| 水稻OsAKT2的钾吸收功能及其在地上部分K+回流中的潜在作用 |
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| 引用本文： | 黄亚楠,李俊林,苏彦华.水稻OsAKT2的钾吸收功能及其在地上部分K+回流中的潜在作用[J].植物营养与肥料学报,2022,28(7):1158-1166. |
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| 作者姓名： | 黄亚楠 李俊林 苏彦华 |
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| 作者单位： | 1.中国科学院南京土壤研究所/土壤与农业可持续发展国家重点实验室，江苏南京 210008 |
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| 基金项目： | 国家重点研发专项(2016YFD0100700)；国家自然科学基金项目(31672230)；国家转基因植物研发专项(2009ZX08009-129B)。 |
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| 摘 要： | 【目的】 研究水稻钾通道OsAKT2的基本功能和调控特征，揭示其在地上部K+回流中的潜在作用。 【方法】 通过构建系统进化树和关键氨基酸区域序列比对，对不同物种来源的Shaker类钾离子通道基因进行了同源性分析；利用蛙卵电生理技术，研究水稻OsAKT2的膜电位敏感性及其对钾离子的吸收特征、离子选择性和对钾通道抑制剂的响应变化；并利用实时荧光定量PCR技术，探究了水稻OsAKT2的表达与钾浓度、铵转运及胁迫处理间的相互关系。 【结果】 OsAKT2与AtAKT2等典型通道高度同源(56%)，属于AKT2类弱电压依赖—双向整流型钾离子通道。OsAKT2所介导的K+转运过程，与典型该类通道表现出不同的性质，主要体现在以介导K+的吸收为主，缺失了AKT2通道标志性的K+外排活性，且其K+吸收过程转变为明显的电压依赖性。OsAKT2对K+吸收Km值为43 mmol/L，是一典型的低亲和钾离子通道(>1 mmol/L)；与典型Shaker通道相比，钾通道抑制剂Ba2+对OsAKT2的K+吸收活性的抑制效率(<78%)较低，而且表现出一定程度的NH4+通透性(约占K+的22%)。进一步模拟田间种植水稻可能遇到的胁迫环境，发现水稻地上部OsAKT2基因的表达丰度在缺铵、缺钾及山梨醇处理下显著提高，且表现出一定的避光性(黑暗中基因表达水平较高)。 【结论】 水稻OsAKT2能够提高植物K+吸收能力，或将有助于增强其在地上部K+回流和再利用中的功能，且对水稻体内氮素营养吸收转运具有潜在的贡献。
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| 关 键 词： | 水稻 OsAKT2 电生理 功能特异性 铵转运 |
| 收稿时间： | 2021-11-11 |
The function of OsAKT2 in K+ uptake and the aboveground K+ reflux of rice |
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| HUANG Ya-nan,LI Jun-lin,SU Yan-hua.The function of OsAKT2 in K+ uptake and the aboveground K+ reflux of rice[J].Plant Nutrition and Fertilizer Science,2022,28(7):1158-1166. |
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| Authors: | HUANG Ya-nan LI Jun-lin SU Yan-hua |
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| Institution: | 1.Institute of Soil Science, Chinese Academy of Sciences/State Key Laboratory of Soil and Sustainable Agriculture, Nanjing, Jiangsu 210008, China |
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| Abstract: | 【Objectives】 The electrophysiological functions and regulatory characteristics of OsAKT2 were investigated to unravel its K+ uptake mechanisms and its potential influence on the aboveground K+ reflux . 【Methods】 The Phylogenetic tree and sequence alignment were constructed to analyze the homology of Shaker potassium channel genes. The two-electrode voltage-clamp experiments were performed on OsAKT2-expressing Xenopus oocytes to study the electrophysiological characteristics of OsAKT2. The relationship between OsAKT2 gene expression and K+ concentration, NH4+ concentration, and stress conditions in rice was studied. 【Results】 The phylogenetic analysis showed that OsAKT2 was closest related to the weakly rectifying potassium channel with 56% to AtAKT2. The results showed that OsAKT2 function mainly as an inwardly rectifying K+ channel with strong voltage dependency. However, the outward activity of a typical leak-like AKT2 channel was notably suppressed. The electrophysiological results indicated that OsAKT2 was a typical low-affinity potassium channel (Km = 43 mmol/L, >1 mmol/L) with high selectivity for K+. Compared with the Shaker-type channel, OsAKT2 was inhibited by Ba2+, but the inhibition rate was lower (<78%). OsAKT2 had some permeability to NH4+ (about 22% of K+ uptake). The gene expression abundance of OsAKT2 increased significantly under nitrogen deficiency, potassium deficiency, and sorbitol conditions, and had a circadian rhythm whereby the gene expression level was higher in the dark. 【Conclusions】 This study suggests that OsAKT2 mainly mediate the K+ uptake in rice, which is sensitive to the change of external K+ concentration. OsAKT2 may play an important role in plant adaptation to stress, which also provides a way to improve the reflux of K+. Further, OsAKT2 has a potential contribution to ammonium transport in rice. |
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