Protandric Transcriptomes to Uncover Parts of the Crustacean Sex-Differentiation Puzzle

Abstract

Hermaphrodite systems offer unique opportunities to study sexual differentiation, due to their high degree of sexual plasticity and to the fact that, unlike gonochoristic systems, the process is not confined to an early developmental stage. In protandric shrimp species, such as Hippolyte inermis and Pandalus platyceros, male differentiation is followed by transformation to femaleness during adulthood. The mechanisms controlling sexual differentiation have not been fully elucidated in crustaceans, but a key role has been attributed to the insulin-like hormone (IAG) produced by the androgenic gland (AG), a crustacean masculine endocrine organ. To uncover further transcriptomic toolkit elements affecting the sexual differentiation of H. inermis, we constructed eye and whole body RNA libraries of four representative stages during its protandric life cycle (immature, male, young female and mature female). The body libraries contained transcripts related to the reproductive system, among others, while the eye libraries contained transcripts related to the X-organ-sinus gland, a central endocrine complex that regulates crustacean reproduction. Binary pattern analysis, performed to mine for genes expressed differentially between the different life stages, yielded 19,605 and 6,175 transcripts with a specific expression pattern in the eye and body, respectively. Prominent sexually biased transcriptomic patterns were recorded for the IAG and vitellogenin genes, representing, respectively, a key factor within the masculine IAG-switch, and a precursor of the yolk protein, typical of feminine reproductive states. These patterns enabled the discovery of novel putative protein-coding transcripts exhibiting sexually biased expression in the H. inermis body and eye transcriptomes of males and females. Homologs to the above novel genes have been found in other decapod crustaceans, and a comparative study, using previously constructed transcriptomic libraries of another protandric shrimp, P. platyceros, showed similar sexually biased results, supporting the notion that such genes, mined from the H. inermis transcriptome, may be universal factors related to reproduction and sexual differentiation and their control in other crustaceans. This study thus demonstrates the potential of transcriptomic studies in protandric species to uncover unexplored layers of the complex crustacean sex-differentiation puzzle.

Ferroptosis precedes apoptosis to facilitate specific death signalling by fatty acids

“…A total of 487 865 035 clean reads were retained for further analysis. For constructing the transcriptome assembly, these reads were combined with an additional 1 022 880 897 clean reads from H. inermis body samples from different reproductive stages [ 30 ]. The transcriptome was de novo assembled using Trinity v. 2.8.4 [ 31 ] and then filtered to exclude transcripts with very low expression.…”

A refined roadmap to decapod sexual manipulation

“…49 It remains to be seen whether sex change can be achieved in C. quadricarinatus, attempts that will be greatly facilitated by the recent discovery of genetic sex markers. 50,51 The fact that metamorphosis in the juvenile at 1 g. 14 At this stage, the AG is not yet differentiated and there is no significant expression of iag until around 2 years later, when low-level iag expression is detected in immature males (>400 g; Figure 3), indicating that IAG is unlikely to be mediating sexual differentiation in this species. 52,53 Results of this study suggest that there are other factors involved in regulating male sexual differentiation in this species.…”

“…In C. quadricarinatus , iag was shown to be expressed as early as 8 days following the release of juveniles from the mother, 11 while the differentiation of primary and secondary sexual characters commenced only several weeks later 49 . It remains to be seen whether sex change can be achieved in C. quadricarinatus , attempts that will be greatly facilitated by the recent discovery of genetic sex markers 50,51 . The fact that iag ‐expressing intersex individuals have an ovary argues against sex manipulation being accomplished in this species.…”

Editorial: Cyanobacterial and microalgal compounds: Chemical ecology and biotechnological potentials

“…Consequently, we can hypothesize that a common chemical language reinforces the relationships among definite benthic communities. However, infochemicals not only modulate the chemotactic reactions of consumers but often influence their physiology, indicating a potential role as "functional foods", as in the case of the protandrous shrimp Hippolyte inermis and of the co-evolved diatoms of the genus Cocconeis which influence its sex regulation, triggering apoptosis of androgenic gland in early postlarvae (Zupo and Messina, 2007;Levy et al, 2021). Small lipophilic compounds present in the diatoms are able to selectively destroy such tissues and this peculiar relationship will be worth producing interesting biotechnologies in the fields of aquaculture and medicine.…”