不同盐碱胁迫对棉花离子组稳态及Na^+相关基因表达影响

Ionic Homeostasis and Expression of Na^+ Related Genes of Cotton under Different Salt and Alkali Stresses

【目的】维持细胞内离子稳态是作物重要的耐盐机制之一。研究不同盐碱胁迫下棉花离子组响应特征和耐盐基因表达的差异,为深入认识棉花耐盐机理和提高棉花耐盐性提供依据。【方法】以鲁棉研24号为试验材料,在盆栽控制条件下设置3种盐碱胁迫类型(盐胁迫、碱胁迫和复合盐碱胁迫)和2个梯度水平(低盐碱和高盐碱),并以无盐碱胁迫处理为对照。测定棉花植株干物质质量以及根系形态指标根长、根表面积和根体积。采用电感耦合等离子体原子发射光谱仪(ICP-AES)测定棉花各器官P、Na、K、Ca、Mg等13种元素含量,并采用实时荧光定量聚合酶链式反应技术测定了耐盐相关基因GhDFR1、GhSOS1、GhNHX1和GhAKT1的相对表达量。【结果】1)不同盐碱胁迫显著抑制棉花生长,复合盐碱胁迫棉花生长抑制率(48.7%~57.9%)显著高于盐胁迫(27.6%~49.9%)和碱胁迫(21.2%~35.5%)。盐胁迫和复合盐碱胁迫下,棉花地上部和根系生长均显著受抑制,地上部干物质质量、根长、根表面积和根体积显著降低;而碱胁迫对根系的抑制作用相对较小。2)3种盐碱胁迫下,棉花体内Na含量显著增加;各器官Mo含量也均显著增加,叶片和根系N含量降低。3)盐胁迫下,棉花Ca、Mg、Fe、Mn、Zn吸收受抑制,通过促进这些离子以及P、K的转运,维持体内离子平衡。4)碱胁迫下,除Ca、Mg、Fe、Mn、Zn以外,P的吸收也受到抑制,但K的吸收以及P、K、Ca、Mg、Fe、Mn、Zn向地上部转运受到促进。5)复合盐碱胁迫尤其是高盐和pH值环境下,主要营养元素吸收均受抑制,Ca、Mg、Zn、Mn、Fe转运能力降低。6)盐胁迫下,GhSOS1和GhAKT1基因相对表达量显著增加,在碱胁迫和复合盐碱胁迫下呈先增后降趋势;3种盐碱胁迫下,表现为碱>盐>复合盐碱胁迫。GhNHX1基因相对表达量随土壤盐碱度增加先增后降,表现为盐>碱>复合盐碱。【结论】复合盐碱胁迫由于高盐度和pH叠加效应显著抑制棉花生长和离子吸收,制约P、K、Ca、Mg、Zn、Mn、Fe向地上部转运,使棉花K、Na离子调控能力下降导致离子失衡。

[Objective]Maintaining intracellular ion homeostasis is one of the important salt-tolerant mechanisms of crops.This study aims to analyze differences in response characteristics of cotton ionome and salt-tolerant gene expression under different saline-alkali stresses,which provides a basis for understanding the mechanism of salt tolerance and improving salt tolerance of cotton.[Method]Using Lumianyan 24 as the experimental material,three kinds of salt and alkali stress types(salt stress,alkali stress,and mixed salt-alkali stress)and two concentration gradients(low and high concentrations)were set under pot cultivation conditions.Meanwhile,non-saline-alkali stress treatment was set as control.The dry matter weight of cotton plants and root morphological parameters including root length,root surface area,and root volume were measured in this study.The concentrations of 13 elements such as P,Na,K,Ca and Mg in different organs of cotton plants were determined by inductively coupled plasma atomic emission spectrometry(ICP-AES).The relative expressions of salt tolerance related genes GhDFR1,GhSOS1,GhNHX1 and GhAKT1 were determined by the quantitative real-time polymerase chain reaction method.[Result]1)Salt and alkali stresses significantly inhibited cotton growth.The growth inhibition rate of cotton under mixed salt-alkali stress treatments(48.7%–57.9%)was significantly higher than that under salt stress(27.6%–49.9%)and alkali stress(21.2%–35.5%)treatments.Under salt stress and mixed salt-alkali stress treatments,both shoot and root growth of cotton were significantly inhibited,dry matter weight,root length,root surface area and root volume were significantly reduced,while root growth was less inhibited under alkali stress treatments.2)Under three types of saline-alkali stresses,Na content and Mo content in different organs of cotton plant increased significantly,but N content in leaves and roots decreased.3)Under salt stress treatments,the uptake of Ca,Mg,Fe,Mn and Zn in cotton was inhibited,and the ion balance was maintained by promoting the transport of these ions and P,K.4)In addition to Ca,Mg,Fe,Mn and Zn,P uptake was also inhibited under alkali stress treatments,but K uptake and P,K,Ca,Mg,Fe,Mn and Zn transport were promoted.5)Under mixed salt-alkali stress treatments,especially under high salinity and pH conditions,most of nutrients uptake was inhibited,and the transport capacity of Ca,Mg,Zn,Mn and Fe was reduced.6)The relative expression of GhSOS1 and GhAKT1 genes increased significantly under salt stress treatments,but increased first and then decreased under alkali stress and mixed salt-alkali stress treatments.The relative expression levels of GhSOS1 and GhAKT1 genes under three types of saline-alkali stresses were alkali>salt>mixed saline-alkali stress.With the increase of soil salinity and pH value,the relative expression of GhNHX1 gene increased first and then decreased.The expression levels of GhNHX1 gene were salt>alkali>mixed salt-alkali stress.[Conclusion]Due to high salinity and pH value,mixed salt-alkali stress significantly inhibits cotton growth and ions uptake,which restricts the transport of P,K,Ca,Mg,Zn,Mn and Fe.The decrease of K and Na regulation ability leads to ions imbalance.