Distinct Functions of the Atypical Terminal Hydrophilic Domain of the HKT Transporter in the Liverwort Marchantia polymorpha.
Distinct Functions of the Atypical Terminal Hydrophilic Domain of the HKT Transporter in the Liverwort Marchantia polymorpha.
复制标题
地钱中 HKT 转运蛋白非典型末端亲水结构域的独特功能。
DOI：
10.1093/pcp/pcac044
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Horie T.
中科院分区：
文献类型：
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作者：
Imran S;Oyama M;Horie R;Kobayashi NI;Costa A;Kumano R;Hirata C;Tran STH;Katsuhara M;Tanoi K;Kohchi K;Ishizaki K;Horie T.
K+/Na+动态平衡对陆地植物非常重要，特别是在盐胁迫下。本研究研究了海苔（marchantia polymorpha）高亲和K+转运体（HKT）的结构和离子传输特性。在m的基因组中只鉴定出一个hktgene， MpHKT1。polymorpha。对HKT蛋白的系统发育分析表明，非种子植物具有独立于被子植物HKT的另外两个支系的HKT。在MpHKT1的c端发现了一个明显的长亲水结构域。利用截断的MpHKT1（t-MpHKT1）编码MpHKT_Δ596-812蛋白的互补DNA （cDNA）来检测c端结构域的功能。在水稻原生质体中表达时，两种与n端增强的绿色荧光蛋白融合的mphkt1转运蛋白都定位在质膜上。利用非洲爪蟾卵细胞进行的双电极电压钳实验表明，mphkt1介导的单价碱阳离子的转运对Na+和K+具有较高的选择性，但c端结构域的截断显著降低了转运活性，降低了Na+的通透性。mphkt1或t-MpHKT1inM过表达。与野生型植物相比，多态赋予了更高的Na+积累水平和更高的Na+吸收率；然而，t-MpHKT1的表型始终比MpHKT1的表型弱。总之，这些发现表明亲水性c端结构域在调控MpHKT1的转运活性和离子选择性中起着独特的作用。
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 liverwortMarchantia polymorphawere investigated. Only oneHKTgene, MpHKT1, was identified in the genome ofM. 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 MpHKT1transporters 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 usingXenopus laevisoocytes indicated that MpHKT1mediated 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 MpHKT1or t-MpHKT1inM. polymorphaconferred accumulation of higher Na+levels and showed higher Na+uptake rates, compared to those of wild-type plants; however, phenotypes with t-MpHKT1were 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.