Comparative transcriptome analysis of abalone Haliotis discus hannai with green and gray egg colors

Haliotis discus hannai is an important marine economic species in China. Its egg color was found to be associated with economic traits, which provides a new idea for breeding. However, the molecular mechanism of the egg-color formation has not been reported. Thus, the pigment composition and comparative transcriptome analyses of H. discus hannai with green and gray egg color were conducted using high-performance liquid chromatography (HPLC) and RNA-Seq methods. Results show that individuals with green and gray eggs both possess the fucoxanthin. Lutein existed in gray-egged individuals, but not in green-egged individuals. In transcriptome analysis, 272 310 unigenes were received from 461 162 transcripts with a mean length of 985 bp and N50 of 1 524 bp, respectively. A total of 185 unigenes were identified as differentially expressed genes (DEGs). The DEGs involved in “flavin-containing compound metabolic process”, “melanosome”, “glutathione metabolism”, and “cytochrome b6f complex” were likely related to the formation of the egg color. Our results provide foundational information for the functional analysis of egg-color related genes and are beneficial to the selective breeding of H. discus hannai.