Study On The Effects Of Four Elicitors On The Of Fucoxanthin Accumulation In Phaeodactylum Tricornutum And Its Mechanim

In the present study,the diatom Phaeodactylum tricornutum was used to the research object to explore the effects of four inducers including methylene blue（MB）,methyl viologen（MV）,zeatin（ZT）and rapamycin（RPM）on cell growth fucoxanthin and lipid content in P.tricornutum.In addition,real-time fluorescence quantitative PCR was employed to investigate the effect of elicitor on fucoxanthin synthesis and photosynthesis-related gene expression.The principal component analysis（PCA）was used to determine the principal component of fucoxanthin content,which can provide essential research reference for further obtaining high-yield fucoxanthin and elucidating the synthesis mechanism fucoxanthin.（1）The effects of four elicitors on the cell growth and fucoxanthin content of P.tricornutum were studied in this paper.The results showed that the growth of P.tricornutum cells presented an upward and then a downward trend with the concentration of MB and MV increasing.The biomass of P.tricornutum cells were promoted by ZT and RPM.The fucoxanthin content in P.tricornutum was highest when ZT concentration was 0.1mg/L.In addition,the fucoxanthin’s content reached2.88 mg/g DW,which is 69.78%higher than the control.When P.tricornutum was treated with 2×10^-4mmol/L MB,the range of fucoxanthin per algal cell was the highest,reaching 0.0756 mg/g DW（P＜0.01）.The treatment of P.tricornutum with four elicitors contributed to a slight increase in the algae cells’neutral lipid content.When P.tricornutum was treated with 0.05 mg/L ZT,its chlorophyll content was the highest,which was 61.65%higher than the control group（P＜0.01）.（2）The effects of four elicitors on the biosynthesis of P.tricornutum and the expression of photosynthesis-related genes were studied.The results shows that MB and RPM treatments can increase the expression level of the photosynthesis-related genes including psb A,rbc L,rbc S and fcpb of P.tricornutum.MV treatment significantly increased P.tricornutum photosynthesis-related genes including psb A,rbc L,rbc S,and fcpb.The high concentration of ZT significantly increased photosynthesis-related genes in P.tricornutum（P＜0.01）.Regarding gene expression associated with the biosynthesis of neutral lipids in P.tricornutum by several elicitors,MB,MV,and ZT all up-regulated the transcriptional expression of lipid synthesis genes gpat and FAD2.In contrast,the content of neutral lipids increased.When the RPM elicitor treated P.tricornutum,the expression of genes related to lipid synthesis exhibited an overall downward-regulation trend.（3）The PCA of fucoxanthin content by factors such as P.tricornutum chlorophyll a,neutral lipid,and related gene expression were measured.Results showed that the content of neutral lipid,and chlorophyll a,and the transcripts of photosynthesis-related genes（rbc S,gpat,and rbc L）,fucoxanthin synthesis-related genes（pds,lcyb）,and lipid synthesis-related gene FAD2 had positive correlations with fucoxanthin accumulation after MB treatment.Under MV treatment,the expression of rbc L,pds,rbc S,gpat,and fcpb were positively associated with fucoxanthin accumulation.Under ZT treatment,the expression of genes pds,lcyb,psb A,rbc L,and fcpb were positively associated with fucoxanthin accumulation.Under RPM treatment,the first three principal components that influence fucoxanthin synthesis are rbc S,psb A,and rbc L expression,with a cumulative contribution rate of 88%.Rbc S,psb A,and rbc L were all photosynthesis-related genes,which indicated that photosynthesis is an essential factor for accumulating fucoxanthin in P.tricornutum.