BiP-overexpressing soybean shows differential hypersensitivity response (HR) altering protein and metabolite profiles involved in the plant defense

Soybean plants overexpressing the molecular chaperone BiP have shown enhanced drought tolerance, delaying hypersensitive cell death in response to bacterial infection. Proteomic and metabolomic analyzes were performed on BiP-overexpressing plants under hypersensitivity response (HR) induced by a non-compatible bacterium Pseudomonas syringae pv. tomato . Transgenic plants showed molecular and phenotypic differences related to wild-type plants. Photosynthetic apparatus proteins were down-regulated, while others involved in the antioxidative metabolism were up-regulated. Furthermore, the expressions of the Bet v1 and MYC3 TF proteins, which participate in the JA-dependent plant defense, were also altered. Both proteomic and metabolomic profiles indicated that the phenylpropanoid pathway responded differently to HR. Proteins involved in biosynthesis and modification of phenolic compounds chalcone-flavone isomerase, UDP-glucose pyrophosphorylase, caffeoyl coenzyme A O-methyltransferase and caffeoyl coenzyme A O-methyltransferase were up-regulated in transgenic plants. In addition, BiP-overexpressing increased Caffeoyl coenzyme A ester O-methyltransferase levels in the absence of stress. Moreover, LC/MS profiles revealed the accumulation of some methylated flavonoids and compounds involved in lignin biosynthesis and antimicrobial defense. Overall, soybean genetic modification to overexpress BiP affected its drought tolerance and the dynamic of the hypersensitive response, affecting the plant molecular defense against pathogens.