Characterization and Expression of KT/HAK/KUP Transporter Family Genes in Willow under Potassium Deficiency, Drought, and Salt Stresses

Abstract

The K+ transporter/high-affinity K+/K+ uptake (KT/HAK/KUP) transporters dominate K+ uptake, transport, and allocation that play a pivotal role in mineral homeostasis and plant adaptation to adverse abiotic stresses. However, molecular mechanisms towards K+ nutrition in forest trees are extremely rare, especially in willow. In this study, we identified 22 KT/HAK/KUP transporter genes in purple osier willow (designated as SpuHAK1 to SpuHAK22) and examined their expression under K+ deficiency, drought, and salt stress conditions. Both transcriptomic and quantitative real-time PCR (qRT-PCR) analyses demonstrated that SpuHAKs were predominantly expressed in stems, and the expression levels of SpuHAK1, SpuHAK2, SpuHAK3, SpuHAK7, and SpuHAK8 were higher at the whole plant level, whereas SpuHAK9, SpuHAK11, SpuHAK20, and SpuHAK22 were hardly detected in tested tissues. In addition, both K+ deficiency and salt stress decreased the tissue K+ content, while drought increased the tissue K+ content in purple osier plant. Moreover, SpuHAK genes were differentially responsive to K+ deficiency, drought, and salt stresses in roots. K+ deficiency and salt stress mainly enhanced the expression level of responsive SpuHAK genes. Fifteen putative cis-acting regulatory elements, including the stress response, hormone response, circadian regulation, and nutrition and development, were identified in the promoter region of SpuHAK genes. Our findings provide a foundation for further functional characterization of KT/HAK/KUP transporters in forest trees and may be useful for breeding willow rootstocks that utilize potassium more efficiently.

Isolation and Functional Determination of SKOR Potassium Channel in Purple Osier Willow, Salix purpurea

“…K + deficiency treatment was carried out as previously described in Liang et al [ 25 ]. 1-year-old female purple osier cutting asexual cloning plants were subjected to K + deficiency and collected at 0 h, 4 h, 12 h, 36 h, and 72 h before qRT-PCR analysis.…”

“…As previously described in Liang et al [ 25 ], RNA extraction was carried out using MiniBEST Plant RNA Extraction Kit (TaKaRa, Dalian, China), and the 1st cDNA was synthesized using PrimeScriptTM RT reagent Kit (TaKaRa, Dalian, China). Specific primers for SpuSKOR and Ubiquitin control gene were designed from NCBI/Primer-BLAST online server ( Table 1 ).…”

Cloning and Functional Determination of Ammonium Transporter PpeAMT3;4 in Peach

“…Fulllength amino acid sequences of PpeAMT transporters were aligned by ClustalX2.1 and imported into the Molecular Evolutionary Genetics Analysis (MEGA) package version 4.1. Phylogenetic analyses were conducted according to the description of Liang et al [28]. Branch lengths indicate the corresponding phylogenetic distances.…”

“…Sequence logos of AMT1 and AMT2 subfamilies were shown on the right, generated using WEBLOGO (http://weblogo.berkeley.edu/logo .cgi). The grand average of hydropathicity (GRAVY) and aliphatic index analyses of PpeAMT3;4 were calculated using the ProtParam tool (http://web.expasy.org/protparam/), as described by Liang et al [28].…”

Regulation of AtKUP2 Expression by bHLH and WRKY Transcription Factors Helps to Confer Increased Salt Tolerance to Arabidopsis thaliana Plants

“…The large family of high affinity potassium transporters (HAK/KUP/KT) in plants mainly contribute to root K + acquisition under a wide range of external K + levels. They also mediate K + movement within the plant and K + efflux into the environment, thereby maintaining ion homeostasis ( Liang et al, 2020 ). Among these transporters, HAKs have been extensively studied.…”