Engineering sulfur storage in maize seed proteins without apparent yield loss.

Sulfur assimilation may limit the pool of methionine and cysteine available for incorporation into zeins, the major seed storage proteins in maize. This hypothesis was tested by producing transgenic maize with deregulated sulfate reduction capacity achieved through leaf-specific expression of the Escherichia coli enzyme 3'-phosphoadenosine-5'-phosphosulfate reductase (EcPAPR) that resulted in higher methionine accumulation in seeds. The transgenic kernels have higher expression of the methionine-rich 10-kDa δ-zein and total protein sulfur without reduction of other zeins. This overall increase in the expression of the S-rich zeins describes a facet of regulation of these proteins under enhanced sulfur assimilation. Transgenic line PE5 accumulates 57.6% more kernel methionine than the high-methionine inbred line B101. In feeding trials with chicks, PE5 maize promotes significant weight gain compared with nontransgenic kernels. Therefore, increased source strength can improve the nutritional value of maize without apparent yield loss and may significantly reduce the cost of feed supplementation.

Overexpression of serine acetyltransferase in maize leaves increases seed-specific methionine-rich zeins.

Maize kernels do not contain enough of the essential sulphur-amino acid methionine (Met) to serve as a complete diet for animals, even though maize has the genetic capacity to store Met in kernels. Prior studies indicated that the availability of the sulphur (S)-amino acids may limit their incorporation into seed storage proteins. Serine acetyltransferase (SAT) is a key control point for S-assimilation leading to Cys and Met biosynthesis, and SAT overexpression is known to enhance S-assimilation without negative impact on plant growth. Therefore, we overexpressed Arabidopsis thaliana AtSAT1 in maize under control of the leaf bundle sheath cell-specific rbcS1 promoter to determine the impact on seed storage protein expression. The transgenic events exhibited up to 12-fold higher SAT activity without negative impact on growth. S-assimilation was increased in the leaves of SAT overexpressing plants, followed by higher levels of storage protein mRNA and storage proteins, particularly the 10-kDa δ-zein, during endosperm development. This zein is known to impact the level of Met stored in kernels. The elite event with the highest expression of AtSAT1 showed 1.40-fold increase in kernel Met. When fed to chickens, transgenic AtSAT1 kernels significantly increased growth rate compared with the parent maize line. The result demonstrates the efficacy of increasing maize nutritional value by SAT overexpression without apparent yield loss. Maternal overexpression of SAT in vegetative tissues was necessary for high-Met zein accumulation. Moreover, SAT overcomes the shortage of S-amino acids that limits the expression and accumulation of high-Met zeins during kernel development.

Chromosome-scale genome assemblies and annotations for Poales species Carex cristatella, Carex scoparia, Juncus effusus, and Juncus inflexus.

The majority of sequenced genomes in the monocots are from species belonging to Poaceae, which include many commercially important crops. Here, we expand the number of sequenced genomes from the monocots to include the genomes of 4 related cyperids: Carex cristatella and Carex scoparia from Cyperaceae and Juncus effusus and Juncus inflexus from Juncaceae. The high-quality, chromosome-scale genome sequences from these 4 cyperids were assembled by combining whole-genome shotgun sequencing of Nanopore long reads, Illumina short reads, and Hi-C sequencing data. Some members of the Cyperaceae and Juncaceae are known to possess holocentric chromosomes. We examined the repeat landscapes in our sequenced genomes to search for potential repeats associated with centromeres. Several large satellite repeat families, comprising 3.2-9.5% of our sequenced genomes, showed dispersed distribution of large satellite repeat clusters across all Carex chromosomes, with few instances of these repeats clustering in the same chromosomal regions. In contrast, most large Juncus satellite repeats were clustered in a single location on each chromosome, with sporadic instances of large satellite repeats throughout the Juncus genomes. Recognizable transposable elements account for about 20% of each of the 4 genome assemblies, with the Carex genomes containing more DNA transposons than retrotransposons while the converse is true for the Juncus genomes. These genome sequences and annotations will facilitate better comparative analysis within monocots.

Clinical characteristics of patients with asymptomatic and symptomatic COVID-19 admitted to a tertiary referral centre in the Philippines.

Objectives: To describe the clinical profile and outcomes of hospitalized patients with coronavirus disease 2019 (COVID-19) across the spectrum of disease severity. Methods: This retrospective study included adult patients with confirmed COVID-19 infection admitted to a referral hospital. Descriptive statistics, tests for trend, Kaplan-Meier curve and log-rank test were used to compare characteristics and outcomes across disease severity categories. Results: Of 1500 patients with COVID-19, 14.8% were asymptomatic, 13.5% had mild disease, 36.6% had moderate disease, 12.3% had severe disease and 22.7% had critical disease. Asymptomatic patients were admitted for a concurrent condition or for isolation. Patients aged >60 years, male gender and with co-morbidities had more severe disease. Fever, cough, shortness of breath, malaise, gastrointestinal symptoms and decreased sensorium were more common in patients with severe disease. Bilateral pulmonary infiltrates were common (51.1%), with sicker patients having more abnormal findings. The overall mortality rate was 15.1%. Adopting a symptom-based strategy reduced the length of hospitalization from a median of 13 [interquartile range (IQR) 7-21] days to 9 (IQR 5-14) days. Conclusion: The clinical profile and outcomes for this cohort of patients with COVID-19 was consistent with published reports. Asymptomatic infection was common, and universal testing may be a valuable strategy in the correct context, given the implications for infection control. A symptom-based strategy was found to reduce the length of hospitalization considerably.

Predictors of mortality among inpatients with COVID-19 infection in a tertiary referral center in the Philippines.

Objectives: The aim of this study was to determine the predictors of mortality and describe laboratory trends among adults with confirmed COVID-19. Methods: The medical records of adult patients admitted to a referral hospital with COVID-19 were retrospectively reviewed. Demographic and clinical characteristics, and laboratory parameters, were compared between survivors and non-survivors. Predictors of mortality were determined by multivariate analysis. Mean laboratory values were plotted across illness duration. Results: Of 1215 patients, 203 (16.7%) had mild, 488 (40.2%) moderate, 183 (15.1%) severe, and 341 (28.1%) critical COVID-19 on admission. In-hospital mortality was 18.2% (0% mild, 6.1% moderate, 15.8% severe, 47.5% critical). Predictors of mortality were age ≥ 60 years, COPD, qSOFA score ≥ 2, WBC > 10 × 109/L, absolute lymphocyte count < 1000, neutrophil ≥ 70%, PaO2/FiO2 ratio ≤ 200, eGFR < 90 mL/min/1.73 m2, LDH > 600 U/L, and CRP > 12 mg/L. Non-survivors exhibited an increase in LDH and decreases in PaO2/FiO2 ratio and eGFR during the 2nd-3rd week of illness. Conclusion: The overall mortality rate was high. Predictors of mortality were similar to those of other reports globally. Marked inflammation and worsening pulmonary and renal function were evident among non-survivors by the 2nd-3rd week of illness.

Quality Protein Maize Based on Reducing Sulfur in Leaf Cells.

Low levels of the essential amino acids lysine (Lys) and methionine (Met) in a maize-based diet are a major cost to feed and food. Lys deficiency is due to the abundance of Lys-poor proteins in maize kernels. Although a maize mutant, opaque-2 (o2), has sufficient levels of Lys, its soft kernel renders it unfit for storage and transportation. Breeders overcame this problem by selecting quantitative trait loci (QTL) restoring kernel hardness in the presence of o2, a variety called Quality Protein Maize (QPM). Although at least one QTL acts by enhancing the expression of the γ-zein proteins, we could surprisingly achieve rebalancing of the Lys content and a vitreous kernel phenotype by targeting suppression of γ-zeins without the o2 mutant. Reduced levels of γ-zeins were achieved with RNA interference (RNAi). Another transgenic event, PE5 expresses the Escherichia coli enzyme 3'-phosphoadenosine-5'-phosphosulfate reductase involved in sulfate assimilation, specifically in leaves. The stacked transgenic events produce a vitreous endosperm, which has higher Lys level than the classical opaque W64Ao2 variant. Moreover, due to the increased sulfate reduction in the leaf, Met level is elevated in the seed. Such a combination of transgenes produces hybrid seeds superior to classical QPMs that would neither require a costly feed mix nor synthetic Met supplementation, potentially creating a novel and cost-effective means for improving maize nutritional quality.