Differential induction of cinnamyl alcohol dehydrogenase during defensive lignification in wheat ( Triticum aestivum L.): characterisation of the major inducible form

Abstract

The induction and substrate speci®city of cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195) was investigated in relation to the deposition of a defensive, syringyl-rich lignin at wound margins in wheat (Triticum aestivum L. cv. Brigadier). Column chromatography of untreated, wounded and elicitor-treated tissues revealed three major CAD forms (CAD-A, -B and -C) of which only CAD-C was responsive to elicitors. Examination of the substrate preference of these fractions indicated p-coumaryl alcohol to be the preferred substrate of CAD-A and CAD-B, whereas sinapyl alcohol was favoured by CAD-C. Activity-stained isoelectric focussing gels revealed in untreated and wounded leaves four CAD isoenzymes with isoelectric points of 4.59 (i), 4.67 (ii), 4.81 (iii), 4.93 (iv). Elicitor treatment generally enhanced the staining of all isoenzymes and resulted in the appearance of two new isoenzymes of 5.22 (v) and pI 5.31 (vi). In activity stained non-denaturing PAGE gels, CAD-C further resolved into two distinct zones of CAD activity. Cinnamyl alcohol dehydrogenase-C was puri®ed to apparent homogeneity and characterisation revealed a 45-kDa subunit peptide which in its native form demonstrated a marked substrate preference for sinapyl alcohol. Overall, the dierential induction and substrate preference of CAD-C are consistent with a defensive role during defensive ligni®cation at wound margins in wheat.Abbreviations: CAD = cinnamyl alcohol dehydrogenase; IEF = isoelectric focussing; pI = isoelectric point Correspondence to: M.S. Barber;

Differential accumulation of monolignol-derived compounds in elicited flax (Linum usitatissimum) cell suspension cultures

“…Similarly, Mitchell et al (1994Mitchell et al ( , 1999 reported on the induction of a sinapyl alcohol-specific CAD activity (SAD activity) in wheat leaves inoculated with spores of B. cinerea associated with the deposition of a syringyl-rich defence lignin.…”

A Sphingolipid Elicitor-Inducible Mitogen-Activated Protein Kinase Is Regulated by the Small GTPase OsRac1 and Heterotrimeric G-Protein in Rice

“…The PAL gene has been shown to be involved in defense signaling in tobacco and rice by its rapid induction in response to pathogens or an elicitor (Zhu et al, 1995;Shadle et al, 2003;Tanaka et al, 2003). This enzyme represents the entry point of the phenylpropanoid pathway for the synthesis of antimicrobial compounds, such as phytoalexins (Dixon, 2001), or of the lignin polymer, which can act as an inducible physical barrier against pathogen ingress (Mitchell et al, 1999). A rice phytoalexin, Sakuranetin, is synthesized through the phenylpropanoid pathway (Kodama et al, 1992).…”

Phenolic compounds in Catharanthus roseus

“…flavonoids, isoflavonoids, stilbenes, monolignols and lignans (Dixon 2001), or as physical barrier against pathogen infiltration e.g. the phenylpropanoid polymer: lignin (Boudet et al 1995;Mitchell et al 1999). Activation of PAL is considered as a marker for ongoing SAR in a plant.…”