Alkyl gallates display elicitor activities in tobacco plants

Alkyl gallates showed elicitor activities on tobacco in both whole plants and cell suspensions. Methyl gallate (MG), ethyl gallate (EG) and n- propyl gallate (PG) infiltration into tobacco leaves induced hypersensitive reaction-like lesions and topical production of autofluorescent compounds revealed under UV light. When sprayed on tobacco plants at 5 mM, EG promoted upregulation of defence-related genes such as the antimicrobial PR1 , β-1,3-glucanase PR2 , chitinase PR3 and osmotin PR5 target genes. Tobacco BY-2 cells challenged with EG underwent cell death in 48 h, significantly reduced in the presence of the protease inhibitor aprotinin. The three alkyl gallates all caused alkalinisation of the BY-2 extracellular medium, whereas gallic acid did not trigger any pH variation. Using EGTA or LaCl3, we showed that Ca2+ mobilisation occurred in BY-2 cells elicited with EG. Overall, our findings are the first evidence of alkyl gallate elicitor properties with early perception events on plasma membrane, potential hypersensitive reactions and PR-related downstream defence responses in tobacco. Highlights