HKT1在植物耐盐机制中的研究进展

doi:10.13560/j.cnki.biotech.bull.1985.2020-1379

摘要/Abstract

摘要：

土地盐碱化是导致作物产量降低的重要影响因素之一。在盐胁迫下,植物进化出一系列应对盐胁迫的策略,其中,离子转运蛋白在植物应对盐胁迫的过程中发挥着举足轻重的作用。HKT1转运蛋白是一类具有转运Na⁺功能的离子转运蛋白,主要定位在维管束组织附近,广泛存在于单子叶植物和双子叶植物中,参与植物体内Na⁺的长距离运输,调节植物中Na⁺浓度,有助于维持植物体内的离子平衡。分别讨论了不同植物中HKT1蛋白的功能以及相应的调控过程,总结了HKT1参与Na⁺长距离运输的作用模型。通过综合近年来对HKT1的研究,合理运用分子育种等手段,以期为增加农作物的耐盐胁迫能力,提高农作物的质量和产量奠定理论基础。

关键词: 盐胁迫, HKT1, HKT1的调控, 钠离子, 长距离运输

Abstract:

Soil salinization is an important factor affecting the reduction of crop yield. Under salt stress,plants have evolved a series of strategies to deal with salt. In these strategies,ion transporters play a pivotal role in plant response to salt stress. HKT1 transporters are a kind of ion transporters with the function of transporting Na⁺,which are mainly located near vascular bundles and widely found in monocotyledons and dicotyledons. In plants,they participate in the long-distance transport of Na⁺,regulate the concentration of Na⁺,and help to maintain ion balance. In this paper,the functions and corresponding regulatory processes of HKT1 proteins in different plants are discussed,and the different action models of HKT1 participating in Na⁺ long-distance transportation are summarized. By making a synthesis of the research on HKT1 in recent years and rational use of molecular breeding,it lays a theoretical foundation for increasing the salt stress tolerance of crops and improving the quality and yield of crops.

Key words: salt stress, HKT1, HKT1 regulation, Na⁺, long-distance transport

张永兰, 解莉楠. HKT1在植物耐盐机制中的研究进展[J]. 生物技术通报, 2021, 37(6): 213-224.

ZHANG Yong-lan, XIE Li-nan. Advances in HKT1 Study on the Mechanism of Salt Tolerance in Plants[J]. Biotechnology Bulletin, 2021, 37(6): 213-224.

图/表 4

图1 HKT转运蛋白结构示意图 HKT类转运蛋白是具有8个跨膜结构域,中间包括4个P环的膜转运蛋白。HKT家族蛋白序列较为保守,但在第一、二个跨膜结构域之间的第一蛋白孔域,存在氨基酸组成差异,这些差异决定蛋白转运的离子类型。除了第一蛋白孔域之外,在HKT转运蛋白的其他位置中也发现影响离子转运特性的氨基酸,但并不作为HKT家族蛋白分类依据

Fig. 1 Schematic diagram of HKT transport protein structure HKT transporters are membrane transporters with eight transmembrane domains and four P loops in the middle. The HKT family protein sequence is relatively conservative,but there are differences in amino acid composition in the first protein pore domain between the first and second transmembrane domains,and these differences determine the type of ion transported by the protein. In addition to the first protein pore domain,amino acids that affect ion transport properties are also found in other positions of the HKT transport protein,but they are not used as the basis for the classification of HKT family proteins

表1 HKT类转运蛋白的分类

Table 1 Classification of HKT transporters

基因名称 Gene name	物种 Species	表达位置 Express position	在植物中的功能 Function in plants	异源表达时的功能 Function in heterologous expression
EcHKT1;2	蓝桉树 Eucalyptus camalduensis	根、茎、叶均有表达^[15]	转运K^+[15]	大肠杆菌:K⁺转运非洲爪蟾卵母细胞:Na⁺、K⁺、Rb⁺、Li⁺转运
McHKT1;1	冰叶日中花 Mesembryantemum crystallinum	根:表皮细胞、维管束组织^[16] 叶:木质部薄壁细胞、导管细胞	根中表皮细胞转运K⁺进入细胞^[16]	酿酒酵母:K⁺转运非洲爪蟾卵母细胞^[16]:Rb⁺、Cs⁺、K⁺、Na⁺、Li ⁺转运
TsHKT1;2	盐芥 Thellungiella salsuginea	根和叶的维管束,木质部薄壁细胞^[18]	转运K^+[17]	酿酒酵母^[18]:K⁺转运
SvHKT1;1	鼠尾栗 Sporobolus virginicus	500 mmol/L氯化钠处理,根中表达量明显升高^[19]	防止地上部分Na⁺积累过高^[19]	酿酒酵母:Na⁺转运
AtHKT1;1	拟南芥 Arabidopsis thaliana	根和叶的维管束,木质部薄壁细胞^[20]	在地上部分,将Na⁺转运到韧皮部中; 在根中,将Na⁺从木质部中转运出来^[21]	大肠杆菌^[20]:K⁺转运酿酒酵母:Na⁺转运
OsHKT1;1	水稻 Oryza sativa L.	根:表皮、分化为通气组织的内皮,根中柱(尤其是韧皮部) 叶:叶肉细胞和维管束^[22]		酿酒酵母:Na⁺转运非洲爪蟾卵母细胞:Na⁺转运^[23]
OsHKT1;4	水稻 Oryza sativa L.	叶鞘^[24]	控制叶鞘叶片之间的Na⁺转移^[25]
OsHKT1;5	水稻 Oryza sativa L.	根和叶的维管束^[26]	在根中,将Na⁺从木质部中转运出来^[27]	非洲爪蟾卵母细胞:Na⁺转运
TaHKT1;4	小麦 Triticum aestivum	根、叶鞘和叶片^[28]	将Na⁺从木质部中转运到木质部薄壁细胞^[29]
TaHKT1;5	小麦 Triticum aestivum	根中表达,地上部分不表达^[30]	将Na⁺从木质部中转运到木质部薄壁细胞^[28]	酿酒酵母:Na⁺转运非洲爪蟾卵母细胞^[31]:Na⁺转运
SlHKT1;1	番茄 Solanum lycopersicum	根、茎、叶、花、果实中广泛表达^[32]		酿酒酵母:Na⁺转运非洲爪蟾卵母细胞^[32]:Na⁺转运
SlHKT1;2	番茄 Solanum lycopersicum	根、茎、叶、花、果实中广泛表达^[32]		酿酒酵母、非洲爪蟾卵母细胞^[32]:无转运活性
HvHKT1;1	大麦 Hordeum vulgare L.	根和叶的维管束^[33]	根中横向Na⁺运输,减少地上部分的Na⁺积累^[33]	酿酒酵母、非洲爪蟾卵母细胞^[34]:K⁺转运
HvHKT1;5	大麦 Hordeum vulgare L.	根和叶的维管束^[35]	将Na⁺从木质部薄壁细胞转运到木质部中^[35]	非洲爪蟾卵母细胞:Na⁺转运^[35],但受K⁺抑制

表1 HKT类转运蛋白的分类

Table 1 Classification of HKT transporters

基因名称 Gene name	物种 Species	表达位置 Express position	在植物中的功能 Function in plants	异源表达时的功能 Function in heterologous expression
EcHKT1;2	蓝桉树 Eucalyptus camalduensis	根、茎、叶均有表达^[15]	转运K^+[15]	大肠杆菌:K⁺转运非洲爪蟾卵母细胞:Na⁺、K⁺、Rb⁺、Li⁺转运
McHKT1;1	冰叶日中花 Mesembryantemum crystallinum	根:表皮细胞、维管束组织^[16] 叶:木质部薄壁细胞、导管细胞	根中表皮细胞转运K⁺进入细胞^[16]	酿酒酵母:K⁺转运非洲爪蟾卵母细胞^[16]:Rb⁺、Cs⁺、K⁺、Na⁺、Li ⁺转运
TsHKT1;2	盐芥 Thellungiella salsuginea	根和叶的维管束,木质部薄壁细胞^[18]	转运K^+[17]	酿酒酵母^[18]:K⁺转运
SvHKT1;1	鼠尾栗 Sporobolus virginicus	500 mmol/L氯化钠处理,根中表达量明显升高^[19]	防止地上部分Na⁺积累过高^[19]	酿酒酵母:Na⁺转运
AtHKT1;1	拟南芥 Arabidopsis thaliana	根和叶的维管束,木质部薄壁细胞^[20]	在地上部分,将Na⁺转运到韧皮部中; 在根中,将Na⁺从木质部中转运出来^[21]	大肠杆菌^[20]:K⁺转运酿酒酵母:Na⁺转运
OsHKT1;1	水稻 Oryza sativa L.	根:表皮、分化为通气组织的内皮,根中柱(尤其是韧皮部) 叶:叶肉细胞和维管束^[22]		酿酒酵母:Na⁺转运非洲爪蟾卵母细胞:Na⁺转运^[23]
OsHKT1;4	水稻 Oryza sativa L.	叶鞘^[24]	控制叶鞘叶片之间的Na⁺转移^[25]
OsHKT1;5	水稻 Oryza sativa L.	根和叶的维管束^[26]	在根中,将Na⁺从木质部中转运出来^[27]	非洲爪蟾卵母细胞:Na⁺转运
TaHKT1;4	小麦 Triticum aestivum	根、叶鞘和叶片^[28]	将Na⁺从木质部中转运到木质部薄壁细胞^[29]
TaHKT1;5	小麦 Triticum aestivum	根中表达,地上部分不表达^[30]	将Na⁺从木质部中转运到木质部薄壁细胞^[28]	酿酒酵母:Na⁺转运非洲爪蟾卵母细胞^[31]:Na⁺转运
SlHKT1;1	番茄 Solanum lycopersicum	根、茎、叶、花、果实中广泛表达^[32]		酿酒酵母:Na⁺转运非洲爪蟾卵母细胞^[32]:Na⁺转运
SlHKT1;2	番茄 Solanum lycopersicum	根、茎、叶、花、果实中广泛表达^[32]		酿酒酵母、非洲爪蟾卵母细胞^[32]:无转运活性
HvHKT1;1	大麦 Hordeum vulgare L.	根和叶的维管束^[33]	根中横向Na⁺运输,减少地上部分的Na⁺积累^[33]	酿酒酵母、非洲爪蟾卵母细胞^[34]:K⁺转运
HvHKT1;5	大麦 Hordeum vulgare L.	根和叶的维管束^[35]	将Na⁺从木质部薄壁细胞转运到木质部中^[35]	非洲爪蟾卵母细胞:Na⁺转运^[35],但受K⁺抑制

图2 HKT1在Na+长距离运输中的作用在拟南芥中,地上部分的过量的Na+通过HKT1蛋白运输到韧皮部,而后通过韧皮部向下运输到根中,这被称为“再循环”模型;而根中的HKT1将Na+从木质部中运输到木质部薄壁细胞,避免Na+通过木质部中的蒸腾流向上运输到地上部分,这被称为“外排”模型。而HKT1在茎中维管束的定位,则有力的支持了Christa Testerink提出的HKT1在拟南芥Na+长距离运输中的观点,即在拟南芥中,“外排”模型与“再循环”模型可能同时存在

Fig. 2 The role of HKT1 in Na+ long-distance transportation In Arabidopsis,the excess Na+ in the aerial part is transported to the phloem through the HKT1 protein,and then transported down to the root through the phloem,which is called a”recirculation” model. The HKT1 in the root transports Na+ from the xylem to the parenchyma cells of the xylem,and prevents Na+ from being transported upwards to the above-ground part through transpiration in the xylem. This is called the “exhaust” model. The positioning of HKT1 in the vascular bundles in the stem strongly supports Christa Testerink’s view of HKT1 in Arabidopsis Na + long-distance transportation,that is,in Arabidopsis,the “exhaust” model and the “recirculation” model may be at the same time

图3 植物细胞离子响应策略以及HKT1表达调控途径细细胞中存在的与盐胁迫有关的离子转运蛋白,一部分定位在细胞膜上,参与钠钾平衡的维持过程;一部分定位在囊泡膜与液泡膜上,参与Na+在细胞内的固存。而参与HKT1表达调控的各类因子成分复杂,植物激素(细胞分裂素),第二信使(Ca+,ROS)、表观调控因子(SUVH7)不同程度的同时参与该过程,且最终对HKT1的影响效果也不同。除了在表达过程中进行调控,HKT1蛋白在细胞膜上还受PP2C49的直接抑制

Fig. 3 Plant cell ion response strategy and HKT1 expression regulation pathway Some ion transporters related to salt stress in cells are located on the cell membrane and participate in the maintenance of sodium and potassium balance;some are located on the vesicle membrane and the vacuole membrane and participate in the retention of Na+ in the cell. The various factors involved in the regulation of HKT1 expression are complex. Plant hormones(cytokinins),second messengers(Ca+,ROS),and apparent regulatory factors(SUVH7)participate in the process at the same time to varying degrees,and ultimately affect HKT1 and the effect is also different. In addition to regulation during the expression process,HKT1 protein is directly inhibited by PP2C49 on the cell membrane

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