Molecular characterization and expression of buffalo (Bubalus bubalis) DEAD-box family VASA gene and mRNA transcript variants isolated from testis tissue

Identification and characterization of the vasa gene in the diamondback moth, Plutella xylostella

Vasa is an ATP-dependent RNA helicase, participating in multiple biological processes. It has been widely used as a germ cell marker and its promoter has become a key component of several genetic pest control systems. Here we present the vasa gene structure and its promoter activity in Plutella xylostella, one of the most destructive pests of cruciferous crops. Full length Pxvasa cDNA sequences were obtained, revealing 14 exons and at least 30 alternatively spliced transcripts. Inferred amino acid sequences showed nine conserved DEAD-box family protein motifs with partial exclusion from some isoforms. Real-time quantitative PCR indicated the up-regulation of Pxvasa in both female and male adults compared with other developmental stages, and the expression levels of Pxvasa were found to be much higher in adult gonads, especially ovaries, than in other tissues. The putative promoter region of Pxvasa was sequenced and several ecdysone-induced transcription factor (TF) binding sites were predicted in silico. To further analyze the promoter region, two upstream regulatory fragments of different lengths were tested as putative promoters in transient cell and embryo expression assays, one of which was subsequently utilized to drive Cas9 expression in vivo. A transgenic line was recovered and the expression patterns of Cas9 and native Pxvasa were profiled in adult tissues and eggs with RT-PCR. This work provides the foundation for further studies on the gene functions of Pxvasa as well as the potential application of its promoter in genetic manipulation of P. xylostella.

Alternative splice variants and differential relative abundance patterns of vasa mRNAs during gonadal development in the Chinese mitten crab Eriocheir sinensis

Gonadal development usually involves alternative splicing of sex-related genes. Vasa, a highly conserved ATP-dependent RNA helicase present mainly in germ cells, has an important function in gonadal development. As an important sex-related gene, recent evidence indicates that different splice variants of vasa exist in many species. In this study, there was identification of two types of vasa splice variants in the Chinese mitten crab Eriocheir sinensis, termed Esvasa-l and Esvasa-s, respectively. Furthermore, splice variants of Esvasa-s were sub-divided into Esvasa-s1, Esvasa-s2, Esvasa-s3, Esvasa-s4, and Esvasa-s5, based on differing numbers of TGG repeats. Results from genomic structure analyses indicated that these forms are alternatively spliced transcripts from a single vasa gene. Results from tissue distribution assessments indicate the vasa splice variants were exclusively expressed in the gonads of male and female adult crabs. In situ hybridization results indicate Esvasa mRNA was mainly present in the cytoplasm of previtellogenic oocytes. As oocyte size increased, relative abundance of Esvasa mRNA decreased and became distributed near the cellular membrane. The Esvasa mRNA was not detectable in mature oocytes. In testis, Esvasa mRNA was detected in spermatids and spermatozoa, but not in spermatogonia and spermatocytes. Notably, results from qPCR analysis of Esvasa-l and Esvasa-s indicate there are different relative proportions during gametogenesis, implying that splice variants of the Esvasa gene may have different biological functions during crab gonadal development.