强光照对雨生红球藻合成虾青素的影响

在不同的光照强度下研究了雨生红球藻细胞内虾青素的合成与初级代谢的关系.在强光(HL)和中等强度(ML)的光照条件下,雨生红球藻细胞内1,5-二磷酸核酮糖羧化酶 (Rubisco)和硝酸还原酶(NR)的活性第1天大幅度提高,2天后又迅速下降.与此同时,硝酸盐浓度也快速降低.当虾青素在第4天(HL)和第6天(ML)开始合成时, HL中Rubisco和NR活性以及NO3-浓度分别下降了75.5%,71.5% 和96.2%,而ML中则下降了76.5%,74.7% 和94.3%.相比之下,在低光照(LL)条件下,实验结束时三个指标仅下降了25.9%,29.8% 和56.8%,细胞中没有虾青素积累.结果表明强光提高了Rubisco 和 NR活性,导致硝酸盐浓度迅速降低而最终又抑制了这两种酶的活性,造成雨生红球藻光合作用效率下降即"碳饥饿".在此状态下,为了生存,细胞内合成虾青素的相关基因被激活,藻细胞开始合成并积累虾青素.

Effect of High Irradiance on Astaxanthin Synthesis in Haematococcus pluvialis

The relationship between astaxanthin synthesis and primary metabolism in Haematococcus pluvialis was studied under different intensities of light. The results show that the activities of ribulose-1,5-bisphosphate carboxylase (Rubisco) and nitrate reductase (NR) increase significantly on the first day under high (HL) and medium (ML) light intensities, and fall drastically after two days. At the same time, nitrate concentration also decreases markedly. When astaxanthin synthesis was triggered on 4th (under HL) and 6th (under ML) days, Rubisco and NR activities as well as nitrate concentration decline 75.5%, 71.5%, 96.2% under HL and 76.5%, 74.7%, 94.3% under ML, respectively. On the other hand, under low light intensity (LL), these three parameters decrease only 25.9%, 29.8% and 56.8% at the end of the experiment and with no astaxanthin accumulated in the algal cells. These results suggest that the high irradiance stimulates the activities of Rubisco and NR, which leads to rapid decrease of nitrate concentration and ultimately inhibits the activitied of these two enzymes, and consequently H. pluvialis becomes "carbon starvation" in terms of photosynthesis. For survival, the astaxanthin-related genes are activated, and the algal cells begin to synthesize and accumulate astaxanthin.