The Research In The Effects Of Microcystis Aeruginosa On The Expression Of Three Genes In Daphnia Similodies Sinensis

Since global warming and eutrophication,cyanobacterial bloom has become one of the problems of water environmental pollution.Daphnia species have some resistance to environmental stress on the life history and molecular mechanisms,form some adaptative strategies,and even can transfer this resistance to the offspring through maternal effect.This paper studied the effects of Microcystis aeruginosa on the expressions of Daphnia similoides sinensis three gene types,major results were as follows:1.Nuclear receptor(NR)genes are a conserved superfamily,which are involved in organism metabolism,reproduction,development,homeostasis and resource allocation.A total of 18 NRs of D.similoides sinensis were identified in this study based on previous transcriptome data.With the increase of M.aeruginosa concentration,the gene expression of NR1 subfamily(E75a E75b HR3,HR96,NHR-1,HR97a,HR97g and NHR97)down-regulated in the proportion cut from 54%(80%M + 20%S)up to 63%(60%M + 40%S).In the treatments containing M.aeruginosa,the expressions of 79%of NR2 subfamily(RXR,TLL,PNR and SVP)genes down-regulated,and the NR6 subfamily HR4 genes did also down-regulate.Although the expression of 78%of 18 nuclear receptor genes showed a similar trend in clones 1 and 2,the expression of 42%of the genes in clone 3 showed the opposite trend compared with clones 1 and 2.The differences among different clones or different nuclear receptor genes at the same clone in D.similoides sinensis suggested that the adaptability and molecular mechanism of D.similoides sinensis individuals to M.aeruginosa were different.2.Hox genes are important regulatory factors of transcription in metazoan,which are involved in the growth and development of organisms.A total of 14 Hox genes were identified in this study based on previous transcriptome data.Under three food treatments and two clones,the survival rate of the mother in clone 2 in the 40%M+60%S food treatment was significantly higher than that of clone 1(P<0.05).The expressions of Abd-B,HOX-2,HOXA1 and HOXB7 genes in the 40%M+60%food treatment upregulated in clone 2 compared with the 100%S food treatment,whereas the expressions of HOX-2 and HOXA1 genes in the 40%+60%food treatment upregulated in clone 1.In clone 1,the survival rate of the offspring in the 40%M+60%S food treatment was significantly higher than that of the mother(P<0.05),and six genes(CDX-1,HOXC7,Dll,HOXC4,HOXD10 and HOXC8)of both the offspring in the 40%M+60%S food treatment and the mother in 20%M+80%S food treatment upregulated.Moreover,the relative expressions of HOX7,Dll,HOXD10 and HOXC8 genes of the offspring in clone 1 in the 40%M+60%S food treatment were significantly higher than those in the 100%S food treatment(P<0.05).The mother-offspring transfer response of Hox genes expression in D.similoides sinensis to M.aeruginosa suggested that the offspring of D.similoides sinensis produced by the mother prior to exposure to M.aeruginosa had stronger adaptability under higher M.aeruginosa concentration,and this adaptability had the differences among different clones.3.Vitellogenin is the precursor of vitellogenin.Vitellogenin genes,as important reproductive genes of oviparous animals,usually expressed specifically at time to maturation.A total of 13 Vitellogenin genes were identified in this study based on previous transcriptome data,namely VG1-1,VG1-2,VG2-1,VG2-2,VG2-3,VG6-1,VG6-2,VG6-3,VG6-4,VGX2-1,VGX2-2,VGApoB and VG,among which VG1-1,VG1-2,VG2-1,VG2-2,VG2-3,VG6-1,VG6-2,VG6-3 and VG6-4 genes had the complete ORF.Under the treatments containing M.aeruginosa,total number of offspring produced by per female,the body length at maturity and in the end of the experiment in all clones were significantly less than those in the 100%S food treatment(P<0.05),whereas their time to maturiation were significantly higher than in the 100%S food treatment(P<0.05).Most of the vitellogenin genes in three clones from the mother up-regulated.The expressions of vitellogenin genes of D.similoides sinensis offspring were mostly higher than those of their mothers under all food treatments.The results suggested that the vitellogenin genes of D.similoides sinensis in reproductive function were important and various.