Dataset Information

The physical and genetic framework of the maize B73 genome.

ABSTRACT: Maize is a major cereal crop and an important model system for basic biological research. Knowledge gained from maize research can also be used to genetically improve its grass relatives such as sorghum, wheat, and rice. The primary objective of the Maize Genome Sequencing Consortium (MGSC) was to generate a reference genome sequence that was integrated with both the physical and genetic maps. Using a previously published integrated genetic and physical map, combined with in-coming maize genomic sequence, new sequence-based genetic markers, and an optical map, we dynamically picked a minimum tiling path (MTP) of 16,910 bacterial artificial chromosome (BAC) and fosmid clones that were used by the MGSC to sequence the maize genome. The final MTP resulted in a significantly improved physical map that reduced the number of contigs from 721 to 435, incorporated a total of 8,315 mapped markers, and ordered and oriented the majority of FPC contigs. The new integrated physical and genetic map covered 2,120 Mb (93%) of the 2,300-Mb genome, of which 405 contigs were anchored to the genetic map, totaling 2,103.4 Mb (99.2% of the 2,120 Mb physical map). More importantly, 336 contigs, comprising 94.0% of the physical map ( approximately 1,993 Mb), were ordered and oriented. Finally we used all available physical, sequence, genetic, and optical data to generate a golden path (AGP) of chromosome-based pseudomolecules, herein referred to as the B73 Reference Genome Sequence version 1 (B73 RefGen_v1).

SUBMITTER: Wei F

PROVIDER: S-EPMC2774505 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

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The physical and genetic framework of the maize B73 genome.

Wei Fusheng F Zhang Jianwei J Zhou Shiguo S He Ruifeng R Schaeffer Mary M Collura Kristi K Kudrna David D Faga Ben P BP Wissotski Marina M Golser Wolfgang W Rock Susan M SM Graves Tina A TA Fulton Robert S RS Coe Ed E Schnable Patrick S PS Schwartz David C DC Ware Doreen D Clifton Sandra W SW Wilson Richard K RK Wing Rod A RA

PLoS genetics 20091120 11

Maize is a major cereal crop and an important model system for basic biological research. Knowledge gained from maize research can also be used to genetically improve its grass relatives such as sorghum, wheat, and rice. The primary objective of the Maize Genome Sequencing Consortium (MGSC) was to generate a reference genome sequence that was integrated with both the physical and genetic maps. Using a previously published integrated genetic and physical map, combined with in-coming maize genomic ...[more]

PMID: 19936061

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Project description:Recent comprehensive sequence analysis of the maize genome now permits detailed discovery and description of all transposable elements (TEs) in this complex nuclear environment. Reiteratively optimized structural and homology criteria were used in the computer-assisted search for retroelements, TEs that transpose by reverse transcription of an RNA intermediate, with the final results verified by manual inspection. Retroelements were found to occupy the majority (>75%) of the nuclear genome in maize inbred B73. Unprecedented genetic diversity was discovered in the long terminal repeat (LTR) retrotransposon class of retroelements, with >400 families (>350 newly discovered) contributing >31,000 intact elements. The two other classes of retroelements, SINEs (four families) and LINEs (at least 30 families), were observed to contribute 1,991 and approximately 35,000 copies, respectively, or a combined approximately 1% of the B73 nuclear genome. With regard to fully intact elements, median copy numbers for all retroelement families in maize was 2 because >250 LTR retrotransposon families contained only one or two intact members that could be detected in the B73 draft sequence. The majority, perhaps all, of the investigated retroelement families exhibited non-random dispersal across the maize genome, with LINEs, SINEs, and many low-copy-number LTR retrotransposons exhibiting a bias for accumulation in gene-rich regions. In contrast, most (but not all) medium- and high-copy-number LTR retrotransposons were found to preferentially accumulate in gene-poor regions like pericentromeric heterochromatin, while a few high-copy-number families exhibited the opposite bias. Regions of the genome with the highest LTR retrotransposon density contained the lowest LTR retrotransposon diversity. These results indicate that the maize genome provides a great number of different niches for the survival and procreation of a great variety of retroelements that have evolved to differentially occupy and exploit this genomic diversity.

Project description:Genome-wide gene expression atlas of maize inbred line B73. Maize inbred B73 was used for constructing the gene atlas. Plants were grown in Plano silt loam soil at the West Madison Agricultural Research Station, Verona, WI during Summer 2008. During field preparation, 200 kg/acre of Urea (46-0-0) was applied. One day after planting, herbicides including Callisto (142 g/acre), Dual II (710 ml/acre), and Simazine (227 g/acre) were applied. For collection of seed tissues, shoots were covered before silk emergence avoiding any injury to the plants. Plants were self-pollinated on the same day to establish a common time initiation point for the harvest timeline. Greenhouse-grown plants were propagated by growing five plants per pot (30 cm top diameter, 28 cm height, 14.5 L volume) containing Metro-Mix 300 (Sun Gro Horticulture, Bellevue, WA, USA) with no additional fertilization. The growing conditions were 27 deg. C day and 24 deg. C night temperature with a 16h light (5:00am to 9:00pm) and 8h dark regime. Germinating seed tissue was generated by soaking seeds in distilled water in a Petri dish for 12h and then placing seeds between layers of moist paper towels for another 12h to allow germination. The field samples were collected between 8:00am and 10:00am, approximately 3 hours after sunrise. The greenhouse samples were collected between 8:00am and 9:00am, three hours after turning on the lights. Three biological replicates were collected for each tissue type. For all the tissues except germinating seeds, a biological replicate was constituted by collecting and pooling samples from three competitive randomly chosen plants. For germinating seed, ten randomly chosen seeds were pooled to form a biological replicate. The harvested tissues were immediately frozen in liquid nitrogen and stored at -80 deg. C. Total RNA was extracted using TRIZOL reagent (Invitrogen, http://www.invitrogen.com) following the manufacturer's protocol, and purified using RNeasy MinElute Cleanup Kit (Qiagen, http://www.qiagen.com) following the manufacturer's instructions. PLEXdb (http://www.plexdb.org) has submitted this series at GEO on behalf of the original contributor, Rajandeep S Sekhon. The equivalent experiment is ZM29 at PLEXdb.

Dataset Information

The physical and genetic framework of the maize B73 genome.

Publications

The physical and genetic framework of the maize B73 genome.

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