Responses of root hair development to elevated CO2

This review highlights a potential signaling pathway of CO₂-dependent stimulation in root hair development. Elevated CO₂ firstly increases the carbohydrates production, which triggers the auxin or ethylene responsive signal transduction pathways and subsequently stimulates the generation of intracellular nitric oxide (NO). The NO acts on target Ca²⁺ and ion channels and induces activation of MAPK. Meanwhile, reactive oxygen species (ROS) activates cytoplasmic Ca²⁺ channels at the plasma membrane in the apex of the root tip. This complex pathway involves transduction cascades of multiple signals that lead to the fine tuning of epidermal cell initiation and elongation. The results suggest that elevated CO₂ plays an important role in cell differentiation processes at the root epidermis.Key words: elevated CO₂, root hairs, carbohydrate, auxin, ethylene, NO, ROS, Ca²⁺, genetic elementsIncreasing concentration of atmospheric CO₂ in the 21st century will impact many aspects of the human and natural world. Elevated CO₂ has some beneficial physiological effects on plants but nutrient limitation has generally been found to suppress these beneficial effects.¹ Therefore, under conditions of suboptimal supply of nutrients and elevated CO₂, the plants need to develop adaptive mechanisms to enhance nutrient acquisition, among which the plasticity of root development is of crucial importance.Root hairs make a significant contribution to increasing root surface area and facilitating physical anchorage to a substrate and providing a large interface for nutrient uptake.² Root-hair cells are highly polarized cellular structures resulting from tip growth of specific epidermal cells, which are controlled by multiple cellular factors and genetic processes.^3,4 Previous studies have shown that root hair development can influenced by various environmental factors, such as nutritional status,⁵ mycorrhizal infection and water stress,⁶ salinity⁷ and light intensity.⁸ Our current research has demonstrated a profound effect of elevated CO₂ on development of root hairs in Arabidopsis, which works through the well-characterized auxin signal transduction pathway.⁹ Since root hairs are an efficient strategy to alleviate the limitation of nutrients, one promising area of future research will be to discover the pathway that control root hair differentiation in crops under elevated CO₂. In this paper, we discussed a layer pathway in the interaction between CO₂ and some classical signals on regulating gene regulatory network to control development of root hairs.