萌芽菊芋块茎对盐碱土壤胁迫的生理响应

Physiological response of sprouting Jerusalem artichoke tubers to saline-alkali stress

土壤盐碱化是影响全球农业生产和生态环境的重要问题。在农田、轻度盐碱草地和重度盐碱草地设置样地以块茎种植菊芋,次年5月块茎萌发阶段取块茎样品测定丙二醛、游离脯氨酸、可溶性糖含量以及抗氧化酶活性并进行蛋白质组学分析,分析了萌芽菊芋块茎对盐碱土壤胁迫的生理响应。0—20 cm土层的电导率(表征土壤可溶盐含量)表明从农田到轻度、重度盐碱草地土壤盐碱胁迫逐渐增强,丙二醛含量变化反映出菊芋块茎受害程度逐渐增加,并且基于游离脯氨酸的渗透调节能力也在逐渐增强。蛋白质组学分析结果显示与遗传信息加工相关的差异蛋白数量最多(占28.75%)且多为表达上调,意味着DNA复制和转录、蛋白质合成和折叠的相关蛋白在响应盐碱胁迫中发挥关键作用。碳水化合物及多糖代谢(占15%)、氨基酸代谢(占11.25%)以及能量代谢(占7.5%)相关的差异蛋白数量也较多,说明调节物质代谢平衡在萌芽菊芋块茎应对盐碱土壤胁迫过程中有重要作用。这些结果为揭示萌芽菊芋块茎适应盐胁迫的生理机制奠定了基础。

Soil salinization is one of the most common abiotic stresses affecting plant growth and is becoming an important issue, owing to its impact on agricultural production and the environment. Saline-alkali soil is becoming particularly widespread and may cover more than 50% of all arable lands by the year 2050. The combination of soil salinization and high pH conditions represents a major impediment for plant growth and crop productivity. The study area was a typical alkalinized grassland in northeastern China. Jerusalem artichoke （Helianthus tuberosus） is an annual flowering plant that has been cultivated as a vegetable, fodder crop, and bioenergy material in many countries, owing to its high levels of polysaccharides, especially inulin. The ability to survive in the saline-alkali soils of semiarid areas is one of the most important characters of Jerusalem artichoke. Jerusalem artichoke tubers were sown in farmland, light saline-alkali, or severe saline-alkali soil and sprouting tubers were collected from the sample in May of the following year. The malondialdehyde, free proline, and soluble sugar contents, antioxidant enzyme activity, and protein profile were quantified, in order to assess the physiological response of Jerusalem artichoke to saline-alkali stress. The soil electrical conductivity （0-20 cm） indicated that the soluble salt contents of the three soil types were significantly different, with the lowest soluble salt content in the farmland soil and the greatest content in the severe saline-alkali soil. With increasing soluble salt content, the malondialdehyde content increased, obviously indicating higher levels of stress, and increased free proline content indicated that Jerusalem artichoke could enhance its resistance to salt stress via osmotic adjustment. To investigate the proteomic response of the sprouting tubers to saline-alkali stress, two-dimensional gel electrophoresis （2-DE） gels from three biological experiments were analyzed. Then, using ImageMaster 2D Platinum Software, we identified more than 1000 highly reproducible protein spots on the coomassie brilliant blue （CBB）-stained 2D gels. A total of 80 differentially expressed proteins were successfully identified using MALDI-TOF/TOF analysis, according to the peptide matching results provided by MASCOT. Among these proteins, 42 were detected in the sprouting H. tuberosus tubers from the light saline-alkali soil and 38 of the proteins accumulated differentially in the tubers grown in the severe saline-alkali soil. KEGG pathway analysis attributed these proteins to eleven different metabolic pathways, which included carbohydrate and polysaccharide metabolism （15%）, energy metabolism （7.5%）, genetic information processing （28.75%）, amino acid metabolism （11.25%）, nucleotide metabolism （2.5%）, biosynthesis of secondary metabolites （3.75%）, signal transduction （17.5%）, transport and catabolism （2.5%）, cell motility （2.5%）, and unknown （8.75%）. The differentially expressed proteins were mainly involved in genetic information processing, which might indicate that the regulation of proteins involved in DNA replication, transcription, protein synthesis, and protein folding are responsive to saline-alkali stress and play a pivotal role in salinity tolerance. Carbohydrate, energy, and amino acid metabolism-related proteins constituted one-third of the differentially expressed proteins, which suggests that metabolism homeostasis is important for the survival of seedlings exposed to saline-alkali stress. These findings provide new insight into the underlying molecular mechanisms of saline-alkali resistance in Jerusalem artichoke.