Heterologous expression of strawberry FvCPS suppresses salicylic acid-mediated defense in Arabidopsis thaliana

Strawberry ( Fragaria×ananassa Duch) a fruit of high nutritional and economic value, suffers substantial yield losses from pathogen infection. In this study, the CPS gene was cloned from Fragaria vesca , and its gene structure, promoter elements, physicochemical properties, secondary and tertiary protein structures, and evolutionary relationships with homologous proteins in other species were systematically analyzed. Fluorescence microscopy of an FvCPS -GFP fusion placed the protein in chloroplasts. Expression profiling revealed that FvCPS was upregulated in F. vesca upon infection with Colletotrichum fragariae and Fusarium oxysporum . To further investigate its function, FvCPS was heterologously expressed in Arabidopsis thaliana . Following inoculation with Pseudomonas syringae , bacterial proliferation was significantly greater in three independent overexpression lines than in Col-0 wild type. RT-qPCR of the overexpressors returned lower transcripts of the SA-pathway genes ICS1 , EDS5 , NPR1 , PR1 , and PR5 and higher transcripts of the JA-responsive gene PDF1.2 . Targeted hormone quantification confirmed lower salicylic acid in the strongest overexpression line together with elevated OPDA, an early jasmonate intermediate, while jasmonoyl-isoleucine, JA, gibberellin 4, and gibberellin 7 were unchanged. FvCPS overexpression therefore suppresses SA biosynthesis and shifts the SA/OPDA balance toward a non-canonical, OPDA-dependent branch, compromising Arabidopsis resistance to P. syringae.