Transcript analysis of stress defence genes in a white poplar clone inoculated with the arbuscular mycorrhizal fungus Glomus mosseae and grown on a polluted soil.

In this study we investigated if the symbiosis with the arbuscular mycorrhizal fungus Glomus mosseae, which contributes to alleviate heavy metal stress in plants, may affect the transcription of genes involved in the stress defence in the white poplar clone 'AL35' grown on a multimetal (Cu and Zn) contaminated soil. The results obtained showed that the symbiosis with G. mosseae reduced transcript abundance of genes involved in antioxidant defence in leaves and roots of 'AL35' plants grown on the heavy metal-polluted soil. Moreover, the interaction between this poplar clone and the arbuscular mycorrhizal fungus induced the gene coding for phytochelatin synthase in leaves, whereas the expression of genes involved in heavy metal homeostasis did not change in roots. The present results suggest that, in presence of high levels of heavy metals, inoculation with G. mosseae may confer to 'AL35' a more efficient control of the oxidant level. Moreover, in mycorrhizal plants heavy metal chelation pathways appear involved in the defence strategies in leaves, whereas in roots they do not seem to contribute to increase the plant tolerance of heavy metals.