Transcriptome analysis of signal transduction pathway involved in light inducing astaxanthin accumulation in Haematococcus pluvialis

The unicellular green alga Haematococcus pluvialis is the best source of natural astaxanthin(AST)in the world due to its high content under stress conditions.Although high light(HL)can effectively induce AST biosynthesis,the specific mechanisms of light signal perception and transduction are unclear.In the current study,we used transcriptomic data of normal(N),high white light(W),and high blue light(B)to study the mechanisms of light inducing AST accumulation from the point of photoreceptors.The original data of 4.0 G,3.8 G,and 3.6 G for N,W,and B were obtained,respectively,by the Illumina Hi-seq 2000 sequencing technology.Totally,51 954 unigenes(at least 200 bp in length)were generated,of which,20 537 unigenes were annotated into at least one database(NR,NT,KO,SwissProt,Pfam,GO,or KOG).There were 1 255 DEGs in the W vs N,1 494 DEGs in the B vs N,and 1 008 DEGs in the both W vs N and B vs N.KEGG enrichment analysis revealed that photosynthesis,oxidative phosphorylation,carotenoid biosynthesis,fatty acids biosynthesis,DNA replication,nitrogen metabolism,and carbon metabolism were the significantly enriched pathways.Moreover,a large number of genes encoding photoreceptors and predicted interacting proteins were predicted in Haematococcus transcriptome data.These genes showed significant differences at transcriptional expression levels.In addition,15 related DEGs were selected and tested by qRT-PCR and the results were significantly correlated with the transcriptome data.The above results indicate that the signal transduction pathway of "light signal-photoreceptors-interaction proteins-(interaction proteins-transcription factor/transcriptional regulator)-gene expression-AST accumulation" might play important roles in the regulation process,and provide reference for further understanding the transcriptional regulation mechanisms of AST accumulation under HL stress