Disease resistance of SlJAZ7 and its interaction with SlTGA7 in tomato

Objective Bacterial spot disease is one of the main factors leading to tomato (Solanum lycopersicum) yield reduction, and Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) is one of the pathogenic factors of bacterial spot disease. Transient silencing of JAZ7 gene in tomato results in its increased susceptibility to Pst DC3000. At present, there are a few reports to verify the resistance function and mechanism of JAZ7 gene in tomato. In this study, we cloned SlJAZ7 gene in tomato leaves, and a stable genetic transgenic tomato with overexpression of SlJAZ7 was created to analyze its resistance function and mechanism, and the relationship between SlJAZ7 and SlTGA7, which is closely related to disease resistance, was studied at the transcriptional and protein levels, providing a theoretical basis for effective prevention and control of bacterial spot disease.

Method The resistance function of SlJAZ7 gene was determined by the phenotypic difference between wild type and transgenic tomato inoculated with Pst DC3000. RT-qPCR was used to analyze the tissue-specific expression of SlJAZ7 gene and SlTGA7 gene under Pst DC3000, methyl jasmonate (MeJA) and salicylic acid (SA) treatments. The subcellular localization of SIJAZ7 and SlTGA7 proteins was studied by transient expression of tobacco. The interaction between SlJAZ7 and SlTGA7 was verified by Y2H, BiFC and pull down experiments, to verify the disease resistance function and possible mechanism of SlJAZ7.

Result Transgenic tomato leaves overexpressing SlJAZ7 gene had lower peroxidation damage than wild type when treated with pathogens, the expression level of SlTGA7 in transgenic lines increased. SlJAZ7 gene was highly expressed in nutrient tissues. SlJAZ7 gene was induced by Pst DC3000 and in response to MeJA and SA treatments. SlTGA7 gene showed opposite change trend under the same treatment. Both SlJAZ7 and SlTGA7 proteins were located in the nucleus. All Y2H, BiFC and pull down experiments proved the interaction between SlJAZ7 and SlTGA7.

Conclusion Overexpression of SlJAZ7 gene can reduce the accumulation of reactive oxygen species and improve tomato disease resistance. SlJAZ7 positively regulates SlTGA7 gene expression at the transcriptional level. SlJAZ7 interacts with SlTGA7. It is speculated that SIJAZ7 gene may improve the disease resistance of transgenic tomato by increasing the expression level of SITGA7 gene during pathogen infection, initiating the expression of downstream resistance genes of SITGA7, or by binding with SITGA7 protein, affecting its regulation of MYC and other transcription factors. The result lays a foundation for further research on the mechanism of SlJAZ7.