The expressed sequence tags (ESTs) of Japanese flounder, Paralichthys olivaceus, were selected from GenBank to iden-tify simple sequence repeats (SSRs) or microsatellites.A bioinformatic analysis of 11111 ESTs identified 751 SSR-containing ESTs, including 440 dinucleotide, 254 trinucleotide, 53 tetranucleotide, 95 pentanucleotide and 40 hexanucleotide microsatellites respec-tively.The CA/TG and GA/TC repeats were the most abundant microsatellites.AT-rich types were predominant among trinucleotide and tetranucleotide microsatellites.PCR primers were designed to amplify 10 identified microsatellites loci.The PCR results from eight pairs of primers showed polymorphisms in wild populations.In 30 wild individuals, the mean observed and expected het-erozygosities of these 8 polymorphic SSRs were 0.71 and 0.83 respectively and the average PIC value was 0.8.These microsatellite markers should prove to be a useful addition to the microsatellite markers that are now available for this species.
YU Haiyang JIANG Liming CHEN Wei WANG Xubo WANG Zhigang ZHANG Quanqi
Half-smooth tongue sole (Cynoglossus semilaevis) is a rare marine flatfish whose mature ovary and testis greatly differ in volume and weight. The length and weight of mature females are over twice greater than those of mature males. To obtain sufficient information on gonad differentiation and the relationship between gonad development and growth in the fish, we compared gene expression between the ovary and testis using suppression subtractive hybridization (SSH). Testis cDNAs are subtracted from ovary cDNAs and are used to es- tablish an ovary testis-subtracted cDNA library. A total of 41 nonredundant clones are identified, including 20 known cDNAs, 9 unchar-acterized cDNAs (EST clones), and 12 novel sequences. For selected genes such as ZPC, RacGAP, survivin, aquaporin, CPEB, O5, O15, and O18, gene expression patterns are analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). The results confirm that these genes are only expressed in the ovary and not in the testis, or at higher levels in the ovary than in the testis. At the same time, expressions of certain genes such as ZPC, survivin, aquaporin, CPEB, and O15 are demonstrated to possess sexual dimorphism in the kidney or muscle, and spleen. The results suggest that these genes could play key roles not only in the ovary but in other female tissues as well.
Yeying SunQuanqi ZhangJie QiYanjie ChenQiwang ZhongChunmei Li
