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Background Data on antibody kinetics are limited among individuals previously infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). From a cohort of healthcare personnel and other frontline workers in 6 US states, we assessed antibody waning after messenger RNA (mRNA) dose 2 and response to dose 3 according to SARS-CoV-2 infection history. Methods Participants submitted sera every 3 months, after SARS-CoV-2 infection, and after each mRNA vaccine dose. Sera were tested for antibodies and reported as area under the serial dilution curve (AUC). Changes in AUC values over time were compared using a linear mixed model. Results Analysis included 388 participants who received dose 3 by November 2021. There were 3 comparison groups: vaccine only with no known prior SARS-CoV-2 infection (n = 224); infection prior to dose 1 (n = 123); and infection after dose 2 and before dose 3 (n = 41). The interval from dose 2 and dose 3 was approximately 8 months. After dose 3, antibody levels rose 2.5-fold (95% confidence interval [CI] = 2.2–3.0) in group 2 and 2.9-fold (95% CI = 2.6–3.3) in group 1. Those infected within 90 days before dose 3 (and median 233 days [interquartile range, 213–246] after dose 2) did not increase significantly after dose 3. Conclusions A third dose of mRNA vaccine typically elicited a robust humoral immune response among those with primary vaccination regardless of SARS-CoV-2 infection >3 months prior to boosting. Those with infection

ImportanceData on the epidemiology of mild to moderately severe COVID-19 are needed to inform public health guidance.ObjectiveTo evaluate associations between 2 or 3 doses of mRNA COVID-19 vaccine and attenuation of symptoms and viral RNA load across SARS-CoV-2 viral lineages.Design, Setting, and ParticipantsA prospective cohort study of essential and frontline workers in Arizona, Florida, Minnesota, Oregon, Texas, and Utah with COVID-19 infection confirmed by reverse transcriptase–polymerase chain reaction testing and lineage classified by whole genome sequencing of specimens self-collected weekly and at COVID-19 illness symptom onset. This analysis was conducted among 1199 participants with SARS-CoV-2 from December 14, 2020, to April 19, 2022, with follow-up until May 9, 2022, reported.ExposuresSARS-CoV-2 lineage (origin strain, Delta variant, Omicron variant) and COVID-19 vaccination status.Main Outcomes and MeasuresClinical outcomes included presence of symptoms, specific symptoms (including fever or chills), illness duration, and medical care seeking. Virologic outcomes included viral load by quantitative reverse transcriptase–polymerase chain reaction testing along with viral viability.ResultsAmong 1199 participants with COVID-19 infection (714 [59.5%] women; median age, 41 years), 14.0% were infected with the origin strain, 24.0% with the Delta variant, and 62.0% with the Omicron variant. Participants vaccinated with the second vaccine dose 14 to 149 days before Delta infection were significantly less likely to be symptomatic compared with unvaccinated participants (21/27 [77.8%] vs 74/77 [96.1%]; OR, 0.13 [95% CI, 0-0.6]) and, when symptomatic, those vaccinated with the third dose 7 to 149 days before infection were significantly less likely to report fever or chills (5/13 [38.5%] vs 62/73 [84.9%]; OR, 0.07 [95% CI, 0.0-0.3]) and reported significantly fewer days of symptoms (10.2 vs 16.4; difference, −6.1 [95% CI, −11.8 to −0.4] days). Among those with Omicron infection, the risk of symptomatic infection did not differ significantly for the 2-dose vaccination status vs unvaccinated status and was significantly higher for the 3-dose recipients vs those who were unvaccinated (327/370 [88.4%] vs 85/107 [79.4%]; OR, 2.0 [95% CI, 1.1-3.5]). Among symptomatic Omicron infections, those vaccinated with the third dose 7 to 149 days before infection compared with those who were unvaccinated were significantly less likely to report fever or chills (160/311 [51.5%] vs 64/81 [79.0%]; OR, 0.25 [95% CI, 0.1-0.5]) or seek medical care (45/308 [14.6%] vs 20/81 [24.7%]; OR, 0.45 [95% CI, 0.2-0.9]). Participants with Delta and Omicron infections who received the second dose 14 to 149 days before infection had a significantly lower mean viral load compared with unvaccinated participants (3 vs 4.1 log10 copies/μL; difference, −1.0 [95% CI, −1.7 to −0.2] for Delta and 2.8 vs 3.5 log10 copies/μL, difference, −1.0 [95% CI, −1.7 to −0.3] for Omicron).Conclusions and RelevanceIn a cohort of US essential and frontline workers with SARS-CoV-2 infections, recent vaccination with 2 or 3 mRNA vaccine doses less than 150 days before infection with Delta or Omicron variants, compared with being unvaccinated, was associated with attenuated symptoms, duration of illness, medical care seeking, or viral load for some comparisons, although the precision and statistical significance of specific estimates varied.

We sought to evaluate the impact of changes in estimates of COVID-19 vaccine effectiveness on the incidence of laboratory-confirmed infection among frontline workers at high risk for SARS-CoV-2.We analyzed data from a prospective frontline worker cohort to estimate the incidence of COVID-19 by month as well as the association of COVID-19 vaccination, occupation, demographics, physical distancing, and mask use with infection risk. Participants completed baseline and quarterly surveys, and each week self-collected mid-turbinate nasal swabs and reported symptoms.Among 1018 unvaccinated and 3531 fully vaccinated workers, the monthly incidence of laboratory-confirmed SARS-CoV-2 infection in January 2021 was 13.9 (95% confidence interval [CI]: 10.4-17.4), declining to 0.5 (95% CI -0.4-1.4) per 1000 person-weeks in June. By September 2021, when the Delta variant predominated, incidence had once again risen to 13.6 (95% CI 7.8-19.4) per 1000 person-weeks. In contrast, there was no reportable incidence among fully vaccinated participants at the end of January 2021, and incidence remained low until September 2021 when it rose modestly to 4.1 (95% CI 1.9-3.8) per 1000. Below average facemask use was associated with a higher risk of infection for unvaccinated participants during exposure to persons who may have COVID-19 and vaccinated participants during hours in the community.COVID-19 vaccination was significantly associated with a lower risk of SARS-CoV-2 infection despite Delta variant predominance. Our data demonstrate the added protective benefit of facemask use among both unvaccinated and vaccinated frontline workers.

Summary Wheat contains abundant xylan in cell walls of all tissues, but in endosperm, there is an unusual form of xylan substituted only by arabinose (arabinoxylan; AX) that has long chains and low levels of feruloylation, a fraction of which is extractable in water (WE‐AX). WE‐AX acts as soluble dietary fibre but also gives rise to viscous extracts from grain, a detrimental trait for some non‐food uses of wheat. Here, we show that a glycosyl transferase family 43 wheat gene abundantly expressed in endosperm complements the Arabidopsis irx9 mutant and so name the three homoeologous genes TaIRX9b. We generated wheat lines with a constitutive knockout of TaIRX9b by stacking loss‐of‐function alleles for these homeologues from a mutagenized hexaploid wheat population resulting in decreases in grain extract viscosity of 50%–80%. The amount and chain length of WE‐AX molecules from grain of these triple‐stack lines was decreased accounting for the changes in extract viscosity. Imaging of immature wheat grain sections of triple‐stacks showed abolition of immunolabelling in endosperm with LM11 antibody that recognizes epitopes in AX, but also showed apparently normal cell size and shape in all cell types, including endosperm. We identified differentially expressed genes from endosperm of triple‐stacks suggesting that compensatory changes occur to maintain this endosperm cell wall integrity. Consistent with this, we observed increased ferulate dimerization and increased cross‐linking of WE‐AX molecules in triple‐stacks. These novel wheat lines lacking functional TaIRX9b therefore provide insight into control of wheat endosperm cell walls.

BackgroundBread wheat (Triticum aestivum) is a major source of nutrition globally, but yields can be seriously compromised by water limitation. Redistribution of growth between shoots and roots is a common response to drought, promoting plant survival, but reducing yield. Gibberellins (GAs) are necessary for shoot and root elongation, but roots maintain growth at lower GA concentrations compared with shoots, making GA a suitable hormone for mediating this growth redistribution. In this study, the effect of progressive drought on GA content was determined in the base of the 4th leaf and root tips of wheat seedlings, containing the growing regions, as well as in the remaining leaf and root tissues. In addition, the contents of other selected hormones known to be involved in stress responses were determined. Transcriptome analysis was performed on equivalent tissues and drought-associated differential expression was determined for hormone-related genes.ResultsAfter 5 days of applying progressive drought to 10-day old seedlings, the length of leaf 4 was reduced by 31% compared with watered seedlings and this was associated with significant decreases in the concentrations of bioactive GA1 and GA4 in the leaf base, as well as of their catabolites and precursors. Root length was unaffected by drought, while GA concentrations were slightly, but significantly higher in the tips of droughted roots compared with watered plants. Transcripts for the GA-inactivating gene TaGA2ox4 were elevated in the droughted leaf, while those for several GA-biosynthesis genes were reduced by drought, but mainly in the non-growing region. In response to drought the concentrations of abscisic acid, cis-zeatin and its riboside increased in all tissues, indole-acetic acid was unchanged, while trans-zeatin and riboside, jasmonate and salicylic acid concentrations were reduced.ConclusionsReduced leaf elongation and maintained root growth in wheat seedlings subjected to progressive drought were associated with attenuated and increased GA content, respectively, in the growing regions. Despite increased TaGA2ox4 expression, lower GA levels in the leaf base of droughted plants were due to reduced biosynthesis rather than increased catabolism. In contrast to GA, the other hormones analysed responded to drought similarly in the leaf and roots, indicating organ-specific differential regulation of GA metabolism in response to drought.

BACKGROUND Assessing the real-world effectiveness of COVID-19 vaccines and understanding the incidence and severity of SARS-CoV-2 illness in children is essential to inform policy and guide healthcare professionals advising parents and caregivers of children who test positive for SARS-CoV-2. OBJECTIVE This report describes the objectives and methods for conducting the Pediatric Research Observing Trends and Exposures in COVID-19 Timelines (PROTECT) study. PROTECT is a longitudinal prospective pediatric cohort study designed to estimate SARS-CoV-2 incidence and COVID-19 vaccine effectiveness (VE) against infection among children aged 6 months to 17 years as well as differences in SARS-CoV-2 infection and vaccine response between children and adolescents. METHODS The PROTECT multisite network was initiated in July 2021 and aims to enroll approximately 2,305 children across four U.S. locations and collect data over a two-year surveillance period; the enrollment target was based on prospective power calculations and account for expected attrition and nonresponse. Study sites recruit parents and legal guardians (PLGs) of age-eligible children participating in the existing HEROES-RECOVER network as well as from surrounding communities. Child demographics, medical history, COVID-19 exposure, vaccination history, and PLGs’ knowledge and attitudes about COVID-19 are collected at baseline and throughout the study. Mid-turbinate nasal specimens are self- or PLG-collected weekly, regardless of symptoms, for SARS-CoV-2 and influenza testing via reverse transcription-polymerase chain reaction (RT-PCR) assay, and the presence of COVID-like-illness (CLI) is reported. Children who test positive for SARS-CoV-2 or influenza or report CLI are monitored weekly by online surveys to report exposure and medical utilization until no longer ill. Children, with their PLG’s permission, may elect to contribute blood at enrollment, following SARS-CoV-2 infection, following COVID-19 vaccination, and at the end of the study period. PROTECT uses electronic medical records (EMR) linkages where available and verifies COVID-19 and influenza vaccinations through EMR or state vaccine registries. RESULTS Data collection began in July 2021 and is expected to continue through Spring 2023. As of 02/07/2022, 2,161 children are enrolled in PROTECT. Enrollment is ongoing at all study sites. CONCLUSIONS As COVID-19 vaccine products are authorized for use in pediatric populations, PROTECT study data will provide real-world estimates of VE in preventing infection. In addition, this prospective cohort provides a unique opportunity to further understand SARS-CoV-2 incidence, clinical course, and key knowledge gaps that may inform public health.

Background Workers critical to emergency response and continuity of essential services during the COVID-19 pandemic are at a disproportionally high risk of SARS-CoV-2 infection. Prospective cohort studies are needed for enhancing the understanding of the incidence of symptomatic and asymptomatic SARS-CoV-2 infections, identifying risk factors, assessing clinical outcomes, and determining the effectiveness of vaccination. Objective The Research on the Epidemiology of SARS-CoV-2 in Essential Response Personnel (RECOVER) prospective cohort study was designed to estimate the incidence of symptomatic and asymptomatic SARS-CoV-2 infections, examine the risk factors for infection and clinical spectrum of illness, and assess the effectiveness of vaccination among essential workers. Methods The RECOVER multisite network was initiated in August 2020 and aims to enroll 3000 health care personnel (HCP), first responders, and other essential and frontline workers (EFWs) at 6 US locations. Data on participant demographics, medical history, and vaccination history are collected at baseline and throughout the study. Active surveillance for the symptoms of COVID-19–like illness (CLI), access of medical care, and symptom duration is performed by text messages, emails, and direct participant or medical record reports. Participants self-collect a mid-turbinate nasal swab weekly, regardless of symptoms, and 2 additional respiratory specimens at the onset of CLI. Blood is collected upon enrollment, every 3 months, approximately 28 days after a reverse transcription polymerase chain reaction (RT-PCR)–confirmed SARS-CoV-2 infection, and 14 to 28 days after a dose of any COVID-19 vaccine. From February 2021, household members of RT-PCR–confirmed participants are self-collecting mid-turbinate nasal swabs daily for 10 days. Results The study observation period began in August 2020 and is expected to continue through spring 2022. There are 2623 actively enrolled RECOVER participants, including 280 participants who have been found to be positive for SARS-CoV-2 by RT-PCR. Enrollment is ongoing at 3 of the 6 study sites. Conclusions Data collected through the cohort are expected to provide important public health information for essential workers at high risk for occupational exposure to SARS-CoV-2 and allow early evaluation of COVID-19 vaccine effectiveness. International Registered Report Identifier (IRRID) DERR1-10.2196/31574

Law Enforcement Officers (LEOs), firefighters, and other first responders are at increased risk of SARS-CoV-2 infection compared to healthcare personnel but have relatively low COVID-19 vaccine uptake. Resistance to COVID-19 vaccine mandates among first responders has the potential to disrupt essential public services and threaten public health and safety. Using data from the HEROES-RECOVER prospective cohorts, we report on the increased illness burden of COVID-19 among unvaccinated first responders. From January to September 2021, first responders contributed to weekly active surveillance for COVID-19-like illness (CLI). Self-collected respiratory specimens collected weekly, irrespective of symptoms, and at the onset CLI were tested by Reverse Transcription Polymerase Chain Reaction (RT-PCR) assay for SARS-CoV-2. Among 1415 first responders, 17% were LEOs, 68% firefighters, and 15% had other first responder occupations. Unvaccinated (41%) compared to fully vaccinated (59%) first responders were less likely to believe COVID-19 vaccines are very or extremely effective (17% versus 54%) or very or extremely safe (15% versus 54%). From January through September 2021, among unvaccinated LEOs, the incidence of COVID-19 was 11.9 per 1,000 person-weeks (95%CI=7.0-20.1) compared to only 0.6 (95%CI=0.2-2.5) among vaccinated LEOs. Incidence of COVID-19 was also higher among unvaccinated firefighters (9.0 per 1,000 person-weeks; 95%CI=6.4-12.7) compared to those vaccinated (1.8 per 1,000; 95%CI=1.1-2.8). Once they had laboratory-confirmed COVID-19, unvaccinated first responders were sick for a mean±SD of 14.7±21.7 days and missed a mean of 38.0±46.0 hours of work. These findings suggest that state and local governments with large numbers of unvaccinated first responders may face major disruptions in their workforce due to COVID-19 illness.

Noise-induced hearing loss (NIHL) represents the second most common occupational disease in the United States. Although the Occupational Safety and Health Administration (OSHA) has promulgated an occupational noise exposure standard and associated recordkeeping requirements, OSHA inspections increasingly document practices that violate both the noise standard and recordkeeping regulation. This article describes five deviations from good clinical practices masking the true societal costs of NIHL, leading to missed prevention opportunities, and creating burdens for individuals and society. These include attributing NIHL to nonoccupational sources, exculpating the workplace because of audiogram patterns without careful documentation, ignoring symptoms or physical examination findings, and simply denying work-relatedness, leading to employers inappropriately lining out cases from the OSHA 300 log. The practices identified by OSHA suggest that many individuals are not following widely recognized and accepted practices when administering hearing conservation programs.

The aim of this study was to determine the efficacy of an evidence-based opioid guidelines-based program implemented at the largest worker's compensation insurer in Utah.All new claims, including surgeries, were included. Pre- and post-intervention comparisons included percentage of claims treated with an opioid, provision of a second opioid prescription, opioid use above 50 mg morphine equivalent dose (MED), opioid use more than 90 mg MED, and opioid use over 90 days.There were significant (P 0.001) reductions in all primary outcomes, with a reduction in MEDs in the 18 months after implementation totaling 65,502 mg.This program significantly reduced the usage of opioids among acute claims. The year of program implementation, Utah experienced a 19.8% reduction in opioid-related fatalities, which may be partly related to the reduction in MEDs. Regardless, this study suggests that the implementation of an evidence-based guideline is impactful and feasible.

Nitrate, one of the main nitrogen (N) sources for crops, acts as a nutrient and key signaling molecule coordinating gene expression, metabolism and various growth processes throughout the plant life cycle. It is widely accepted that nitrate-triggered developmental programs cooperate with hormone synthesis and transport, to finely adapt plant architecture to N availability. Here, we report that nitrate, acting through its signaling pathway, promotes growth in Arabidopsis and wheat, in part by modulating the accumulation of gibberellin (GA)-regulated DELLA growth repressors. We show that nitrate reduces the abundance of DELLAs by increasing GA contents through activation of GA metabolism gene expression. Consistently, the growth restraint conferred by nitrate deficiency is partially rescued in global-DELLA mutant that lacks all DELLAs. At the cellular level, we show that nitrate enhances both cell proliferation and elongation in a DELLA-dependent and -independent manner, respectively. Our findings establish a connection between nitrate and GA signaling pathways that allow plants to adapt their growth to nitrate availability.

BACKGROUND Workers critical to emergency response and continuity of essential services during the COVID-19 pandemic are at a disproportionally high risk of SARS-CoV-2 infection. Prospective cohort studies are needed for enhancing the understanding of the incidence of symptomatic and asymptomatic SARS-CoV-2 infections, identifying risk factors, assessing clinical outcomes, and determining the effectiveness of vaccination. OBJECTIVE The Research on the Epidemiology of SARS-CoV-2 in Essential Response Personnel (RECOVER) prospective cohort study was designed to estimate the incidence of symptomatic and asymptomatic SARS-CoV-2 infections, examine the risk factors for infection and clinical spectrum of illness, and assess the effectiveness of vaccination among essential workers. METHODS The RECOVER multisite network was initiated in August 2020 and aims to enroll 3000 health care personnel (HCP), first responders, and other essential and frontline workers (EFWs) at 6 US locations. Data on participant demographics, medical history, and vaccination history are collected at baseline and throughout the study. Active surveillance for the symptoms of COVID-19–like illness (CLI), access of medical care, and symptom duration is performed by text messages, emails, and direct participant or medical record reports. Participants self-collect a mid-turbinate nasal swab weekly, regardless of symptoms, and 2 additional respiratory specimens at the onset of CLI. Blood is collected upon enrollment, every 3 months, approximately 28 days after a reverse transcription polymerase chain reaction (RT-PCR)–confirmed SARS-CoV-2 infection, and 14 to 28 days after a dose of any COVID-19 vaccine. From February 2021, household members of RT-PCR–confirmed participants are self-collecting mid-turbinate nasal swabs daily for 10 days. RESULTS The study observation period began in August 2020 and is expected to continue through spring 2022. There are 2623 actively enrolled RECOVER participants, including 280 participants who have been found to be positive for SARS-CoV-2 by RT-PCR. Enrollment is ongoing at 3 of the 6 study sites. CONCLUSIONS Data collected through the cohort are expected to provide important public health information for essential workers at high risk for occupational exposure to SARS-CoV-2 and allow early evaluation of COVID-19 vaccine effectiveness. INTERNATIONAL REGISTERED REPORT DERR1-10.2196/31574

BACKGROUNDInformation is limited on messenger RNA (mRNA) BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) COVID-19 vaccine effectiveness (VE) in preventing SARS-CoV-2 infection or attenuating disease when administered in real-world conditions.METHODSProspective cohorts of 3,975 healthcare personnel, first responders, and other essential and frontline workers completed weekly SARS-CoV-2 testing during December 14 2020—April 10 2021. Self-collected mid-turbinate nasal swabs were tested by qualitative and quantitative reverse-transcription–polymerase-chain-reaction (RT-PCR). VE was calculated as 100%×(1−hazard ratio); adjusted VE was calculated using vaccination propensity weights and adjustments for site, occupation, and local virus circulation.RESULTSSARS-CoV-2 was detected in 204 (5.1%) participants; 16 were partially (≥14 days post-dose-1 to 13 days after dose-2) or fully (≥14 days post-dose-2) vaccinated, and 156 were unvaccinated; 32 with indeterminate status (CONCLUSIONSAuthorized mRNA vaccines were highly effective among working-age adults in preventing SARS-CoV-2 infections when administered in real-world conditions and attenuated viral RNA load, febrile symptoms, and illness duration among those with breakthrough infection despite vaccination.

Background Information is limited regarding the effectiveness of the two-dose messenger RNA (mRNA) vaccines BNT162b2 (Pfizer–BioNTech) and mRNA-1273 (Moderna) in preventing infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and in attenuating coronavirus disease 2019 (Covid-19) when administered in real-world conditions. Methods We conducted a prospective cohort study involving 3975 health care personnel, first responders, and other essential and frontline workers. From December 14, 2020, to April 10, 2021, the participants completed weekly SARS-CoV-2 testing by providing mid-turbinate nasal swabs for qualitative and quantitative reverse-transcriptase–polymerase-chain-reaction (RT-PCR) analysis. The formula for calculating vaccine effectiveness was 100%×(1−hazard ratio for SARS-CoV-2 infection in vaccinated vs. unvaccinated participants), with adjustments for the propensity to be vaccinated, study site, occupation, and local viral circulation. Results SARS-CoV-2 was detected in 204 participants (5%), of whom 5 were fully vaccinated (≥14 days after dose 2), 11 partially vaccinated (≥14 days after dose 1 and

Background Assessing the real-world effectiveness of COVID-19 vaccines and understanding the incidence and severity of SARS-CoV-2 illness in children are essential to inform policy and guide health care professionals in advising parents and caregivers of children who test positive for SARS-CoV-2. Objective This report describes the objectives and methods for conducting the Pediatric Research Observing Trends and Exposures in COVID-19 Timelines (PROTECT) study. PROTECT is a longitudinal prospective pediatric cohort study designed to estimate SARS-CoV-2 incidence and COVID-19 vaccine effectiveness (VE) against infection among children aged 6 months to 17 years, as well as differences in SARS-CoV-2 infection and vaccine response between children and adolescents. Methods The PROTECT multisite network was initiated in July 2021, which aims to enroll approximately 2305 children across four US locations and collect data over a 2-year surveillance period. The enrollment target was based on prospective power calculations and accounts for expected attrition and nonresponse. Study sites recruit parents and legal guardians of age-eligible children participating in the existing Arizona Healthcare, Emergency Response, and Other Essential Workers Surveillance (HEROES)-Research on the Epidemiology of SARS-CoV-2 in Essential Response Personnel (RECOVER) network as well as from surrounding communities. Child demographics, medical history, COVID-19 exposure, vaccination history, and parents/legal guardians’ knowledge and attitudes about COVID-19 are collected at baseline and throughout the study. Mid-turbinate nasal specimens are self-collected or collected by parents/legal guardians weekly, regardless of symptoms, for SARS-CoV-2 and influenza testing via reverse transcription-polymerase chain reaction (RT-PCR) assay, and the presence of COVID-like illness (CLI) is reported. Children who test positive for SARS-CoV-2 or influenza, or report CLI are monitored weekly by online surveys to report exposure and medical utilization until no longer ill. Children, with permission of their parents/legal guardians, may elect to contribute blood at enrollment, following SARS-CoV-2 infection, following COVID-19 vaccination, and at the end of the study period. PROTECT uses electronic medical record (EMR) linkages where available, and verifies COVID-19 and influenza vaccinations through EMR or state vaccine registries. Results Data collection began in July 2021 and is expected to continue through the spring of 2023. As of April 13, 2022, 2371 children are enrolled in PROTECT. Enrollment is ongoing at all study sites. Conclusions As COVID-19 vaccine products are authorized for use in pediatric populations, PROTECT study data will provide real-world estimates of VE in preventing infection. In addition, this prospective cohort provides a unique opportunity to further understand SARS-CoV-2 incidence, clinical course, and key knowledge gaps that may inform public health. International Registered Report Identifier (IRRID) RR1-10.2196/37929

Root elongation depends on the action of the gibberellin (GA) growth hormones, which promote cell production in the root meristem and cell expansion in the elongation zone. Sites of GA biosynthesis in the roots of 7-d-old Arabidopsis thaliana seedlings were investigated using tissue-specific GA inactivation in wild-type (Col-0) or rescue of GA-deficient dwarf mutants. Tissue-specific GA depletion was achieved by ectopic expression of the GA-inactivating enzyme AtGA2ox2, which is specific for C-GAs, and AtGA2ox7, which acts on C-GA precursors. In addition, tissue-specific rescue of ga20ox triple and ga3ox double mutants was shown. Furthermore, GUS reporter lines for major GA20ox, GA3ox and GA2ox genes were used to observe their expression domains in the root. The effects of expressing these constructs on the lengths of the root apical meristem and cortical cells in the elongation zone confirmed that roots are autonomous for GA biosynthesis, which occurs in multiple tissues, with the endodermis a major site of synthesis. The results are consistent with the early stages of GA biosynthesis within the root occurring in the meristematic region and indicate that the penultimate step of GA biosynthesis, GA 20-oxidation, is required in both the meristem and elongation zone., Biotechnology and Biological Sciences Research Council. Grant Numbers: BBS/E/C/00005202, BBS/E/C/000I0220, P16508 European Regional Developmental Fund. Grant Number: CZ.02.1.01/0.0/0.0/16_019/0000738 Grantová Agentura České Republiky. Grant Numbers: 18-10349S, 20-17984S Lawes Agricultural Trust Studentship

Generating new ideas and scientific hypotheses is often the result of extensive literature and database reviews, overlaid with scientists’ own novel data and a creative process of making connections that were not made before. We have developed a comprehensive approach to guide this technically challenging data integration task and to make knowledge discovery and hypotheses generation easier for plant and crop researchers. KnetMiner can digest large volumes of scientific literature and biological research to find and visualise links between the genetic and biological properties of complex traits and diseases. Here we report the main design principles behind KnetMiner and provide use cases for mining public datasets to identify unknown links between traits such grain colour and pre-harvest sprouting inTriticum aestivum, as well as, an evidence-based approach to identify candidate genes under anArabidopsis thalianapetal size QTL. We have developed KnetMiner knowledge graphs and applications for a range of species including plants, crops and pathogens. KnetMiner is the first open-source gene discovery platform that can leverage genome-scale knowledge graphs, generate evidence-based biological networks and be deployed for any species with a sequenced genome. KnetMiner is available athttp://knetminer.org.

Nitrate, one of the main nitrogen (N) sources for crops, acts as a nutrient and key signaling molecule coordinating gene expression, metabolism, and various growth processes throughout the plant life cycle. It is widely accepted that nitrate-triggered developmental programs cooperate with hormone synthesis and transport to finely adapt plant architecture to N availability. Here, we report that nitrate, acting through its signaling pathway, promotes growth in Arabidopsis and wheat, in part by modulating the accumulation of gibberellin (GA)-regulated DELLA growth repressors. We show that nitrate reduces the abundance of DELLAs by increasing GA contents through activation of GA metabolism gene expression. Consistently, the growth restraint conferred by nitrate deficiency is partially rescued in global-DELLA mutant that lacks all DELLAs. At the cellular level, we show that nitrate enhances both cell proliferation and elongation in a DELLA dependent and independent manner, respectively. Our findings establish a connection between nitrate and GA signaling pathways that allow plants to adapt their growth to nitrate availability plants to adapt their growth to nitrate availability

Advances in genome sequencing and assembly technologies are generating many high quality genome sequences, but assemblies of large, repeat-rich polyploid genomes, such as that of bread wheat, remain fragmented and incomplete. We have generated a new wheat whole-genome shotgun sequence assembly using a combination of optimised data types and an assembly algorithm designed to deal with large and complex genomes. The new assembly represents more than 78% of the genome with a scaffold N50 of 88.8kbp that has a high fidelity to the input data. Our new annotation combines strand-specific Illumina RNAseq and PacBio full-length cDNAs to identify 104,091 high confidence protein-coding genes and 10,156 non-coding RNA genes. We confirmed three known and identified one novel genome rearrangements. Our approach enables the rapid and scalable assembly of wheat genomes, the identification of structural variants, and the definition of complete gene models, all powerful resources for trait analysis and breeding of this key global crop. [Supplemental material is available for this article.]

Awns are bristle-like structures formed at the tip of the lemma on the florets of some cereal grasses. Wild-type wheat is awned, but awnletted and awnless variants have been selected and nowadays all forms are cultivated. In this study, we dissected the genetic control underlying variation of this characteristic feature by association mapping in a large panel of 1110 winter wheat cultivars of worldwide origin. We identified the B1 (Tipped 1) locus on chromosome 5A as the major determinant of awnlessness globally. Using a combination of fine-mapping and expression analysis, we identified a putative C2H2 zinc finger protein with an EAR domain, characteristic of transcriptional repressors, as a likely candidate for Tipped 1. This gene was found to be up-regulated in awnless B1 compared with awned b1 plants, indicating that misexpression of this transcriptional regulator may contribute to the reduction of awn length in B1 plants. Taken together, our study provides an entry point towards a better molecular understanding of the evolution of morphological features in cereals through selection and breeding., We identified a candidate for the awnedness inhibitor Tipped 1, and showed that misexpression of this transcriptional repressor is the likely molecular cause underlying the evolution of awnlessness in wheat.

Objective American College of Occupational and Environmental Medicine's (ACOEM's) evidence-based guidelines for acute low back pain (LBP) were used to assess relationships between guideline adherence and worker's compensation costs. Methods Treatments at first appointments were abstracted. Two scoring tools were utilized to assess each patient's treatment plan. One score assessed ACOEM Guideline compliance while the second utilized mean expert scores of the perceived value of each treatment. Claim costs were log-transformed and compared with scores. Results There is a significant trend between increased compliance and decreasing costs. Medical and total costs trended lower by an average $352.90 and $586.20 per unit of compliance score respectively. No outlier cost claims were in the best guidelines compliance groups. Conclusion This study shows a statistically significant trend in the relationship between adherence to ACOEM guidelines for initial management of work-related LBP and decreasing claim costs.

Summary Targeted selection and inbreeding have resulted in a lack of genetic diversity in elite hexaploid bread wheat accessions. Reduced diversity can be a limiting factor in the breeding of high yielding varieties and crucially can mean reduced resilience in the face of changing climate and resource pressures. Recent technological advances have enabled the development of molecular markers for use in the assessment and utilisation of genetic diversity in hexaploid wheat. Starting with a large collection of 819,571 previously characterised wheat markers, here we describe the identification of 35,143 single nucleotide polymorphism-based markers, which are highly suited to the genotyping of elite hexaploid wheat accessions. To assess their suitability, the markers have been validated using a commercial high density Affymetrix Axiom® genotyping array (the Wheat Breeders’ Array), in a high throughput 384 microplate configuration, to characterise a diverse global collection of wheat accessions including landraces and elite lines derived from commercial breeding communities. We demonstrate that the Wheat Breeders’ Array is also suitable for generating high density genetic maps of previously uncharacterised populations and for characterising novel genetic diversity produced by mutagenesis. To facilitate the use of the array by the wheat community, the markers, the associated sequence and the genotype information have been made available through the interactive web site “CerealsDB”. This article is protected by copyright. All rights reserved.

In this opinion article we examine the relationship between penetrometer resistance and soil depth in the field. Assuming that root growth is inhibited at penetrometer resistances > 2.5 MPa, we conclude that in most circumstances the increases in penetrometer resistance with depth are sufficiently great to confine most deep roots to elongating in existing structural pores. We suggest that deep rooting is more likely related to the interaction between root architecture and soil structure than it is to the ability of a root to deform strong soil. Although the ability of roots to deform strong soil is an important trait, we propose it is more closely related to root exploration of surface layers than deep rooting.

Background and aims We were interested in the effect of impedance to root growth on root and shoot architecture of wheat. It is known that Rht-1 semi-dwarfing alleles decrease the degree of leaf stunting due to root impedance. We compared commercial wheat cultivars containing different Rht-1 alleles to determine whether leaf stunting caused by root impedance differed between cultivars. We investigated effects of impedance to root growth on the angular spread of roots. Methods The wheat cultivars Avalon, Robigus and Battalion, carrying semi-dwarfing alleles of Rht-1, and cv. Cadenza, carrying the tall, wild-type allele, were grown under two levels of soil strength in a sand culture system designed to allow the mechanical impedance of the root growth environment to be adjusted independently of water and nutrient availability. Results Impeded roots grew more steeply than non-impeded roots: the angular spread of roots decreased from 55° to 43° from the vertical, but the genotypic effects were weak. Root impedance reduced leaf elongation and the number of tillers. Leaf area and total root length provided a common relationship across all genotype x treatment combinations. Leaf stunting in Cadenza was more severe. Conclusion Our data support the hypothesis that the severity of leaf stunting due to root impedance is related to the Rht allele. Impeded roots had a smaller angular spread.

Key message Linear modelling approaches detected significant gradients in organ growth and patterning across early flowers of the Arabidopsis inflorescence and uncovered evidence of new roles for gibberellin in floral development. Abstract Most flowering plants, including the genetic model Arabidopsis thaliana, produce multiple flowers in sequence from a reproductive shoot apex to form a flower spike (inflorescence). The development of individual flowers on an Arabidopsis inflorescence has typically been considered as highly stereotypical and uniform, but this assumption is contradicted by the existence of mutants with phenotypes visible in early flowers only. This phenomenon is demonstrated by mutants partially impaired in the biosynthesis of the phytohormone gibberellin (GA), in which floral organ growth is retarded in the first flowers to be produced but has recovered spontaneously by the 10th flower. We presently lack systematic data from multiple flowers across the Arabidopsis inflorescence to explain such changes. Using mutants of the GA 20-OXIDASE (GA20ox) GA biosynthesis gene family to manipulate endogenous GA levels, we investigated the dynamics of changing floral organ growth across the early Arabidopsis inflorescence (flowers 1–10). Modelling of floral organ lengths identified a significant, GA-independent gradient of increasing stamen length relative to the pistil in the wild-type inflorescence that was separable from other, GA-dependent effects. It was also found that the first flowers exhibited unstable organ patterning in contrast to later flowers and that this instability was prolonged by exogenous GA treatment. These findings indicate that the development of individual flowers is influenced by hitherto unknown factors acting across the inflorescence and also suggest novel functions for GA in floral patterning. Electronic supplementary material The online version of this article (10.1007/s00497-017-0320-3) contains supplementary material, which is available to authorized users.

In this study, the degradation mechanism of InGaN/GaN laser diodes has been investigated using cross-sectional electron beam induced current (EBIC) imaging, combined with scanning electron microscopy (SEM). By comparing the EBIC images of an untested and a degraded laser from the same laser bar, we show that the p-n junction position of the degraded laser has shifted towards the n-doped region and the carrier interface at the p-side of the p-n junction of the degraded laser became less sharp than in the original laser diode. This p-n junction position shift leads to carrier compensation in the active and the n-doped regions, which subsequently leads to an imbalance in the hole and electron concentrations in the active region and a reduction in the emission efficiency of InGaN quantum wells. This occurs because a displacement of the p-n junction, from its optimal position, results in a minority carrier loss, as the latter has a higher probability of recombining non-radiatively en-route to the active region. The minority carrier diffusion lengths were also calculated using two different theoretical models. The results show that the electron diffusion length in the p-doped region in the degraded laser is longer than that in the untested laser. The reason may also be related to the compensation effect or the reduced recombination rate in the degraded laser, which will result in an increase in the threshold current of the laser and the degradation of the laser.

Food security is a global concern and substantial yield increases in crops are required to feed the growing world population. Mutagenesis is an important tool in crop improvement and is free of the regulatory restrictions imposed on genetically modified organisms. Targeting Induced Local Lesions in Genomes (TILLING), which combines traditional chemical mutagenesis with high-throughput genome-wide screening for point mutations in desired genes, offers a powerful way to create novel mutant alleles for both functional genomics and improvement of crops. TILLING is generally applicable to genomes whether small or large, diploid or even allohexaploid, and shows great potential to address the major challenge of linking sequence information to the function of genes and to modulate key traits for plant breeding. TILLING has been successfully applied in many crop species and recent progress in TILLING is summarized below, especially on the developments in mutation detection technology, application of TILLING in gene functional studies and crop breeding. The potential of TILLING/EcoTILLING for functional genetics and crop improvement is also discussed. Furthermore, a small-scale forward strategy including backcross and selfing was conducted to release the potential mutant phenotypes masked in M2 (or M3) plants.

Excessive gibberellin (GA) signalling, mediated through the DELLA proteins, has a negative impact on plant fertility. Loss of DELLA activity in the monocot rice (Oryza sativa) causes complete male sterility, but not in the dicot model Arabidopsis (Arabidopsis thaliana) ecotype Landsberg erecta (Ler), in which DELLA function has been studied most extensively, leading to the assumption that DELLA activity is not essential for Arabidopsis pollen development. A novel DELLA fertility phenotype was identified in the Columbia (Col-0) ecotype that necessitates re-evaluation of the general conclusions drawn from Ler. Fertility phenotypes were compared between the Col-0 and Ler ecotypes under conditions of chemical and genetic GA overdose, including mutants in both ecotypes lacking the DELLA paralogues REPRESSOR OF ga1-3 (RGA) and GA INSENSITIVE (GAI). Ler displays a less severe fertility phenotype than Col-0 under GA treatment. Col-0 rga gai mutants, in contrast with the equivalent Ler phenotype, were entirely male sterile, caused by post-meiotic defects in pollen development, which were rescued by the reintroduction of DELLA into either the tapetum or developing pollen. We conclude that DELLA activity is essential for Arabidopsis pollen development. Differences between the fertility responses of Col-0 and Ler might be caused by differences in downstream signalling pathways or altered DELLA expression.

The experimentally obtained luminescence characteristics of a praseodymium (Pr $$^{3+})$$ doped chalcogenide glass fiber are studied numerically using a rate equation approach. The numerical model includes both the radiative and non-radiative transition paths whilst it neglects the up-conversion processes. Photoluminescence spectra at mid-infrared wavelengths ranging from 3.5 to 6 $${\upmu }$$ m were obtained by using two pump wavelengths: 1.55 and 1.94 $${\upmu }$$ m. A good agreement between the experiment and theory is obtained for the photoluminescence decay profiles.

The concept of root-sourced chemical signals that affect shoot growth in response to drought is widely reported; in particular the role of ABA in regulating stomatal conductance has received much attention. ABA, alone, does not fully explain all the effects of abiotic stresses in the root zone on shoot architecture. An increase in mechanical impedance, which can occur on even relatively modest soil drying, results in reduced root and shoot growth, processes that are potentially regulated by gibberellins (GAs). In this study we explored the role of mechanical impedance and exogenous gibberellin (GA3) on root and shoot architecture in wheat seedlings containing the Rht-B1a (tall), Rht-B1b (semi-dwarf) or Rht-B1c (dwarf) alleles in the April-Bearded or Mercia backgrounds. Our experiments were based on the use of the sand culture system which allows the mechanical impedance of the root growth environment to remain constant and independent of water and nutrient availability. We investigated the effects of the application of exogenous GA3 to the root system. We found that impeding soil reduced leaf elongation in the tall and semi-dwarf lines, confirming the stunting effect of mechanical impedance which is widely reported. However, leaf elongation in the dwarf lines was not affected by root impedance. Application of GA3 to the roots restored leaf elongation in the tall and semi-dwarf lines growing in impeding soil, with some growth response even in the dwarf line, the longest leaves being obtained when GA was applied to impeded roots of a tall line. Both exogenous GA and root impedance reduced the number of tillers, but there was no interaction with the Rht genotype. The genetic background did not affect the results. We suggest that the GA signalling pathway has an unidentified role in the leaf elongation response to mechanical impedance to root growth.

International audience; Deployment of fast-evolving disease-resistance genes is one of the most successful strategies used by plants to fend off pathogens(1,2). In gene-for-gene relationships, most cloned disease-resistance genes encode intracellular nucleotide-binding leucine-rich-repeat proteins (NLRs) recognizing pathogen-secreted isolate-specific avirulence (Avr) effectors delivered to the host cytoplasm(3,4). This process often triggers a localized hypersensitive response, which halts further disease development(5). Here we report the map-based cloning of the wheat Stb6 gene and demonstrate that it encodes a conserved wall-associated receptor kinase (WAK)-like protein, which detects the presence of a matching apoplastic effector(6-8) and confers pathogen resistance without a hypersensitive response(9). This report demonstrates gene-for-gene disease resistance controlled by this class of proteins in plants. Moreover, Stb6 is, to our knowledge, the first cloned gene specifying resistance to Zymoseptoria tritici, an important foliar fungal pathogen affecting wheat and causing economically damaging septoria tritici blotch (STB) disease(10-12).

Gibberellin (GA) biosynthesis is necessary for normal plant development, with later GA biosynthetic stages being governed by multigene families. Arabidopsis thaliana contains five GA 20-oxidase (GA20ox) genes, and past work has demonstrated the importance of GA20ox1 and -2 for growth and fertility. Here, we show through systematic mutant analysis that GA20ox1, -2, and -3 are the dominant paralogs; their absence results in severe dwarfism and almost complete loss of fertility. In vitro analysis revealed that GA20ox4 has full GA20ox activity, but GA20ox5 catalyzes only the first two reactions of the sequence by which GA12 is converted to GA9. GA20ox3 functions almost entirely redundantly with GA20ox1 and -2 at most developmental stages, including the floral transition, while GA20ox4 and -5 have very minor roles. These results are supported by analysis of the gene expression patterns in promoter:β-glucuronidase reporter lines. We demonstrate that fertility is highly sensitive to GA concentration, that GA20ox1, -2, and -3 have significant effects on floral organ growth and anther development, and that both GA deficiency and overdose impact on fertility. Loss of GA20ox activity causes anther developmental arrest, with the tapetum failing to degrade. Some phenotypic recovery of late flowers in GA-deficient mutants, including ga1-3, indicated the involvement of non-GA pathways in floral development., This work was supported by a Rothamsted quota studentship to A.R.G.P. and by Grant P16508, both funded by the Biotechnology and Biological Sciences Research Council of the UK, which also provides strategic support to Rothamsted Research. We thank the Japanese Society for the Promotion of Science for a fellowship to P.H., the Spanish Ministry of Education and Science for a fellowship to N.F.-G. (Ref: EX2004-0398), and the Czech Ministry of Education (Grants CZ.1.07/2.3.00/09.0035. and 522/08/4003) and Academy of Sciences (Grant KAN 2003 80801) to T.U.

A mutant population of spring wheat cv. Cadenza was produced at Rothamsted Research in 2004–5, both for TILLING and to generate variation in the contents of phytochemical components studied in the Healthgrain program. The agronomic and morphological properties of this mutant hexaploid wheat population (generations M3–M6) were studied in a 3-year field experiment. Most of the traits were scored according to UPOV TG/3/11, namely the time of ear emergence, plant height, ear glaucosity, shape, density and length, presence of awns and scurs, seasonal type, and grain colour. Other characters such as visible mutant phenotypes, ear sterility, heterogeneity of head rows, leaf colour and responses to powdery mildew and leaf rust were also studied. Variation in certain breadmaking quality parameters was also studied. The EMS mutant Cadenza lines studied showed wide diversity in terms of morphological and agronomic properties. The variation in agronomic properties was lower in 2007 and 2008 than in 2006, partly because of the SSD (single seed descent) in the M4 generation and partly because of the loss of late heading genotypes. The diversity was lowest in 2007, probably due to the extremely dry weather.

Given the important role that starch plays in food and non-food uses of many crops, particularly wheat, efforts are being made to manipulate its composition through modification of the amylose/amylopectin ratio. Approaches used to achieve this goal include the manipulation of the genes involved in the starch biosynthetic pathway using natural or induced mutations and transgenic methods. The use of mutagenesis to produce novel allelic variation represents a powerful tool to increase genetic diversity and this approach seems particularly appropriate for starch synthase genes for which limited variation exists. In this work, an EMS-mutagenised population of bread wheat cv. Cadenza has been screened by combining SDS–PAGE analysis of granule bound starch proteins with a TILLING (Targeting Induced Local Lesions IN Genomes) approach at the gene level. In particular we have focused on two groups of synthase genes, those encoding the starch synthase II (Sgp-1) and those corresponding to the waxy proteins (Wx). SDS–PAGE analysis of granule bound proteins allowed the identification of single null genotypes associated with each of the three homoeologous loci. Molecular characterization of induced mutants has been performed using genome specific primer pairs for Sgp-1 and Wx genes. Additional novel allelic variation has also been detected at the different Sgp-1 homoeoloci by using a reverse genetic approach (TILLING). In particular single nucleotide substitutions, introducing a premature stop codon and creating amino acid substitutions, have been identified.

Sugar beet, Beta vulgaris spp. vulgaris is a biennial long day plant with an obligate requirement for vernalization (prolonged exposure to low temperature). As a spring crop in temperate European climates, it is vulnerable to vernalization-induced premature bolting and flowering, resulting in reduced crop yield and quality. Gibberellins (GAs) play important roles in key physiological processes including stem elongation (bolting) and flowering and are, therefore, potential targets for controlling reproductive growth in sugar beet. We show that the BvGA20ox gene, which encodes an enzyme necessary for GA biosynthesis, was transcriptionally activated in apices of sugar beet plants after vernalization and that GA metabolism can be manipulated to delay bolting in vernalized plants. We demonstrate that down-regulation of GA responses by transformation with the Arabidopsis thaliana gai gene (which represses GA signalling), under its own promoter (pgai::gai) or deactivation of GA by over-expression of the Phaseolus coccineus (bean) GA2ox1 gene, which inactivates GA, increased the required post vernalization thermal time (an accurate and stable measure of physiological time), to bolt by approximately 300 degrees Cd. This resulted in agronomically significant bolting time delays of approximately 2 weeks and 3 weeks in the pgai::gai and 35S::PcGA2ox1 plants, respectively. Our data represent the first transgenic sugar beet model to (1) show that GA signalling can be used to improve crops by manipulation of the transition to reproductive growth; and (2) provide evidence that GA is required for seed set in sugar beet.

Many developmental processes regulated by gibberellin (GA) impact on crop yield and quality, and genetic variants affected in GA biosynthesis or signalling have been widely exploited in agriculture. Notably, these include alleles of Rht‐1 and Sd‐1 that confer a semi‐dwarf habit to wheat and rice, respectively, underpinning the Green Revolution that increased yields in the latter half of the twentieth century. The chapter discusses the utility of various alleles at these and other GA loci in controlling stature, mainly in cereal crops. The scope for the development of additional variants in the GA pathway through mutagenesis or transgenic approaches is also reviewed.

Auxin represents a key signal in plants, regulating almost every aspect of their growth and development. Major breakthroughs have been made dissecting the molecular basis of auxin transport, perception, and response. In contrast, how plants control the metabolism and homeostasis of the major form of auxin in plants, indole-3-acetic acid (IAA), remains unclear. In this paper, we initially describe the function of the Arabidopsis thaliana gene DIOXYGENASE FOR AUXIN OXIDATION 1 (AtDAO1). Transcriptional and translational reporter lines revealed that AtDAO1 encodes a highly root-expressed, cytoplasmically localized IAA oxidase. Stable isotope-labeled IAA feeding studies of loss and gain of function AtDAO1 lines showed that this oxidase represents the major regulator of auxin degradation to 2-oxoindole-3-acetic acid (oxIAA) in Arabidopsis. Surprisingly, AtDAO1 loss and gain of function lines exhibited relatively subtle auxin-related phenotypes, such as altered root hair length. Metabolite profiling of mutant lines revealed that disrupting AtDAO1 regulation resulted in major changes in steady-state levels of oxIAA and IAA conjugates but not IAA. Hence, IAA conjugation and catabolism seem to regulate auxin levels in Arabidopsis in a highly redundant manner. We observed that transcripts of AtDOA1 IAA oxidase and GH3 IAA-conjugating enzymes are auxin-inducible, providing a molecular basis for their observed functional redundancy. We conclude that the AtDAO1 gene plays a key role regulating auxin homeostasis in Arabidopsis, acting in concert with GH3 genes, to maintain auxin concentration at optimal levels for plant growth and development.

Ethylene, or its precursor 1-aminocyclopropane-1-carboxylic acid (ACC), can stimulate hypocotyl elongation in the light. It is questioned whether gibberellins (GAs) play a role in this response. Tests with light of different wavelengths demonstrated that the ethylene response depends on blue light and functional cryptochrome signalling. Levels of bio-active GA(4) were reduced in seedlings showing an ethylene response. Furthermore, ACC treatment of seedlings caused accumulation of the DELLA protein RGA, a repressor of growth. Concurrently, transcript levels of several GA biosynthesis genes were up-regulated and GA inactivation genes down-regulated by ACC. Hypocotyl elongation in response to ACC was strongly reduced in seedlings with a diminished GA signal, while being vigorously stimulated in a quadruple DELLA knock-out mutant with constitutive GA signalling. These data show that ethylene-driven hypocotyl elongation is mainly blue light-dependent and that this ethylene response, although GA dependent, hence needing a basal GA level, is not mediated by GA, but rather acts via a separate pathway.

The activity of the gibberellin (GA) biosynthetic enzymes GA 20-oxidases (GA20ox) is of particular importance in determining GA concentration in many plant species. In Arabidopsis these enzymes are encoded by a family of five genes: AtGA20ox1-AtGA20ox5. Transcript analysis indicated that they have different expression patterns and may thus participate differentially in GA-regulated developmental processes. We have used reverse genetics to determine the physiological roles of AtGA20ox1 and AtGA20ox2, the most highly expressed GA20ox genes during vegetative and early reproductive development. AtGA20ox1 and AtGA20ox2 act redundantly to promote hypocotyl and internode elongation, flowering time, elongation of anther filaments, the number of seeds that develop per silique and elongation of siliques, with AtGA20ox1 making the greater contribution to internode and filament elongation, and AtGA20ox2 making the greater contribution to flowering time and silique length. Pollination of the double mutant with wild-type pollen indicated that the GA promoting silique elongation is of maternal origin. The ga20ox2 phenotype revealed that GA promotes the number of stem internodes that elongate upon bolting, and does so independently of its effect on internode elongation. Comparison of the phenotype of the double mutant with that of the highly GA-deficient ga1-3 mutant indicates that other GA20ox genes contribute to all the developmental processes examined, and, in some cases such as root growth and leaf expansion, make major contributions, as these processes were unaffected in the double mutant. In addition, the effects of the mutations are mitigated by the homeostatic mechanism that acts on expression of other GA dioxygenase and GID1 receptor genes.