Proteomic Analysis of Seedling Roots of Two Maize Inbred Lines That Differ Significantly in the Salt Stress Response

Salinity is a major abiotic stress that limits plant productivity and quality throughout the world. Roots are the sites of salt uptake. To better understand salt stress responses in maize, we performed a comparative proteomic analysis of seedling roots from the salt-tolerant genotype F63 and the salt-sensitive genotype F35 under 160 mM NaCl treatment for 2 days. Under salinity conditions, the shoot fresh weight and relative water content were significantly higher in F63 than in F35, while the osmotic potential was significantly lower and the reduction of the K+/Na+ ratio was significantly less pronounced in F63 than in F35. Using an iTRAQ approach, twenty-eight proteins showed more than 2.0- fold changes in abundance and were regarded as salt-responsive proteins. Among them, twenty-two were specifically regulated in F63 but remained constant in F35. These proteins were mainly involved in signal processing, water conservation, protein synthesis and biotic cross-tolerance, and could be the major contributors to the tolerant genotype of F63. Functional analysis of a salt-responsive protein was performed in yeast as a case study to confirm the salt-related functions of detected proteins. Taken together, the results of this study may be helpful for further elucidating salt tolerance mechanisms in maize.

盐胁迫是全球范围内限制植物产量与品质的主要非生物胁迫因子。根系是植物吸收盐分的核心部位。为深入解析玉米的盐胁迫响应机制，本研究对耐盐基因型F63与盐敏感基因型F35的幼苗根系在160 mM氯化钠处理2天后的样本开展了比较蛋白质组学分析。盐胁迫条件下，F63的地上部鲜重与相对含水量均显著高于F35，而其渗透势显著更低，且K+/Na+比值的降幅显著弱于F35。本研究采用iTRAQ（同位素标记相对定量技术）鉴定出28种丰度变化超过2.0倍的蛋白质，将其归为盐响应蛋白质。其中22种蛋白质仅在F63中发生表达调控，在F35中无显著变化。这些蛋白质主要参与信号转导、水分保持、蛋白质合成及生物交叉耐性调控过程，可能是赋予F63耐盐特性的核心功能蛋白。本研究以酵母为模式生物，对其中一种盐响应蛋白质开展功能验证分析，以证实所鉴定蛋白质的盐相关功能。综上，本研究结果可为进一步解析玉米的耐盐胁迫机制提供重要参考。