Strategies for optimization of mineral nutrient transport in plants: multilevel regulation of nutrient-dependent dynamics of root architecture and transporter activity.

How do sessile plants cope with irregularities in soil nutrient availability? The uptake of essential minerals from the soil influences plant growth and development. However, most environments do not provide sufficient nutrients; rather nutrient distribution in the soil can be uneven and change temporally according to environmental factors. To maintain mineral nutrient homeostasis in their tissues, plants have evolved sophisticated systems for coping with spatial and temporal variability in soil nutrient concentrations. Among these are mechanisms for modulating root system architecture in response to nutrient availability. This review discusses recent advances in knowledge of the two important strategies for optimizing nutrient uptake and translocation in plants: root architecture modification and transporter expression control in response to nutrient availability. Recent studies have determined (i) nutrient-specific root patterns; (ii) their physiological consequences; and (iii) the molecular mechanisms underlying these modulation systems that operate to facilitate efficient nutrient acquisition. Another mechanism employed by plants in nutrient-heterogeneous soils involves modification of nutrient transport activities in a nutrient concentration-dependent manner. In recent years, considerable progress has been made in characterizing the diverse functions of transporters for specific nutrients; it is now clear that the expression and activities of nutrient transporters are finely regulated in multiple steps at both the transcriptional and post-transcriptional levels for adaptation to a wide range of nutrient conditions.