Transcriptome analyses reveal the synergistic effects of feeding and eyestalk ablation on ovarian maturation in black tiger shrimp

Abstract

Unilateral eyestalk ablation in the female black tiger shrimp Penaeus monodon is commonly employed to induce ovarian maturation. However, the importance of complementing this practice with the provision of live feed supplement (such as polychaetes) has not been emphasized in previous studies. Indeed, it has been less emphasized that female broodstock must be fed with live feeds such as polychaetes for this practice to be effective. While the effects of eyestalk ablation have been thoroughly studied in various aspects, the synergistic effects of feeding with live feeds and the ablation have never been elucidated at a transcriptome-wide level. With recent advances in the next-generation sequencing platforms, it is now possible to investigate the effects of eyestalk ablation and live feeds at the transcriptomic levels. This study employed both short-read Illumina RNA sequencing and long-read Pacific Biosciences (PacBio) isoform sequencing (Iso-seq) to generate the first high-quality ovarian reference transcriptome in P. monodon. This novel assembly allowed us to dissect the effects of feeds and eyestalk ablation and reveal their synergistic effects at the transcriptomic level through the regulation of important genes involved in fatty acid regulation, energy production, and hormonemediated oocyte maturation pathways. The synergistic effects between the polychaete feeding and the eyestalk ablation in the process of ovarian maturation in black tiger shrimp suggest that without having proper nutrients from the polychaetes, female broodstock might not be ready to develop its ovary. However, even with proper nutrients, the eyestalk ablation is still necessary to perhaps manipulate the female endocrine of the black tiger shrimp. These findings shed the light on molecular mechanisms and key molecular pathways that lead to successful ovarian maturation. The black tiger shrimp (Penaeus monodon) is the second most widely cultured shrimp species in the world (FAO 2016). Albeit high demand worldwide, the shrimp production level remains stagnant mainly due to the outbreak of diseases and lack of selective breeding programs. The future success of the shrimp industry will depend upon increasing supplies of healthy, high-quality seed for stocking ponds and decreasing reliance on wild broodstock, which might potentially be a disease carrier and have seasonal variation 1. To overcome these challenges, it is vital to be able to enhance reproductive maturation of captive broodstock. Ovarian maturation is a well-orchestrated and complex molecular process that requires the regulation of large sets of genes to ensure proper oocyte development for embryogenesis. In penaeid shrimp, the process can be categorized into four stages: (I) previtellogenesis, (II) vitellogenesis, (III) early cortical rod, and (IV) late cortical rod 2. Numerous factors and methods have been investigated to improve reproductive maturation in female black tiger shrimp. Dietary choices have been shown to be important for the maturation. Although nutritional

Transcriptomic analysis of the black tiger shrimp (Penaeus monodon) reveals insights into immune development in their early life stages

“…Transcriptomic analysis has been widely applied in aquaculture to understand underlying molecular mechanisms related to various biological processes 24 , 39 , 40 . In penaeid shrimp, gene expression profiles related to growth, metabolic activities and immune responses have mostly been identified in juvenile and adult stages 33 , 35 , 41 , while little is still known in shrimp at early life stages including nauplius, zoea, mysis and postlarva. Particularly, their morphological and physiological were dramatically changed from nauplii into postlarva in their early life, and they can be more susceptible to diseases due to their underdeveloped immune systems 17 .…”

Effects of Salinity on Physiological, Biochemical and Gene Expression Parameters of Black Tiger Shrimp (Penaeus monodon): Potential for Farming in Low-Salinity Environments

“…Following a comprehensive literature review on crustaceans, candidate genes were selected based on their inferred functional roles [ 7 , 22 , 23 ]. Primer sequences of the eight candidate genes for Penaeus monodon were obtained ( Table 1 ) from earlier studies [ 7 , 48 , 49 ]. EF1α was used as the reference gene because it was previously found to be a suitable reference gene for RT-qPCR studies in P. monodon [ 49 , 50 , 51 ].…”

A chromosome‐level assembly of the black tiger shrimp (Penaeus monodon) genome facilitates the identification of growth‐associated genes

“…While such a high-quality draft genome sequence has not been reported for P. monodon, over the past two decades, several attempts have been made to investigate the genetic architecture of this important species. BAC library construction (Wuthisuthimethavee et al, 2009), fosmid library end sequencing (Huang et al, 2011), molecular marker development (Brooker et al, 2000;Tassanakajon et al, ,1997Tassanakajon et al, , , 1998, linkage map construction (Baranski et al, 2014;Wilson et al, 2002), and transcriptome analysis (Huerlimann et al, 2018;Karoonuthaisiri et al, 2009;Leelatanawit et al, 2011;Lehnert et al, 1999;Pootakham et al, 2020;Sittikankaew et al, 2020;Supungul et al, 2002;Tassanakajon et al, 2006;Tong et al, 2002;Uengwetwanit et al, 2018) were successfully explored, but these attempts yielded rather limited genome information. Previous attempts to obtain genome sequence data of the black tiger shrimp relied primarily on short-read sequencing platforms.…”