Mineral Nutrient Sensing and Signaling

Macronutrients such as nitrogen, phosphate, sulphate and micronutrients such as iron, copper and zinc are essential for various aspects of plant growth and development, but these elements may also be toxic if accumulated in the plant cell in excess. Non-essential elements like cadmium, arsenic, and aluminum are potentially highly toxic; however they are increasingly being emitted into the environment due to anthropogenic activities. Soils often challenge sessile plants with poor availability of essential minerals or elevated concentrations of toxic elements. These challenges are often exacerbated by soil type. For example, NO3− is the main source of inorganic nitrogen for plants in aerobic soil conditions; however due to the net negative charge of clay minerals, NO3− mobility is high and thus the NO3− concentration fluctuates in the soil by four orders of magnitude. Bioavailability of iron in aerobic soils with neutral to basic pH is also below the limits required to sustain plant growth and development because insoluble ferrous chelates prevail under these conditions. Consequently, alkaline soils occupying approximately 30% of the world’s arable land are considered iron-limiting. Alkaline soils also provide a hostile environment for availability of zinc and copper and thus, a deficiency for more than one mineral nutrient occurs. In contrast, acidic soils that occupy up to 40% of arable land, challenge plants with aluminum toxicity and accompanying phosphate deficiency while providing a good environment for iron and manganese availability.

To grow in environments with fluctuating concentrations of mineral nutrients and toxic elements plants have developed a set of physiological and morphological responses to match resource availability to growth requirements and to prevent metal poisoning. Physiological responses include regulation of the expression of transport systems that are involved in uptake of elements into roots, intracellular trafficking and compartmentation, and long-distance transport to developing tissues. In addition to these strategies, plant roots undergo morphological changes which, depending on the mineral nutrient, may include formation of epidermal transfer cells, increased root hair density and enhanced lateral root formation, all directed at increasing surface area for the promotion of mineral uptake into roots. These physiological and morphological responses are under tight control of complex sensing and signaling mechanisms that allow plants to monitor the external and internal concentration of minerals, both in absolute terms and in relation to the status of other minerals.

This research topic will provide the reader with recent advances in our understanding of components of sensing and signaling pathways and underlying transcriptional regulatory networks that orchestrate the physiological and morphological responses of plants to the fluctuations of minerals in the environments. We welcome articles showing novel aspects of physiological and morphological adjustments of plants in response to local and systemic signaling of minerals and involvement of hormones in these processes. This research topic will present different types of articles including comprehensive reviews, mini-reviews, opinions, perspectives and original research, all designed to stimulate discussions and allow sharing of opinions on the topic of Mineral Nutrients Sensing and Signaling.