We have studied the physical organization of genes and non-coding DNA in two Allium species, A. cepa and A. fistulosum. Expressed sequence tags (ESTs) clones and polymerase chain reaction (PCR) products of gene fragments obtained with primers designed for the gene sequences available in the public GenBank were physically mapped onto chromosomes using a Tyr-FISH technique. The allinase and lacrymatory factor synthase (LFS) genes that encoded enzymes operating in one metabolic way were cloned sequences and physically mapped onto A. cepa and A. fistulosum chromosomes. The alliinase gene probe (1100 bp) hybridized to the distal region of the long arm of chromosome 4 of A. cepa. The LFS gene probe (550 bp) hybridized to the proximal region of the long arm of chromosome 5 in both species. Inter-simple sequence repeats (ISSRs) that are located between SSR loci were used for chromosomal location of microsatellites in A. fistulosum using common FISH. The chromosomal organization of the Tyl-copia group retrotransposons were investigated in A. fistulosum. Dispersed hybridization of the probe along the chromosome arms apart from telomeric ends was detected. Chromosomal distribution of DNA methylation pattern in A. fistulosum L. was studied using a specific antibodies against 5-methylcytosine (anti-5mC). Highly methylated distal regions in all chromosomes were found. Differences in the methylation level between corresponding regions of homologue chromosomes were shown. We describe recent progress in exploiting the ultrasensitive Tyr-FISH technique for development of visual gene maps for chromosomes of A. cepa and A. fistulosum. The results on the chromosomal location of individual genetic loci aided in assembling physical and genetic maps. We related the physical organization of expressed genes to the contrasting patterns of chiasma distribution and to the organization of repetitive DNA family and highly methylated DNA in these two Allium species.
|Titel||Proceedings of the VI International Symposium on Edible Alliaceae|
|Uitgeverij||International Society for Horticultural Science|
|ISBN van geprinte versie||978-90-66056-95-4|
|Status||Gepubliceerd - 2012|