Integrated signaling mechanisms governing root hair growth via transcriptional master regulators.

Root hairs (RH), single cells that develop from the root epidermis, are key for anchorage in the soil and the absorption of water, macronutrients, and micronutrients as well as for establishing symbiotic relationships with soil microorganisms. RH has become a significant cell model system for investigating plant growth and the mechanisms by which plants adjust their growth in response to intrinsic cellular and environmental stimuli. Here, we focus on our current understanding of the molecular mechanisms that govern the growth of Arabidopsis thaliana RH at the intersection of environmental responses (e.g., nutrients like nitrate and phosphate, as well as microorganisms), hormonal signals (e.g., auxin, ethylene, jasmonic acid, etc) and the main transcriptional regulators. The regulation of RH development is governed by several transcription factors including the master regulators RHD6 and RSL2/RSL4, which are subject to stringent control at multiple levels. In this review, we summarize the latest advances in the signaling integration pathways that may increase our capacity to enhance nutrient uptake by the roots in the context of abiotic stresses for a more sustainable agriculture.