Abstract
Haptophytes are biogeochemically and industrially important protists with underexplored genomic diversity. We present a nuclear genome assembly for the class Pavlovales, which was assembled with PacBio long-read data into highly contiguous sequences. We sequenced strain Diacronema lutheri NIVA-4/92, formerly known as Pavlova lutheri, because it has established roles in aquaculture and has been a key organism for studying microalgal lipid biosynthesis. Our data show that D. lutheri has the smallest and most streamlined haptophycean genome assembled to date, with an assembly size of 43.503 Mb and 14,446 protein-coding genes. Together with its high nuclear GC content, Diacronema is an important genus for investigating selective pressures on haptophyte genome evolution, contrasting with the much larger and more repetitive genome of the coccolithophore Emiliania huxleyi. The D. lutheri genome will be a valuable resource for resolving the genetic basis of algal lipid biosynthesis and metabolic remodeling that takes place during adaptation and stress response in natural and engineered environments.
Highlights
Haptophytes comprise a major proportion of the phytoplankton community that globally have large-scale impacts on carbon cycling and ocean biogeochemistry (Liu et al 2009; Gutowska et al 2017; Heureux et al 2017)
NIVA-4/92,” which we identify as D. lutheri based on its mitochondrial, plastid, and 18S sequences (Hulatt et al 2020)
The C. tobin genome encodes fewer single-exon genes whereas E. huxleyi, with the largest sequenced genome, encodes only 27% single-exon genes, with 50% of genes containing two or more introns. Such variation raises questions on patterns of genome-wide intron gain and loss in haptophytes, and the extent to which posttranscriptional regulation by alternative splicing is prevalent across different clades
Summary
Haptophytes comprise a major proportion of the phytoplankton community that globally have large-scale impacts on carbon cycling and ocean biogeochemistry (Liu et al 2009; Gutowska et al 2017; Heureux et al 2017). Further developments in large-scale microalgae cultivation could expand the production of sustainable foods, oils, and plastic replacement materials in the future (Cottrell et al 2020; Naduthodi et al 2021) Despite their impact and their intriguing evolutionary history, high-quality haptophyte genome sequences remain scarce, and the available data do not reflect their diversity ß The Author(s) 2021. New discoveries (Burki et al 2012; Sibbald and Archibald 2017; Kawachi et al 2021) To bridge this knowledge gap, we assembled and annotated a high-quality genome for Diacronema lutheri (Pavlova lutheri), for the purpose of understanding its architecture, sequence evolution, and capacity to synthesize diverse natural products, lipids. Our data will be valuable for applied studies of genomeinformed strain improvement and models of cell metabolic flux
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