PMID:17971036

Citation	Mirabella, R, Rauwerda, H, Struys, EA, Jakobs, C, Triantaphylidès, C, Haring, MA and Schuurink, RC (2008) The Arabidopsis her1 mutant implicates GABA in E-2-hexenal responsiveness. Plant J. 53:197-213
Abstract	When wounded or attacked by herbivores or pathogens, plants produce a blend of six-carbon alcohols, aldehydes and esters, known as C6-volatiles. Undamaged plants, when exposed to C6-volatiles, respond by inducing defense-related genes and secondary metabolites, suggesting that C6-volatiles can act as signaling molecules regulating plant defense responses. However, to date, the molecular mechanisms by which plants perceive and respond to these volatiles are unknown. To elucidate such mechanisms, we decided to isolate Arabidopsis thaliana mutants in which responses to C6-volatiles were altered. We observed that treatment of Arabidopsis seedlings with the C6-volatile E-2-hexenal inhibits root elongation. Among C6-volatiles this response is specific to E-2-hexenal, and is not dependent on ethylene, jasmonic and salicylic acid. Using this bioassay, we isolated 18 E-2-hexenal-response (her) mutants that showed sustained root growth after E-2-hexenal treatment. Here, we focused on the molecular characterization of one of these mutants, her1. Microarray and map-based cloning revealed that her1 encodes a gamma-amino butyric acid transaminase (GABA-TP), an enzyme that degrades GABA. As a consequence of the mutation, her1 plants accumulate high GABA levels in all their organs. Based on the observation that E-2-hexenal treatment induces GABA accumulation, and that high GABA levels confer resistance to E-2-hexenal, we propose a role for GABA in mediating E-2-hexenal responses.
Links	PubMed Online version:10.1111/j.1365-313X.2007.03323.x
Keywords	Aldehydes/pharmacology; Alleles; Arabidopsis/drug effects; Arabidopsis/genetics; Arabidopsis/growth & development; Arabidopsis/metabolism; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; Cyclopentanes/metabolism; Ethylenes/metabolism; Gene Expression Regulation, Plant; Mutation; Oxylipins/metabolism; Plant Roots/growth & development; Salicylic Acid/metabolism; Transaminases/genetics; Transaminases/metabolism; gamma-Aminobutyric Acid/metabolism
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