主要研究：Torreya plants produce dry fruits with assorted functions. Here, we report the 19-Gb chromosome-level genome assembly of T. grandis. 

结果1-基础分析：The genome is shaped by ancient whole-genome duplications and recurrent LTR retrotransposon bursts. Comparative genomic analyses reveal key genes involved in reproductive organ development, cell wall biosynthesis and seed storage.

结果2-金松酸合成：Two genes encoding a C18 Δ⁹-elongase and a C20 Δ⁵-desaturase are identified to be responsible for sciadonic acid biosynthesis and both are present in diverse plant lineages except angiosperms. We demonstrate that the histidine-rich boxes of the Δ⁵-desaturase are crucial for its catalytic activity. 

结果3-种子甲基化组：Methylome analysis reveals that methylation valleys of the T. grandis seed genome harbor genes associated with important seed activities, including cell wall and lipid biosynthesis. Moreover, seed development is accompanied by DNA methylation changes that possibly fuel energy production. 

结论：This study provides important genomic resources and elucidates the evolutionary mechanism of sciadonic acid biosynthesis in land plants.

香榧属的植物会生产具有多种功能的干果。本文中，作者报道了香榧19Gb的基因组组装。香榧基因组主要由古老的全基因组复制事件和反复发生的LTR逆转座子爆发所共同塑造。比较基因组分析鉴定到了参与生殖器官发育、细胞壁生物合成以及种子贮藏的关键基因。另外，作者鉴定到了一个编码C18 Δ⁹延长酶和一个编码C20 Δ⁵脱氢酶的基因，这两个基因与金松酸的生物合成有关，并且在除了被子植物以外的多个植物谱系中都存在。作者发现Δ⁵脱氢酶中的富含组氨酸区域对于其催化活性是非常重要的。甲基化组分析显示，香榧种子基因组中的甲基化谷包含许多与种子活力相关的重要基因，包括细胞壁和脂质生物合成。此外，种子发育通常伴随着与促进能量生产相关的DNA甲基化变化。本文的研究提供了珍贵的基因组资源，并揭示了陆地植物金松酸生物合成的演化机制。

** 吴家胜 **