Regulation of K+ Nutrition in Plants.

Paula Ragel,Francisco J Quintero,José M Pardo,Eduardo O Leidi,Natalia Raddatz

doi:10.3389/fpls.2019.00281

Abstract

Modern agriculture relies on mineral fertilization. Unlike other major macronutrients, potassium (K+) is not incorporated into organic matter but remains as soluble ion in the cell sap contributing up to 10% of the dry organic matter. Consequently, K+ constitutes a chief osmoticum to drive cellular expansion and organ movements, such as stomata aperture. Moreover, K+ transport is critical for the control of cytoplasmic and luminal pH in endosomes, regulation of membrane potential, and enzyme activity. Not surprisingly, plants have evolved a large ensemble of K+ transporters with defined functions in nutrient uptake by roots, storage in vacuoles, and ion translocation between tissues and organs. This review describes critical transport proteins governing K+ nutrition, their regulation, and coordinated activity, and summarizes our current understanding of signaling pathways activated by K+ starvation.

Highlights

Potassium (K+) is of paramount importance in plant cell physiology
The Arabidopsis CIPK23/CBL1,9 complex enabled the activation of various members from clade I of KT/ HAK/KUP transporters, such as pepper CaHAK1 (Ragel et al, 2015) and Venus flytrap DmHAK5 (Scherzer et al, 2015), but not of tomato SlHAK5 or the Eutrema salsuginea EsHAK5 (Ragel et al, 2015). These results suggested that the activation mechanism by CIPK23/calcineurin B-like protein (CBL) complexes is evolutionarily conserved, but not the phosphorylation site and/or the target sequence recognition, which may vary among distant plant species
Mutation of AKT1 or CIPK23 cancelled the formation of lateral roots under low-K+ (Kellermeier et al, 2014). These nitrate-specific effects occurred over a concentration range that triggers phosphorylation of NRT1.1 by CIPK23. These results suggest that N and K+ availability determines root architecture and that CIPK23 serves as the regulatory node acting through both AKT1 and NRT1.1

Summary

Introduction

Potassium (K+) is of paramount importance in plant cell physiology. K+ is an essential macronutrient that fulfills critical functions related to enzyme activation, osmotic adjustment, turgor generation, cell expansion, regulation of membrane electric potential, and pH homeostasis (Hawkesford et al, 2012). AKT1-like channels and HAK1-like transporters are thought to constitute the main systems for K+ uptake in plants under low-K+ concentrations (Table 2).

Results

Conclusion