Phōsphoros, the bearer of light in Greek mythology and chemical carrier of light energy into the biosphere, attracts attention of the Nutrient Sensing Group. Inorganic phosphate (Pi), a genuinely limiting mineral nutrient of terrestrial primary production (together with N), and its derivative P-anhydrides and P-esters act at the nexus of bioenergetics and metabolism. Thus, vital plant functions and crop productivity are exquisitely sensitive to Pi status. However, Pi bioavailability and mobility are often severely restricted by complex soil chemistries, foremost by co-occurrence of abundant metal cations (Al, Fe, Ca, Mg), which form notoriously insoluble Pi salts. Application of Pi fertilizers, derived from finite and non-renewable, high-grade Pi rock sediments, is therefore inherently inefficient and associated with considerable environmental risks. To secure future global food production, it is imperative to understand Pi nutrition of plants and their acclimation to external Pi availability. Such knowledge will provide the basis for designing rational strategies to improve Pi use efficiency of crops.
To cope with inadequate Pi availability, which is a common situation in many ecosystems, plants activate a set of biochemical and developmental responses that reprioritize internal Pi allocation and maximize external Pi interception. Such countermeasures include dynamic reprogramming of metabolism to maintain systemic Pi homeostasis as well as restructuring of root system architecture to accelerate soil exploration for local Pi acquisition. In most dicotyledonous plants, Pi limitation favors development of a shallow root system and large root surface area by attenuating primary root growth, promoting lateral root branching, and stimulating root hair formation (topsoil foraging). Adjustment of root development is coordinated with biochemical processes and chemical modification of the rhizosphere, which mineralize, mobilize and acquire scarce external Pi sources. For example, secreted P-hydrolases access organophosphates, exuded carboxylates or phenolic compounds release mineral-bound Pi by chelation of metallic cations, and induced high-affinity transport systems facilitate more efficient Pi uptake.
Our research aims to dissect the signaling networks plants employ to sense external Pi availability in the context of associated metal toxicities (Al, Fe) and other macronutrients (N). We wish to understand how plants counteract Pi shortage by reprogramming metabolism, root exudation profiles, and root development for maintaining Pi homeostasis.