Search Results (11)

Sequentially hermaphroditic fish begin life as one sex and change to another at some stage of their lifecycle. To date, the majority of research into this fascinating process has focused on sex change in sexually mature fish. The current study on the New Zealand spotty wrasse (Notolabrus celidotus) seeks to describe sex change in sexually immature females that are transitioning to become so called initial-phase males. This was achieved through analysis of gonadal histology, and the expression of key genes involved in sex differentiation (amh, dmrt1, and cyp19a1a) and methylation (dnmt1 and dnmt3a). It was found that initial-phase (IP) male spotty wrasse likely reach sexual maturity at a much earlier developmental stage and smaller size than previously realised. This study furthermore shows that all juvenile spotty wrasse are female first, before some individuals undergo pre-maturational sex change to become IP males. Thus, we confirm diandry in the protogynous New Zealand spotty wrasse and provide clarity around the definitions of primary male formation. Full article

As a fundamental taxonomic group within vertebrates, fish represent an invaluable resource for investigating the mechanisms underlying sex determination and differentiation owing to their extensive geographical distribution and rich biodiversity. Within this biological cohort, the processes of sex determination and differentiation are intricately governed by both genetic factors and the complex interplay of environmental cues. While variations in external environmental factors, particularly temperature, can exert a modulatory influence on sex differentiation in fish to a limited degree, genetic factors remain the primary determinants of sexual traits. Hermaphroditic fish display three distinct types of sexual transitions: protandry (male to female), protogyny (female-to-male), bidirectional sex change (both directions serially). These fish, characterized by their unique reproductive strategies and sexual plasticity, serve as exemplary natural models for elucidating the mechanisms of sex differentiation and sexual transitions in fish. The present review delves into the histological dynamics during gonadal development across three types of sequential hermaphroditic fish, meticulously delineating the pivotal characteristics at each stage, from the inception of primordial gonads to sexual specialization. Furthermore, it examines the regulatory genes and associated signaling pathways that orchestrate sex determination and differentiation. By systematically synthesizing these research advancements, this paper endeavors to offer a comprehensive and profound insight into the intricate mechanisms governing sex differentiation in sequential hermaphroditic fish. Full article

Juglans mandshurica, a notable woody oil tree species, possesses both fruit and timber value. However, the complete heterodichogamous flowering mechanism in this species remains elusive. SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) is a crucial regulator of flower bud development in Arabidopsis thaliana. In this study, we cloned the coding DNA sequence (CDS) of the JmSOC1 gene, revealing a 705 base pair (bp) sequence that encodes a protein of 234 amino acids. The JmSOC1 protein contains a highly conserved MADS-box domain, indicating its role as a transcription factor, and is predominantly localized in the nucleus. The JmSOC1 gene expressed the highest in flower buds. The peak expression level of JmSOC1 during the physiological differentiation phase occurred earlier in male flower buds of protandry (MPD) on April 10th compared to female flower buds of protandry (FPD) on April 14th; similarly, the peak expression in female flower buds of protogyny (FPG) on April 2nd preceded that in male flower buds of protogyny (MPG) on April 14th. This may be the primary reason for the earlier differentiation of the male flowers in protandry individuals and the female flowers in protogyny individuals. Overexpression of JmSOC1 in wild-type A. thaliana resulted in earlier flowering, accompanied by an upregulation of key flowering-related genes such as LEAFY (LFY), APETALA1 (AP1), and FLOWERING LOCUS T (FT). To further explore the function of JmSOC1, a 782 bp promoter sequence of JmSOC1 gene was cloned, which has been verified to have promoter activity by GUS staining. Furthermore, the interaction between the JmSOC1 gene promoter and its upstream regulatory protein JmSVP was verified using a yeast one-hybrid. These results offer valuable insights into the molecular mechanisms underpinning the promotion of early flowering in J. mandshurica and hold promise for laying a theoretical foundation for the flowering regulation network of this species. Full article

The GRAS gene family, derived from GAI, RGA, and SCR, plays a crucial role in plant growth and development. In the diploid Cyclocarya paliurus (2n = 2x = 32) with heterodichogamous characteristics, 51 CpGRAS genes were identified and phylogenetically classified into 10 subfamilies. Structural analysis revealed that CpGRAS genes possessed a canonical GRAS domain, but 70% lacked introns. WGD/segmental duplication was the major driver in the expansion of the CpGRAS family. In addition, a Ka/Ks ratio below 1 for these genes implied functional constraints and evolutionary conservation. Transcriptional profiling revealed significant differential expressions of CpGRAS genes between male and female flowers from two mating types, protogyny (PG) and protandry (PA). Notably, members of the DELLA subfamily exhibited significant upregulation in female flowers at the inflorescence elongation (S3) stage. The expression level of CpSCL6-2 in late-flowering samples (PA-F and PG-M) was higher than in early-flowering ones (PA-M and PG-F). Co-expression analysis identified that CpRGL1 and CpGAI-2 of the DELLA subfamily, along with CpSCL6-2, acted as hub genes, implying their crucial roles in floral development and potential involvement in the heterodichogamous flowering mechanism in C. paliurus. These findings broaden our understanding of CpGRAS genes and provide new insights into the molecular basis of heterodichogamy. Full article

The andromonoecy is an unusual sex expression in trees in which an individual plant bears both functionally staminate and hermaphrodite flowers on the inflorescences. This study aims to investigate the effect of crown layers on the floral biology and reproductive effort of Aesculus indica (Wall. ex Camb.) Hook. The results revealed that the peak period of anthesis was between 06:00 and 08:00 h of the day. Male flower production was predominantly higher as compared to the perfect flowers on the inflorescences. There was no significant variation between total pollen production in staminate and perfect flowers. Features like protogyny and inter-level asynchrony promote xenogamy; however, intra-level asynchrony results in geitonogamy. Controlled pollination treatments revealed the existence of self-incompatibility in flowers. Pollination syndromes in flowers support ambophily. A trend of consistent improvement in reproductive success from lower canopy layers to upper crown layers in the analyzed trees was recorded. The crown layers have a significant impact on flower production, fruit, and seed set. An increase in male flower production due to the increment in the crown is a mechanism of reproductive assurance as a pollen donor and pollinator recipient and also due to the differential cost of expenditure of reproduction in crown layers. Andromonoecy in A. indica promotes self-incompatibility, and there was a tapering trend of reproductive success in the crown layers. Full article

We investigated reproductive behavior and sexual patterns in two odacid fish—Rainbow cale Heteroscarus acroptilus and Herring cale Olisthops cyanomelas—inhabiting temperate reefs in Australia on the basis of underwater observations and histological studies. The males of both species established a territory and continuously courted females they encountered in the territory. The males and females went up in the water column to release gametes in pairs. We found ovarian cavities in the gonadal tissue of H. acroptilus males, suggesting that protogynous sex change occurred in this species. Dichromatism is reported in O. cyanomelas, with males having a dark blue body color while females have a brown body color; however, we found small mature males also included among brown individuals. Furthermore, we diagnosed O. cyanomelas with gonochorism, which is rare in closely related labrids. We compared the similarities and differences in reproductive behavior and sexual patterns between the two species and with labrids. Full article

The lack of data on the age, growth, and reproduction of the Atlantic Goliath Grouper Epinephelus itajara off the coasts of Florida (USA) makes it difficult to estimate the extent of their population recovery following the 1990 fishery closure, as well as the potential effects of the recent (2023) opening of a fishery for juveniles. Goliath Grouper from the Atlantic coast of Florida were non-lethally sampled for size (total length, TL), age (via fin rays), and sex and reproductive stage (via gonad biopsies, milt/egg expression, gonopores) from May to October 2010–2016. Of 653 unique fish captured (not including 118 recaptures), 257 (39.4%) were females (122–228 cm TL; 5–20 years old), 264 (40.0%) were males (104–225 cm TL; 4–22 years old), 100 (15.3%) were unsexed (82–211 cm TL; 3–15 years old), and 32 (4.9%) were protogynous hermaphrodites (108–209 cm TL; 5–20 years old). Protogyny was conclusively determined in two fish recaptured and re-biopsied that had transitioned from female to male. However, an overlap in the age and size of males and females, a 1:1 sex ratio, and the presence of relatively small, young, mature males, in combination with an apparently low functional sex change rate, all indicated that the sexual pattern of Goliath Grouper was functionally gonochoristic with the potential for diandric protogyny. Females > 10 years old were larger-at-age than males, and Goliath Grouper from the Atlantic coast were larger-at-age than fish from the Gulf of Mexico. These differences in age, growth, and reproductive strategy—as well as the nascent fishery for juveniles—need to be monitored closely so that the current and future reproductive capacity of the population continues to ensure growth and sustainability. Full article

Cyclocarya paliurus is an important medical plant owing to the diverse bioactive compounds in its leaves. However, the heterodichogamy with female and male functions segregation within protandry (PA) or protogyny (PG) may greatly affect seed quality and its plantations for medicinal use. To speculate on the factor playing the dominant role in regulating heterodichogamy in C. paliurus, based on phenotypic observations, our study performed a multi comparison transcriptome analysis on female and male buds (PG and PA types) using RNA-seq. For the female and male bud comparisons, a total of 6753 differentially expressed genes (DEGs) were detected. In addition, functional analysis revealed that these DEGs were significantly enriched in floral development, hormone, and GA-related pathways. As the dominant hormones responsible for floral differentiation and development, gibberellins (GAs) in floral buds from PG and PA types were quantified using HPLC-MS. Among the tested GAs, GA₃ positively regulated the physiological differentiation (S0) and germination (S2) of floral buds. The dynamic changes of GA₃ content and floral morphological features were consistent with the expression levels of GA-related genes. Divergences of GA₃ contents at S0 triggered the asynchronism of physiological differentiation between male and female buds of intramorphs (PA-M vs. PA-F and PG-F vs. PG-M). A significant difference in GA₃ content enlarged this asynchronism at S2. Thus, we speculate that GA₃ plays the dominant role in the formation of heterodichogamy in C. paliurus. Meanwhile, the expression patterns of GA-related DEGs, including CPS, KO, GA20ox, GA2_OX, GID1, and DELLA genes, which play central roles in regulating flower development, coincided with heterodichogamous characteristics. These results support our speculations well, which should be further confirmed. Full article

17α-Methyltestosterone (MT) is a synthetic steroid that has been widely used to masculinize many fish species when administered early during larval development, however, reports on its efficacy on adults is limited. To this end, this study investigated the efficacy of MT in the masculinization of the eastern mosquitofish (G. holbrooki) at two adult stages (maiden and repeat gravid females). The treated females were fed control or respective MT incorporated feed (0–200 mg/kg diet) for 50 days. Effects of the hormone on secondary sexual characteristics, internal gonad morphology, expression of the Anti-Müllerian Hormone (amh) gene and sexual behavior of the treated females were investigated. The results showed that MT at the dose of 50 mg/kg feed stimulated secondary sexual character development, upregulated expression of amh, formation of testicular tissue and a shift in the behavior similar to those of normal males, prominently so in treated maiden gravid females. Post-treatment, long-term observations indicated that only two masculinized females reverted back to being females and gave birth to young. Induction of masculinizing effects in most individuals suggests that the sexual phenotype of this species appears to be highly plastic with potential to sex reverse at adulthood. This in combination with its small size and short reproductive cycle could provide an ideal system to explore the mechanisms of sequential hermaphroditism in fish and contribute to genetic control of this pest fish. Full article

Cyclocarya paliurus (Batal.) Iljinskaja, a unique species growing in southern China, is a multi-function tree species with medicinal, healthcare, material, and ornamental values. So far, sexual reproduction is the main method for extensive cultivation of C. paliurus plantations, but this is limited by low seed plumpness resulted from the character of heterodichogamy. Phenological observations have revealed the asynchronism of flower development in this species. However, its molecular mechanism remains largely unknown. To reveal molecular mechanism of heterodichogamy in C. paliurus, transcriptome of female (F) and male (M) buds from two mating types (protandry, PA; protogyny, PG) at bud break stage were sequenced using Illumina Hiseq 4000 platform. The expression patterns of both 32 genes related to flowering and 58 differentially expressed transcription factors (DETFs) selected from 6 families were divided four groups (PG-F, PG-M, PA-F, and PA-M) into two categories: first flowers (PG-F and PA-M) and later flowers (PA-F and PG-M). The results indicated that genes related to plant hormones (IAA, ABA, and GA) synthesis and response, glucose metabolism, and transcription factors (especially in MIKC family) played significant roles in regulating asynchronism of male and female flowers in the same mating type. The expression of DETFs showed two patterns. One contained DETFs up-regulated in first flowers in comparison to later flowers, and the other was the reverse. Nine genes related to flowering were selected for qRT-PCR to confirm the accuracy of RNA-seq, and generally, the RPKM values of these genes were consistent with the result of qRT-PCR. The results of this work could improve our understanding in asynchronism of floral development within one mating type in C. paliurus at transcriptional level, as well as lay a foundation for further study in heterodichogamous plants. Full article

Research Highlights: Cyclocarya paliurus, native to the subtropical region of China, is a monoecious species with a heterodichogamous mating system. Its flowering phenology and low seed success characteristics differ from other typical heterodichogamous Juglandaceae species. This could be caused by the existence of polyploidy in the population. Background and Objectives: C. paliurus has been attracting more attention as a result of its medicinal value. To meet the needs for leaf harvest, cultivation expansion is required, but this is limited by a shortage of seeds. This study aims to profile the flowering phenology and the efficacy of pollen dispersal as well as elucidate on the mechanism of low seed success in the population. Materials and Methods: The flowering phenology pattern of C. paliurus was observed in a juvenile plantation containing 835 individuals of 53 families from 8 provenances at the individual (protandry, PA and protogyny, PG) and population levels for 5 consecutive years (2014–2018). Slides with a culture medium of 10% sucrose and 0.01% boric acid were used to estimate pollen density and viability in the population, and seeds were collected from 20 randomly selected PA and PG individuals to assess seed success during 2017–2018. Results: Four flowering phenotypes and strongly skewed ratios of PA/PG and male/female occurred in the juvenile population. Sexual type and ratio changed significantly with the growth of the population over the years, showing an increasing monoecious group (11.1% to 57.2%) and a decreasing unisexual group (33.6% to 16.3%), as well as a tendency for the sexual ratio to move towards equilibrium (5.42:1 to 1.39:1 for PG:PA). Two flowering phases and bimodality in gender were displayed, as in other heterodichogamous species. However, the high overlap of inter-phases and within individuals was quite different from many previous reports. Owing to the low pollen viability of C. paliurus (~30%), low seed success was monitored in the plantation, as well as in the investigated natural populations. Conclusions: Female-bias (PG and F) and a skewed ratio of mating types corresponded to nutrient accumulation in the juvenile population. Heterodichogamy in C. paliurus was verified, but was shown to be different from other documented species in Juglandaceae. The latest finding of major tetraploidy in a natural population could explain the characteristics of the flowering phenology and seed set of C. paliurus and also give rise to more questions to be answered. Full article