Cloning and olfactory expression of progestin receptors in the Chinese black sleeper Bostrichthys sinensis

Abstract

Our previous studies suggested that 17α,20β-dihydroxy-4-pregnen-3-one (DHP), an oocyte maturation inducing progestin, also acts as a sex pheromone in Chinese black sleeper Bostrichthys sinensis, a fish species that inhabits intertidal zones and mates and spawns inside a muddy burrow. The electroolfactogram response to DHP increased during the breeding season. In the present study, we cloned the cDNAs of the nine progestin receptors (pgr, paqr5, 6, 7(a, b), 8, 9, pgrmc1, 2) from B. sinensis, analyzed their tissue distribution, and determined the expression in the olfactory rosette during the reproductive cycle in female and male fish. The deduced amino acid sequences of the nine progestin receptors share high sequence identities with those of other fish species and relatively lower homology with their mammalian counterparts, and phylogenetic analyses classified the nine B. sinensis progestin receptors into their respective progestin receptor groups. Tissue distribution of B. sinensis progestin receptors showed differential expression patterns, but all these nine genes were expressed in the olfactory rosette. Interestingly, paqr5 mRNA was found in the intermediate and basal parts of the olfactory epithelium but not in the central core using in situ hybridization, and its expression level was the highest in the olfactory rosette among the tissues examined. These results suggested Paqr5 may have an important role for transmitting progestin signaling in the olfactory system. The expression levels of paqr7a and paqr7b, pgr and pgrmc2 mRNA peaked around the mid meiotic stage, and that of paqr8 peaked at late meiotic stage in the olfactory rosette in males, while the olfactory expression of paqr5 decreased gradually as spermatogenesis progressed. In contrast, the expression of the progestin receptors did not change significantly during the development of the ovary in the olfactory rosette in females, except that of pgr. Interestingly, the changes of paqr8 expression in the olfactory rosette in males mirrored the changes of plasma DHP levels in females during the reproductive cycle, suggesting the Paqr8 may also be important for deciphering progestin signaling released by female. To our knowledge, this is the first time to demonstrate the presence of all known progestin receptors in a teleost olfactory rosette, and to show different expressions between the males and females during the reproductive cycle. This study provides the first evidence on changes of all purported progestin receptors during a reproductive cycle in teleost olfactory rosette, and suggests that distinct olfactory sensitivities to DHP may be due to the changes and compositions of each progestin receptor in B. sinensis.

Involvement of Membrane Progestin Receptor Beta (mPRβ/Paqr8) in Sex Pheromone Progestin-Induced Expression of Luteinizing Hormone in the Pituitary of Male Chinese Black Sleeper (Bostrychus Sinensis)

“…Transcript levels of β -actin gene were stable (Supplemental Figure 1 ). The specificity and efficiency of the specific primers for β -actin and progestin receptors have been described and validated in previous studies ( 25 , 20 ).…”

“…The fixed testes were dehydrated through a graded series of ethanol concentrations (70–100%), embedded in paraplast (Leica, Germany), and 5 μm sections were obtained on a retracting microtome and stained with hematoxylin. Classification of male maturation state in B. sinensis was modified from the previous study ( 20 ). The testicular development was classified into five stages according to analyses of histology sections: stage I (spermatogonial proliferation stage), stage II (early meiosis stage), stage III (mid meiosis stage), stage IV (late meiosis stage), stage V (maturation stage) (Table 1 ).…”

“…Mature male B. sinensis displayed greater electro-olfactogram (EOG) response to DHP than immature fish ( 19 ). All known progestin receptors were expressed in the olfactory rosette, and the expression levels of the progestin receptors changed in the olfactory rosette of male fish during reproductive cycle ( 20 ). These results from our previous studies suggest that DHP is a sex pheromone in B. sinensis .…”

Integrated analysis of mRNA-seq and miRNA-seq reveals the potential roles of sex-biased miRNA-mRNA pairs in gonad tissue of dark sleeper (Odontobutis potamophila)

“…The pieces of gonad from each fish were fixed in 4% PFA and sectioned at 5 μm for hematoxylin and eosin (HE) staining and observation by light microscopy to verify that the gonad sampled were in same development stage. Classification of gonad maturation state in this study refers to the Chinese black sleeper, Bostrichthys sinensis [ 26 ]. All experiments were performed according to the Guidelines for the Care and Use of Laboratory Animals in China.…”

Molecular characterization of three caspases from Bostrychus sinensis and their transcriptional responses to bacteria and viruses

“…Bostrychus sinensis is regarded as a food fish and belongs to the family Eleotridae (Ip et al, 2001) and the Goldfish suborder (Zhang, Liu, Zhu, Chen, & Hong, 2016). This species is a burrowing animal and inhabits intertidal zones (Wang, Lin, Zhang, & Ding, 2011).…”