Vascular transcription factors control epidermal responses to limiting phosphate conditions

Optimal plant growth is hampered by limiting amounts of the essential macronutrient phosphate in most soils. As a response, plant roots produce root hairs to capture this immobile nutrient. Although vital to high-yielding crops, this response remains poorly understood. By generating and exploiting a high spatial and temporal resolution single cell atlas of the Arabidopsis root, we show a remarkable enrichment of TMO5/LHW target genes in root hair epidermal cells. Moreover, these vascular bHLH factors are sufficient to induce a root hair formation response in the epidermal cells, similar as observed during low phosphate conditions, via the downstream cytokinin signaling. We further show that root hair formation under low phosphate conditions is almost absent when TMO5 function or cytokinin signaling is perturbed. In conclusion, cytokinin signaling links the adaptation of roots under low phosphate conditions in the epidermis to perception in vascular cells. Overall design: Single-cell RNA-seq experiments were performed in triplicate on protoplast cells extracted from the root-tips of 6 day old Arabidopsis thaliana seedlings.