高盐下条斑紫菜光合特性和S-腺苷甲硫氨酸合成酶基因表达的变化

Photosynthetic characteristics and SAMS gene expression in the red alga Porphyra yezoensis Ueda under high salinity

为了研究条斑紫菜耐盐机理,对条斑紫菜叶状体进行了高盐胁迫处理,继而采用氧电极法测量了光合放氧速率和呼吸耗氧速率的变化,采用实时荧光定量PCR技术测量了S-腺苷甲硫氨酸合成酶(命名为PySAMS)基因的表达变化。结果显示藻体的光合与呼吸作用均受到高盐度海水的显著影响,随着盐度的增加,光合放氧率逐渐降低,呼吸耗氧率也逐渐降低。高盐度海水对PySAMS基因表达量也产生了显著影响,40和50盐度的海水诱导了PySAMS表达,但60至80盐度的海水却不同程度地抑制了PySAMS表达。据此推测,在面对较高盐度胁迫时条斑紫菜叶状体将逐步降低体内新陈代谢以度过不良环境。

The intertidal red alga Porphyra yezoensisis an important marine crop which has a high stress tolerance. The salinity of the remaining water on the surface of the P. yezoensis thalli increases significantly during emersion, however, thalli can survive this severe osmotic dehydration. In order to investigate the mechanism of high salinity tolerance in P.yezoensis, the effects of high salinity on S-Adenosylmethionine synthetase （designated as PySAMS） gene expression and photosynthetic characteristics in P. yezoensis were determined. At first the thalli of P. yezoensis were subjected to seawater with high salinities （40, 50, 60, 70 or 80 salinity） for lh. Then the oxygen evolution and consumption in cellular processes of photosynthesis and respiration were measured using the Oxygraph oxygen electrode system. And the relative mRNA expression levels of PySAMS gene were investigated using the real-time PCR. The results show that both photosynthesis and respiration were significantly influenced by seawater with 50, 60, 70 or 80 salinity in P. yezoensis thalli. The higher was the salinity of seawater, the lower was the oxygen evolution rate, and the lower was the oxygen consumption rate. The PySAMS gene expression was also influenced by seawater with high salinities significantly in P. yezoensis thalli. Seawater with 40 and 50 salinity induced the expression of PySAMS gene. However sawater with 60, 70 and 80 salinity repressed the expression of PySAMS gene. Based upon these we speculated that P. yezoensis thalli reduce the metabolism rate gradually to survive the unsuitable environmental condition when thalli suffer high salinity stress.