Department of Plant Science and Technology, College of Biotechnology, Chung-Ang University, Anseong, 17546, Republic of Korea.
Research Center for Plant Plasticity, Seoul National University, Seoul, 08826, Republic of Korea.
Plant J. 2022 Jun;110(6):1578-1591. doi: 10.1111/tpj.15755. Epub 2022 Apr 25.
Methylglyoxal (MG) is a toxic by-product of the glycolysis pathway in most living organisms and was previously shown to inhibit seed germination. MG is detoxified by glyoxalase I and II family proteins in plants. MG is abundantly produced during early embryogenesis in Arabidopsis seeds. However, the mechanism that alleviates the toxic effect of MG in maturing seeds is poorly understood. In this study, by T-DNA mutant population screening, we found that mutations in a glyoxalase I gene (named GERMINATION-IMPAIRED GLYOXALASE 1, GIG1) led to significantly impaired germination compared with wild-type seeds. Transformation of full-length GIG1 cDNA under the constitutively active cauliflower mosaic virus 35S promoter in the gig1 background completely recovered the seed germination phenotype. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) analyses revealed that GIG1 is uniquely expressed in seeds and is upregulated by abscisic acid (ABA) and downregulated by gibberellic acid (GA) during seed germination. An ABA signaling component, ABI3, directly activated GIG1 in maturing seeds. In addition, PHYTOCHROME INTERACTING FACTOR 1 (PIF1) also plays cooperatively with ABI3 in the regulation of GIG1 expression in the early stage of imbibed seeds. Furthermore, GIG1 expression is stably silenced by epigenetic repressors such as polycomb repressor complexes. Altogether, our results indicate that light and ABA signaling cooperate to enhance seed germination by the upregulation of GIG1 to detoxify MG in maturing seeds.
甲基乙二醛（MG）是大多数生物体内糖酵解途径的一种有毒副产物，先前的研究表明它能抑制种子萌发。植物中的甘油醛-1,3-二磷酸醛缩酶 I 和 II 家族蛋白能将 MG 解毒。在拟南芥种子的早期胚胎发生过程中，MG 大量产生。然而，在成熟种子中缓解 MG 毒性的机制尚未得到充分理解。在这项研究中，通过 T-DNA 突变体群体筛选，我们发现一个甘油醛-1,3-二磷酸醛缩酶 I 基因（命名为 GERMINATION-IMPAIRED GLYOXALASE 1，GIG1）的突变导致种子萌发显著受损，与野生型种子相比。在 gig1 背景下，组成型活性的花椰菜花叶病毒 35S 启动子下全长 GIG1 cDNA 的转化完全恢复了种子萌发表型。定量逆转录聚合酶链反应（qRT-PCR）分析表明，GIG1 在种子中特异性表达，在种子萌发过程中受脱落酸（ABA）上调，受赤霉素（GA）下调。一个 ABA 信号成分，ABI3，直接在成熟种子中激活 GIG1。此外，PHYTOCHROME INTERACTING FACTOR 1（PIF1）也在吸水种子的早期阶段与 ABI3 合作调节 GIG1 的表达。此外，GIG1 的表达被表观遗传抑制剂如多梳抑制复合物稳定沉默。总之，我们的研究结果表明，光和 ABA 信号通过上调 GIG1 来解毒成熟种子中的 MG，从而协同增强种子萌发。
