Detailed mapping of the chloroplast genome of barley, Hordeum vulgare L.

The chloroplast DNA (ctDNA) of barley (Hordeum vulgare L.) was isolated from young green leaves and fragments after partial digestion with Sau3A were cloned into a lambda phage vector. Using an overlapping clone bank of the entire chloroplast genome of barley, we mapped the cleavage sites for the enzymes XbaI, HindIII, PstI, SalI and PuvII precisely on the circular DNA. The chloroplast genome of barley was found to be 137 kbp long and to contain a pair of inverted repeat regions of 23.7 - 21.1 kbp that separated two single-copy regions of 81.7 - 81.1 kbp and 13.2 - 10.6 kbp, respectively. The restriction map of the barley chloroplast genome showed a high degree of conservation of restriction sites relative to those in the chloroplast genomes of wheat and rye. The genes for 13 transfer RNAs and 33 chloroplast proteins were identified and located on the barley chloroplast genome by hybridization with fragments of rice ctDNA that contained the corresponding genes. The locations of the various genes are very similar to the respective positions on the chloroplast genome of rice and maize.