Transcriptome analysis of male and female mature gonads of Japanese scallop Patinopecten yessonsis

The Japanese scallop Patinopecten yessoensis is an important commercial culture shellfish in China and Japan. In addition to its commercial interest, it has also attracted much attention because of its value in studying sex determination and differentiation mechanisms. Herein, two transcriptome libraries from male and female gonads at maturing stage were constructed. The two libraries were paired-end sequenced using Illumina sequencing techniques. A total of 81,986,898 cleaned reads were obtained, and assembled into 29,897 unigenes by using Trinity software and removing redundancy. Compared with the public Swiss-Prot and NR databases by BlastX, 9354 unigenes were significantly matched to known unique proteins. As determined by GO annotation and KEGG pathway mapping, functional annotation of the unigenes uncovered diverse biological functions and processes. After comparing the two transcriptome libraries, 8652 up-regulated and 2973 down-regulated genes were identified in the male gonads. According to annotation information, at least 30 genes related to sex determination and differentiation, such as Dmrt1, Sox9, fem1 and vasa, were identified and characterized. The expression patterns of the random eight genes were then validated by quantitative real-time PCR (qRT-PCR) suggesting the high reliability of RNA-Seq results. The study provides an archive for further studies of molecular mechanisms of bivalve sex determination and differentiation.