Journal
PLANT AND CELL PHYSIOLOGY
Volume 54, Issue 5, Pages 793-807Publisher
OXFORD UNIV PRESS
DOI: 10.1093/pcp/pct035
Keywords
Dwarfism; Fruit; GABA; GABA-TP; TG; Infertility; Tomato
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Funding
- Japan Society for the Promotion of Science (JSPS) [225336]
- JSPS Bilateral Joint Research Project
- Japan-France Joint Laboratory Project
- Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan
- Research and Development Program for New Bio-industry Initiatives (BRAIN)
- Grants-in-Aid for Scientific Research [10J05336] Funding Source: KAKEN
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Tomatoes accumulate gamma-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 alpha-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.
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