Carotenoids are important pigments in photosynthetic organisms where they play essential roles in photoreception and photoprotection.Chromochloris zofingiensis is a unicellular green alga that is able to accumulate hi...Carotenoids are important pigments in photosynthetic organisms where they play essential roles in photoreception and photoprotection.Chromochloris zofingiensis is a unicellular green alga that is able to accumulate high amounts of ketocarotenoids including astaxanthin,canthaxanthin and ketolutein when growing heterotrophically or mixotrophically with glucose as a carbon source.Here we elucidate the ketocarotenoid biosynthesis pathway in C.zofingiensis by analyzing five algal mutants.The mutants were shown to have a single nucleotide insertion or substitution in β-carotene ketolase(BKT) gene 1,which resulted in a lack of ketocarotenoid production in Cz-bktl-1,and decreased ketocarote noid co ntent in the other four mutants.These mutants accumulated much higher amounts of non-ketocarotenoids(β-carotene,zeaxanthin and lutein).Interestingly,the Cz-bktl-5 mutant synthesized 2-fold the ketolutein and only 1/30 of the canthaxanthin and astaxanthin as its parent strain,suggesting that the mutated BKT1 exhibits much higher activity in catalyzing lutein to ketolutein but lower activity in ketolating β-carotene and zeaxanthin.Mutant and WT BKT2 gene sequences did not differ.Taken together,we conclude that BKT1 is the key gene involved in ketocarotenoid biosynthesis in C.zofingiensis.Our study provides insight into the biosynthesis of ketocarotenoids in green algae.Furthermore,Cz-bktl mutants may serve as a natural source for the production of zeaxanthin,lutein,and β-carotene.展开更多
Nanoparticles,or particles in size of 1-100 nm,are extensively used in the world in different applications.For instance,single-walled carbon nanotubes(SWCNTs) are commonly used in consumer products,such as biosensors,...Nanoparticles,or particles in size of 1-100 nm,are extensively used in the world in different applications.For instance,single-walled carbon nanotubes(SWCNTs) are commonly used in consumer products,such as biosensors,drug and vaccine delivery transporters,and novel biomaterials.Although nanoparticles do not cause safety concerns to consumers who use nanoparticle-containing products,these small particles are potentially harmful for workers who produce them in factories or in cases of discharge to aquatic ecosystems.SWCNTs do not have a natural analogue,so the effects on health of their disposal remain largely unknown.In this study,we evaluated the effects of SWCNTs on a population of the green microalga Chromochloris zofingiensis and the profile and production of pigments and fatty acids.The alga was incubated with SWCNTs for 6 days in 0(control),40,80,160,or 320 mg/L concentrations.SWCNTs showed both positive and negative effects on the growth of C.zofingiensis,with a biomass enhancement at low levels(40-160 mg/L) but inhibition at high levels(320 mg/L).By contrast,a decreased accumulation of fatty acids and pigments of C.zofingiensis was observed over the range of the tested concentrations.These results indicate that the markers on the inhibitive toxicity of SWCNTs are increasingly sensitive in the following order:biomass and fatty acids < primary carotenoids < chlorophylls < secondary carotenoids.C.zofingiensis is a suitable microalga for evaluating the ecotoxicological hazards of SWCNTs,especially in terms of pigmentation response.展开更多
文摘Carotenoids are important pigments in photosynthetic organisms where they play essential roles in photoreception and photoprotection.Chromochloris zofingiensis is a unicellular green alga that is able to accumulate high amounts of ketocarotenoids including astaxanthin,canthaxanthin and ketolutein when growing heterotrophically or mixotrophically with glucose as a carbon source.Here we elucidate the ketocarotenoid biosynthesis pathway in C.zofingiensis by analyzing five algal mutants.The mutants were shown to have a single nucleotide insertion or substitution in β-carotene ketolase(BKT) gene 1,which resulted in a lack of ketocarotenoid production in Cz-bktl-1,and decreased ketocarote noid co ntent in the other four mutants.These mutants accumulated much higher amounts of non-ketocarotenoids(β-carotene,zeaxanthin and lutein).Interestingly,the Cz-bktl-5 mutant synthesized 2-fold the ketolutein and only 1/30 of the canthaxanthin and astaxanthin as its parent strain,suggesting that the mutated BKT1 exhibits much higher activity in catalyzing lutein to ketolutein but lower activity in ketolating β-carotene and zeaxanthin.Mutant and WT BKT2 gene sequences did not differ.Taken together,we conclude that BKT1 is the key gene involved in ketocarotenoid biosynthesis in C.zofingiensis.Our study provides insight into the biosynthesis of ketocarotenoids in green algae.Furthermore,Cz-bktl mutants may serve as a natural source for the production of zeaxanthin,lutein,and β-carotene.
基金Supported by the National Natural Science Foundation of China(No.50904051)the Science and Technology Planning Project of Yantai,China(No.2010247)the Open Fund of Shandong Oriental Ocean Sci-Tech Co.,Ltd.(No.200803)
文摘Nanoparticles,or particles in size of 1-100 nm,are extensively used in the world in different applications.For instance,single-walled carbon nanotubes(SWCNTs) are commonly used in consumer products,such as biosensors,drug and vaccine delivery transporters,and novel biomaterials.Although nanoparticles do not cause safety concerns to consumers who use nanoparticle-containing products,these small particles are potentially harmful for workers who produce them in factories or in cases of discharge to aquatic ecosystems.SWCNTs do not have a natural analogue,so the effects on health of their disposal remain largely unknown.In this study,we evaluated the effects of SWCNTs on a population of the green microalga Chromochloris zofingiensis and the profile and production of pigments and fatty acids.The alga was incubated with SWCNTs for 6 days in 0(control),40,80,160,or 320 mg/L concentrations.SWCNTs showed both positive and negative effects on the growth of C.zofingiensis,with a biomass enhancement at low levels(40-160 mg/L) but inhibition at high levels(320 mg/L).By contrast,a decreased accumulation of fatty acids and pigments of C.zofingiensis was observed over the range of the tested concentrations.These results indicate that the markers on the inhibitive toxicity of SWCNTs are increasingly sensitive in the following order:biomass and fatty acids < primary carotenoids < chlorophylls < secondary carotenoids.C.zofingiensis is a suitable microalga for evaluating the ecotoxicological hazards of SWCNTs,especially in terms of pigmentation response.
