C6). Increases in the activities of these isoenzymes are concurrent with or slightly precede the accumulation of lignin in elicited 6-day cultures. By 12 hours after addition of elicitor, Cl becomes the most abundant extracellular isoperoxidase. The differential regulation of expression of peroxidase isoenzymes following elicitor treatment suggests that individual isoenzymes of peroxidase may have specific functional roles in the biosynthesis of disease-lignin.Resistance of plants to pathogens is frequently a result of the rapid establishment ofa localized 'hypersensitive response' by the plant at regions of attempted infection. There are

Cationic peroxidase related to basal resistance of Betula platyphylla var. japonica plantlet No.^|^#8201;8 against canker-rot fungus Inonotus obliquus strain IO-U1

“…Moreover, POD was activated more rapidly than phenolic compound accumulation in all the treated plantlets (Figures 1 to 3). These results were in agreement with the previous reports that PODs are involved in polymerization of phenolics, and synthesis of phenolic compounds in relation to plant defense responses against infection and wounding (Bruce and West 1989;Deborah et al 2001;Egea et al 2001;Gayoso et al 2010;Lagrimini 1991;Morkunas and Gmerek 2007). However, B. platyphylla var.…”

Induction of phenolics, lignin and key defense enzymes in eggplant (Solanum melongena L.) roots in response to elicitors

“…Lignin was extracted according to the method of Bruce and West (1982) with modifications. Root samples were homogenized in 80% methanol.…”

Inhibition of the Plastidic ATP/ADP Transporter Protein Primes Potato Tubers for Augmented Elicitation of Defense Responses and Enhances Their Resistance against Erwinia carotovora

“…This has repeatedly been demonstrated for the so-called gene-for-gene disease resistance (Boch et al, 1998;Yu et al, 1998) and for various induced resistance phenomena . Dependent on both the type of pathogen and the plant species attacked, pathogen-induced defense responses include a reinforcement of the cell wall (Bruce and West, 1989;Kauss, 1992;Lamb and Dixon, 1997), the synthesis of antimicrobial phytoalexins (Kombrink et al, 1991), the activation of various defense-related genes including those coding for antimicrobial, so-called pathogenesis-related (PR) proteins (Van Loon and Van Strien, 1999), and the generation of reactive oxygen species such as superoxide anion radicals and hydrogen peroxide (H 2 O 2 ; Bolwell et al, 1999).…”