Involvement of the ethylene-signalling pathway in sugar-induced tolerance to the herbicide atrazine in Arabidopsis thaliana seedlings.
الكلمات الدالة
نبذة مختصرة
Soluble sugars can induce tolerance to otherwise lethal concentrations of the herbicide atrazine in Arabidopsis thaliana seedlings. This sugar-induced tolerance involves modifications of gene expression which are likely to be related to sugar and xenobiotic signal transduction. Since it has been suggested that ethylene- and sugar-signalling pathways may interact, the effects of glucose (Glc) and sucrose (Suc) on seedling growth and tolerance to atrazine were analysed in etr1-1, ein2-1, ein4, and sis1/ctr1-12 ethylene-signalling mutant backgrounds, where key steps of ethylene signal transduction are affected. Both ethylene-insensitive and ethylene-constitutive types of mutants were found to be affected in sugar-induced chlorophyll accumulation and root growth and in sugar-induced tolerance to atrazine. Interactions between ethylene and sugars were thus shown to take place during enhancement of seedling growth by low-to-moderate (up to 80 mM) sugar concentrations. The strong impairment of sugar-induced atrazine tolerance in etr1-1, ein2-1, and ein4 mutants demonstrated that this tolerance required active signalling pathways and could not be ascribed to mere metabolic effects nor to mere growth enhancement. Sugar-induced atrazine tolerance thus seemed to involve activation by sugar and atrazine of hexokinase-independent sugar signalling pathways and of ethylene signalling pathways, resulting in derepression of hexokinase-mediated Glc repression and in induction of protection mechanisms against atrazine injury.