| Jujube witches'broom (JWB) is a destructive disease caused by phytoplasma. The disease are found in Shaanxi, Shanxi, Henan, Hebei, Shandong provinces(cities) of China etc., direct economic losses is up to several hundred million dollars, seriously hindered the development of the jujube industry. Phytoplasmas strictly parasitic in the phloem of plant, there were some difficulty of culturing phytoplasmas in vitro ,and the content of phytoplasma in plants are too low, which restricted the study about the nature of their genetic, biochemical and molecular mechanism. So far, the scientists of Japan and Korea have reported the16S rRNA gene fragments in the literature. In China, 16S rRNA is mainly used to test disease, the relationship between jujube witches'broom and wide jujube witches'broom, the phytoplasma related gene sequences were not reported in the literature. Therefore, the study of JWB is an important problem for a long time.In this paper, We cloned the 16S rRNA, tuf, rp and secY genes, and carred out the Homology analysis for sequences, forecast the molecular characteristics of secreted proteins secY by bioinformatics methods.The results are as follows:(1) The relationship between jujube witches'broom and wide jujube witches'broom: Jujube witches'broom and wild jujube witches'broom were investigated in Binxian,Yanlia- ng,Wugong,Yangling,Jiaxian of Shaanxi, Cangzhou of Hebei, Xingxiang of Henan. The 16S rRNA and tuf gene were cloned by polymerase chain reaction from samples of JWB and wild jujube witches'broom, and sequenced. The Homology analysis for sequences of 16S rRNA and tuf gene shows that pathogens from Shaanxi, Hebei, Shandong are same, and belong to 16Srâ…¤-B group. The sequences of 16S rRNA and tuf gene of jujube witches'broom were submitted to the GenBank,the numbers were DQ919060 and EF088198 respectivly. Because there are five different nucleotides in 16S rRNA between JWB and wild jujube witches'broom , and homology rate of nucleotide sequences of tuf gene is 99.6%, we can estimate that wild jujube witches'broom is infected by different strain of JWB pathogen. The sequences of 16S rRNA and tuf gene of wide jujube witches'broom were submitted to the GenBank,the numbers were DQ886426 and DQ919061 respectivly. (2) Cloning and sequence analysis of rp and secY from Jujube witches'broom phytoplasma: The ribosomal protein rp gene and translocation protein secY gene are cloned by polymerase chain reaction from the samples of JWB which were collected from Shaanxi. After sequenced, it is found that rp gene is 1199bp, which included partial rps19, rpl22 and rps3. rpl22 and rps3 coded 129 and 252 amino acids respectively, and these two genes aren't overlapped. secY gene is 1421bp, which contains partial rp gene(rpl15) and secY gene. secY gene coded 465 amino acids. The homologic analysis shows that it is similar in character among JWB, cherry lethal yellows and peach yellows isolate PY-In phytoplasmas, and is basically same with the reports of Jung, H.-Y. This part identified that JWB phytoplasma belongs to 16S râ…¤-B,the secY gene was as same as rp gene, as an assisted analysis of phytoplasma classification system, is also a reliable and easy way.(3) Molecular Characterization of secY gene from jujube witches'broom phytoplasma: Through the analysis of ANTHEPROT5.0,the results show the molecular weight of secY is 45.2KDa,the protein is of good antigenicity. The secondary structure contain helixes, sheets and coils,without turns.There are eight transmembranous regions and several potential cleavage sites of signal peptide. Cleavage sites are mainly located in the section between 50-250 amino acids. the most cleavage sites are located in the 221st amino acids (Ala). In the 81st amino acids (Ala) and 151st amino acids (glycine), there are also strong cleavage sites. In other parts of the protein, the potential weak signal peptide cleavage sites is also found. secY protein of JWB phytoplasma belong to the same type with those of Elm yellows (EY), Cherry lethal yellows(CLY-5) phytoplasmas. The assay provide theoretic basis for studying function of secY gene and hope that it can reavel pathogenic mechanism.
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