Abstract
Genes generated by whole genome duplications (WGD) can be co-opted by changing their regulation process or altering their coding proteins, which has been shown contributable to the emergence of vertebrate morphological novelties such as vertebrate cartilage. Mouse khdrbs genes, differing from its invertebrate orthologs, were mainly expressed in brain, hinting that khdrbs gene family as a member of genetic toolkit may be linked to vertebrate brain development. However, the evolutionary relationship between khdrbs gene family and vertebrate brain development is unclear. First, we analyzed the evolutionary history of khdrbs gene family in metazoans, and then investigated their expression patterns during early development and in adulthood of zebrafish. We found that the duplication of khdrbs gene family by WGD took place in zebrafish, and all zebrafish khdrbs genes were predominantly expressed in the substructures of brain during early development. Given the expression of invertebrate khdrbs gene in germ line, the distinct expression domains of zebrafish khdrbs genes in brain suggested that the duplicated khdrbs genes are co-opted for promoting the evolutionary origin of vertebrate brain.
Highlights
One of the key questions of evolution is to answer how the morphological complexity takes place among extant animals including vertebrates
We found that khdrbs gene family was expanded by whole genome duplications (WGD) in zebrafish, and all zebrafish khdrbs genes were predominantly expressed in the substructures of brain during early development
The results revealed that the flanking genes beside both khdrbs1a and khdrbs1b could be found in the neighboring region around spotted gar and human khdrbs1, which meant that khdrbs1 in zebrafish was orthology to spotted gar and human khdrbs1 and remained an evolutionarily conserved synteny
Summary
One of the key questions of evolution is to answer how the morphological complexity takes place among extant animals including vertebrates. The molecular phylogeny of these toolkit genes will provide us an insight into the evolutionary origin of morphological novelties. Whole genome duplication (WGD) could enrich the genomic complexity, and generate new functions. Co-option of khdrbs for Brain of duplicated genes by co-option (Ohno, 1970; True and Carroll, 2002; Dehal and Boore, 2005; Conant and Wolfe, 2008; Cañestro et al, 2013). WGD occurred around the origin of vertebrate lineage, has been shown to be related to vertebrate morphological innovations (Manzanares et al, 2000; True and Carroll, 2002). The origin of vertebrate cartilage was found to be attributable to the duplication of chordate fibrillar collagen genes (Wada et al, 2006; Zhang et al, 2006), and the emergence of vertebrate vascular vessels to the duplication of kank genes (Hensley et al, 2016)
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