Steroidal glycoalkaloids (SGAs) are cholesterol-derived molecules found in the family Solanaceae. SGA content varies among different plant species and varieties. However, the genetic mechanisms regulating SGA content remain unclear. Here, we demonstrate that genetic variation in GLYCOALKALOID METABOLISM 9 (GAME9) is responsible for the variation in SGA content in tomato (Solanum lycopersicum). During a sequential analysis we found a 1 bp substitution in the AP2/ERF binding domain of GAME9. The 1 bp substitution in GAME9 was significantly associated with high SGA content and determined the binding capacity of GAME9 with the promoter of GAME17, a core SGA biosynthesis gene. The high-SGA GAME9 allele is mainly present in S. pimpinellifolium and S. lycopersicum var. cerasiforme populations and encodes a protein that can bind the GAME17 promoter. In contrast, the low-SGA GAME9 allele is mainly present in the big-fruited varieties of S. lycopersicum and encodes a protein that shows weak binding to the GAME17 promoter. Our findings provide new insight into the regulation of SGA biosynthesis and the factors that affect the accumulation of SGA in tomato.

中文翻译：

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GAME9的等位基因变体决定了其与GAME17启动子的结合能力，可调节番茄中甾体生物碱的生物合成。

甾体类生物碱（SGA）是茄科中发现的胆固醇衍生分子。不同植物物种和品种中SGA含量不同。但是，调节SGA含量的遗传机制仍不清楚。在这里，我们证明了糖醇代谢9（GAME9）的遗传变异是番茄（Solanum lycopersicum）SGA含量变异的原因。在顺序分析中，我们在GAME9的AP2 / ERF结合域中发现了1 bp取代。GAME9中的1 bp取代与高SGA含量显着相关，并确定了GAME9与核心SGA生物合成基因GAME17的启动子的结合能力。高SGA GAME9等位基因主要存在于S. pimpinellifolium和S. lycopersicum var中。cerasiforme种群，并编码可以结合GAME17启动子的蛋白质。相比之下，低SGA GAME9等位基因主要存在于番茄果实链球菌的大果变种中，并编码与GAME17启动子结合弱的蛋白质。我们的发现为SGA生物合成的调控以及影响SGA在番茄中积累的因素提供了新的见识。