Liu Jia, Wang Zhennan, Su Xinyao, Leng Liang, Liu Jiarou, Zhang Feng, Chen Shilin, Zhang Yujun, Wang Caixia
State Key Laboratory for Quality Ensurance and Sustainable Use of Dao-di Herbs, Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China.
Innovative Institute of Chinese Medicine and Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, China.
Nat Commun. 2025 Mar 17;16(1):2603. doi: 10.1038/s41467-025-57722-9.
Meliaceous plants such as Azadirachta indica (neem) and Melia azedarach (chinaberry) contain large amounts of limonoids with unique anti-insect activities. However, genes responsible for downstream modifications of limonoids are not well known. Here, we improve the genome assemblies of neem and chinaberry to the telomere-to-telomere (T2T) level. Allopatric speciation of the two plants is confirmed by the lineage-specific inversion of chromosome 12 in the neem lineage. We further identify two BAHD-acetyltransferases (ATs) in chinaberry (MaAT8824 and MaAT1704) that catalyse acetylation at both the C-12 and C-3 hydroxyl groups of limonoids, whereas the syntenic neem copy (AiAT0635) does not possess this activity. A critical N-terminal region (SAGAVP) is crucial for the acetylation of AiAT0635, and swapping it into the MaAT8824 version (CHRSSG) can endow it with acetylation activity. Our improved genome assemblies provide insights into allopatric speciation of neem, as well as limonoid biosynthesis and chemical diversity in meliaceous plants.
印楝（Azadirachta indica）和苦楝（Melia azedarach）等楝科植物含有大量具有独特抗虫活性的柠檬苦素。然而，负责柠檬苦素下游修饰的基因尚不清楚。在这里，我们将印楝和苦楝的基因组组装提升到了端粒到端粒（T2T）水平。通过印楝谱系中12号染色体的谱系特异性倒位，证实了这两种植物的异域物种形成。我们进一步在苦楝中鉴定出两种BAHD-乙酰基转移酶（ATs）（MaAT8824和MaAT1704），它们催化柠檬苦素的C-12和C-3羟基乙酰化，而印楝中同线性的拷贝（AiAT0635）不具备这种活性。一个关键的N端区域（SAGAVP）对AiAT0635的乙酰化至关重要，将其替换为MaAT8824版本（CHRSSG）可赋予其乙酰化活性。我们改进的基因组组装为印楝的异域物种形成以及楝科植物中柠檬苦素的生物合成和化学多样性提供了见解。
