Cytokinin signalling regulates two-stage inflorescence arrest in Arabidopsis

To maximise their reproductive success, flowering plants must correctly time their entry into and exit from the reproductive phase (flowering). While much is known about the mechanisms that regulate the initiation of flowering, the regulation of end-of-flowering remains largely uncharacterised. End-of-flowering in Arabidopsis thaliana consists of the quasi-synchronous arrest of individual inflorescences, but it is unclear how this arrest is correctly timed with respect to environmental stimuli and ongoing reproductive success. Here we show that Arabidopsis inflorescence arrest is a complex developmental phenomenon which includes a decline in size and cessation of activity in the inflorescence meristem (IM), coupled with a separable developmental arrest in all unopened floral primordia (floral arrest); these events occur well before the visible arrest of the inflorescence. We show that global removal of inflorescences can delay both IM arrest and floral arrest, but that local fruit removal only delays floral arrest, emphasising the separability of these processes. We test a role for cytokinin in regulating inflorescence arrest, and find that cytokinin treatment can delay arrest. We further show that gain-of-function cytokinin receptor hypersensitive mutants can delay floral arrest, and also IM arrest, depending on the expression pattern of the receptor; conversely, loss-of-function mutants prevent extension of flowering in response to inflorescence removal. Collectively, our data suggest that the dilution of cytokinin among an increasing number of sink organs leads to end-of-flowering in Arabidopsis by triggering IM and floral arrest, conversely meaning that a lack of reproductive success can homeostatically extend flowering in compensation.

A standardized approach for case selection and genomic data analysis of maternal exomes for the diagnosis of oocyte maturation and early embryonic developmental arrest in IVF

ABSTRACTOBJECTIVETo develop a methodology for case selection and whole-exome sequencing (WES) analysis in infertile women due to recurrent oocyte maturation defects(OOMD) and/or preimplantation embryo lethality (PREMBL).DESIGNRetrospective cohort study.SETTINGIVF patients attending the Istanbul Memorial Hospital (2015-2021). WES and bioinformatics were performed at Igenomix and National Research Council, Italy.PATIENTSA statistical methodology for identification of infertile endophenotypes (recurrent low oocyte maturation rate, LMR, low fertilization rate, LFR, and preimplantation developmental arrest, PDA, was developed using a large IVF dataset (11,221 couples). 28 OOMD/PREMBL infertile women were subsequently enrolled for WES.INTERVENTION30X-WES was performed on women’s gDNA. Pathogenic variants were prioritized using a custom-made bioinformatic pipeline set to minimize false positive discoveries through resampling in control cohorts (i.e., HGDP and 1,343 WES from oocyte donors). Individual scRNAseq data from 18 human MII oocytes and antral granulosa cells(AGC) was used for genome-wide validation.MAIN OUTCOME MEASUREIdentification of High-impact variants causative of OOMD/PREMBL endophenotypes.RESULTSVariant prioritization analysis identified 265 unique variants in 248 genes (average per sample 22.4). 87.8% of genes harbouring high-impact variants are expressed by MII oocytes and/or AGC, significantly higher compared to a random sample of controls. Seven of the 28 women (25%) are homozygous carriers of missense pathogenic variants in known candidate genes for OOMD/PREMBL, including PATL2, NLRP5 (N=2), TLE6,PADI6, TUBB8 and TRIP13. Furthermore, novel gene-disease associations were identified. One LMR woman was a homozygous carrier of high impact variants in ELSA, an essential gene for phopase I meiotic transition in mice, whereas three women carried biallelic pathogenic variants in CEP128 gene, participating in the formation of the spindle in mitosis and ciliogenesis.CONCLUSIONSThis analytical framework revealed known and new genes associated with isolated recurrent OOMD/PREMBL, providing essential indications for scaling this strategy to larger studies.

Activity of terpenes derived from essential oils against Sarcoptes scabiei eggs

Background The limited ovicidal activity of currently available acaricides is a significant obstacle to efficacious scabies treatment. Several essential oils or their respective components have proved to be active against the eggs of arthropods, mainly lice and ticks. Information on the activity of these oils and/or components against the eggs of mites remains very limited. The aim of this study was to assess the activity of six terpenes (carvacrol, eugenol, geraniol, citral, terpinen-4-ol and linalool) commonly found in essential oils against the eggs of Sarcoptes scabiei. Methods Sarcoptes eggs were exposed to paraffin oil containing 1, 2.5, or 5% of each terpene tested. After a 12-h exposure period, the eggs were washed and placed in paraffin oil for hatching. Embryonic development following treatment was assessed every day to determine the stage of developmental arrest. Results The median effective concentration to obtain 50% egg mortality (EC50) was 0.5, 0.9, 2.0, 4.8, 5.1 and 9.8% for carvacrol, eugenol, geraniol, citral, terpinen-4-ol and linalool, respectively. The microscopic images of eggs after each treatment indicated that these six terpenes may act by penetrating through the aeropyles on the egg surface. Conclusions In conclusion, carvacrol, eugenol and geraniol possess significant ovicidal activities, which should be considered as promising ovicidal agents for the treatment of scabies. Graphical Abstract

VpreB Surrogate Light Chain Expression in B-Lineage ALL: A Report from the Children's Oncology Group

Immunotherapies directed against B-cell surface markers have been a common developmental strategy to treat B-cell malignancies. The IgH surrogate light chain (SLC), comprised of the VpreB1 (CD179a) and Lamda5 (CD179b) subunits is expressed on pro- and pre-B cells where it governs preBCR-mediated autonomous survival signaling. We hypothesized that the pre-BCR might merit the development of targeted immunotherapies to decouple "autonomous" signaling in B-lineage acute lymphoblastic leukemia (B-ALL). We used the COG minimal residual disease (MRD) flow panel to assess pre-BCR expression in 36 primary patient samples accrued to COG standard and high-risk B-ALL studies through AALL03B1. We also assessed CD179a expression in 16 cases with Day 29 end-induction samples, pre-selected to have ≥1% MRD. All analyses were performed on a 6-color Becton-Dickinson flow cytometer in a CLIA/CAP-certified laboratory. Among 36 cases tested, thirty-two were at the pre-B and four were at the pro-B stages of developmental arrest. One or both mAbs showed that CD179a was present in ≥20% of the B-lymphoblast population. All cases expressed CD179a in the end-induction B-lymphoblast population. The CD179a component of the SLC is commonly expressed in B-ALL, regardless of genotype, stage of developmental arrest or NCI risk-status.

Hormonal Regulation of Diapause and Development in Nematodes, Insects, and Fishes

Diapause is a state of developmental arrest adopted in response to or in anticipation of environmental conditions that are unfavorable for growth. In many cases, diapause is facultative, such that animals may undergo either a diapause or a non-diapause developmental trajectory, depending on environmental cues. Diapause is characterized by enhanced stress resistance, reduced metabolism, and increased longevity. The ability to postpone reproduction until suitable conditions are found is important to the survival of many animals, and both vertebrate and invertebrate species can undergo diapause. The decision to enter diapause occurs at the level of the whole animal, and thus hormonal signaling pathways are common regulators of the diapause decision. Unlike other types of developmental arrest, diapause is programmed, such that the diapause developmental trajectory includes a pre-diapause preparatory phase, diapause itself, recovery from diapause, and post-diapause development. Therefore, developmental pathways are profoundly affected by diapause. Here, I review two conserved hormonal pathways, insulin/IGF signaling (IIS) and nuclear hormone receptor signaling (NHR), and their role in regulating diapause across three animal phyla. Specifically, the species reviewed are Austrofundulus limnaeus and Nothobranchius furzeri annual killifishes, Caenorhabditis elegans nematodes, and insect species including Drosophila melanogaster, Culex pipiens, and Bombyx mori. In addition, the developmental changes that occur as a result of diapause are discussed, with a focus on how IIS and NHR pathways interact with core developmental pathways in C. elegans larvae that undergo diapause.

Wenshen Shengjing Decoction Improves Early Embryo Development by Maintaining Low H3K27me3 Levels in Sperm and Pronuclear Embryos of Spermatogenesis Impaired Mice

Many ingredients in Wenshen Shengjing Decoction (WSSJD) can cause epigenetic changes in the development of different types of cells. It is not yet known whether they can cause epigenetic changes in sperms or early embryos. Here, we investigated the role of WSSJD in epigenetic modifications of sperms or early embryos and early embryo development. A mouse model with spermatogenesis disorders was established with cyclophosphamide (CPA). WSSJD was administrated for 30 days. The male model mice after the treatment were mated with the female mice treated with superovulation. The embryo development rate of each stage was calculated. Immunofluorescence staining was used to detect the expression of H3K27me3 in sperm, pronuclear embryos, and 2-cell embryos. Western blotting was used to detect the expression of histone demethylase KDM6A and methyltransferase EZH2 in 2-cell embryos with developmental arrest. The expressions of zygotic genome activation genes (ZSCAN4, E1F1AX, HSPA1A, ERV4-2, and MYC) in 2-cell embryos with developmental arrest were analyzed with qRT-PCR. Comparing with the control group, CPA destroyed the development of seminiferous epithelium, significantly increased the expression level of H3K27me3 in sperm, reduced the expression ratio of H3K27me3 in female and male pronuclei, delayed the development of 2-cell embryos, and increased the developmental arrest rate and degeneration rate of 2-cell embryos. Moreover, the expressions of EZH2 and H3K27me3 were significantly increased in the 2-cell embryos with developmental arrest, and the expression of zygotic genome activation genes (ZSCAN4, E1F1AX, HSPA1A, ERV4-2, and MYC) was significantly decreased. Compared with the CPA group, WSSJD promoted the development of seminiferous epithelium, maintained a low level of H3K27me3 modification in sperm and male pronucleus, significantly increased the development rate of 2-cell embryos and 3-4 cell embryos, and reduced the developmental arrest rate and degeneration rate of 2-cell embryos. WSSJD may promote early embryonic development by maintaining a low level of H3K27me3 modification in sperm and male pronucleus and regulating the zygotic genome activation in mice with spermatogenesis disorders induced by CPA.

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.

Overexpression of Douglas-Fir LEAFY COTYLEDON1 (PmLEC1) in Arabidopsis Induces Embryonic Programs and Embryo-Like Structures in the lec1-1 Mutant but Not in Wild Type Plants

Somatic embryogenesis (SE) is the most promising method for the quick propagation of desirable plant genotypes. However, application of SE to conifers remains challenging due to our limited knowledge about the genes involved in embryogenesis and the processes that lead to somatic embryo formation. Douglas-fir, an economically important lumber species, possesses a homolog of the angiosperm embryo-regulatory LEC1 gene. In the present study, we analyzed the potential of Douglas-fir PmLEC1 to induce embryonic programs in the vegetative cells of a heterologous host, Arabidopsis thaliana. PmLEC1 complemented the Arabidopsis lec1-1 null mutant and led to a variety of phenotypes ranging from normal morphology to developmental arrest at various stages in the T1 generation. PmLEC1 did not affect the morphology of wild type Arabidopsis T1 plants. More profound results occurred in T2 generations. PmLEC1 expression induced formation of recurrent somatic embryo-like structures in vegetative tissues of the rescued lec1-1 mutant but loss of apical dominance (bushy phenotype) in wild type plants. The activation of embryonic programs in the lec1-1PmLEC1 T2 plants was confirmed by the presence of the embryo-specific transcripts, OLEOSIN and CRUCIFERIN. In contrast, no embryo-like structures, and no OLEOSIN or CRUCIFERIN were observed in PmLEC1-expressing bushy wild type T2 plants.