Suppression of γ-aminobutyric acid (GABA) transaminases induces prominent GABA accumulation, dwarfism and infertility in the tomato (solanum lycopersicum L.)

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Abstract

Tomatoes accumulate γ-aminobutyric acid (GABA) at high levels in the immature fruits. GABA is rapidly converted to succinate during fruit ripening through the activities of GABA transaminase (GABA-T) and succinate semialdehyde dehydrogenase (SSADH). Although three genes encoding GABA-T and both pyruvate- and α-ketoglutarate-dependent GABA-T activities have been detected in tomato fruits, the mechanism underlying the GABA-T-mediated conversion of GABA has not been fully understood. In this work, we conducted loss-of-function analyses utilizing RNA interference (RNAi) transgenic plants with suppressed pyruvate- and glyoxylate-dependent GABA-T gene expression to clarify which GABA-T isoforms are essential for its function. The RNAi plants with suppressed SlGABA-T gene expression, particularly SlGABA-T1, showed severe dwarfism and infertility. SlGABA-T1 expression was inversely associated with GABA levels in the fruit at the red ripe stage. The GABA contents in 35S::SlGABA-T1 RNAi lines were 1.3-2.0 times and 6.8-9.2 times higher in mature green and red ripe fruits, respectively, than the contents in wild-type fruits. In addition, SlGABA-T1 expression was strongly suppressed in the GABA-accumulating lines. These results indicate that pyruvate- and glyoxylate-dependent GABA-T is the essential isoform for GABA metabolism in tomato plants and that GABA-T1 primarily contributes to GABA reduction in the ripening fruits. © 2013 The Author 2013. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved.

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Koike, S., Matsukura, C., Takayama, M., Asamizu, E., & Ezura, H. (2013). Suppression of γ-aminobutyric acid (GABA) transaminases induces prominent GABA accumulation, dwarfism and infertility in the tomato (solanum lycopersicum L.). Plant and Cell Physiology, 54(5), 793–807. https://doi.org/10.1093/pcp/pct035

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