低氮对金色奥杜藻色素-蛋白复合物特性及全细胞蛋白表达的影响

Effects of low nitrate-nitrogen concentration on photosynthetic pigment protein complexes and differential expression of proteins in Odontella aurita

采用SDS-PAGE圆盘电泳分离技术,研究两种氮浓度下17.6 mmol·L-1(高氮组)、5.87 mmol·L-1(低氮组)金色奥杜藻色素蛋白复合物的变化规律。结果表明,从两种氮浓度所培养的金色奥杜藻细胞光合膜上,均可分离得到6种色素蛋白复合物条带,按照迁移速率从小到大依次为CPⅠa、CPⅠ、CPa1、CPa2、LHCP1、LHCP2。与高氮组相比,低氮下电泳分离的复合物条带颜色明显变浅,尤其CPⅠ、CPa1、CPa2三条带仅隐约可见。低温荧光发射光谱显示CPa1的荧光发射主峰也较高氮组蓝移10 nm左右,说明低氮主要影响光系统Ⅱ。双向电泳和质谱分析结果表明,氮浓度降低后藻细胞中有6种蛋白表达下调,3种蛋白表达上调,这些差异蛋主要白涉及光合作用、氮素吸收、碳同化、能量转换等生理过程,大多与维持叶绿体功能有关。

Six pigment-protein complex bands including CPIa, CPI, CPal, CPa2, LHCP1, LHCP2 were firstly separated from the marine diatom Odontella aurita cell grown in two initial nitrate concentrations of sodium nitrate 17.6 mmol·L-1 （high nitrogen concentration） and 5.87 mmol·L-1（low nitrogen concentration） using disc SDS-PAGE electrophoresis. The results showed that bands color of pigment protein complexes CP I, CPal, CPa2 of low concentration nitrogen group became light obviously and the fluorescence emission peak of CPal hypochromatic shifted 10 nm compared with the high concentration nitrogen group. The result indicated that low concentration nitrogen possesses certain influence on pigment protein complexes of PS II. The whole cellular proteins of O. aurita grown in low concentration nitrogen medium were separated by two-dimension electrophoresis and analyzed using proteomic mass spectrometry. The analysis of differential expression of proteins showed that six up-regulation and three down-regulation proteins were found in O. aurita grown with low concentration nitrogen medium, respectively. These differential expressed proteins mainly involved in photosynthesis, nitrogen up-take, carbon assimilation, energy conversion, and most of them were in relationship with the maintenance of chloroplast functions.