Review: Adaptation of plants to phosphorus scarcity: From nutritional crosstalk to organellar function

Plants respond to phosphorus scarcity by adjusting root architecture and activating physiological and biochemical processes aimed at optimizing the uptake, transport, and efficient use of this nutrient. Phosphate, the main phosphorus available form is perceived in the root cap in a process involving several molecular components, including the transcription factor SOMBRERO and bacterial-type ferroxidases that enhance the uptake and transport of iron, whose accumulation triggers the production of reactive oxygen species, stops mitosis and halts root growth. In this process, auxins, cytokinins, jasmonic acid, abscisic acid and the neurotransmitter γ-aminobutyric acid orchestrate the formation of root hairs and lateral roots as well as the expression of Pi transporters in roots and anthocyanins in leaves. Low Pi-sensing genes can be classified as drivers or blockers of the root growth repression elicited by Pi scarcity, the drivers encode nitrate-inducible transcription factors, the STOP1-ALMT1 module controlling root exudation of malate, proteins mediating Fe uptake and distribution and MEDIATOR subunit 16. Cations such as Fe and Al trigger accumulation of the transcription factor STOP1 in nuclei to modulate the transcriptional response and promote malate exudation, implying a direct link between cation-Pi complexes at the rhizosphere and root morphogenesis. General cell maintenance mechanisms that acclimate plants during root meristem consumption have been identified including SUMOylation, endoplasmic reticulum stress, proteostasis, autophagy and signaling mediated by MPK6 and MPK4 kinases. These mechanisms unveil the complexity of the signaling pathways to favor plant adaptation and survival when a critical macronutrient is limiting.