Characterization of rice KT/HAK/KUP potassium transporters and K⁺ uptake by HAK1 from <i>Oryza sativa</i>

Abstract

Plant high-affinity K + (HAK) transporters are divided into four major clusters. Cluster I transporters, in particular, are thought to have high-affinity for K +. Of the 27 HAK genes in rice, eight HAK transporters belong to cluster I. In this study, we investigated the temporal expression patterns during K + deficiency and K + transport activity of these eight HAK transporters. The expression of seven HAK genes except OsHAK20 was detected. Expression of OsHAK1, OsHAK5 and OsHAK21 was induced in response to K + deficiency; however, that of other genes was not. Six of the eight HAK transporters-OsHAK1, OsHAK5, OsHAK19, OsHAK20, OsHAK21, and OsHAK27-complemented the K +transporter-deficient yeast or bacterial strain. Further, the yeast cells expressing OsHAK1 were more sensitive to Na + than those expressing OsHAK5. Mutant analysis showed that the high-affinity K + uptake activity was almost undetectable in oshak1 mutants in a low-K + medium (0.02 mM). In addition, the high-affinity K + uptake activity of wild-type plants was inhibited by mild salt stress (20 mM NaCl); however, Na + permeability of OsHAK1 was not detected in Escherichia coli cells. The high-affinity K + uptake activity by leaf blades was detected in wild-type plants, while it was not detected in oshak1 mutants. Our results suggest that OsHAK1 and OsHAK5 are the two important components of cluster I corresponding to low-K + conditions, and that the transport activity of OsHAK1, unlike that of OsHAK5, is sensitive to Na +. Further, OsHAK1 is suggested to involve in foliar K + uptake.

Optimization of nitrogen fertilizer management for improving rice grain yield and nutrient accumulation and mobilization in saline‐alkaline soils

“…), and cotton ( Gossypium hirsutum L.), the absorption of K by plant roots is close or equal to that of N (Fageria & Santos, 2015). Besides its involvement in plant metabolism, K plays an important role in plant salt tolerance; the ability to retain K + in root cells under salt stress correlates with salt tolerance in rice (Okada et al., 2018; Shabala, Bose, Fuglsang, & Pottosin, 2016). In general, sufficient K is necessary for plants to achieve their maximum yield potential.…”

Halophytic Hordeum brevisubulatum HbHAK1 Facilitates Potassium Retention and Contributes to Salt Tolerance

“…HAK/KUP/KT transporters could not generate K + currents in cells, thus, their function studies mainly carried out in yeast or bacteria mutants defective for K + uptake like yeast Cy162 strains. Interestingly, the HbHAK1 transformants can grow in the presence of extremely low external K + (10 μM), as the same experiments confirm HvHAK1, OsHAK5, CcHAK1 and CaHAK1 transformants recover the growth at 0.1-mM K + added [ 12 , 33 , 34 ] and OsHAK1 or AtHAK5 expressing strains can grow at 0.3-mM external K + content [ 8 , 10 ]. The best performance of HbHAK1 in complementation of Cy162 strains indicated its strong K + transport activity and extended the minimum threshold of K + uptake operated by HAK-type transporters.…”

The bacterial potassium transporter gene MbtrkH improves K+ uptake in yeast and tobacco

“…K + is the most abundant cation in plant cells and plays a vital role in many fundamental processes, including plant growth and development [44,45]. K + deficiency affects crop yield and WT is the wild-type line; L1 and L4 are two independent MbtrkH transgenic lines.…”

“…K + is the most abundant cation in plant cells and plays a vital role in many fundamental processes, including plant growth and development [ 44 , 45 ]. K + deficiency affects crop yield and quality [ 46 ], and overexpression of K + transporter genes is an effective way to resolve these issues [ 47 ].…”