ISSN:
1432-0983
Keywords:
Restriction maps
;
Gene organization
;
Chloroplast DNA
;
Inversion
;
Asteraceae
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary We have cloned into plasmids 17 of 18 lettuce chloroplast DNA SacI fragments covering 96% of the genome. The cloned fragments were used to construct cleavage maps for 10 restriction enzymes for the chloroplast genomes of lettuce (Lactuca sativa) and Barnadesia caryophylla, two distantly related species in the sunflower family (Asteraceae). Both genomes are approximately 151 kb in size and contain a 25 kb inverted repeat. We also mapped the position and orientation of 37 chloroplast DNA genes. The mapping studies reveal that chloroplast DNAs of lettuce and Barnadesia differ by a 22 kb inversion in the large single copy region. Barnadesia has retained the primitive land plant genome arrangement, while the inversion has occurred in a lettuce lineage. The endpoints of the derived lettuce inversion were located by comparison to the well-characterized spinach and tobacco genomes. Both endpoints are located in intergenic spacers within tRNA gene clusters; one cluster being located downstream from the atpA gene and the other upstream from the psbD gene. The endpoint near the atpA gene is very close to one endpoint of a 20 kb inversion in wheat (Howe et al. 1983; Quigley and Weil 1985). Comparison of the restriction site maps gives an estimated sequence divergence of 3.7% for the lettuce and Barnadesia genomes. This value is relatively low compared to previous estimates for other angiosperm groups, suggesting a high degree of sequence conservation in the Asteraceae.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00384619
