Tissue culture of Arabidopsis thaliana explants reveals a stimulatory effect of alkamides on adventitious root formation and nitric oxide accumulation

Alkamides and N-acylethanolamines represent a new class of lipid compounds related to animal endocannabinoids, which regulate different aspects of plant morphogenesis. To elucidate further the plant regenerative properties of alkamides and their role on plant development, we used an in vitro system to cultivate Arabidopsis thaliana explants under varied concentrations of N-isobutyl decanamide and N-isobutyl-2E,6Z,8E-decatrienamide (affinin). Cultivation of explants that harbor the shoot apical meristem on MS 0.2 x medium lacking alkamides resulted in formation of mature plants with fully developed shoot and root systems. On the contrary, explants obtained from stems or primary roots resulted in development of two main classes of regenerative structures: adventitious roots and lateral roots, depending on the source of explants. N-Isobutyl decanamide treatments showed a dose-dependent effect on adventitious and lateral root formation from stein and primary root explants, respectively, and in growth of regenerated plants. The stimulatory effect of N-isobutyl decanamide and affinin on adventitious root formation was further confirmed in A. thaliana seedlings. Although the effects of alkamides were similar to those produced by auxins on adventitious root development, the ability of shoot explants to respond to alkamides was found to be independent of auxin signaling. Furthermore, we show that N-isobutyl decanamide is able to induce nitric oxide accumulation in sites of adventitious root proliferation. Our results suggest a role for alkamides in regulating adventitious root development, probably operating through the NO signal transduction pathway. (c) 2007 Elsevier Ireland Ltd. All rights reserved.