Genetic and physical fine mapping of the novel brown midrib gene bm6 in maize (Zea mays L.) to a 180 kb region on chromosome 2

Brown midrib mutants in maize are known to be associated with reduced lignin content and increased cell wall digestibility, which leads to better forage quality and higher efficiency of cellulosic biomass conversion into ethanol. Four well known brown midrib (bm) mutants, named bm1–4, were identified several decades ago. Additional recessive brown midrib mutants have been identified by allelism tests and designated as bm5 and bm6. In this study, we determined that bm6 increases cell wall digestibility and decreases plant height. bm6 was confirmed onto the short arm of chromosome 2 by a small mapping set with 181 plants from a F2 segregating population, derived from crossing B73 and a bm6 mutant line. Subsequently, 960 brown midrib individuals were selected from the same but larger F2 population for genetic and physical mapping. With newly developed markers in the target region, the bm6 gene was assigned to a 180 kb interval flanked by markers SSR_308337 and SSR_488638. In this region, ten gene models are predicted in the maize B73 sequence. Analysis of these ten genes as well as genes in the syntenic rice region revealed that four of them are promising candidate genes for bm6. Our study will facilitate isolation of the underlying gene of bm6 and advance our understanding of brown midrib gene functions

The Genetics and Genomics of Virus Resistance in Maize

Viruses cause significant diseases on maize worldwide. Intensive agronomic practices, changes in vector distribution, and the introduction of vectors and viruses into new areas can result in emerging disease problems. Because deployment of resistant hybrids and cultivars is considered to be both economically viable and environmentally sustainable, genes and quantitative trait loci for most economically important virus diseases have been identified. Examination of multiple studies indicates the importance of regions of maize chromosomes 2, 3, 6, and 10 in virus resistance. An understanding of the molecular basis of virus resistance in maize is beginning to emerge, and two genes conferring resistance to sugarcane mosaic virus, Scmv1 and Scmv2, have been cloned and characterized. Recent studies provide hints of other pathways and genes critical to virus resistance in maize, but further work is required to determine the roles of these in virus susceptibility and resistance. This research will be facilitated by rapidly advancing technologies for functional analysis of genes in maize

Profiling the Impact of Medium Formulation on Morphology and Functionality of Primary Hepatocytes in vitro

The characterization of fully-defined in vitro hepatic culture systems requires testing of functional and morphological variables to obtain the optimal trophic support, particularly for cell therapeutics including bioartificial liver systems (BALs). Using serum-free fully-defined culture medium formulations, we measured synthetic, detoxification and metabolic variables of primary porcine hepatocytes (PPHs) - integrated these datasets using a defined scoring system and correlated this hepatocyte biological activity index (HBAI) with morphological parameters. Hepatic-specific functions exceeded those of both primary human hepatocytes (PHHs) and HepaRG cells, whilst retaining biotransformation potential and in vivo-like ultrastructural morphology, suggesting PPHs as a potential surrogate for PHHs in various biotech applications. The HBAI permits assessment of global functional capacity allowing the rational choice of optimal trophic support for a defined operational task (including BALs, hepatocellular transplantation, and cytochrome P450 (CYP450) drug metabolism studies), mitigates risk associated with sub-optimal culture systems, and reduces time and cost of research and therapeutic applications

Genetic and physical fine mapping of the novel brown midrib gene bm6 in maize (Zea mays L.) to a 180 kb region on chromosome 2

Brown midrib mutants in maize are known to be associated with reduced lignin content and increased cell wall digestibility, which leads to better forage quality and higher efficiency of cellulosic biomass conversion into ethanol. Four well known brown midrib (bm) mutants, named bm1–4, were identified several decades ago. Additional recessive brown midrib mutants have been identified by allelism tests and designated as bm5 and bm6. In this study, we determined that bm6 increases cell wall digestibility and decreases plant height. bm6 was confirmed onto the short arm of chromosome 2 by a small mapping set with 181 plants from a F2 segregating population, derived from crossing B73 and a bm6 mutant line. Subsequently, 960 brown midrib individuals were selected from the same but larger F2 population for genetic and physical mapping. With newly developed markers in the target region, the bm6 gene was assigned to a 180 kb interval flanked by markers SSR_308337 and SSR_488638. In this region, ten gene models are predicted in the maize B73 sequence. Analysis of these ten genes as well as genes in the syntenic rice region revealed that four of them are promising candidate genes for bm6. Our study will facilitate isolation of the underlying gene of bm6 and advance our understanding of brown midrib gene functions.This article is published as Chen, Yongsheng, Hongjun Liu, Farhad Ali, M. Paul Scott, Qing Ji, Ursula Karoline Frei, and Thomas Lübberstedt. "Genetic and physical fine mapping of the novel brown midrib gene bm6 in maize (Zea mays L.) to a 180 kb region on chromosome 2." Theoretical and Applied Genetics 125, no. 6 (2012): 1223-1235, doi: 10.1007/s00122-012-1908-5.</p

Development of maize inbred lines with elevated grain methionine concentration from a high methionine population

Methionine is a nutritionally limiting amino acid in poultry diets based on maize (Zea mays L.) grain. Synthetic dietary supplements are available but are costly and not preferred by organic poultry producers. The development of high methionine maize varieties would reduce the need for supplementation. Several approaches have been reported for achieving this goal. Here, we report a novel approach that can produce diverse inbred lines with higher content of methionine than other methods. Inbred lines were developed using doubled haploid technology from a broad-based synthetic population that has undergone mass selection for grain methionine concentration. Out of 18 randomly selected inbred lines, one was significantly higher in methionine concentration than the high methionine check and 11 were not significantly different from it. The inbred lines developed in this way also exhibited useful genetic diversity for several agronomic and kernel quality traits, including flowering date, and orangeness of the kernel. This approach is an excellent complement to other breeding methods for development of varieties for production of poultry feed. Because the approach does not rely on transgenic technology, the resulting lines are suitable for use by organic producers and are well suited to organic production systems.This article is published as Hintch, Taylor D., Adrienne Moran Lauter, Shelly M. Kinney, Thomas Lubberstedt, Ursula Frei, Prakasit Duangpapeng, Jode W. Edwards, and M. Paul Scott. "Development of maize inbred lines with elevated grain methionine concentration from a high methionine population." Crop Science (2023). doi:10.1002/csc2.20983.Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted

Usefulness of Adapted Exotic Maize Lines Developed By Doubled Haploid and Single Seed Descent Methods

Adapted exotic maize (Zea mays L.) germplasm, such as BS39, provides a unique opportunity for broadening the genetic base of U.S. Corn Belt germplasm. In vivo doubled haploid (DH) technology has been used to efficiently exploit exotic germplasm. It can help to purge deleterious recessive alleles. The objectives of this study were to determine the usefulness of BS39-derived inbred lines using both SSD and DH methods, to determine the impact of spontaneous as compared to artificial haploid genome doubling on genetic variance among BS39-derived DH lines, and to identify SNP markers associated with agronomic traits among BS39 inbreds monitored at testcross level. We developed two sets of inbred lines directly from BS39 by DH and SSD methods, named BS39_DH and BS39_SSD. Additionally, two sets were derived from a cross between BS39 and A427 (SHGD donor) by DH and SSD methods, named BS39×A427_DH and BS39×A427_SSD, respectively. Grain yield, moisture, plant height, ear height, stalk lodging, and root lodging were measured to estimate genetic parameters. For genome-wide association (GWAS) analysis, inbred lines were genotyped using Genotype-by-Sequencing (GBS) and Diversity Array Technology Sequencing (DArTSeq). Some BS39-derived inbred lines performed better than elite germplasm inbreds and all sets showed significant genetic variance. The presence of spontaneous haploid genome doubling genes did not affect performance of inbred lines. Five SNPs were significant and three of them located within genes related to plant development or abiotic stresses. These results demonstrate the potential of BS39 to add novel alleles to temperate elite germplasm.This is a preprint made available through Research Square at doi:10.21203/rs.3.rs-799789/v1. This work is licensed under a CC BY 4.0 License

Development and mapping of a public reference set of SSR markers in Lolium perenne L.

We report on the characterization and mapping of 76 simple sequence repeat (SSR) markers for Lolium perenne. These markers are publicly available or obtained either from genomic libraries enriched for SSR motifs or L. perenne expressed sequence tag (EST) clones. Four L. perenne mapping populations were used to map the SSR markers. A consensus linkage map of the four mapping populations containing 65 of the SSR markers is presented, together with primer information and a quality score indicating the usefulness of the SSR marker in different populations. The SSR markers identified all seven L. perenne linkage group