Role of flavones biosynthesis and salicylic acid metabolism in biotic stress responses

SERRA, PALOMA; RIGHINI, S; DILLON, FRANCISCO; FALCONE FERREYRA, MARÍA LORENA; GROTEWOLD, E.; CASATI, PAULA

Congreso; XXXIII Reunión Argentina de Fisiología Vegetal (RAFV); 2021

Two different types of flavone synthases (FNS I and FNSII) catalyze the biosynthesis of the main flavone, apigenin. In Arabidopsis thaliana, Downey Mildew Resistant 6 (DMR6) encodes an FNS I type enzyme. dmr6 mutant plants show increased resistance against Pseudomonas syringae pathogen, which is associated to an accumulation of salicylic acid (SA). When we complemented dmr6 plants with FNS I and II from maize, there was a restoration of susceptibility to the pathogen infection. Thus, the aim of this work is to study the possible interconnection between flavones synthesis and SA metabolism. We analyzed the susceptibility against P. syringae infection in Arabidopsis wild type, transgenic and mutant plants in the SALICYLIC ACID 3-HIDROXYLASE (S3H) gene. S3H catalyzes the conversion of SA to 2,3-dihydrobenzoic acid. Therefore, s3h mutants accumulate SA, which results in enhanced resistance to pathogen infection. Transgenic plants used in this experiment express FNS I and II enzymes from maize in a mutant s3h background. These lines exhibited restoration of susceptibility to Pseudomonas infection. We also quantified the SA and apigenin levels in transgenic lines post-infection, showing that restoration of susceptibility is a consequence of a decrease in SA levels and apigenin accumulation. In order to analyze if other flavonoids were involved in the response of plants to biotic stress, infection experiments were performed using plants with mutations in genes of the flavonoids biosynthetic pathway. In addition, we analyzed the possible regulatory effect of flavonoids on the expression of genes associated with SA metabolism using RT-qPCR