Root Apical Meristem ionic and transcriptomic response to Zinc excess stress

Exploitation of previously industrialized soils is a challenge complicated by the presence of pollutants left by different activities. Among these pollutants, high metallic concentration is strongly affecting the plants growth, and limits the possibilities of site exploitation for agricultural or even ecological purpose. One promising solution for valorization of the soils is phytoremediation. Several species, classed as hyper-accumulative plants, can grow on these polluted soils and actively extract toxic metals and store them in their aerial parts. For instance, some Arabidopsis halleri populations accumulate zinc in its aerial parts up to a level that would be toxic to any other Arabidopsis spp. Under normal conditions, zinc presence in soil is not detrimental for plants, as it is a necessary micronutrient. However, in these polluted soils, its concentration is often excessive and phytotoxic. Absorption starts in the root system and this system’s length will directly limit the depth of the possible phytoremediation. The primary root growth depends on root tip’s homeostasis, which is regulated by hormones balance, and ROS balance. Zinc excess has been shown to have an effect on auxin production and induce ROS in diverse conditions and species. Moreover, it could have a direct effect on cell cycle phases and on other unexpected processes, as zinc is an essential cofactor to many metalloenzymes, zinc-finger transcription factors and F-box containing proteins. Therefore, Arabidopsis root tips are ideal candidates to further study zinc concentration variation responses. Firstly, a description of the effect on the meristem size and root tip organization has been done. Secondly, an assessment of the zinc concentration in the root tip was conducted by ICP-MS to hypothesize if there is an active exclusion from this mitotically active part. Finally, this question and others were further addressed by a description and comparison between a classical and apical root transcriptomic response. By working with the model species Arabidopsis thaliana, we hope to set the bases to understand the metallic stress’ effect on root growth and physiology. We focus on unravelling the exact physiological effect of zinc on the root tip organization, ionic composition and transcriptomic profile