The Response Of Disease Resistance-related Genes In Chinese Jujube (Ziziphus Jujuba Mill.) Under Phytoplasma Stress

The evolutionary of response to pathogen invasion provided plants with a highly sophisticated defense system. Ultimately, the final outcome of resistance depends on the transduction of signal, the expression of resistance genes and generated of secondary metabolites. In our previous study, a series of signaling transport and resistance-related genes were identified from a suppression subtractive hybridization (SSH) library of Ziziphus jujuba Mill.’Xingguang’, a cultivar with high-resistance to jujube witches’ broom (JWB) breeding by Liu Meng-jun. The SSH library was established under JWB disease, which is caused by phytoplasma and induces significant decrease of jujube production. The signaling transport and resistance genes (ZjCIPK, CBL-interacting protein kinase; ZjbZIP, Basic leucine zipper; ZjERF, Ethylene-responsive element binding factor; ZjTLP, Thaumatin-like protein; ZjPR10, Pathogenesis-related protein 10; ZjHSP70, Heat shock protein 70) from the SSH library were firstly isolated from Chinese jujube by homology-based cloning method. The expression of the genes under jujube witches’-broom (JWB) phytoplasma infection were analyzed at different time points using reverse transcription real-time quantitative PCR (RT-qPCR). One novel thymidylate kinase gene TMKZ was amplified from JWB phytoplasma. The relative quantity of TMKZ and ZjH3 (jujube gene) in the total DNA and RNA from the infected tissues were firstly represent the quantity and proliferation activity of JWB phytoplasma respectively. The main results were as follows:16 resistance-related genes (ZjCIPK:KC559754.1,1313bp; ZjbZIP:924bp; ZjbERF3’end,959bp; ZjTLP:KC559753.1,809bp; ZjPR10:KC559756.1,623bp; ZjHSP70:KC559755.1,1965bp) and a thymidylate kinase gene of JWB phytoplasma (TMKZ:KC493615.1,639bp, encoding a polypeptide of 213 amino acids) were isolated from Chinese jujube and JWB phytoplasma respectively by homology-based cloning method.2 A bioinformatics analysis reveals that a high degree of relatedness exists among ZjERF and ERF/B2 subgroup members from other plant species at the amino acid level. ZjTLP was predicted to localize at the extracellular while ZjER and ZjbZIP localized at the nucleus. GFP fusion protein indicated that the ZjTLP was localized at the extracellular.3 The quantity and proliferation activity detection method of JWB phytoplasma were firstly established by qPCR technique. The relative quantity of TMKZ and ZjH3 in the total DNA from the infected tissues was firstly used to represent the phytoplasma quantity. This method is applicable to the quantification of biotrophic pathogens. The relative quantity of TMKZ and ZjH3 in the total RNA from the infected tissues was firstly used to represent the proliferation activity of JWB phytoplasma.4 The quantity of phytoplasma was gradually increased in ’Pozao’ post JWB phytoplasma infection, so does in ’Xingguang’, while its quantity was much less than ’Pozao’. The proliferation activity of JWB phytoplasma was gradually increased in ’Pozao’ post JWB phytoplasma infection except for the 115day post infection. However the JWB phytoplasma has no proliferation activity in ’Xinguang’ post infection.5 The expression profile of resistance-related genes (ZjCIPK, ZjbZIP, ZjERF, ZjTLP, ZjPR10 and ZjHSP70) in ’Xingguang’shows up-regulated in the early stage post infection. However, the expression of resistance-related genes were general down-regulated in ’Pozao’. The expression of the resistance genes was much higher in the heavier diseased leaves.