Mechanism of zju-miR156c-mediated network in regulating witches' broom symptom of Chinese jujube.

Jujube witches' broom, caused by phytoplasma, is a destructive disease of Chinese jujube. Studies have shown that zju-miR156s play an important role in phytoplasma infection in jujube, but the regulatory mechanism between zju-miR156c and witches' broom remains unexplored. In the current study, miRNA-seq and gene expression analysis showed that zju-miR156c was more highly induced in infected jujube plants than the other miRNAs and its target gene was ZjSPL3. In addition, the expression levels of thymidylate kinase gene (TMK) and secreted jujube protein (SJP1) in diseased materials were higher than those in healthy controls. The expression level of zju-miR156c was significantly upregulated, while ZjSPL3 was sharply downregulated and the content of cytokinin (CTK) significantly increased. Overexpression of zju-miR156c in Arabidopsis significantly reduced the expression of AtSPL10 (homologous gene of ZjSPL3) but increased the content of CTK, and the transgenic plants exhibited witches' broom symptoms. In addition, yeast two-hybrid and co-immunoprecipitation assays confirmed that SJP1 interacted with ZjERF18. Yeast one-hybrid analysis showed that ZjERF18 could interact with the promoter of zju-MIR156c. In conclusion, our results demonstrated a novel pathogenic module of ZjERF18-zju-miR156c-ZjSPL3-CTK has an important function in the formation of witches' broom caused by SJP1.