LEAFY and WAPO1 jointly regulate spikelet number per spike and floret development in wheat.

In wheat, the transition of the inflorescence meristem to a terminal spikelet (IM→TS) determines the spikelet number per spike (SNS), an important yield component. In this study, we demonstrate that the plant-specific transcription factor LEAFY (LFY) physically and genetically interacts with WHEAT ORTHOLOG OF APO1 (WAPO1) to regulate SNS and floret development. Loss-of-function mutations in either or both genes result in significant and similar reductions in SNS, as a result of a reduction in the rate of spikelet meristem formation per day. SNS is also modulated by significant genetic interactions between LFY and the SQUAMOSA MADS-box genes VRN1 and FUL2, which promote the IM→TS transition. Single-molecule fluorescence in situ hybridization revealed a downregulation of LFY and upregulation of the SQUAMOSA MADS-box genes in the distal part of the developing spike during the IM→TS transition, supporting their opposite roles in the regulation of SNS in wheat. Concurrently, the overlap of LFY and WAPO1 transcription domains in the developing spikelets contributes to normal floret development. Understanding the genetic network regulating SNS is a necessary first step to engineer this important agronomic trait.

The H3K4 demethylase JMJ1 is required for proper timing of flowering in Brachypodium distachyon.

Flowering is a key developmental transition in the plant life cycle. In temperate climates, flowering often occurs in response to the perception of seasonal cues such as changes in day-length and temperature. However, the mechanisms that have evolved to control the timing of flowering in temperate grasses are not fully understood. We identified a Brachypodium distachyon mutant whose flowering is delayed under inductive long-day conditions due to a mutation in the JMJ1 gene, which encodes a Jumonji domain-containing protein. JMJ1 is a histone demethylase that mainly demethylates H3K4me2 and H3K4me3 in vitro and in vivo. Analysis of the genome-wide distribution of H3K4me1, H3K4me2, and H3K4me3 in wild-type plants by chromatin immunoprecipitation and sequencing combined with RNA sequencing revealed that H3K4m1 and H3K4me3 are positively associated with gene transcript levels, whereas H3K4me2 is negatively correlated with transcript levels. Furthermore, JMJ1 directly binds to the chromatin of the flowering regulator genes VRN1 and ID1 and affects their transcription by modifying their H3K4me2 and H3K4me3 levels. Genetic analyses indicated that JMJ1 promotes flowering by activating VRN1 expression. Our study reveals a role for JMJ1-mediated chromatin modification in the proper timing of flowering in B. distachyon.

CO2 Response Screen in Grass Brachypodium Reveals Key Role of a MAP Kinase in CO2-Triggered Stomatal Closure.

Plants respond to increased CO2 concentrations through stomatal closure, which can contribute to increased water use efficiency. Grasses display faster stomatal responses than eudicots due to dumbbell-shaped guard cells flanked by subsidiary cells working in opposition. However, forward genetic screening for stomatal CO2 signal transduction mutants in grasses has yet to be reported. The grass model Brachypodium distachyon is closely related to agronomically important cereal crops, sharing largely collinear genomes. To gain insights into CO2 control mechanisms of stomatal movements in grasses, we developed an unbiased forward genetic screen with an EMS-mutagenized Brachypodium distachyon M5 generation population using infrared imaging to identify plants with altered leaf temperatures at elevated CO2. Among isolated mutants, a "chill1" mutant exhibited cooler leaf temperatures than wildtype Bd21-3 parent control plants after exposure to increased [CO2]. chill1 plants showed strongly impaired high CO2-induced stomatal closure despite retaining a robust abscisic acid-induced stomatal closing response. Through bulked segregant whole-genome-sequencing analyses followed by analyses of further backcrossed F4 generation plants and generation and characterization of sodium-azide and CRISPR-cas9 mutants, chill1 was mapped to a protein kinase, Mitogen-Activated Protein Kinase 5 (BdMPK5). The chill1 mutation impaired BdMPK5 protein-mediated CO2/HCO3- sensing together with the High Temperature 1 (HT1) Raf-like kinase in vitro. Furthermore, AlphaFold2-directed structural modeling predicted that the identified BdMPK5-D90N chill1 mutant residue is located at the interface of BdMPK5 with the BdHT1 Raf-like kinase. BdMPK5 is a key signaling component that mediates CO2-induced stomatal movements and is proposed to function as a component of the primary CO2 sensor in grasses.

Shiga Toxin-Producing Escherichia coli Testing in New York 2011-2022 Reveals Increase in Non-O157 Identifications.

Shiga toxin-producing Escherichia coli (STEC) are an important cause of bacterial enteric infection. STEC strains cause serious human gastrointestinal disease, which may result in life-threatening complications such as hemolytic uremic syndrome. They have the potential to impact public health due to diagnostic challenges of identifying non-O157 strains in the clinical laboratory. The Wadsworth Center (WC), the public health laboratory of the New York State Department of Health, has isolated and identified non-O157 STEC for decades. A shift from initially available enzyme immunoassay testing to culture-independent diagnostic tests (CIDTs) has increased the uptake of testing at clinical microbiology laboratories. This testing change has resulted in an increased number of specimen submissions to WC. During a 12-year period between 2011 and 2022, WC received 5037 broths and/or stool specimens for STEC confirmation from clinical microbiology laboratories. Of these, 3992 were positive for Shiga toxin genes (stx1 and/or stx2) by real-time PCR. Furthermore, culture methods were utilized to isolate, identify, and characterize 2925 STEC from these primary specimens. Notably, WC observed a >200% increase in the number of STEC specimens received in 2021-2022 compared with 2011-2012 and an 18% increase in the number of non-O157 STEC identified using the same methodologies. During the past decade, the WC testing algorithm has been updated to manage the increase in specimens received, while also navigating the novel COVID-19 pandemic, which took priority over other testing for a period of time. This report summarizes updated methods for confirmation, surveillance, and outbreak detection of STEC and describes findings that may be related to our algorithm updates and the increased use of CIDTs, which is starting to elucidate the true incidence of non-O157 STEC.

A microphysiological system for handling graphene related materials under flow conditions.

The field of nanotechnology has developed rapidly in recent decades due to its broad applications in many industrial and biomedical fields. Notably, 2D materials such as graphene-related materials (GRMs) have been extensively explored and, as such, their safety needs to be assessed. However, GRMs tend to deposit quickly, present low stability in aqueous solutions, and adsorb to plastic materials. Consequently, traditional approaches based on static assays facilitate their deposition and adsorption and fail to recreate human physiological conditions. Organ-on-a-chip (OOC) technology could, however, solve these drawbacks and lead to the development of microphysiological systems (MPSs) that mimic the microenvironment present in human tissues. In light of the above, in the present study a microfluidic system under flow conditions has been optimised to minimise graphene oxide (GO) and few-layer graphene (FLG) adsorption and deposition. For that purpose, a kidney-on-a-chip was developed and optimised to evaluate the effects of exposure to GO and FLG flakes at a sublethal dose under fluid flow conditions. In summary, MPSs are an innovative and precise tool for evaluating the effects of exposure to GRMs and other type of nanomaterials.

Polygenic architecture of flowering time and its relationship with local environments in the grass Brachypodium distachyon.

Synchronizing the timing of reproduction with the environment is crucial in the wild. Among the multiple mechanisms, annual plants evolved to sense their environment, the requirement of cold-mediated vernalization is a major process that prevents individuals from flowering during winter. In many annual plants including crops, both a long and short vernalization requirement can be observed within species, resulting in so-called early-(spring) and late-(winter) flowering genotypes. Here, using the grass model Brachypodium distachyon, we explored the link between flowering-time-related traits (vernalization requirement and flowering time), environmental variation, and diversity at flowering-time genes by combining measurements under greenhouse and outdoor conditions. These experiments confirmed that B. distachyon natural accessions display large differences regarding vernalization requirements and ultimately flowering time. We underline significant, albeit quantitative effects of current environmental conditions on flowering-time-related traits. While disentangling the confounding effects of population structure on flowering-time-related traits remains challenging, population genomics analyses indicate that well-characterized flowering-time genes may contribute significantly to flowering-time variation and display signs of polygenic selection. Flowering-time genes, however, do not colocalize with genome-wide association peaks obtained with outdoor measurements, suggesting that additional genetic factors contribute to flowering-time variation in the wild. Altogether, our study fosters our understanding of the polygenic architecture of flowering time in a natural grass system and opens new avenues of research to investigate the gene-by-environment interaction at play for this trait.

Safety and immunogenicity of varied doses of R21/Matrix-M™ vaccine at three years follow-up: A phase 1b age de-escalation, dose-escalation trial in adults, children, and infants in Kilifi-Kenya.

Background: Falciparum malaria remains a global health problem. Two vaccines, based on the circumsporozoite antigen, are available. RTS, S/AS01 was recommended for use in 2021 following the advice of the World Health Organisation (WHO) Strategic Advisory Group of Experts (SAGE) on Immunization and WHO Malaria Policy Advisory Group (MPAG). It has since been pre-qualified in 2022 by the WHO. R21 is similar to RTS, S/AS01, and recently licensed in Nigeria, Ghana and Burkina Faso following Phase 3 trial results. Methods: We conducted a Phase 1b age de-escalation, dose escalation bridging study after a change in the manufacturing process for R21. We recruited healthy adults and children and used a three dose primary vaccination series with a booster dose at 1-2 years. Variable doses of R21 and adjuvant (Matrix-M ™) were administered at 10µgR21/50 µg Matrix-M™, 5µgR21/25µg Matrix-M™ and 5µgR21/50µg Matrix-M™ to 20 adults, 20 children, and 51 infants. Results: Self-limiting adverse events were reported relating to the injection site and mild systemic symptoms. Two serious adverse events were reported, neither linked to vaccination. High levels of IgG antibodies to the circumsporozoite antigen were induced, and geometric mean titres in infants, the target group, were 1.1 (0.9 to 1.3) EU/mL at day 0, 10175 (7724 to 13404) EU/mL at day 84 and (following a booster dose at day 421) 6792 (5310 to 8687) EU/mL at day 456. Conclusion: R21/Matrix-M™ is safe, and immunogenic when given at varied doses with the peak immune response seen in infants 28 days after a three dose primary vaccination series given four weeks apart. Antibody responses were restored 28 days after a 4 th dose given one year post a three dose primary series in the young children and infants. Registration: Clinicaltrials.gov (NCT03580824; 9 th of July 2018; Pan African Clinical Trials Registry (PACTR202105682956280; 17 th May 2021).