title: Suppression of γ-aminobutyric acid (GABA) transaminases induces prominent GABA accumulation, dwarfism and infertility in the tomato (Solanum lycopersicum L.).
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.
authors: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8572 Japan.
authors: Satoshi
authors: S
authors: Koike
authors: Chiaki
authors: C
authors: Matsukura
authors: Mariko
authors: M
authors: Takayama
authors: Erika
authors: E
authors: Asamizu
authors: Hiroshi
authors: H
authors: Ezura
mesh_terms: D000612:4-Aminobutyrate Transaminase / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism; D035264:Flowers / Q000254:growth & development; D005638:Fruit / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D018698:Glutamic Acid / Q000378:metabolism; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D051479:Plant Infertility; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D018547:Plant Stems / Q000378:metabolism; D030821:Plants, Genetically Modified; D034622:RNA Interference; D013489:Suppression, Genetic; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D000612:4-Aminobutyrate Transaminase
keywords: Dwarfism; Fruit; GABA; GABA-TP/TG; Infertility; Tomato