Centro de Investigaciones Biológicas del Noroeste, S.C. (CIBNOR). Programa de Acuacultura, Av. Instituto Politécnico Nacional No. 195, Col. Playa Palo de Santa Rita, La Paz, Baja California Sur C.P. 23096, Mexico.
Centro de Investigación en Alimentación y Desarrollo A.C., (CIAD) Unidad Mazatlán, Av. Sábalo-Cerritos S/N. Col. Estero del Yugo, C.P. 82000 Mazatlán, Sinaloa, Mexico.
Gene. 2018 Aug 20;668:33-47. doi: 10.1016/j.gene.2018.05.024. Epub 2018 May 11.
The Pacific white shrimp Penaeus vannamei is the most cultured shrimp species around the world. Because females grow larger than males, the culture of 'only females' is of great interest, but knowledge on sex determination and differentiation is required for producing only females. In an effort to obtain information associated with reproduction in P. vannamei, transcriptomic data from female gonads was generated, and partial sequences of a transcript were identified as Sex-lethal (Sxl). Its characterization indicated that, differently from other penaeids in which this gene has been isolated, there are six isoforms of the Sxl transcript in P. vannamei (PvanSxl 1-6). These isoforms result from alternative splicing at three splice sites (SS1, SS2, SS3). The first splice-site is unique to P. vannamei, as it has not been reported for other Arthropod species; the second splice-site (SS2) is common among crustaceans, and the third splice-site (SS3) is also unique to P. vannamei and when spliced-out, it is always together with SS2. All isoforms are expressed during embryogenesis as well as gametogenesis of both genders. The two shorter isoforms, PvanSxl-5 and PvanSxl-6, which result from the splicing of SS2 and SS3, were found mostly expressed in adult testis, but PvanSxl-6 was also expressed in oocytes during gametogenesis. During oogenesis, the second largest isoform, PvanSxl-2, which splices-out only SS1, and PvanSxl-4 that splices-out SS1 and SS2 were highly expressed. These two isoforms were also highly expressed during embryonic development. In situ hybridization allowed pinpointing more specifically the cells where the PvanSxl transcripts were expressed. During embryogenesis, hybridization was observed from the one-cell stage embryo to late gastrula. In the female gonad in previtellogenesis, hybridization occurred in the nucleus of oocytes, whereas in secondary vitellogenesis the transcript also hybridized cytoplasmic granules and cortical crypts. Finally, in situ hybridization corroborated the expression of PvanSxl also in the male gonad during spermatogenesis, mostly occurring in the cytoplasm from spermatogonia and spermatocytes.
凡纳滨对虾（Penaeus vannamei）是全球养殖量最大的虾类。由于雌虾比雄虾生长得更大，因此养殖“全雌虾”具有重要意义，但要实现这一目标，就需要了解性别决定和分化的相关知识。为了获取凡纳滨对虾生殖相关的信息，本研究对其雌虾性腺进行了转录组测序，并鉴定出一个 Sex-lethal（Sxl）基因的部分序列。研究结果表明，与其他已分离出该基因的十足目甲壳动物不同，凡纳滨对虾的 Sxl 基因存在 6 种转录本异构体（PvanSxl1-6），它们通过在 3 个剪接位点（SS1、SS2 和 SS3）的选择性剪接而产生。第一个剪接位点是凡纳滨对虾所特有的，尚未在其他节肢动物中报道过；第二个剪接位点（SS2）在甲壳动物中较为常见，而第三个剪接位点（SS3）则是凡纳滨对虾所特有的，当该位点被剪接时，它总是与 SS2 一起被剪接掉。所有的异构体在胚胎发生和两性配子发生过程中都有表达。两个较短的异构体 PvanSxl-5 和 PvanSxl-6 是由 SS2 和 SS3 的剪接产生的，主要在成年精巢中表达，但在配子发生过程中 PvanSxl-6 也在卵母细胞中表达。在卵发生过程中，第二个最大的异构体 PvanSxl-2 只剪接 SS1，以及 PvanSxl-4 剪接 SS1 和 SS2，这两个异构体表达水平较高。这两个异构体在胚胎发育过程中也高度表达。原位杂交实验更精确地定位了 PvanSxl 转录本表达的细胞。在胚胎发生过程中，从单细胞期胚胎到晚期原肠胚期都观察到杂交信号。在卵母细胞的卵黄发生前期，在细胞核中检测到杂交信号，而在次级卵黄发生期，转录本也在细胞质颗粒和皮质隐窝中杂交。最后，原位杂交实验在雄性精巢的精子发生期也证实了 PvanSxl 的表达，主要发生在精原细胞和精母细胞的细胞质中。
