Regulation of the Cinnamate 4-Hydroxylase (CYP73A1) in Jerusalem Artichoke Tubers in Response to Wounding and Chemical Treatments

Abstract

Recherche Scientifique, 28 ~ frans-Cinnamate 4-hydroxylase (C4H) is a plant-specific cytochrome (P450) that is encoded by the gene CYP73A and catalyzes the second step of the multibranched phenylpropanoid pathway. lncreases in C4H activity in response to physical and chemical stresses have been well documented, but the mechanism of these increases has never been studied i n detail. This paper reports on the regulatory mechanism controlling C4H activity in Jerusalem artichoke (Helianfhus tuberosus) tubers in response to wounding and chemical treatments. We compared induction of C4H and other P450-catalyzed activities. C4H was moderately induced by chemicals relative t o other P450s. lncreases in enzyme activity, C4H protein, and transcripts were quantified and compared in tuber tissue 48 h after wounding and chemical treatments. Our data suggest that induction of the enzyme activity results primarily from gene activation. lime-course experiments were performed after wounding and aminopyrine treatment. Compared with wounded tissues, aminopyrine triggered an additional and delayed peak of transcript accumulation. l h e timing of the induced changes in activity, protein, and transcripts confirms that C4H induction results primarily from an increase in CYP73Al mRNA, in both wounded and aminopyrine-treated tissues. However, posttranscriptional mechanisms might also contribute to the regulation of C4H activity.P450s are ubiquitous enzymes that catalyze the activation of molecular oxygen and the insertion of one of its atoms into physiological and artificial substrates (Porter and Coon, 1991). In plants P450s perform many oxygenation reactions in secondary metabolism, in sterols and fatty acid derivative synthesis, and in the detoxification of xenobiotics (Bolwell et al., 1994;Durst and OKeefe, 1995). More than 16 P450-catalyzed reactions have been reported in the pathway leading to the biosynthesis of phenylpropanoids (Werck-Reichhart, 1995). The influx of metabolites into the pathway is controlled by a sequence of three catalytic steps leading from Phe to activated 4-coumaroyl COA. The second reaction of the sequence is catalyzed by a P450 called C4H. Complete cDNA sequences were recently reported for the enzymes from Jerusalem artichoke (Helianthus tuberosus; Teutsch et al., 1993), mung bean (Vigna radiata; Mizutani et al., 1993), and alfalfa (Medicago sativa;

Atrazine induction of a family 4 cytochrome P450 gene in Chironomus tentans (Diptera: Chironomidae)

“…Several major classes of environmental contaminants induce the cytochrome P450 system (Hoffman et al, 1995). Cytochrome P450 enzymes are inducible through a mechanism that is controlled at the transcriptional level (Batar et al, 1997). The net result of enzyme induction is an increase in enzyme activity.…”

Atrazine induction of cytochrome P450 in Chironomus tentans larvae

“…This enzyme system plays a key role in the metabolism of a wide range of endogenous and exogenous substances. Cytochrome P450 en zymes are inducible through a mechanism shown to be largely controlled at the transcriptional level (Batard et al, 1997). The ecological and physiological signifi cance of induction is uncertain, although with insects, induc tion is believed to provide versatility in the adaptation of insects to their environment (Terriere, 1984;Ahmed et al, 1986).…”

Transgene-Mediated and Elicitor-Induced Perturbation of Metabolic Channeling at the Entry Point into the Phenylpropanoid Pathway

“…13.11;Russell and Conn, 1967;Fahrendorf and Dixon, 1993;Teutsch et al, 1993). C4H is induced by light, elicitors, and wounding (Fahrendorf and Dixon, 1993;Buell and Somerville, 1995;Batard et al, 1997;Bell-Lelong et al, 1997), and its induction often is closely coordinated with PAL induction (Mizutani et al, 1997).…”

“…13.11;Russell and Conn, 1967;Fahrendorf and Dixon, 1993;Teutsch et al, 1993). C4H is induced by light, elicitors, and wounding (Fahrendorf and Dixon, 1993;Buell and Somerville, 1995;Batard et al, 1997;Bell-Lelong et al, 1997), and its induction often is closely coordinated with PAL induction (Mizutani et al, 1997).Enzymes of complex metabolic pathways may be present in the cell in arrays of consecutive, physically associated enzymes that are assembled on membranes or other physical structures (Subramanian et al, 1973;Margna and Margna, 1978;Srere, 1987). Such enzyme organization can result in the channeling of pathway intermediates without their release into general metabolic pools (Stafford, 1981;Hrazdina, 1992).…”