Core circadian clock and light signalling genes brought into genetic linkage across the green lineage

The circadian clock ensures that biological processes are phased to the correct time of day. In plants the circadian clock is conserved at both the level of transcriptional networks as well as core genes. In the model plant Arabidopsis thaliana, the core circadian singleMYB (sMYB) genes CCA1 and RVE4 are in genetic linkage with the PSEUDO-RESPONSE REGULATOR (PRR) genes PRR9 and PRR7 respectively. Leveraging chromosome-resolved plant genomes and syntenic ortholog analysis it was possible to trace this genetic linkage back to the basal angiosperm Amborella and identify an additional evolutionarily conserved genetic linkage between PIF3 and PHYA. The LHY/CCA1-PRR5/9, RVE4/8-PRR3/7 and PIF3-PHYA genetic linkages emerged in the bryophyte lineage and progressively moved within several genes of each other across an array of higher plant families representing distinct whole genome duplication and fractionation events. Soybean maintains all but two genetic linkages, and expression analysis revealed the PIF3-PHYA linkage overlapping with the E4 maturity group locus was the only pair to robustly cycle with an evening phase in contrast to the sMYB-PRR morning and midday phase. While most monocots maintain the genetic linkages, they have been lost in the economically important grasses (Poaceae) such as maize where the genes have been fractionated to separate chromosomes and presence/absence variation results in the segregation of PRR7 paralogs across heterotic groups. The evolutionary conservation of the genetic linkage as well as its loss in the grasses provides new insight in the plant circadian clock, which has been a critical target of breeding and domestication.

Attachment and politics are two functionally distinct systems, and both share genetics with interpersonal trust and altruism

The evolved attachment system maintains proximity and care-giving behavior between parents and offspring, in a way that is argued to shape people’s mental models of how relationships work, resulting in secure, anxious or avoidant interpersonal styles. Several theorists have suggested that the attachment system is closely connected to orientations and behaviors in social and political domains, such that the latter are grounded in the same set of familial experiences as are the different attachment styles. We use a large sample of Norwegian twins (N = 1987) to assess the relationship between attachment styles and two key ideological orientations, right-wing authoritarianism (RWA) and social dominance orientation (SDO), and the role of genetic and environmental influences therein. We also consider the relationship of both sets of traits with the interpersonal orientations of trust and altruism. Results indicate no shared environmental overlap between attachment and ideology, nor even between the two attachment styles or between the two ideological traits, challenging conventional wisdom in developmental, social, and political psychology. Rather, evidence supports two functionally distinct systems, one for navigating intimate relationships and one for navigating social hierarchies, with genetic overlap between traits within each system, and two distinct genetic linkages to trust and altruism. We argue for further genetically informed research in other settings to elucidate the etiology and dynamics of these core aspects of our social and political nature.

Novel CRISPR/Cas applications in plants: from prime editing to chromosome engineering

In the last years, tremendous progress has been made in the development of CRISPR/Cas-mediated genome editing tools. A number of natural CRISPR/Cas nuclease variants have been characterized. Engineered Cas proteins have been developed to minimize PAM restrictions, off-side effects and temperature sensitivity. Both kinds of enzymes have, by now, been applied widely and efficiently in many plant species to generate either single or multiple mutations at the desired loci by multiplexing. In addition to DSB-induced mutagenesis, specifically designed CRISPR/Cas systems allow more precise gene editing, resulting not only in random mutations but also in predefined changes. Applications in plants include gene targeting by homologous recombination, base editing and, more recently, prime editing. We will evaluate these different technologies for their prospects and practical applicability in plants. In addition, we will discuss a novel application of the Cas9 nuclease in plants, enabling the induction of heritable chromosomal rearrangements, such as inversions and translocations. This technique will make it possible to change genetic linkages in a programmed way and add another level of genome engineering to the toolbox of plant breeding. Also, strategies for tissue culture free genome editing were developed, which might be helpful to overcome the transformation bottlenecks in many crops. All in all, the recent advances of CRISPR/Cas technology will help agriculture to address the challenges of the twenty-first century related to global warming, pollution and the resulting food shortage.

Cytogenetic characterisation and chromosomal mapping of microsatellite and telomeric repeats in two gecko species (Reptilia, Gekkonidae) from Thailand

Studies of chromosomes of Cyrtodactylus jarujini Ulber, 1993 and C. doisuthep Kunya et al., 2014 to compare microsatellite and TTAGGG sequences by classical and molecular techniques were conducted in Thailand. Karyological typing from a conventional staining technique of C. jarujini and C. doisuthep showed diploid chromosome numbers of 40 and 34 while the Fundamental Numbers (NF) were 56 in both species. In addition, we created the chromosome formula of the chromosomes of C. jarujini showing that 2n (40) = Lsm1 + Lsm2 + Lt3 + Mm1 + Mt4 + Sm2 + Sa2 + St5 while that of C. doisuthep was 2n (34) = Lsm3 + Lm2 + Lt3 + Mm1 + Mt2 + Sm4 + Sa1 + St1. Ag-NOR staining revealed NOR-bearing chromosomes in chromosome pairs 13 and 14 in C. jarujini, and in chromosome pairs 9 and 13 in C. doisuthep. This molecular study used the FISH technique, as well as microsatellite probes including (A)20, (TA)15, (CGG)10, (CGG)10, (GAA)10, (TA)15 and TTAGGG repeats. The signals showed that the different patterns in each chromosome of the Gekkonids depended on probe types. TTAGGG repeats showed high distribution on centromere and telomere regions, while (A)20, (TA)15, (CGG)10, (CGG)10, (GAA)10 and (TA)15 bearing dispersed over the whole genomes including chromosomes and some had strong signals on only a pair of homologous chromosomes. These results suggest that the genetic linkages have been highly differentiated between the two species.

Cytogenetic characterisation and chromosomal mapping of microsatellite and telomeric repeats in two gecko species (Reptilia, Gekkonidae) from Thailand

Studies of chromosomes of Cyrtodactylus jarujini Ulber, 1993 and C. doisuthep Kunya et al., 2014 to compare microsatellite and TTAGGG sequences by classical and molecular techniques were conducted in Thailand. Karyological typing from a conventional staining technique of C. jarujini and C. doisuthep showed diploid chromosome numbers of 40 and 34 while the Fundamental Numbers (NF) were 56 in both species. In addition, we created the chromosome formula of the chromosomes of C. jarujini showing that 2n (40) = Lsm1 + Lsm2 + Lt3 + Mm1 + Mt4 + Sm2 + Sa2 + St5 while that of C. doisuthep was 2n (34) = Lsm3 + Lm2 + Lt3 + Mm1 + Mt2 + Sm4 + Sa1 + St1. Ag-NOR staining revealed NOR-bearing chromosomes in chromosome pairs 13 and 14 in C. jarujini, and in chromosome pairs 9 and 13 in C. doisuthep. This molecular study used the FISH technique, as well as microsatellite probes including (A)20, (TA)15, (CGG)10, (CGG)10, (GAA)10, (TA)15 and TTAGGG repeats. The signals showed that the different patterns in each chromosome of the Gekkonids depended on probe types. TTAGGG repeats showed high distribution on centromere and telomere regions, while (A)20, (TA)15, (CGG)10, (CGG)10, (GAA)10 and (TA)15 bearing dispersed over the whole genomes including chromosomes and some had strong signals on only a pair of homologous chromosomes. These results suggest that the genetic linkages have been highly differentiated between the two species.

CRISPR/Cas-mediated chromosome engineering: opening up a new avenue for plant breeding

The advent of powerful site-specific nucleases, particularly the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) system, which enables precise genome manipulation, has revolutionized plant breeding. Until recently, the main focus of researchers has been to simply knock-in or knock-out single genes, or to induce single base changes, but constant improvements of this technology have enabled more ambitious applications that aim to improve plant productivity or other desirable traits. One long-standing aim has been the induction of targeted chromosomal rearrangements (crossovers, inversions, or translocations). The feasibility of this technique has the potential to transform plant breeding, because natural rearrangements, like inversions, for example, typically present obstacles to the breeding process. In this way, genetic linkages between traits could be altered to combine or separate favorable and deleterious genes, respectively. In this review, we discuss recent breakthroughs in the field of chromosome engineering in plants and their potential applications in the field of plant breeding. In the future, these approaches might be applicable in shaping plant chromosomes in a directed manner, based on plant breeding needs.

Genomic Epidemiology of Clostridioides difficile Sequence Types 1 and 2 Across Three US Medical Centers

Background:Clostridioides difficile is a toxin-producing bacterium that is the foremost cause of healthcare-associated diarrhea in the United States. Recent epidemiologic and genomic evidence indicates that divergent C. difficile strains have varying propensities for transmission within healthcare settings. We investigated whether and how these differences are reflected in the genomic epidemiology of 2 common C. difficile strains—sequence type (ST) 1 (analogous to Ribotype 027) and ST2 (associated with Ribotypes 014/020)—across 3 geographically distinct US medical centers. Methods: Between 2011 and 2017, a convenience sample of ST1 and ST2 C. difficile clinical isolates were collected from 3 US sites: The University of Michigan Medical Center, Texas Medical Center Hospitals, and Memorial Sloan Kettering Cancer Center. Isolates underwent whole-genome sequencing and in silico multilocus sequence typing to verify strain types. Sequences were mapped to ST1 and ST2 reference genomes and single nucleotide variants (SNVs) were identified, filtered, and used to construct pairwise SNV distance matrices. A range of pairwise SNV distance thresholds were applied to assess genetic linkages consistent with recent transmission within ST1 compared to within ST2. Proportions of genetically linked isolates were compared using 2 tests. Results: We identified 200 ST1 and 188 ST2 isolates across the 3 collection sites. Overall, ST2 was more genetically diverse than ST1 (pairwise SNV distance range, 0–156 SNVs and 0–78 SNVs, respectively). ST2 isolates displayed significantly less evidence of recent transmission: 10 ST2 isolates (5.3%) were within 2 SNVs of another isolate compared to 88 (44%) ST1 isolates (P .001) (Fig. 1). As the SNV threshold increased to 5 and 10 SNVs, this trend was maintained (all P < .001). ST2 isolates were also more likely to be genetically linked to an isolate from a different collection site than ST1 isolates. Among isolates with genetic links to at least 1 other isolate at the 5 SNV and 10 SNV thresholds, 21 of 37 and 74 of 89 ST2 isolates (57%, 83%) were linked to an isolate from a different collection site, compared to 2 of 88 and 48 of 157 ST1 isolates (2% and 31%, respectively; both P < .001). Conclusions: Compared to C. difficile ST1 isolates, ST2 isolates displayed less evidence of recent healthcare transmission and were more likely to be genetically linked to isolates from divergent collection sites. Interpreting genetic linkages among C. difficile isolates requires an understanding of regional and strain-specific genetic diversity to avoid misattribution of genetic linkages to recent transmission.Funding: NoneDisclosures: None

Positive selection alone is sufficient for whole genome differentiation at the early stage of speciation process in the fall armyworm

Background: The process of speciation inherently involves the transition from genetic to genomic differentiation. In the absence of a geographic barrier, the whole genome differentiation may occur only when the homogenizing effect of recombination is overcome across the whole genome. The fall armyworm is observed as two sympatric strains with different host-plant preferences across the entire habitat. These two strains exhibit a very low level of genetic differentiation across the whole genome, suggesting that whole genome differentiation occurred at an early stage of speciation. In this study, we aim at identifying critical evolutionary forces responsible for the whole genome differentiation in the fall armyworm. Results: We found that these two strains exhibit a low level of genomic differentiation (Fst = 0.0176), while 91.3% of 10kb windows have genetically differentiated sequences (Fst > 0). We observed that a genomic reduction in migration rate due to combined effects of mild positive selection and genetic linkages to selectively targeted loci are responsible for the whole genome differentiation. Phylogenetic analysis shows that positive selection generates the whole genome differentiation by sub-setting of variants in one strain from the other. Conclusions: From these results, we concluded that positive selection alone is sufficient for whole genome differentiation during the process of speciation. This study demonstrates that the propensity of adaptation alone determines the speciation events, suggesting that adaptive evolution is a single critical driving force for species diversity.

Temperament gene inheritance

This article is published in Elsevier Meta Gene in September 2020 https://doi.org/10.1016/j.mgene.2020.100728 A temperament gene and its inheritance mechanisms have never been academically addressed. In this study we have tried to explain a genetic basis of a temperament inheritance mode; temperament is regularly inherited by the son from the mother and by the daughter from the father. Such a transmission mode corresponds to the X chromosome-linked inheritance and indicates that a temperament gene locus is on the X chromosome. Here we show that most probable temperament gene candidate is the VAMP7 gene of Xq PAR; besides its role in neuritogenesis, a relationship was proposed between the outward migration mode of the VAMP7 mediated vesicles, the female paternal temperament allele preservation in the secondary oocyte/ovum, and its transmission to the next generation. We have eliminated 113 temperament gene candidates in the distal Xq region, due to their mRNA numbers, expression in the brain and ovary, accordance to our proposed inheritance mode of a silent temperament allele, and genetic linkages.