Abstract: 【Background】With global climate change, the increase of atmospheric CO₂ concentrations is predicted to exert an influence on plant diseases, which seriously affects agricultural production. Plant β-carbonic anhydrases (βCAs) are involved in the immunity of Arabidopsis and tobacco. However, little is known about the functions of βCAs in the regulation of disease resistance in tomato.【Objective】The objective of this study is to explore the role and mechanism of tomato βCA3 in disease resistance, so as to provide scientific basis for resistance regulation of tomato in agricultural production.【Method】Based on the similarity to the amino acid sequences of AtβCAs, four βCAs were identified in the Sol genomics network database. Wild-type (WT) tomato (Solanum lycopersicum) ‘Ailsa Craig’ (AC) was used to inoculate Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) in the study. Then qRT-PCR was used to determine the transcript abundance of βCAs in leaves to screen the Pst DC3000-induced gene βCA3. Furthermore, βCA3 stable over-expression lines (OE-βCA3) were generated by Agrobacterium tumefaciens-mediated genetic transformation technology as the background of AC. OE-βCA3 plants were inoculated with Pst DC3000 to investigate the role of βCA3 in disease defense. For exploring the intrinsic mechanism of βCA3 regulating plant disease resistance, the transcriptome changes of WT and OE-βCA3 plants between inoculation with Pst DC3000 and control conditions were compared, and KEGG (kyoto encyclopedia of genes and genomes) database was used to analyze functions of the differentially expressed genes. It is speculated that sugar metabolism pathways are involved in βCA3-mediated plant immunity. To verify and further analyze the conclusion, the expression of genes related to the sugar metabolism and signaling, as well as the contents of glucose, fructose and sucrose in WT and OE-βCA3 plants were determined.【Result】OE-βCA3 plants enhanced the resistance to Pst DC3000, and showed less disease-associated cell death and a lower number of bacteria compared to the WT controls. RNA-Seq results showed that OE-βCA3 did not greatly change the overall transcript profile in the absence of the pathogen. In total, 2100 Pst DC3000-induced transcripts were differentially changed in abundance. Of these, 63.3% were more abundant following Pst DC3000 inoculation in the OE-βCA3 plants. KEGG analysis showed that Pst DC3000-induced genes, which is dependent on βCA3-overexpression, were enriched in the pathways related to sugar metabolism, including starch and sucrose metabolism, protein processing in the endoplasmic reticulum (glycosylation), amino sugar and nucleotide sugar metabolism, ribosomal biosynthesis in eukaryotes and photosynthesis. Sugar metabolism is closely related to sugar signaling. Further studies found that the expression of genes related to sugar metabolism and signal transduction pathways, as well as the contents of glucose, fructose and sucrose, were higher in the leaves of OE-βCA3 plants than that of WT after inoculation with Pst DC3000.【Conclusion】Overexpression of βCA3 in tomato enhances the resistance of plants to Pst DC3000, possibly related to the role of sugar metabolism and signaling in plant immunity.

Key words: tomato, βCAs, Pst DC3000, disease resistance, sugar metabolism, sugar signaling