ROLE OF FLAVONES BIOSYNTHESIS AND SALICYLIC ACID METABOLISM IN BIOTIC STRESS RESPONSES.

PALOMA SERRA; SILVANA RIGHINI ARAMBURU; FRANCISCO DILLON; LORENA FALCONE FERREYRA; ERICH GROTEWOLD; PAULA CASATI

Congreso; RAFV2020; 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 FNSI type enzyme. dmr6 mutant plants show increased resistance against Pseudomonas syringae attack, 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 attack. Thus, the aim of this work is to study the possible interconnection between flavones synthesis and SA metabolism. We analyzed the susceptibility against Pseudomonas 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. The infection experiments were also carried out in s3h mutants, and also in mutant plants expressing FNS I and II from maize. Transgenic lines exhibited restoration of susceptibility to Pseudomonas infection. We also quantified SA and apigenin levels in transgenic lines post-infection, showing that restoration of susceptibility is a consequence of decreased SA and increased apigenin accumulation. In order to analyze if other flavonoids were also involved in Arabidopsis responses 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.