Fine mapping and positional cloning will eventually improve with the anchoring of additional markers derived from genomic clones such as BACs. From 2,603 new BAC-end genomic sequences from Gossypium hirsutum Acala 'Maxxa', 1,316 PCR primer pairs (designated as MUSB) were designed to flank microsatellite or simple sequence repeat motif sequences. Most (1164 or 88%) MUSB primer pairs successfully amplified DNA from three species of cotton with an average of three amplicons per marker and 365 markers (21%) were polymorphic between G. hirsutum and G. barbadense. An interspecific RIL population developed from the above two entries was used to map 433 marker loci and 46 linkage groups with a genetic distance of 2,126.3 cM covering approximately 45% of the cotton genome and an average distance between two loci of 4.9 cM. Based on genome-specific chromosomes identified in G. hirsutum tetraploid (A and D), 56.9% of the coverage was located on the A subgenome while 39.7% was assigned to the D subgenome in the genetic map, suggesting that the A subgenome may be more polymorphic and recombinationally active than originally thought. The linkage groups were assigned to 23 of the 26 chromosomes. This is the first genetic map in which the linkage groups A01 and A02/D03 have been assigned to specific chromosomes. In addition the MUSB-derived markers from BAC-end sequences markers allows fine genetic and QTL mapping of important traits and for the first time provides reconciliation of the genetic and physical maps. Limited QTL analyses suggested that loci on chromosomes 2, 3, 12, 15 and 18 may affect variation in fiber quality traits. The original BAC clones containing the newly mapped MUSB that tag the QTLs provide critical DNA regions for the discovery of gene sequences involved in biological processes such as fiber development and pest resistance in cotton.

Background: The Cotton Microsatellite Database (CMD) http://www.cottonssr.org is a curated and integrated web-based relational database providing centralized access to publicly available cotton microsatellites, an invaluable resource for basic and applied research in cotton breeding.

Arthrobacter aurescens strain TC1 metabolizes atrazine to cyanuric acid via TrzN, AtzB, and AtzC. The complete sequence of a 160-kb bacterial artificial chromosome clone indicated that trzN, atzB, and atzC are linked on the A. aurescens genome. TrzN, AtzB, and AtzC were shown to be functional in Escherichia coli. Hybridization studies localized trzN, atzB, and atzC to a 380-kb plasmid in A. aurescens strain TC1.The complete nucleotide sequences of over 100 bacterial plasmids are now available, but most of these plasmids are relatively small and of interest primarily in microbial pathogenesis (for example, in the context of antibiotic resistance or toxin production). By contrast, only a limited number of large catabolic plasmids or catabolic islands on chromosomes have been sequenced. Examples include plasmids pNL1 from Sphingomonas aromaticivorans strain F199 (23), pAO1 from Arthrobacter nicotinovorans (11), pACR1 from Pseudomonas resinovorans strain CA10 (13), the TOL plasmid pWW0 from Pseudomonas putida (9), pBD2 from Rhodococcus erythropolis BD2 (31), pADP-1 from Pseudomonas sp. strain ADP (16), and the 105-kb catabolic island from Pseudomonas sp. strain B13 (28). Large catabolic plasmids can be difficult to isolate for sequencing. Thus, to facilitate widespread sequencing of large catabolic gene regions, more innovative strategies are needed. For example, plasmids have been identified via whole-genome shotgun sequencing of Deinococcus radiodurans (41) and Enterococcus faecalis (19).A wide variety of bacteria degrading the herbicide atrazine have been reported (2,14,21,22,32,36,37,43), and in all cases examined except one (3) the genes involved are located on plasmids (5,25,36,39). In Pseudomonas sp. strain ADP (14), the six atrazine-catabolic genes (atzA, atzB, atzC, and atzDEF) have been localized to plasmid pADP-1, from which the complete nucleotide sequence is now available (16). The atzA, atzB, and atzC genes have also been localized to different-sized plasmids in the gram-negative bacteria Chelatobacter heintzii, Stenotrophomonas maltophilia, and Pseudaminobacter spp., and hybridization analyses indicate that the atzB and atzC genes reside on a 117-kb plasmid in the gram-positive bacterium Arthrobacter crystallopoietes (25,36). The presence of nearly identical atrazine genes in Agrobacterium, Clavibacter, Rhizobium, Pseudomonas, Alcaligenes, and Ralstonia strains (2,5,22,24,33,39) further suggests that horizontal gene transfer is involved in the dissemination of atrazine-catabolic genes.Some differences have been observed in the gene content of the gram-positive atrazine-degrading bacteria Nocardioides sp. strains C190, SP12, and C157, Arthrobacter crystallopoietes, and Arthrobacter sp. strain AD1 (3,21,24,25,32,37). Nocardioides sp. strain C190 (37) does not contain atzA, atzB, or atzC, and atrazine degradation is initiated by the product of the trzN gene, which has been cloned and sequenced previously (17). A. crystallopoietes was shown to contain trzN, atzB, and atzC (25).The isolation and characteri...

Rice is the world's most important food crop and a model for cereal research. At 430 megabases in size, its genome is the most compact of the cereals. We report the sequence of chromosome 10, the smallest of the 12 rice chromosomes (22.4 megabases), which contains 3471 genes. Chromosome 10 contains considerable heterochromatin with an enrichment of repetitive elements on 10S and an enrichment of expressed genes on 10L. Multiple insertions from organellar genomes were detected. Collinearity was apparent between rice chromosome 10 and sorghum and maize. Comparison between the draft and finished sequence demonstrates the importance of finished sequence.

Rice (Oryza sativa L.) chromosome 3 is evolutionarily conserved across the cultivated cereals and shares large blocks of synteny with maize and sorghum, which diverged from rice more than 50 million years ago. To begin to completely understand this chromosome, we sequenced, finished, and annotated 36.1 Mb (∼97%) from O. sativa subsp. japonica cv Nipponbare. Annotation features of the chromosome include 5915 genes, of which 913 are related to transposable elements. A putative function could be assigned to 3064 genes, with another 757 genes annotated as expressed, leaving 2094 that encode hypothetical proteins. Similarity searches against the proteome of Arabidopsis thaliana revealed putative homologs for 67% of the chromosome 3 proteins. Further searches of a nonredundant amino acid database, the Pfam domain database, plant Expressed Sequence Tags, and genomic assemblies from sorghum and maize revealed only 853 nontransposable element related proteins from chromosome 3 that lacked similarity to other known sequences. Interestingly, 426 of these have a paralog within the rice genome. A comparative physical map of the wild progenitor species, Oryza nivara, with japonica chromosome 3 revealed a high degree of sequence identity and synteny between these two species, which diverged ∼10,000 years ago. Although no major rearrangements were detected, the deduced size of the O. nivara chromosome 3 was 21% smaller than that of japonica. Synteny between rice and other cereals using an integrated maize physical map and wheat genetic map was strikingly high, further supporting the use of rice and, in particular, chromosome 3, as a model for comparative studies among the cereals.