In pathogenic interactions production may be linked to the plant defense including the modification

Which not necessarily means an increase in total content, but a different composition of flavonoids synthesized by roots, as apparently specific types of these molecules are involved in the interaction. In this study, total flavonoids content did not quantitatively varied in AMF treated roots, but the qualitative pattern of flavonoids might have varied. We are now trying to analyze flavonoids composition of our roots in contact with AMF and PF. With respect to fluorescence images, in a previous work on olive seedling roots using fluorescence probes DHE and DCF-DA, we showed high levels of O22 and H2O2 generated by untreated roots in epidermis cell walls and the vascular cylinder, both presumably related to differentiation processes. After treatment with MeJA or PF, ROS generation in cortex cells was enhanced, in comparison to control and AMF roots. These results are congruent with the above described redox activities in the apoplast, and show the onset of a strong defense response induced by MeJA and PF, while AMF roots presented lower levels of ROS generation and redox activities. Moreover, it is also interesting to point out that in the early steps of AMF contact with roots, ROS generation was restricted to epidermal and vascular tissues, but not to cortical cells. This suggest a role for ROS in driving fungal colonization in the later tissue, as suggested by Dumas-Gaudot et al. and Garcı ´a-Garrido and Ocampo. Sumarizing, our results show that both ROS were strongly generated by roots treated with MeJA or PF, but to a much lesser extent by AMF treated roots. They also show that ROS generation, coincident with redox activities, was restricted to the apoplast at least during the first hours. Later on, other BU 4061T Proteasome inhibitor cytoplasmatic compartments could also begin to be involved in roots treated with PF. With respect to NO production, our data on root response to contact with AMF are in accordance with those recorded by Calcagno et al. for M. truncata roots treated with purified exudate from AMF. The registered lack of NO accumulation in M. truncata was faster than in our case, which could be explained by the difference in NO inductor used: AMF hyphas/ roots in our study instead of purified exudate. In turn, PF induced a significantly higher and more extensive NO production than AMF. The increased production of NO in response to PF was similar to that described by Shi and Li for Arabidopsis leaves, induced by toxins derived from Verticillium and mainly due to the NR pathway. This suggests that roots modulated their response to fungal contact: they responded to AMF signals by inducing an accumulation of NO which was nevertheless lower than with pathogen interactions, when NO levels were much higher, as was observed in tobacco cells treated with the elicitor cryptogein. NO is an important regulator molecule in many physiological processes, especially in response to stress, including the plant-pathogen interaction. The role of NO could be the key to the symbiosis establishment and the defense response to pathogenic attacks. The NO production may be linked to cell walls remodeling during early stages of AMF interactions, as a novel component of the AM signaling pathway.

Leave a Reply