Distinct Functions of the Atypical Terminal Hydrophilic Domain of the HKT Transporter in the Liverwort Marchantia polymorpha

Shahin Imran, Masumi Oyama, Rie Horie, Natsuko I. Kobayashi, Alex Costa, Ryosuke Kumano, Chiho Hirata, Sen Thi Huong Tran, Maki Katsuhara, Keitaro Tanoi, Takayuki Kohchi, Kimitsune Ishizaki, Tomoaki Horie

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


K+/Na+ homeostasis is important for land plants, particularly under salt stress. In this study, the structure and ion transport properties of the high-affinity K+ transporter (HKT) of the liverwort Marchantia polymorpha were investigated. Only one HKT gene, MpHKT1, was identified in the genome of M. polymorpha. Phylogenetic analysis of HKT proteins revealed that non-seed plants possess HKTs grouped into a clade independent of the other two clades including HKTs of angiosperms. A distinct long hydrophilic domain was found in the C-terminus of MpHKT1. Complementary DNA (cDNA) of truncated MpHKT1 (t-MpHKT1) encoding the MpHKT_Δ596-812 protein was used to examine the functions of the C-terminal domain. Both MpHKT1 transporters fused with enhanced green fluorescent protein at the N-terminus were localized to the plasma membrane when expressed in rice protoplasts. Two-electrode voltage clamp experiments using Xenopus laevis oocytes indicated that MpHKT1 mediated the transport of monovalent alkali cations with higher selectivity for Na+ and K+, but truncation of the C-terminal domain significantly reduced the transport activity with a decrease in the Na+ permeability. Overexpression of MpHKT1 or t-MpHKT1 in M. polymorpha conferred accumulation of higher Na+ levels and showed higher Na+ uptake rates, compared to those of wild-type plants; however, phenotypes with t-MpHKT1 were consistently weaker than those with MpHKT1. Together, these findings suggest that the hydrophilic C-terminal domain plays a unique role in the regulation of transport activity and ion selectivity of MpHKT1.

Original languageEnglish
Pages (from-to)802-816
Number of pages15
JournalPlant & cell physiology
Issue number6
Publication statusPublished - Jun 15 2022


  • Marchantia polymorpha
  • HKT
  • K+ transport
  • Na+ transport

ASJC Scopus subject areas

  • Physiology
  • Plant Science
  • Cell Biology


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