A P450 monooxygenase homologue of Pinus taeda in Arabidopsis involves in the regulation of defense and development in plants. 
M. GIRI (1), R. Chaturvedi (1), Z. Chowdhury (1), R. Petros (1), B. Venables (1), J. Shah (1) (1) University of North Texas, U.S.A.

Abietane diterpenoids include a family of tricyclic diterpenoids, many of which are major constituents of oleoresin secretions from conifers, which provide protection against insects and pathogens. Recently, a signaling function has been proposed for the abietane diterpenoid, dehydroabietinal (DA).  DA was shown to be a potent activator of systemic acquired resistance (SAR), an inducible defense mechanism that confers resistance throughout the plant against a broad range of pathogens. We have identified AtAO1, an Arabidopsis thaliana homologue of a Sitka spruce (Picea sitchensis) and loblolly pine (Pinus taeda) P450 enzyme involved in abietane diterpenoid synthesis. Although the basal expression of AtAO1 is very low in leaves of WT plants, its expression is high in leaves of the ssi2 mutant, which accumulates elevated DA levels and exhibits a constitutive SAR phenotype.  This ssi2 defense phenotypes are suppressed by a T-DNA insertion in the AtAO1 gene. The atao1 mutant plants contain lower DA content and exhibit a SAR-deficient phenotype, which is complemented by exogenously applied DA, thus confirming a role for AtAO1 and DA in SAR signaling. Our study also demonstrates the involvement of DA in plant development.  DA promotes the autonomous pathway of flowering in Arabidopsis, which is in coherence with the delayed flowering phenotype of atao mutant lines compared to wild type plants.  The endogenous level of DA also shows a developmental decline as the plants transition to flowering. These results confirm an important signaling function for DA in the activation of SAR as well as the developmental transition to flowering.

Abstract Number: P18-673
Session Type: Poster