The two α-dox genes of Nicotiana attenuata: overlapping but distinct functions in development and stress responses

The transformed lines exhibiting a dwarf growth phenotype are co-silenced for both α-dox genes resulting in a nearly complete suppression of α-DOX activity, which is associated with increases in ABA, JA and anthocyanin levels, all metabolic signatures of oxidative stress. The other lines, only silenced for α-dox1, developed similarly to wild-type plants, exhibited a 40% reduction of α-DOX activity resulting in a 50% reduction of its main product in planta (2-HOT) and showed no signs of oxidative stress. In contrast to α-dox1, the expression of α-dox2 gene is not induced by wounding or elicitors in the oral secretions of Manduca sexta. Instead, α-dox2 is expressed in roots and flowers which lack α-dox1 expression, but both genes are equally regulated during leaf maturation. We transiently silenced α-dox gene copies with gene-specific constructs using virus induced gene silencing and determined the consequences for plant development and phytohormone and 2-HOT levels. While individual silencing of α-dox1 or α-dox2 had no effects on plant growth, the co-suppression of both α-dox genes decreased plant growth. Plants transiently silenced for both α-dox genes had increased constitutive levels of JA and ABA but silencing α-dox1 alone resulted in lower M. sexta-induced levels of JA, 2-HOT and ABA.Thus, both α-dox isoforms function in the development of N. attenuata. In leaf maturation, the two α-dox genes have overlapping functions, but only α-dox2 is involved in root and flower development and only α-dox1 functions in anti-herbivore defense.Fatty acid (FA) hydroperoxides are intermediates in different oxylipin pathways controlling plant development [1] and plant responses to stresses [2]. To date, much of the research on oxylipin signals has focused on jasmonic acid (JA) whose biosynthesis starts with the peroxidation of linolenic acid (C18:3) mediated by 13-lipoxygenase (13-LOX) enzymes. In Nicotiana attenuata, silencing of lox3, a gene coding for a 13-LOX isoform, conside