Dealing with Environmental Fluctuations: Diversity of Potassium Uptake Systems Across the Three Domains of Life

Abstract

Potassium ion (K⁺) constitutes one of the six macronutrients and is implicated in several processes that aid cell survival and growth. Optimal intracellular K⁺ level is achieved through the combination of low and high-affinity transport systems allowing uptake over a wide range (millimolar (mM) to micromolar (μM)) of external K⁺ concentration and is impacted by both biotic and abiotic stress conditions. Plants growing in K⁺-deficient soil are more susceptible to disease and damage caused due to abiotic stress factors like frost, drought, and salinity. The severity decreases with an increase in exogenous K⁺. Exposure to high saline conditions results in an increase in intracellular sodium (Na⁺) and a concurrent decrease in K⁺ levels. Thus, intracellular K⁺ levels are crucially linked to specific uptake and efflux mechanisms operational during a particular stress regime. While molecular pathway(s) operative in K⁺-mediated endurance to multiple stress conditions are not fully understood, studies suggest a positive correlation between capacity for incremented K⁺ levels and survival advantages. In this article we review: K⁺ uptake systems and mechanisms available across life domains with special reference to plant systems. Recent emerging evidence on the involvement of K⁺ in stress management, and the role of K⁺ uptake systems during pathogenicity and symbiotic associations. Approaches aimed at optimizing intracellular K⁺ levels through modulation of (influx and efflux mechanisms) and (vacuole pools) as a viable strategy to support plant growth under stress conditions.