Suppression of γ-Aminobutyric Acid (GABA) Transaminases Induces Prominent GABA Accumulation, Dwarfism and Infertility in the Tomato (Solanum lycopersicum L.)
Suppression of γ-Aminobutyric Acid (GABA) Transaminases Induces Prominent GABA Accumulation, Dwarfism and Infertility in the Tomato (Solanum lycopersicum L.)
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DOI：
10.1093/pcp/pct035
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发表时间：
2013-05-01
影响因子：
4.9
通讯作者：
Ezura, Hiroshi
中科院分区：
文献类型：
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作者：
Koike, Satoshi;Matsukura, Chiaki;Ezura, Hiroshi
番茄在未成熟的果实中积累了大量的γ -氨基丁酸（GABA）。GABA在果实成熟过程中通过GABA转氨酶（GABA- t）和琥珀酸半醛脱氢酶（SSADH）的活性迅速转化为琥珀酸。虽然在番茄果实中已经检测到编码GABA- t以及丙酮酸和α -酮戊二酸依赖的GABA- t活性的三个基因，但GABA- t介导的GABA转化的机制尚不完全清楚。在这项工作中，我们利用RNA干扰（RNAi）转基因植物，抑制丙酮酸盐和乙醛酸盐依赖的GABA-T基因表达，进行了功能丧失分析，以阐明GABA-T的哪些亚型对其功能至关重要。SlGABA-T基因表达受到抑制的RNAi植株，尤其是SlGABA-T1，表现出严重的侏儒症和不育。红熟期果实中SlGABA-T1的表达与GABA水平呈负相关。35S::SlGABA-T1（RNAi）系的GABA含量分别比野生型果实高1.3 ~ 2.0倍和6.8 ~ 9.2倍。此外，SlGABA-T1的表达在gaba积累系中被强烈抑制。这些结果表明，丙酮酸和乙醛酸依赖的GABA- t是番茄植株GABA代谢的必要亚型，GABA- t1主要有助于成熟果实中GABA的减少。
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.