Probing the floral developmental stages, bisexuality and sex reversions in castor (Ricinus communis L.)

Castor (Ricinus communis L) is an ideal model species for sex mechanism studies in monoecious angiosperms, due to wide variations in sex expression. Sex reversion to monoecy in pistillate lines, along with labile sex expression, negatively influences hybrid seed purity. The study focuses on understanding the mechanisms of unisexual flower development, sex reversions and sex variations in castor, using various genotypes with distinct sex expression pattern. Male and female flowers had 8 and 12 developmental stages respectively, were morphologically similar till stage 4, with an intermediate bisexual state and were intermediate between type 1 and type 2 flowers. Pistil abortion was earlier than stamen inhibition. Sex alterations occurred at floral and inflorescence level. While sex-reversion was unidirectional towards maleness via bisexual stage, at high day temperatures (Tmax > 38 °C), femaleness was restored with subsequent drop in temperatures. Temperature existing for 2–3 weeks during floral meristem development, influences sexuality of the flower. We report for first time that unisexuality is preceded by bisexuality in castor flowers which alters with genotype and temperature, and sex reversions as well as high sexual polymorphisms in castor are due to alterations in floral developmental pathways. Differentially expressed (male-abundant or male-specific) genes Short chain dehydrogenase reductase 2a (SDR) and WUSCHEL are possibly involved in sex determination of castor.

Rad21l1 cohesin subunit is dispensable for spermatogenesis but not oogenesis in zebrafish

Meiosis produces haploid gametes that will give rise to the next diploid generation. Chromosome segregation errors occurring at one or both meiotic divisions result in aneuploidy, which can lead to miscarriages or birth defects in humans. During meiosis I, ring-shaped cohesin complexes play important roles to aid in the proper segregation of homologous chromosomes. While REC8 is a specialized meiosis-specific cohesin that functions to hold sister chromatids together, the role of its vertebrate-specific paralog, RAD21L, is poorly understood. Here we tested if Rad21l1, the zebrafish homolog of human and mouse RAD21L, is required for meiotic chromosome dynamics during oogenesis and spermatogenesis. We found that Rad21l1 is an abundant component of meiotic chromosomes where it localizes to both the chromosome axes and the transverse filament of the synaptonemal complex (SC). Knocking out rad21l1 causes nearly the entire mutant population to develop as fertile males, suggesting the mutation triggers a sex reversal from female to male due to a failure in oocyte production. The rad21l1−/− mutant males display normal fertility at sexual maturity. Sex reversal was partially suppressed in the absence of tp53, suggesting that the rad21l1−/− mutation causes defects leading to a Tp53 dependent response, specifically in females. The rad21l1−/−;tp53−/− double mutant females produced elevated rates of decomposing eggs and deformed offspring compared to tp53−/− controls. This response, however, is not linked to a defect in repairing Spo11-induced double-strand breaks since deletion of Spo11 does not suppress the sex reversal phenotype. Overall, our data highlight an exceptional sexually dimorphic phenotype caused by knocking out a meiotic-specific cohesin subunit. We propose that Rad21l1 is required for maintaining the integrity of meiotic chromatin architecture during oogenesis.Author SummaryA prominent symptom of age-linked reproductive decline in women is the increased rate of miscarriage and birth defects due to aneuploidy. Aneuploidy can arise when chromosomes fail to segregate properly during meiosis, the process of creating haploid gametes from a diploid germ cell. Oocyte progression normally arrests prior to anaphase I, after homologous chromosomes have formed crossovers, but before ovulation, which triggers the first round of segregation. This prolonged arrest makes oocytes especially vulnerable to degradation of meiotic chromosome structure and homolog connections over time. Cohesin complexes play a major role in maintaining the meiotic chromosome architecture. Here we assess the role of the vertebrate-specific Rad21l1 cohesin subunit in zebrafish. We find that while males appear mostly unaffected by loss of Rad21l1, oocyte production is massively compromised, leading to sex reversion to males. Sex reversion can be partially prevented in the absence of Tp53, demonstrating that loss or Rad21l1 leads to a Tp53-dependent response in oocytes. Strikingly, double mutant rad21l1 tp53 females produce large numbers of poor quality eggs and malformed offspring. This demonstrates a cohesin-linked vulnerability in female meiosis not present in males and sheds light on a potential mechanism associated with the decline in female reproductive health.

Possibilities of HRT in solving the problem of psychosocial adaptation of girls with primary estrogen deficiency

This study presents the results of testing the hypothesis that girls during the period of normally proceeding puberty experience much more emotional discomfort, difficulties in communication and self-acceptance due to more pronounced hormonal and bodily changes than normally developing boys. Along with this, for the first time, results are presented that indicate some similarity of adaptive responses in boys with normal puberty and in girls with primary estrogen deficiency on the background of hormone replacement therapy (HRT). The development of girls with 450-gonadal dysgenesis (with Turner syndrome) on the background of HRT is considered as adaptive to the tasks of age, less than their passport data. Girls with XY-sex reversion with gonadal dysgenesis are assessed as sufficiently adapted due to certain personal and age characteristics.