Research On Starch Accumulation Promoted By Genetic Transformation In Duckweed

Duckweed,a new energy plant,has been considered as an ideal experimental material for research in biofuel production because of its outstanding advantages,such as high growth rate,high starch and low ligning contents.Increasing the starch content of duckweed is the key to the production of bioethanol,which can be achieved by changing growth rate and starch accumulation ability.In this study,starch metabolic pathway gene granule bound starch synthase(GBSS)and ADP-Glc pyrophosphorylase(APL1)were successfully overexpressed in duckweed(L.turionifera 5511)to improve starch content.Stable transgenic fronds were obtained by transferring the GBSS and APL1 into duckweed by agrobacterium-mediated transformation.Research on the GBSS transgenic duckweed was carried out.The results of RNA level identification,GUS staining and GBSS enzyme activity analysis showed that the transferred GBSS gene was stably expressed.The phenotypic analysis showed that the frond area and the growth rate of the transgenic lines were larger than that of the wild-type.The fresh weight of the transgenic line in each flask increased after 12 days of culture.The dynamic changes of starch content in fronds were measured,which showed that the best sampling time for starch content determination was 12 h after light.The starch content,the total starch content and amylose content of wild-type duckweed and transgenic duckweed were compared with each other.The results show that the starch content,total starch content and amylose content of GBSS-24 were higher than the wild-type duckweed,and its starch content can reach 62.6 mg/g(DW),the amylose content is 39.7 mg/g(DW).The results shows that GBSS-24 was beneficial to the fermentation.It can be used as a preferred strain for large-scale production of biomass energy.GBSS-24 was used to explore the effects of different culture conditions(different photoperiods,nutritional stress,and increased CO₂ concentration in the environment)on the starch content of plants.The results showed that long-day conditions,increased CO₂ concentration in the environment(0.5%),and nutritional stress have both conducive to the accumulation of starch,and the accumulation of starch in the fronds of the GBSS-24 strain was significantly higher than that of the control strain.The experimental results suggest that in the process of starch production using the GBSS-24 strain,it is necessary to adjust the growth conditions to obtain greater benefits.