Plant perception of β-aminobutyric acid is mediated by an aspartyl-tRNA synthetase

• DOI: 10.1038/nchembio.1520
• Publication Date: 2014-04-28T15:54:31Z
• Authors: Estrella Luna; Marieke van Hulten; Yuhua Zhang; Oliver Berkowitz; Ana López; Pierre Pétriacq; Matthew A Sellwood; Beining Chen; Mike Burrell; Allison van de Meene; Corné M J Pieterse; Victor Flors; Jurriaan Ton
• Keywords: Plant Immunity; Hypersensitive response

Specific chemicals can prime the plant immune system for augmented defense. β-aminobutyric acid (BABA) is a priming agent that provides broad-spectrum disease protection. However, BABA also suppresses plant growth when applied in high doses, which has hampered its application as a crop defense activator. Here we describe a mutant of Arabidopsis thaliana that is impaired in BABA-induced disease immunity (ibi1) but is hypersensitive to BABA-induced growth repression. IBI1 encodes an aspartyl-tRNA synthetase. Enantiomer-specific binding of the R enantiomer of BABA to IBI1 primed the protein for noncanonical defense signaling in the cytoplasm after pathogen attack. This priming was associated with aspartic acid accumulation and tRNA-induced phosphorylation of translation initiation factor eIF2α. However, mutation of eIF2α-phosphorylating GCN2 kinase did not affect BABA-induced immunity but relieved BABA-induced growth repression. Hence, BABA-activated IBI1 controls plant immunity and growth via separate pathways. Our results open new opportunities to separate broad-spectrum disease resistance from the associated costs on plant growth.