Trans-organ analysis of gene co-expression networks reveals a mobile long-distance regulator that balances shoot and root development in Arabidopsis

Long-distance regulation between individual organs is a fundamental process for the optimized adaptation of the plant body to diverse environments. However, systematic methods for identifying key genes for long-distance regulation are currently unavailable. Here we present a new approach, trans-organ analysis of gene co-expression networks, which offers a unique way of identifying candidates for such genes. This approach revealed that TGA7 functions as a shoot-to-root mobile bZIP transcription factor in Arabidopsis to activate photosynthetic genes directly in shoots and nitrate-uptake-related genes, both directly and via a transcriptional cascade, in roots. Analysis of grafted chimeras showed that nitrogen-deficiency-induced enhanced TGA7 expression in shoot vascular tissue promotes TGA7 protein accumulation in roots, boosting root growth and nitrate uptake. Furthermore, the loss of TGA7-mediated long-distance regulation perturbed the balance between shoot and root development under nitrogen deficiency. These findings underscore the utility of our approach for uncovering long-distance regulation in plants.