Genetic modifi cation is useful for improving the nutritional qualities of cyanobacteria. To increase the total unsaturated fatty acid content, along with the ratio of ω-3/ω-6 fatty acids, genetic engineering can be...Genetic modifi cation is useful for improving the nutritional qualities of cyanobacteria. To increase the total unsaturated fatty acid content, along with the ratio of ω-3/ω-6 fatty acids, genetic engineering can be used to modify fatty acid metabolism. S ynechococcus sp. PCC7002, a fast-growing cyanobacterium, does not contain a Δ6 desaturase gene and is therefore unable to synthesize γ-linolenic acid(GLA) and stearidonic acid(SDA), which are important in human health. In this work, we constructed recombinant vectors Syd6 D, Syd15 D and Syd6Dd15 D to express the Δ15 desaturase and Δ6 desaturase genes from Synechocystis PCC6803 in Synechococcus sp. PCC7002, with the aim of expressing polyunsaturated fatty acids. Overexpression of the Δ15 desaturase gene in S ynechococcus resulted in 5.4 times greater accumulation of α-linolenic acid compared with the wild-type while Δ6 desaturase gene expression produced both GLA and SDA. Co-expression of the two genes resulted in low-level accumulation of GLA but much larger amounts of SDA, accounting for as much to 11.64% of the total fatty acid content.展开更多
In northeastern Japan,an area of high precipitation and mountains,beech(Fagus creanata Blume),larch(Larix kaempferi Lamb.),cedar(Cryptomeria japonica D.Don)and black locust(Robinia pseudoacacia L.)were evaluated for N...In northeastern Japan,an area of high precipitation and mountains,beech(Fagus creanata Blume),larch(Larix kaempferi Lamb.),cedar(Cryptomeria japonica D.Don)and black locust(Robinia pseudoacacia L.)were evaluated for N resorption and N isotope fractionation in preand post-abscission leaves in comparison to green leaves.The highest leaf N concentration in summer corresponded to the N-fi xing black locust,followed in decreasing order by the deciduous beech and larch and evergreen cedar.On the other hand,the lowest N resorption effi ciency corresponded to black locust and the highest to beech,in increasing order by larch and cedar.All tree species returned signifi cant amounts of N before leaf abscission;however,N isotope fractionation during leaf N resorption was only found for beech,with a depleted N isotope value from green to pre-abscission leaf.The most N,however,was resorbed from pre-abscission to post-abscission.This result may indicate thatδ15 N fractionation took place during N transformation processes,such as protein hydrolysis,when the concentration of free amino acids increased sharply.The diff erence in the type of amino acid produced by each species could have infl uenced the N isotope ratio in beech but not in the other tree species.The results of this study showed that it is possible to infer the type and timing of processes relevant to N resorption by analyzing leafδ15 N variation during senescence.展开更多
基金Supported by the International S&T Cooperation Program of China(No.2012DFA30450)the National Natural Science Foundation of China(No.30871541)+1 种基金the Taishan Scholar Foundation of Shandong Province(No.tshw20091014)the Innovation Program of the University Institutes of Jinan,Shandong Province(No.201004044)
文摘Genetic modifi cation is useful for improving the nutritional qualities of cyanobacteria. To increase the total unsaturated fatty acid content, along with the ratio of ω-3/ω-6 fatty acids, genetic engineering can be used to modify fatty acid metabolism. S ynechococcus sp. PCC7002, a fast-growing cyanobacterium, does not contain a Δ6 desaturase gene and is therefore unable to synthesize γ-linolenic acid(GLA) and stearidonic acid(SDA), which are important in human health. In this work, we constructed recombinant vectors Syd6 D, Syd15 D and Syd6Dd15 D to express the Δ15 desaturase and Δ6 desaturase genes from Synechocystis PCC6803 in Synechococcus sp. PCC7002, with the aim of expressing polyunsaturated fatty acids. Overexpression of the Δ15 desaturase gene in S ynechococcus resulted in 5.4 times greater accumulation of α-linolenic acid compared with the wild-type while Δ6 desaturase gene expression produced both GLA and SDA. Co-expression of the two genes resulted in low-level accumulation of GLA but much larger amounts of SDA, accounting for as much to 11.64% of the total fatty acid content.
基金We thank technicians Daisuke Arai and Yoshiaki Izuka,of Yamagata University Research Forest and the students of the Watershed Preservation Laboratory,Yamagata University,for their very helpful assistance with fi eldwork.
文摘In northeastern Japan,an area of high precipitation and mountains,beech(Fagus creanata Blume),larch(Larix kaempferi Lamb.),cedar(Cryptomeria japonica D.Don)and black locust(Robinia pseudoacacia L.)were evaluated for N resorption and N isotope fractionation in preand post-abscission leaves in comparison to green leaves.The highest leaf N concentration in summer corresponded to the N-fi xing black locust,followed in decreasing order by the deciduous beech and larch and evergreen cedar.On the other hand,the lowest N resorption effi ciency corresponded to black locust and the highest to beech,in increasing order by larch and cedar.All tree species returned signifi cant amounts of N before leaf abscission;however,N isotope fractionation during leaf N resorption was only found for beech,with a depleted N isotope value from green to pre-abscission leaf.The most N,however,was resorbed from pre-abscission to post-abscission.This result may indicate thatδ15 N fractionation took place during N transformation processes,such as protein hydrolysis,when the concentration of free amino acids increased sharply.The diff erence in the type of amino acid produced by each species could have infl uenced the N isotope ratio in beech but not in the other tree species.The results of this study showed that it is possible to infer the type and timing of processes relevant to N resorption by analyzing leafδ15 N variation during senescence.
