BioProject

Plants face temporal and spatial variation in nitrogen (N) availability. This includes heterogeneity in soil nitrate (NO3-) content. More...

Plants face temporal and spatial variation in nitrogen (N) availability. This includes heterogeneity in soil nitrate (NO3-) content. To face these constraints, plants modify their gene expression and physiological processes to optimize N acquisition. This plasticity relies on a complex long-distance root-shoot-root signaling network that remains poorly understood. We previously showed that cytokinin (CK) biosynthesis is required to trigger systemic N signaling. Here, we performed split-root experiments and used a combination of CK-related mutant analyses, hormone profiling, transcriptomic analysis, NO3- uptake assays, and root growth measurements to gain insight into systemic N signaling in Arabidopsis thaliana. By comparing wild-type plants and mutants affected in CK biosynthesis and ABCG14-dependent root-to-shoot translocation of CK, we revealed an important role for active trans-Zeatin (tZ) in systemic N signaling. Both rapid sentinel gene regulation and long-term functional acclimation to heterogeneous NO3- supply, including NO3- transport and root growth regulation, are likely mediated by the integration of tZ content in shoots. Furthermore, shoot transcriptome profiling revealed that glutamate/glutamine metabolism is likely a target of tZ root-to-shoot translocation, prompting an interesting hypothesis regarding shoot-to-root communication. Finally, this study highlights tZ-independent pathways regulating gene expression in shoots as well as NO3- uptake activity in response to total N-deprivation. We used microarrays to detail transcriptional reprogramming occurring in shoots in response to heterogeneous nitrate supply compared to homogeneous nitrate supply in wild-type Arabidopsis thaliana plants and in two mutants affected in cytokinin biosynthesis and transport. Overall design: Plants were grown in homogeneous medium containing sufficient nitrogen and the root system was divided in two parts (around day 14 after germination). The plants were transferred in split-root plates (around Day 18) containing 1mM KNO3 on both sides of the plates (C.KNO3) or in heterogeneous media containing 1mM KNO3 on one side and 1mM KCl on the other side (Split). Plants (Col-0, ipt3,5,7 and abcg14) were collected 24hours after the beginning of the treatment. This experiment has been replicated 4 times (4 independent experiments) and in each experiment three plants have been pooled in one sample. Less...