Transgenic Nicotiana tabacum and Arabidopsis thaliana plants overexpressing allene oxide synthase

Abstract

Allene oxide synthase (AOS), encoded by a single gene in Arabidopsis thaliana (L.) Heynh., catalyzes the first step specific to the octadecanoid pathway. Enzyme activity is very low in control plants, but is upregulated by wounding, octadecanoids, ethylene, salicylate and coronatine (D. Laudert and E.W. Weiler, 1998, Plant J 15: 675-684). In order to study the consequences of constitutive expression of AOS on the level of jasmonates, a complete cDNA encoding the enzyme from A. thaliana was constitutively expressed in both A. thaliana and tobacco (Nicotiana tabacum L.). Overexpression of AOS did not alter the basal level of jasmonic acid; thus, output of the jasmonate pathway in the unchallenged plant appears to be strictly limited by substrate availability. In wounded plants overexpressing AOS, peak jasmonate levels were 2- to 3-fold higher compared to untransformed plants. More importantly, the transgenic plants reached the maximum jasmonate levels significantly earlier than wounded untransformed control plants. These findings suggest that overexpression of AOS might be a way of controlling defense dynamics in higher plants.

Jasmonic acid carboxyl methyltransferase: A key enzyme for jasmonate-regulated plant responses

“…It was also proposed that such external stimuli might activate an alternative JA biosynthetic pathway located in the cytoplasm. However, JA levels in the transgenic plants overexpressing cytoplasm-localized AOS were not increased unless the tissues were damaged (13,19). Thus, even though AOS is a control point in the biosynthesis of jasmonates, there might be other regulatory enzymes or mechanisms for the activation of jasmonate-responsive genes.…”

Jasmonate Biosynthesis, Perception and Function in Plant Development and Stress Responses

“…Overexpression of flax AOS in transgenic potato plants led to 6-12 folds increased of basal JA level (Harms et al, 1995). However, overexpression of Arabidopsis AOS in either Arabidopsis or tobacco did not alter the basal level of JA (Laudert et al, 2000), indicating that the basal expression level of AOS varied in plant species which may be the bottleneck or not for JA production in rest plants. One important property of AOS genes in plants is that they are strongly induced by wounding and JA-/ MeJA-, and OPDA-treatment in many plant species (Harms et al, 1995;Laudert and weiler, 1998).…”

Role of cis-12-Oxo-Phytodienoic Acid in Tomato Embryo Development

“…This allows JA formation within less than 5 min upon any stimulus that finally results in expression of JA biosynthesis genes and other JAresponsive genes (Glauser et al, 2009;). The regulation of JA biosynthesis by substrate availability and by a positive feedback loop is well described by different assays including transgenic approaches (Laudert et al, 2000;Stenzel et al, 2003).…”