CO_2对转基因聚球藻7942生长、表达等的影响

EFFECT OF CO_2 CONCENTRATIONS ON GROWTH, THYMOSIN α1 EXPRESSION AND PHOTOSYNTHESIS OF TRANSGENIC SYNECHOCOCCUS SP.PCC7942

研究了不同浓度CO2 对转基因聚球藻 794 2生长、胸腺素α1表达和光合作用的影响 ,结果表明 :不同浓度的CO2 对藻细胞指数生长期的比生长速率没有明显的影响 ,通入空气与 5 %CO2 空气对藻细胞线性生长速率和最终藻细胞浓度影响也不显著 ;高浓度CO2 会减少NO-3 的吸收 ,提高硝酸还原酶的活性 ,这表明NO-3 的吸收与还原是不偶联的。低浓度CO2 对藻细胞的生化组成和胸腺素α1表达没有影响。而高浓度的CO2 明显降低可溶性蛋白及光合色素叶绿素a、类胡萝卜素和藻蓝蛋白的含量 ,胸腺素α1含量也显著降低。不同CO2 浓度培养的藻细胞P I曲线表明 ,不同浓度的CO2 对藻细胞的光合作用效率没有明显的影响 ,但生长在高浓度CO2 中藻细胞的最大光合速率明显增加。

In recent years, genetic engineering of cyanobacterium has been developed to produce important chemicals, especially pharmaceuticals. The unicellular cyanobacterium Synechococcus sp.PCC7942 is an obligate photoautotrophic blue-green alga and a transformable strain that can be used as an effective host in genetic manipulation. There have been numerous studies on the expression of exogenous proteins in Synechococcus sp.PCC7942. In order to explore the possibility of protein pharmaceutical production with transgenic microalgae,Zhang et al cloned the human thymosin α1 gene that was expressed as a fusion protein with ubiquitin in Synechococcus sp.PCC7942. High cell-density culture of transgenic Synechococcus sp.PCC7942 with high expression level is very critical to its application, but few papers have been published on this aspect.In this paper, the transgenic Synechococcus sp.PCC7942 was batch-cultured in 1.5 L air-lift photobioreactors, and effects of CO 2 concentrations on the growth, thymosin α1 expression and photosynthesis of the transgenic Synechococcus sp.PCC7942 were investigated. The specific growth rate of the alga cells during exponential growth phase was not significantly affected by CO 2 concentrations; biomass and linear growth rate of transgenic Synechococcus sp.PCC7942 under normal CO 2 and high CO 2 concentrations were only slight difference.High CO 2 level reduced NO- 3 assimilation and increased nitrate reductase activity, which indicated that reduction and assimilation of nitrate were uncoupled. Low CO 2 level did not affect cell biochemical composition and thymosin α1 expression; however,the contents of soluble protein, chlorophyll a, carotenoids and phycocyarin of the transgenic alga cells grown under high CO 2 level were significantly diminished, the thymosin α1 content was also markedly reduced at high CO 2 level. On the basis of P-I curves, no difference was observed in photosynthetic efficiency; however, maximum photosynthetic rate was markedly improved by high CO 2 level.