Abstract
Cells bearing pigment have diverse roles and are often under strict evolutionary selection. Here, we explore the regulation of pigmented cells in the purple sea urchin Strongylocentrotus purpuratus, an emerging model for diverse pigment function. We took advantage of single cell RNA-seq (scRNAseq) technology and discovered that pigment cells in the embryo segregated into two distinct populations, a mitotic cluster and a post-mitotic cluster. Gcm is essential for expression of several genes important for pigment function, but is only transiently expressed in these cells. We discovered unique genes expressed by pigment cells and test their expression with double fluorescence in situ hybridization. These genes include new members of the fmo family that are expressed selectively in pigment cells of the embryonic and in the coelomic cells of the adult - both cell-types having immune functions. Overall, this study identifies nodes of molecular intersection ripe for change by selective evolutionary pressures.
Highlights
Crafted pigments are nearly ubiquitous in nature
The pigment cell markers gcm and pks1 were found in clusters 2 and 13, which showed a similar transcriptome profile, and cluster 12, which had a transcriptomic profile that was distinct from clusters 2 and 13
Having defined that there are two distinct sub-populations of pigment cells in embryos that expressed gcm and pks1, we investigated the expression of a class of enzymes that at least one representative modifies the polyketide pigment scaffold, the Flavin-dependent monooxygenases (Fmo)
Summary
Crafted pigments are nearly ubiquitous in nature. Pigmentation can reveal identity, protection, and even have antimicrobial functions. Like most sea urchins, S. purpuratus larvae are pigmented due to the accumulation of a red/orange pigment in single cells embedded in, and scattered throughout, the aboral ectodermal layer (Gibson and Burke, 1985; Griffiths, 1965; Gustafson and Wolpert, 1967; Kominami et al, 2001; McClendon, 1912). The antimicrobial mechanism of echinochrome has not been completely resolved, but evidence suggests its production of hydrogen peroxide and/ or iron chelation, abates microbial proliferation, (Coates et al, 2018; Lebedev et al, 2005; Perry and Epel, 1981) All of these studies agree that sea urchin pigments have anti-microbial activity, and that these small molecules may contribute to states of cell physiology and gene expression (Jeong et al, 2014; Kim et al, 2018). Our study leverages our understanding of the Gcm transcription factor, an essential factor in the development of pigmentation in the larvae (Calestani and Rogers, 2010; Oulhen and Wessel, 2016; Ransick and Davidson, 2006; Ransick and Davidson, 2012; Wessel et al, 2020) and adult (Wessel et al, 2020) and provides deep datasets for exploring evolutionary selection of the biosynthesis of pigmentation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
