The abundance and scattered distribution of simple-sequence repeats (SSR) in eukaryotic genomes prompted us to explore the use of SSR-based oligonucleotide primers in single primer amplification reactions. In a pilot experiment, 23 primers were used across a panel of evolutionarily diverse eukaryotic genomes, including grapes, lettuce, tomato, pine, maize, salmon, chicken, Holstein cows and humans. The primers were 16-20 bases in length and represented SSRs of di-, tri-, tetra-, and pentanucleotide repeats. The results showed that tetranucleotide repeat primers were most effective in amplifying polymorphic patterns. Of 11 such primers tested, 70% produced polymorphic patterns from the DNA of one or more species. Primers representing a combination of two tetranucleotide repeats, or compound microsatellites, were equally effective. The polymorphisms contained in such fingerprints were able to identify individuals of vertebrate species as well as lines or varieties of plants. Inheritance of the polymorphic bands was studied in a maize recombinant inbred population, DE811 x B73. Thirty-two polymorphic bands, derived from two amplification patterns, were mapped as dominant markers on an existing RFLP map of the same population. The bands were distributed across nine of the ten chromosomes.

The quality of canola oil is determined by its constituent fatty acids such as oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3). Most canola cultivars normally produce oil with about 55-65% oleic acid and 8-12% linolenic acid. High concentrations of linolenic acid lead to oil instability and off-type flavor, while high levels of oleic acid increase oxidative stability and nutritional value of oil. Therefore, development of canola cultivars with increased oleic acid and reduced linolenic acid is highly desirable for canola oil quality. In this study, we have mapped one locus that has a major effect and one locus that has a minor effect for high oleic acid and two loci that have major effects for low linolenic acid in a doubled haploid population. The major locus for high C18:1 was proven to be the fatty acid desaturase-2 (fad2) gene and it is located on the linkage group N5; the minor locus is located on N1. One major QTL for C18:3 is the fatty acid desaturase-3 gene of the genome C (fad3c) and it is located on N14. The second major QTL resides on N4 and is the fad3a gene of the A genome. We have sequenced genomic clones of the fad2 and fad3c genes amplified from an EMS-induced mutant and a wild-type canola cultivar. A comparison of the mutant and wild-type allele sequences of the fad2 and fad3c genes revealed single nucleotide mutations in each of the genes. Detailed sequence analyses suggested mechanisms by which both the mutations can cause altered fatty acid content. Based on the sequence differences between the mutant and wild-type alleles, two single nucleotide polymorphism (SNP) markers, corresponding to the fad2 and fad3c gene mutations, were developed. These markers will be highly useful for direct selection of desirable fad2 and fad3c alleles during marker-assisted trait introgression and breeding of canola with high oleic and low linolenic acid.

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Oilseed crops, especially soybean (Glycine max) and canola/rapeseed (Brassica napus), produce seeds that are rich in both proteins and oils and that are major sources of energy and nutrition worldwide. Most of the nutritional content in the seed is accumulated in the embryo during the seed filling stages of seed development. Understanding the metabolic pathways that are active during seed filling and how they are regulated are essential prerequisites to crop improvement. In this review, we summarize various omics studies of soybean and canola/rapeseed during seed filling, with emphasis on oil and protein traits, to gain a systems-level understanding of seed development. Currently, most (80-85%) of the soybean and rapeseed reference genomes have been sequenced (950 and 850 megabases, respectively). Parallel to these efforts, extensive omics datasets from different seed filling stages have become available. Transcriptome and proteome studies have detected preponderance of starch metabolism and glycolysis enzymes to be the possible cause of higher oil in B. napus compared to other crops. Small RNAome studies performed during the seed filling stages have revealed miRNA-mediated regulation of transcription factors, with the suggestion that this interaction could be responsible for transitioning the seeds from embryogenesis to maturation. In addition, progress made in dissecting the regulation of de novo fatty acid synthesis and protein storage pathways is described. Advances in high-throughput omics and comprehensive tissue-specific analyses make this an exciting time to attempt knowledge-driven investigation of complex regulatory pathways.

The cyanophycin granule polypeptide (CGP) is known to serve as a nitrogen reserve protein in cyanobacteria and is mobilized during nitrogen starvation. An exopeptidase, provisionally called cyanophycinase, which degraded CGP in vitro has been studied, and its product characterized, in two N,-fixing Anabaena species. The enzyme had a pH optimum of 8.5, had no requirement for monovalent or divalent cations and was inhibited by L-arginine and L-aspartic acid. The product of this enzyme was an aspartic acid-arginine dipeptide. A higher activity of both arg-poly (asp) synthetase and cyanophycinase was observed in extracts of heterocysts of both Anabaena species than in vegetative cells. This supports the view that CGP has a dynamic role in nitrogen metabolism of cyanobacteria as well as a storage function.

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It has been suggested that the middle repetitive class of sequences that make up a large proportion of the eukaryotic genome have been amplified and dispersed by DNA transposition. Transposition is a phenomenon first postulated by Barbara McClintock on the basis of her genetic analysis of mutants in Zea mays. Since then, DNA transposition has been studied genetically in various plant systems and is well documented on the molecular level in both prokaryotes and eukaryotes. This has included the isolation of DNA inserts at various loci in several plants; however, the prevalence of transposition in plants is not established. We report here DNA nucleotide sequence data which show that some members of the Cin1 middle repetitive family of maize have features characteristic of known transposable elements. One cloned Cin1 repeat has a 6-base pair (bp) perfect inverted repeat sequence at its ends. The terminal five base pairs (5' TGTTG . . . CAACA 3') are identical to the termini of Drosophila copia transposable elements. Two other Cin1 alleles are flanked by 5-bp direct repeats. A comparison is made with the long terminal repeat (LTR) of the copia-Ty1-retrovirus families of moveable genetic elements.