Cloning and sequence analysis of 18S rRNA gene fragment from succulent xerophyte Zygophyllum xanthoxylum

In order to reveal the relationship between succulent xerophyte Zygophyllum xanthoxylum and other plants and to provide evidences for the biologically evolution，total DNA was extracted from leaves of Z. xanthoxylum seedlings, and the 18S rRNA gene was cloned by PCR using general primers and cloned into pGEMT vector．The positive clone identified by PCR was sequenced．The sequencing result revealed that the 18S rRNA gene fragment from Z. xanthoxylum contains 1808 bp．Homology comparison with other plants 18S rRNA gene sequences in the GenBank showed that it shared over 96% nucleotide sequence homology, so it is concluded that 18S rRNA is very conservative gene in plants. However，Homology matrix and Blast showed that Z. xanthoxylum shared high similarity (98%) with the identified 18S rRNA in Galearia filiformis, Cnidoscolus aconitifolius and Hevea brasiliensis. Phylogenetic tree analysis indicated that Z. xanthoxylum and Panax notoginseng were most consanguineously grouped.