Broccoli (Brassica oleracea var. italica Plenck) is an important vegetable crop, as it is rich in health-beneficial glucosinolates (GSLs). However, the genetic basis of the GSL diversity in Brassicaceae remains unclear. Here, we report a chromosome-level genome assembly of broccoli generated using PacBio HiFi reads and Hi-C technology. The final genome assembly is 613.79 Mb in size, with a contig N50 of 14.70 Mb. The GSL profile and content analysis of different Brassicas oleracea varieties, combined with a phylogenetic tree analysis, sequence alignment, and the construction of a three-dimensional model of the methylthioalkylmalate synthase 1 (MAM1) protein, which revealed that the gene copy number and amino acid sequence variation both contributed to the diversity of GSL biosynthesis in Brassica oleracea. The overexpression of BoMAM1 (BolI0108790) in broccoli resulted in high accumulation and a high ratio of C4-GSLs, demonstrating that BoMAM1 is the key enzyme in C4-GSLs biosynthesis. These results provide valuable insights for future genetic studies and nutritive component applications of Brassica crops.

中文翻译：

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西兰花（Brassica oleracea var. italica Plenck）的染色体规模参考基因组提供了对芥子油苷生物合成的见解

西兰花 (Brassica oleracea var. italica Plenck) 是一种重要的蔬菜作物，因为它富含有益健康的芥子油苷 (GSL)。然而，十字花科 GSL 多样性的遗传基础仍不清楚。在这里，我们报告了使用 PacBio HiFi 读取和 Hi-C 技术生成的西兰花染色体水平基因组组装。最终基因组组装大小为 613.79 Mb，重叠群 N50 为 14.70 Mb。对不同甘蓝品种的GSL谱和含量进行分析，结合系统发育树分析、序列比对，并构建甲硫基烷基苹果酸合酶1（MAM1）蛋白的三维模型，揭示了该基因的拷贝数和氨基酸序列变异均导致甘蓝中GSL生物合成的多样性。BoMAM1 (BolI0108790) 在西兰花中的过表达导致 C4-GSL 的高积累和高比例，表明 BoMAM1 是 C4-GSL 生物合成的关键酶。这些结果为未来芸苔属作物的遗传研究和营养成分应用提供了宝贵的见解。