Asymmetrically reduced expression of handl homeologs involving a single nucleotide substitution in a cis-regulatory element

作者：Ochi Haruki^*; Suzuki Nanoka; Kawaguchi Akane; Ogino Hajime

来源：Developmental Biology, 2017, 425(2): 152-160.

DOI：10.1016/j.ydbio.2017.03.021

• Tetraploidization
• Hand
• Whole genome duplication
• Cis-regulatory element
• Xenopus laevis (X. laevis)
• Xenopus tropicalis (X. tropicalis)

During vertebrate evolution, whole genome duplications resulted in a number of duplicated genes, some of which eventually changed their expression patterns and/or levels via alteration of cis-regulatory sequences. However, the initial process involved in such cis-regulatory changes remains unclear. Therefore, we investigated this process by analyzing the duplicated handl genes of Xenopus laevis (handl.L and handl.S), which were generated by allotetraploidization 17-18 million years ago, and compared these with their single ortholog in the ancestral-type diploid species X. tropicalis. A dN/dS analysis indicated that handl.L and handl.S are still under purifying selection, and thus, their products appear to retain ancestral functional properties. RNA-seq and in situ hybridization analyses revealed that handl.L and handl.S have similar expression patterns to each other and to X. tropicalis handl, but the handl.S expression level was much lower than the handl.L expression level in the primordial heart. A comparative sequence analysis, luciferase reporter analysis, ChIP-PCR analysis, and transgenic reporter analysis showed that a single nucleotide substitution in the handl.S promoter was responsible for the reduced expression in the heart. These findings demonstrated that a small change in the promoter sequence can trigger diversification of duplicated gene expression prior to diversification of their encoded protein functions in a young duplicated genome.

• 出版日期2017-5-15