Abstract
Haematococcus pluvialis is a freshwater species of Chlorophyta, family Haematococcaceae. It is well known for its capacity to synthesize high amounts of astaxanthin, which is a strong antioxidant that has been utilized in aquaculture and cosmetics. To improve astaxanthin yield and to establish genetic resources for H. pluvialis, we performed whole-genome sequencing, assembly, and annotation of this green microalga. A total of 83.1 Gb of raw reads were sequenced. After filtering the raw reads, we subsequently generated a draft assembly with a genome size of 669.0 Mb, a scaffold N50 of 288.6 kb, and predicted 18,545 genes. We also established a robust phylogenetic tree from 14 representative algae species. With additional transcriptome data, we revealed some novel potential genes that are involved in the synthesis, accumulation, and regulation of astaxanthin production. In addition, we generated an isoform-level reference transcriptome set of 18,483 transcripts with high confidence. Alternative splicing analysis demonstrated that intron retention is the most frequent mode. In summary, we report the first draft genome of H. pluvialis. These genomic resources along with transcriptomic data provide a solid foundation for the discovery of the genetic basis for theoretical and commercial astaxanthin enrichment.
Highlights
Haematococcus pluvialis is a unicellular green alga and is considered as the best natural resource for astaxanthin, which is a high-value carotenoid with strong biological activity for the food, feed, and pharmaceutical industries (Ambati et al 2014)
Carotene biosynthetic genes cooperate with b-carotene ketolase (CRTO) and hydroxylase (CRTR-B) to synthesize astaxanthin under high irradiation and salinity, which are the most common stresses that occur during H. pluvialis cultivation (Boussiba and Vonshak 1991)
It seems that the genome of H. pluvialis is very complicated, we added the PacBio transcriptome data to fill up more gene regions
Summary
Haematococcus pluvialis is a unicellular green alga and is considered as the best natural resource for astaxanthin, which is a high-value carotenoid with strong biological activity for the food, feed, and pharmaceutical industries (Ambati et al 2014). It has an interesting life cycle with a remarkable division between green motile and red immobile stages It enters the green motile stage under favorable environmental conditions. During their vegetative growth, H. pluvialis cells are spherical, ellipsoidal, or pear-shaped with flagella and chloroplasts We performed additional transcriptome sequencing on stressed cells to reveal additional genes that are potentially involved in the synthesis, accumulation, and regulation of astaxanthin production
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