Study On Metabolism Regulation Of Ipp Biosynthetic Pathway In Haematococcus Pluvialis Under Different Stressors

Haematococcus pluvialis is a unicellular green alga. When green cells encounterstress conditions such as nitrogen deficiency, high light intensity, the alga rapidlydifferentiates from a vegetative stage into a resting stage, forming aplanospores.Withina fewdays, cells increase in volume, produce a very tough cell wall, and accumulatelarge amounts of a red astaxanthin.Isopentenyl diphosphate(IPP) pathway is upstream of carotenoid and chlorophyllsynthesis pathway. The genes of the IPP biosynthetic pathway from Haematococcuspluvialis was cloned by using RACE technology, and analyzed by the bioinformationmethod. The correlation between the pigments content and the amount of IPPpathway genes expression under the inducement of N starvation（-N）,high light （HL）and high light with nritron free(HL-N) were studied in this paper, in order to primarilyelucidate the reason and mechanism of pigments accumulation at the molecular level,which could provide a theoretical foundation for cosmically manufacturingastaxanthin.In order to discuss the expression regulation, H.pluvialis was inducedby-N,HL,HL-N. The expression patterns of genes involved in isopentenyl diphosphate(IPP) biosynthetic pathway were analyzed by qtRT-PCR. The results showed all ofgenes were up-regulated. Under the condition of nitrogen deficiency, CMS,CMK,MCSshowed significantly up-regulated expression level (P<0.05), with57.3-,63.3-,34.2-fold higher than that of control respectively. Under the condition of HL, the fourgenes namely CMS,CMK,MCS,HDS showed obviously up-regulated at the transcriptlevel with78.9-,127.3-,69.98-,41.2-fold higher than control, respectively. Under thecondition of HL-N, the transcript levels of DXS,DXR,CMS changed most significantly,with10.87-,11.76-,8.77-fold higher than control, respectively.Maximum PSII photochemical efficiency (Fv/Fm)and NPQ of cells subjected todifferent conditions(-N, HL,HL-N)were examined by Dual-PAM.The data showed thatH.pluvialis was under NL,HL-N conditions, Fv/Fm reached its highest point from the7day, while the NPQ increased, after which they returned to their normal levels slowly. These results demonstrated that short-term-N, HL, HL-N conditions were stresscondition for H.pluvialis, but the algal cells can accommodate the longer periods of-N,HL-N stress.