DNA Methylation Causes Predominant Maternal Controls of Plant Embryo Growth

The parental conflict hypothesis predicts that the mother inhibits embryo growth counteracting growth enhancement by the father. In plants the DNA methyltransferase MET1 is a central regulator of parentally imprinted genes that affect seed growth. However the relation between the role of MET1 in imprinting and its control of seed size has remained unclear. Here we combine cytological, genetic and statistical analyses to study the effect of MET1 on seed growth. We show that the loss of MET1 during male gametogenesis causes a reduction of seed size, presumably linked to silencing of the paternal allele of growth enhancers in the endosperm, which nurtures the embryo. However, we find no evidence for a similar role of MET1 during female gametogenesis. Rather, the reduction of MET1 dosage in the maternal somatic tissues causes seed size increase. MET1 inhibits seed growth by restricting cell division and elongation in the maternal integuments that surround the seed. Our data demonstrate new controls of seed growth linked to the mode of reproduction typical of flowering plants. We conclude that the regulation of embryo growth by MET1 results from a combination of predominant maternal controls, and that DNA methylation maintained by MET1 does not orchestrate a parental conflict

Tocilizumab in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Background: In this study, we aimed to evaluate the effects of tocilizumab in adult patients admitted to hospital with COVID-19 with both hypoxia and systemic inflammation. Methods: This randomised, controlled, open-label, platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing several possible treatments in patients hospitalised with COVID-19 in the UK. Those trial participants with hypoxia (oxygen saturation <92% on air or requiring oxygen therapy) and evidence of systemic inflammation (C-reactive protein ≥75 mg/L) were eligible for random assignment in a 1:1 ratio to usual standard of care alone versus usual standard of care plus tocilizumab at a dose of 400 mg–800 mg (depending on weight) given intravenously. A second dose could be given 12–24 h later if the patient's condition had not improved. The primary outcome was 28-day mortality, assessed in the intention-to-treat population. The trial is registered with ISRCTN (50189673) and ClinicalTrials.gov (NCT04381936). Findings: Between April 23, 2020, and Jan 24, 2021, 4116 adults of 21 550 patients enrolled into the RECOVERY trial were included in the assessment of tocilizumab, including 3385 (82%) patients receiving systemic corticosteroids. Overall, 621 (31%) of the 2022 patients allocated tocilizumab and 729 (35%) of the 2094 patients allocated to usual care died within 28 days (rate ratio 0·85; 95% CI 0·76–0·94; p=0·0028). Consistent results were seen in all prespecified subgroups of patients, including those receiving systemic corticosteroids. Patients allocated to tocilizumab were more likely to be discharged from hospital within 28 days (57% vs 50%; rate ratio 1·22; 1·12–1·33; p<0·0001). Among those not receiving invasive mechanical ventilation at baseline, patients allocated tocilizumab were less likely to reach the composite endpoint of invasive mechanical ventilation or death (35% vs 42%; risk ratio 0·84; 95% CI 0·77–0·92; p<0·0001). Interpretation: In hospitalised COVID-19 patients with hypoxia and systemic inflammation, tocilizumab improved survival and other clinical outcomes. These benefits were seen regardless of the amount of respiratory support and were additional to the benefits of systemic corticosteroids. Funding: UK Research and Innovation (Medical Research Council) and National Institute of Health Research

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

Background: Many patients with COVID-19 have been treated with plasma containing anti-SARS-CoV-2 antibodies. We aimed to evaluate the safety and efficacy of convalescent plasma therapy in patients admitted to hospital with COVID-19. Methods: This randomised, controlled, open-label, platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]) is assessing several possible treatments in patients hospitalised with COVID-19 in the UK. The trial is underway at 177 NHS hospitals from across the UK. Eligible and consenting patients were randomly assigned (1:1) to receive either usual care alone (usual care group) or usual care plus high-titre convalescent plasma (convalescent plasma group). The primary outcome was 28-day mortality, analysed on an intention-to-treat basis. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936. Findings: Between May 28, 2020, and Jan 15, 2021, 11558 (71%) of 16287 patients enrolled in RECOVERY were eligible to receive convalescent plasma and were assigned to either the convalescent plasma group or the usual care group. There was no significant difference in 28-day mortality between the two groups: 1399 (24%) of 5795 patients in the convalescent plasma group and 1408 (24%) of 5763 patients in the usual care group died within 28 days (rate ratio 1·00, 95% CI 0·93–1·07; p=0·95). The 28-day mortality rate ratio was similar in all prespecified subgroups of patients, including in those patients without detectable SARS-CoV-2 antibodies at randomisation. Allocation to convalescent plasma had no significant effect on the proportion of patients discharged from hospital within 28 days (3832 [66%] patients in the convalescent plasma group vs 3822 [66%] patients in the usual care group; rate ratio 0·99, 95% CI 0·94–1·03; p=0·57). Among those not on invasive mechanical ventilation at randomisation, there was no significant difference in the proportion of patients meeting the composite endpoint of progression to invasive mechanical ventilation or death (1568 [29%] of 5493 patients in the convalescent plasma group vs 1568 [29%] of 5448 patients in the usual care group; rate ratio 0·99, 95% CI 0·93–1·05; p=0·79). Interpretation: In patients hospitalised with COVID-19, high-titre convalescent plasma did not improve survival or other prespecified clinical outcomes. Funding: UK Research and Innovation (Medical Research Council) and National Institute of Health Research

MINISEED3 (MINI3), a WRKY family gene, and HAIKU2 (IKU2), a leucine-rich repeat (LRR) KINASE gene, are regulators of seed size in Arabidopsis

We have identified mutant alleles of two sporophytically acting genes, HAIKU2 (IKU2) and MINISEED3 (MINI3). Homozygotes of these alleles produce a small seed phenotype associated with reduced growth and early cellularization of the endosperm. This phenotype is similar to that described for another seed size gene, IKU1. MINI3 encodes WRKY10, a WRKY class transcription factor. MINI3 promoter::GUS fusions show the gene is expressed in pollen and in the developing endosperm from the two nuclei stage at ≈12 hr postfertilization to endosperm cellularization at ≈96 hr. MINI3 is also expressed in the globular embryo but not in the late heart stage of embryo development. The early endosperm expression of MINI3 is independent of its parent of origin. IKU2 encodes a leucine-rich repeat (LRR) KINASE (At3g19700). IKU2::GUS has a similar expression pattern to that of MINI3. The patterns of expression of the two genes and their similar phenotypes indicate they may operate in the same genetic pathway. Additionally, we found that both MINI3 and IKU2 showed decreased expression in the iku1-1 mutant. IKU2 expression was reduced in a mini3-1 background, whereas MINI3 expression was unaltered in the iku2-3 mutant. These data suggest the successive action of the three genes IKU1, IKU2, and MINI3 in the same pathway of seed development

Transgene Expression and Transgene-Induced Silencing in Diploid and Autotetraploid Arabidopsis

Previous studies have suggested that transgene expression in plants can be affected by ploidy. Here we show that three different transgenes, a reporter transgene, an antisense transgene, and a hairpin RNA (hpRNA) transgene, are all expressed at a lower level in autotetraploid (4n) than in diploid (2n) Arabidopsis. RNA silencing of two endogenous genes was induced by the antisense and hpRNA transgenes and this silencing is significantly less effective in 4n than in 2n Arabidopsis; furthermore, the reduced silencing in 4n Arabidopsis correlated with reduced accumulation of silencing-inducer RNAs. Methylation analysis both of independent 2n and 4n transgenic lines and of 2n and 4n progeny derived from the same 3n transgenic parent, indicated that transgenes are more methylated in 4n than 2n Arabidopsis. These results suggest that transgenes are transcriptionally repressed in the 4n background, resulting in expression levels lower than in the 2n background. Transgenes designed to silence endogenous genes express lower concentrations of silencing-inducer RNAs in 4n Arabidopsis plants, resulting in less effective silencing of target genes than in 2n Arabidopsis plants