Multiple High-Affinity K⁺ Transporters and ABC Transporters Involved in K⁺ Uptake/Transport in the Potassium-Hyperaccumulator Plant Phytolacca acinosa Roxb

Potassium is an important essential element for plant growth and development. Long-term potassium deprivation can lead to a severe deficiency phenotype in plants. Interestingly, Phytolacca acinosa is a plant with an unusually high potassium content and can grow well and complete its lifecycle even in severely potassium deficient soil. In this study, we found that its stems and leaves were the main tissues for high potassium accumulation, and P. acinosa showed a strong ability of K+ absorption in roots and a large capability of potassium accumulation in shoots. Analysis of plant growth and physiological characteristics indicated that P. acinosa had an adaptability in a wide range of external potassium levels. To reveal the mechanism of K+ uptake and transport in the potassium-hyperaccumulator plant P. acinosa, K+ uptake-/transport-related genes were screened by transcriptome sequencing, and their expression profiles were compared between K+ starved plants and normal cultured plants. Eighteen members of HAK/KT/KUPs, ten members of AKTs, and one member of HKT were identified in P. acinosa. Among them, six HAKs, and two AKTs and PaHKT1 showed significantly different expression. These transporters might be coordinatively involved in K+ uptake/transport in P. acinosa and lead to high potassium accumulation in plant tissues. In addition, significantly changed expression of some ABC transporters indicated that ABC transporters might be important for K+ uptake and transport in P. acinosa under low K+ concentrations.