中图分类号：S661.1：Q781 文献标识号：A 文章编号：1001-4942（2025）06-0028-09

AbstractPotassium （K）is one of the essential mineral elements for plant growth and development， which is very important for yield and quality formation. HAK5 is an important high-affinity K transporter gene， which mainly mediates K uptake under low K conditions.However，litle is known about the functional role of HAK5 in Malus. In this study，Malus haliana was used as experimental material，and its HAK5 （MhHAK5） gene was cloned and analyzed.The physicochemical properties and tissue expression specificity were analyzed by bioinformatics analysis，and the response to low K was studied through overexpressing MhHAK5 in Arabidopsis thaliana by genetic transformation.The results showed that the full length of MhHAK5 gene was 1 830 bp with the open reading frame （ORF）as 1695bp ，and it encoded 518 amino acids. The MhHAK5 protein had the molecular weight of 60.05kDa and the isoelectric point of 7.45， had four transmembrane structures， was an unstable hydrophilic transmembrane protein，and was located in nucleus.Phylogenetic analysis showed that MhHAK5 had the highest similarity with AtHAK5，AtHAK1O in Arabidopsis thaliana and OsHAK5 in rice.Furthermore，it had Ser-Gly-Gly-Gly amino acid sequence.The results of tissue expresson specificity analysis showed that MhHAK5 had the highest expression level in roots of M. halliana，and was induced by low potassium. Compared with wild type （WT），overexpression of MhHAK5 could effctively improve K⁺ absorption and growth-promoting plant hormone synthesis of Arabidopsis plants under low K conditions，thus ensuring root development.In summary，MhHAK5 played an important role in response to K deficiency stress.The results ofthis study could provide theoretical bases for gene improvement and breeding of K deficiency tolerant apple rootstocks.

KeywordsMalus haliana ; MhHAK5 gene； Bioinformatics analysis; Potassium deficiency stress ； Geneexpression

钾（K）是植物必需的矿质养分之一，与氮、磷的利用方式不同，K在植物体中不会被同化为有机物，主要以钾离子（ K⁺ ）形态存在并发挥作用[1]。 K⁺ 参与许多植物生理过程，例如调节渗透压、维持细胞膨压、促进蛋白质生物合成、调控膜极化以及同化产物的运输等[2]，影响着植物产量和品质的形成。全球钾资源分布极不均匀，当植物生长在K有效含量较低的土壤中时，生长发育和生理代谢都会受到消极影响[3]。我国土壤钾主要以矿物态存在，造成土壤有效钾含量偏低，再加上钾肥资源短缺及植物钾利用效率较低，使得植物体内钾含量不足，已成为目前导致其产品质量欠佳的重要原因[4] 。

研究表明，植物具有复杂的信号通路以应对根围 K⁺ 浓度的变化，当根围 K⁺ 浓度低于 2mmolL 时，高亲和力转运系统（HATs）被诱导通过 H⁺/K⁺ 质子泵方式发挥主要作用，而当 K⁺ 浓度高于 2mmol/L 时，低亲和力转运系统（LATs）则起主要作用[1，5-6]。高亲和力钾转运蛋白（HAK）是钾离子转运体KT/KUP/HAK超家族的重要组成部分，具有单价阳离子转运特性[]。HAK家族蛋白具有4＼～12个跨膜区域[8，通常在第2个与第3个跨膜区域之间存在着1个带电荷的中央亲水环[7]，第3个与第4个跨膜区域之间存在着首个PA环保守位点的氨基酸序列[9]。该家族蛋白不仅是 K⁺-Na⁺ 协同转运蛋白，也是 ΔNa⁺，K⁺ 的单向转运蛋白[10]。研究表明，HAK成员具有增强植物抗旱、耐盐碱及抗病性的作用[7，11]，尤其在缺钾情况下可诱导植物根系促生长激素的合成，促进根系生长，并且调节植物对 K⁺ 的吸收，目前已发现 HAKI、HAK5、HAK7 基因参与低钾胁迫下的钾