UV-B对雨生红球藻生长及虾青素积累的影响

ULTRAVIOLET-B RADIATION ENHANCES THE GROWTH AND ASTAXANTHIN PRODUCTION IN HAEMATOCOCCUS PLUVIALIS

  • 摘要: 以雨生红球藻(Haematococcus pluvialis)为材料, 研究不同强度的UV-B对雨生红球藻生长、光合作用及虾青素积累的影响和其作用机理。设置5种紫外线强度, 分别在正常光照培养条件下补充不同强度UV-B(100—500 lx), 标记为CK、U100、U200、U300、U400和U500六组。结果表明, 经UV-B辐射后雨生红球藻细胞密度、PSⅡ最大光化学效率(Fv/Fm)、非光化学淬灭系数(NPQ)和叶绿素(Chl.a和Chl.b)含量等均呈现下降趋势, 且与辐射强度相关。相反, 虾青素含量在100—400 lx强度下随UV-B辐射强度的增加而升高。与对照相比, 高强度UV-B辐射(U400)36h和72h后藻细胞虾青素含量分别提高了35.68%和56.23%, 达到5.82和7.06 mg/L。qRT-PCR检测发现雨生红球藻虾青素合成关键酶基因(IPIPSYBCHBKT)的表达量随紫外辐射强度和辐射时间的增加均有不同程度升高。UV-B辐射亦调控紫外光受体UVR8及其信号转导通路核心元件(COP1、SPA1、HYHHY5)的基因表达, 暗示上述基因参与了UV-B诱导雨生红球藻虾青素积累的过程。研究揭示紫外光受体UVR8介导的信号转导通路可能参与虾青素合成的转录调控, 为建立应用UV-B辅助光源促进雨生红球藻富集虾青素的工艺提供了基础, 同时为解析光诱导雨生红球藻虾青素积累的转录调控机制提供了新的视角。

     

    Abstract: Haematococcus pluvialis is recognized as the ideal astaxanthin producer since high levels of astaxanthin can be accumulated in its cells under stress conditions. Although appropriate amount of ultraviolet-B (UV-B) can effectively induce astaxanthin biosynthesis, it remains to be elucidated whether the specific light signal perception and transduction mechanisms regulate astaxanthin accumulation in this alga. The present study was conducted to investigate the effects of different intensity of UV-B on the growth, photosynthesis and production of astaxanthin of H. pluvialis under six cultivation conditions (100-500 lux of UV-B was supplemented under LED light culture conditions). A series of physiological and biochemical parameters were examined under these six UV-B treatments designed as CK, U100, U200, U300, U400 and U500, respectively. The results revealed that UV-B radiation decreased the cell density, maximal quantum yield of PSⅡ (Fv/Fm), non-photochemical quenching parameter (NPQ) and chlorophyll (Chl. a and Chl. b) content in H. pluvialis. On the contrary, the astaxanthin content were enhanced with the increase of UV-B radiation intensity (100-400 lx). Compared with the control algal cells without UV-B treatment, astaxanthin content increased by 35.68% and 56.23% in the algal cells treated by 36h and 72h of high-intensity UV-B radiation (U400), with the level up to 5.82 and 7.06 mg/L. Expression analysis by qRT-PCR demonstrated that both 200 and 400 lx UV-B treatments significantly upregulated transcriptional expression of the four carotenoid biosynthesis-related genes (IPI, PSY, BCH and BKT) in H. pluvialis despite their expression profiles were different. UV-B radiation also upregulated the expression of UVR8 and the downstream genes COP1, SPA1, HYH and HY5 which are the core elements in UV-B signal transduction pathway. These findings indicated that the UV-B light signal transduction pathway may function importantly in the regulation of astaxanthin biosynthesis pathway, providing a scientific basis for optimizing culture system to increase astaxanthin accumulation in H. pluvialis by UV-B auxiliary light source. The present data also lay the foundation for further understanding the transcriptional regulation mechanisms of astaxanthin accumulation in this special agal under stress conditions, particularly in response to UV-B radiation.

     

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