Dataset Information

Fast-Flowering Mini-Maize: Seed to Seed in 60 Days.

ABSTRACT: Two lines of Zea mays were developed as a short-generation model for maize. The Fast-Flowering Mini-Maize (FFMM) lines A and B are robust inbred lines with a significantly shorter generation time, much smaller stature, and better greenhouse adaptation than traditional maize varieties. Five generations a year are typical. FFMM is the result of a modified double-cross hybrid between four fast-flowering lines: Neuffer's Early ACR (full color), Alexander's Early Early Synthetic, Tom Thumb Popcorn, and Gaspe Flint, followed by selection for early flowering and desirable morphology throughout an 11-generation selfing regime. Lines A and B were derived from different progeny of the initial hybrid, and crosses between Mini-Maize A and B exhibit heterosis. The ancestry of each genomic region of Mini-Maize A and B was inferred from the four founder populations using genotyping by sequencing. Other genetic and genomic tools for these lines include karyotypes for both lines A and B, kernel genetic markers y1 (white endosperm) and R1-scm2 (purple endosperm and embryo) introgressed into Mini-Maize A, and ?24× whole-genome resequencing data for Mini-Maize A.

SUBMITTER: McCaw ME

PROVIDER: S-EPMC5012399 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Fast-Flowering Mini-Maize: Seed to Seed in 60 Days.

McCaw Morgan E ME Wallace Jason G JG Albert Patrice S PS Buckler Edward S ES Birchler James A JA

Genetics 20160720 1

Two lines of Zea mays were developed as a short-generation model for maize. The Fast-Flowering Mini-Maize (FFMM) lines A and B are robust inbred lines with a significantly shorter generation time, much smaller stature, and better greenhouse adaptation than traditional maize varieties. Five generations a year are typical. FFMM is the result of a modified double-cross hybrid between four fast-flowering lines: Neuffer's Early ACR (full color), Alexander's Early Early Synthetic, Tom Thumb Popcorn, a ...[more]

PMID: 27440866

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Project description:Maize (Zea mays ssp. mays) is a popular genetic model due to its ease of crossing, well-established toolkits, and its status as a major global food crop. Recent technology developments for precise manipulation of the genome are further impacting both basic biological research and biotechnological application in agriculture. Crop gene editing often requires a process of genetic transformation in which the editing reagents are introduced into plant cells. In maize, this procedure is well-established for a limited number of public lines that are amenable for genetic transformation. Fast-Flowering Mini-Maize (FFMM) lines A and B were recently developed as an open-source tool for maize research by reducing the space requirements and the generation time. Neither line of FFMM were competent for genetic transformation using traditional protocols, a necessity to its status as a complete toolkit for public maize genetic research. Here we report the development of new lines of FFMM that have been bred for amenability to genetic transformation. By hybridizing a transformable maize genotype high Type-II callus parent A (Hi-II A) with line A of FFMM, we introgressed the ability to form embryogenic callus from Hi-II A into the FFMM-A genetic background. Through multiple generations of iterative self-hybridization or doubled-haploid method, we established maize lines that have a strong ability to produce embryogenic callus from immature embryos and maintain resemblance to FFMM-A in flowering time and stature. Using an Agrobacterium-mediated standard transformation method, we successfully introduced the CRISPR-Cas9 reagents into immature embryos and generated transgenic and mutant lines displaying the expected mutant phenotypes and genotypes. The transformation frequencies of the tested genotypes, defined as the numbers of transgenic event producing T1 seeds per 100 infected embryos, ranged from 0 to 17.1%. Approximately 80% of transgenic plants analyzed in this study showed various mutation patterns at the target site. The transformable FFMM line, FFMM-AT, can serve as a useful genetic and genomic resource for the maize community.

Project description:BACKGROUND:In order to investigate the rate and limits of the response to selection from highly inbred genetic material and evaluate the respective contribution of standing variation and new mutations, we conducted a divergent selection experiment from maize inbred lines in open-field conditions during 7 years. Two maize commercial seed lots considered as inbred lines, F252 and MBS847, constituted two biological replicates of the experiment. In each replicate, we derived an Early and a Late population by selecting and selfing the earliest and the latest individuals, respectively, to produce the next generation. RESULTS:All populations, except the Early MBS847, responded to selection despite a short number of generations and a small effective population size. Part of the response can be attributed to standing genetic variation in the initial seed lot. Indeed, we identified one polymorphism initially segregating in the F252 seed lot at a candidate locus for flowering time, which explained 35% of the trait variation within the Late F252 population. However, the model that best explained our data takes into account both residual polymorphism in the initial seed lots and a constant input of heritable genetic variation by new (epi)mutations. Under this model, values of mutational heritability range from 0.013 to 0.025, and stand as an upper bound compare to what is reported in other species. CONCLUSIONS:Our study reports a long-term divergent selection experiment for a complex trait, flowering time, conducted on maize in open-field conditions. Starting from a highly inbred material, we created within a few generations populations that strikingly differ from the initial seed lot for flowering time while preserving most of the phenotypic characteristics of the initial inbred. Such material is unique for studying the dynamics of the response to selection and its determinants. In addition to the fixation of a standing beneficial mutation associated with a large phenotypic effect, a constant input of genetic variance by new mutations has likely contributed to the response. We discuss our results in the context of the evolution and mutational dynamics of populations characterized by a small effective population size.

Project description:ObjectivesTo determine methylprednisolone's dose, duration, and administration from onset of symptoms and association with 60 days in hospital survival of coronavirus disease 2019 pneumonia.DesignCohort study.SettingThirteen hospitals in New Jersey, United States during March to June 2020.PatientsSeven-hundred fifty-nine hospitalized coronavirus disease 2019 patients.InterventionsWe performed a propensity matched cohort study between patients who received methylprednisolone and no methylprednisolone. Patients in the methylprednisolone group were further differentiated into dose (high dose and low dose), duration, and administration from onset of symptoms.Measurements and main resultsIn the propensity matched sample, 99 out of 380 (26%) in no methylprednisolone, 69 out of 215 (31.9%) in low-dose methylprednisolone, and 74 out of 164 (55.2%) high-dose methylprednisolone expired. Overall median survival for no methylprednisolone (25.0 d), low-dose methylprednisolone (39.0 d), high-dose methylprednisolone (20.0 d), less than or equal to 7 days duration (19.0 d), 7-14 days duration (30.0 d), greater than 14 days duration (44.0 d), onset of symptoms less than or equal to 7 days (20.0 d), and onset of symptoms 7-14 days (27.0 d) were statistically significant (log-rank p ≤ 0.001). Multivariate Cox regression showed nursing home residents, coronary artery disease, and invasive mechanical ventilation were independently associated with mortality. Methylprednisolone was associated with reduced mortality compared with no methylprednisolone (hazard ratio, 0.40; 95% CI, 0.27-0.59; p < 0.001) but no added benefit with high dose. Low-dose methylprednisolone for 7-14 days was associated with reduced mortality compared with less than or equal to 7 days (hazard ratio, 0.45; 95% CI, 0.22-0.91; p = 0.0273), and no additional benefit if greater than 14 days (hazard ratio, 1.27; 95% CI, 0.60-2.69; p = 0.5434). Combination therapy with tocilizumab was associated with reduced mortality over monotherapy (p < 0.0116).ConclusionsLow-dose methylprednisolone was associated with reduced mortality if given greater than 7 days from onset of symptoms, and no additional benefit greater than 14 days. High dose was associated with higher mortality.

Dataset Information

Fast-Flowering Mini-Maize: Seed to Seed in 60 Days.

Publications

Fast-Flowering Mini-Maize: Seed to Seed in 60 Days.

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