A chromosome-level genome assembly for the astaxanthin-producing microalga Haematococcus pluvialis
Chao Bian, Chenglong Liu, Guiying Zhang, Ming Tao, Danqiong Huang, Chaogang Wang, Sulin Lou, Hui Li, Qiong Shi, Zhangli Hu
Abstract
The green microalga Haematococcus pluvialis can synthesize high amounts of astaxanthin, which is a valuable antioxidant that has been utilized in human health, cosmetics, and aquaculture. To illustrate detailed molecular clues to astaxanthin yield, we performed PacBio HIFI along with Hi-C sequencing to construct an improved chromosome-level haplotypic genome assembly with 32 chromosomes and a genome size of 316.0 Mb. Its scaffold N50 (942.6 kb) and contig N50 (304.8 kb) have been upgraded remarkably from our previous genome draft, and a total of 32,416 protein-coding genes were predicted. We also established a high-evidence phylogenetic tree from seven representative algae species, with the main aim to calculate their divergence times and identify expanded/contracted gene families. We also characterized genome-wide localizations on chromosomes of some important genes such as five BKTs (encoding beta-carotene ketolases) that are putatively involved in astaxanthin production. In summary, we reported the first chromosome-scale map of H. pluvialis, which provides a valuable genetic resource for in-depth biomedical investigations on this momentous green alga and commercial astaxanthin bioproduction.