Data_Sheet_3_Physiological and Proteomic Analysis of Different Molecular Mechanisms of Sugar Beet Response to Acidic and Alkaline pH Environment.DOCX

Soil pH is a major constraint to crop plant growth and production. Limited data are available on sugar beet growth status under different pH conditions. In this study, we analyzed the growth status and phenotype of sugar beet under pH 5, pH 7.5, and pH 9.5. It was found that the growth of sugar beet was best at pH 9.5 and worst at pH 5. The activities of superoxide dismutase (SOD) and peroxidase (POD) in leaves and roots increased as pH decreased from 9.5 to 5. Moreover, compared with pH 9.5, the levels of soluble sugar and proline in leaves increased significantly at pH 5. To explore the mechanisms of sugar beet response to different soil pH environments, we hypothesized that proteins play an important role in plant response to acidic and alkaline pH environment. Thus, the proteome changes in sugar beet modulated by pH treatment were accessed by TMT-based quantitative proteomic analysis. A total of three groups of differentially expressed proteins (DEPs) (pH 5 vs. pH 7.5, pH 9.5 vs. pH7.5 and pH 5 vs. pH 9.5) were identified in the leaves and roots of sugar beet. Several key proteins related to the difference of sugar beet response to acid (pH 5) and alkaline (pH 9.5) and involved in response to acid stress were detected and discussed. Moreover, based on proteomics results, QRT-PCR analysis confirmed that expression levels of three N transporters (NTR1, NRT2.1, and NRT2.5) in roots were relatively high under alkaline conditions (pH 9.5) compared with pH 5 or pH 7.5. The total nitrogen content of pH 9.5 in sugar beet was significantly higher than that of pH 7.5 and pH 5. These studies increase our understanding of the molecular mechanism of sugar beet response to different pH environments.

土壤pH值是制约作物生长与产量的关键环境因子。目前针对不同pH条件下甜菜生长状态的相关研究数据较为匮乏。本研究针对pH 5、pH 7.5及pH 9.5三种梯度下的甜菜生长状态与表型特征展开分析。结果显示，甜菜在pH 9.5环境下生长最佳，而在pH 5环境下生长最差。甜菜叶片与根系中超氧化物歧化酶（superoxide dismutase, SOD）、过氧化物酶（peroxidase, POD）的活性随pH从9.5降至5时显著升高。此外，与pH 9.5组相比，pH 5组甜菜叶片中的可溶性糖与脯氨酸含量显著升高。为解析甜菜响应不同土壤pH环境的分子机制，本研究提出假设：蛋白质在植物应对酸碱pH环境的过程中发挥关键调控作用。因此，本研究采用基于串联质量标签（tandem mass tag, TMT）的定量蛋白质组学技术，分析了pH处理调控下甜菜的蛋白质组变化。最终在甜菜叶片与根系中鉴定出3组差异表达蛋白（differentially expressed proteins, DEPs），分别为pH 5 vs. pH 7.5、pH 9.5 vs. pH 7.5以及pH 5 vs. pH 9.5。本研究检测并探讨了若干与甜菜酸碱响应差异相关、且参与酸性胁迫应答的关键蛋白质。此外，基于蛋白质组学分析结果，实时定量聚合酶链反应（quantitative real-time PCR, QRT-PCR）验证显示，与pH 5或pH 7.5组相比，3种氮转运蛋白（NTR1、NRT2.1及NRT2.5）在根系中的表达量在碱性环境（pH 9.5）下相对更高。甜菜在pH 9.5环境下的总氮含量显著高于pH 7.5与pH 5组。本研究加深了学界对甜菜响应不同土壤pH环境的分子机制的认知。