Wounding Induces One of Two Isoenzymes of 3-Deoxy-d-arabino-Heptulosonate 7-Phosphate Synthase in Solanum tuberosum L.

Abstract

In bacteria and plants, the first enzyme of the shikimate pathway, DAHP3 synthase (EC 4.1.2.15), catalyzes the condensation ofphosphoenolpyruvate and erythrose-4-phosphate to form DAHP and Pi ( 11, 2 1). The role of this enzyme as an important regulator has been clearly demonstrated in bacteria, where modulation of the enzyme activity by feedback inhibition is the major mechanism to control carbon flow into the shikimate pathway (18). The aromatic amino acids phenylalanine, tyrosine, and tryptophan serve as specific inhibitors for three different isoenzymes encoded by three separate genes (11,21).In plants, the shikimate pathway provides the precursors not only for the synthesis of the aromatic amino acids but also for a variety of derived secondary metabolites, such as lignins, alkaloids, and flavonoids (9). Plant DAHP synthases are not inhibited by the aromatic amino acids (20, 28), but two DAHP synthase isoenzymes are distinguishable through their metal requirements and their sensitivity to various metabolic intermediates in a variety ofplants (8). DAHP synthase-

Impaired Wound Induction of 3-Deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) Synthase and Altered Stem Development in Transgenic Potato Plants Expressing a DAHP Synthase Antisense Construct

“…Elicitor and light increase DAHP synthase activity in parsley (McCue and Conn, 1989), and wounding increases DAHP synthase activity, polypeptide, and mRNA in potato (Dyer et al, 1989;Muday and Herrmann, 1992). In 5 of our 11 lines with antisense constructs, wound-induced DAHP synthase activity was reduced substantially (Fig.…”

Metabolic Profiling Allows Comprehensive Phenotyping of Genetically or Environmentally Modified Plant Systems

“…Amino acid biosynthesis in potato tubers in particular and in storage tissues in general is poorly understood. Although recently several genes for amino acid biosynthesis have been cloned from the potato tuber (Muday and Herrmann, 1992;Riedel et al, 1999;Casazza et al, 2000;Maimann et al, 2000), it is not known whether tubers possess the necessary machinery to synthesize all amino acids. The data presented in this study, although indirect, provide the first evidence that the potato tuber is likely to contain the required machinery to produce all amino acids de novo.…”

5-enol-Pyruvyl-Shikimate-3-Phosphate Synthase from Zea mays Cultured Cells (Purification and Properties)

“…This would be consistent with data previously described for both DAHP synthase and anthranilate synthase. Steadystate mRNA levels and enzyme specific activities of anthranilate synthase-1 and Mn-dependent DAHP synthase increased dramatically following both wounding and bacterial pathogen infiltration, whereas the other isoforms were unaffected (Dyer et al, 1989;McCue and Conn, 1989;Niyogi and Fink, 1990;Muday and Herrmann, 1992). This has been interpreted as being due to the synthesis ex novo of aromatic metabolites as indole-glucosinolates and phytoalexins required in the plant defense response.…”

“…The supematant was analyzed for EPSP synthase isoform content as above. The activity of marker enzymes (alcohol dehydrogenase, catalase, Cyt c oxidase, Mn-dependent DAHP synthase, and ribulose-1,5-bisphosphate carboxylase) in crude and in density-gradient-purified plastidial extracts was determined as described previously (Kerster and Deley, 1966;Lück, 1962;Wharton and Tzagoloff, 1967;Muday and Herrmann, 1992;Lilley and Walker, 1974, respectively).…”