In order to learn the sex determination and differentiation process in shrimp, we performed sex-specific transcriptome sequencing of the Zoea I larvae in Litopenaeus vannamei (L. vannamei) using a DNA/RNA co-extraction method. The sex-specific genes and the sex-linked SNPs were identified. De novo assembly of all the clean reads generated 41,270 unigenes with an average length of 1026 bp and an N50 of 1922 bp. A total of 60 differentially expressed genes (DEGs) between females and males at Zoea I stage were obtained, in which 41 unigenes had annotations. DEGs that might be related to sex development in L. vannamei were analyzed. Besides, paralogous genes of some known sex-related genes in model organisms such as sex-lethal (Sxl) showed no sex-biased difference, which indicated they may not play roles in sex development at Zoea I stage. Candidate sex-linked SNPs were validated in six populations of L. vannamei, and SNPs in Unigene0020898 and Unigene0020336 were fully linked to genders, suggesting the two genes located in the sex-determining region of L. vannamei. Our report provided the sex-specific gene expression in early developmental stage of L. vannamei, and found some sex-biased genes that may participate in the sex development process. We also detected two sex-linked genes which may be located in the sex determination region of L. vannamei through bulked segregant analysis, and the SNPs on these genes also provided a method for genetic sex identification at transcriptional level. Our findings will facilitate further researches on molecular mechanism of sex determination and differentiation in shrimps.

中文翻译：

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南美白对虾南美白对虾Zoea I幼虫的性别特异性转录组测序和使用性别隔离基因的性别相关基因鉴定。

为了了解虾的性别决定和分化过程，我们使用DNA / RNA共提取方法对凡纳滨对虾（L. vannamei）中的佐伊I幼虫进行了性别特异性转录组测序。确定了性别特异性基因和与性别相关的SNP。从头开始，所有纯净读段均会产生41,270个单基因，平均长度为1026 bp，N50为1922 bp。总共获得了60个在Zoea I阶段的雌性和雄性之间的差异表达基因（DEG），其中41个单基因带有注释。分析了可能与南美白对虾的性发育有关的DEG 。此外，模型生物中一些​​已知的性相关基因的旁系同源基因，例如性致死（Sxl）没有显示出性别偏见的差异，这表明它们在Zoea I阶段可能不会在性别发展中发挥作用。在六个南美白对虾中验证了与性别相关的候选SNP，Unigene0020898和Unigene0020336中的SNP与性别完全相关，表明这两个基因位于南美白对虾的性别决定区域。我们的报告提供了南美白对虾发育早期的性别特异性基因表达，并发现了一些可能参与性别发育过程的性别偏向基因。我们还检测了两个可能位于南美白对虾性别决定区域的性别相关基因通过大量的segregant分析，这些基因上的SNPs也为转录水平的遗传性别鉴定提供了一种方法。我们的发现将促进对虾性别决定和分化的分子机制的进一步研究。