浙江大学方磊研究小组发现，海南梧桐高质量基因组提供关于锦葵科亚科演化及其木材密度形成机制的见解。2024年12月19日，《遗传学报》在线发表了这一最新研究成果。

研究人员为一种代表性的梧桐属物种——海南梧桐（F. hainanensis）提供了染色体水平的基因组组装，2n=40，总基因组大小为1536 Mb。系统发育分析显示，海南梧桐与榴莲（Durio zibethinus）之间的演化关系最为接近，估计分化时间约为2100万年。两者的演化历程中均经历了不同的多倍化事件。演化轨迹分析表明，染色体的裂解和融合可能在染色体数目变异（2n=14至2n=96）中发挥了关键作用。

对锦葵科中重复元素的分析揭示，Tekay亚科（属于Gypsy类群）在基因组大小变异中起到了重要作用，基因组大小从324 Mb到1620 Mb不等。此外，与P450酶、过氧化物酶和微管相关的基因，这些基因与细胞壁合成相关，在海南梧桐中显著收缩，这可能导致其木材密度低于坡垒（Hopea hainanensis）。

总体而言，该研究为锦葵科物种染色体数目、基因组大小的演化以及细胞壁合成遗传基础提供了新的见解。

据悉，锦葵科是锦葵目中最具多样性的科，包含九个亚科。在梧桐属（Firmiana）的梧桐亚科中，大多数物种被认为是全球性濒危物种，但其基因组尚未被探索。

附：英文原文

Title: High-quality genome of Firmiana hainanensis provides insights into the evolution of Malvaceae subfamilies and the mechanism of their wood density formation

Author: Lei Fang a b

Issue&Volume: 2024/12/19

Abstract: The Malvaceae family, the most diverse family in the order Malvales, consists of nine subfamilies. Within the Firmiana genus of the Sterculioideae subfamily, most species are considered globally vulnerable, yet their genomes remain unexplored. Here, we present a chromosome-level genome assembly for a representative Firmiana species, F. hainanensis, 2n = 40, totaling 1536 Mb. Phylogenomic analysis shows that F. hainanensis and Durio zibethinus have the closest evolutionary relationship, with an estimated divergence time of approximately 21 MYA and distinct polyploidization events in their histories. Evolutionary trajectory analyses indicate that fissions and fusions may play a crucial role in chromosome number variation (2n = 14 to 2n = 96). Analysis of repetitive elements among Malvaceae reveals that the Tekay subfamily (belonging to the Gypsy group) contributes to variation in genome size (ranging from 324 Mb to 1620 Mb). Additionally, genes associated with P450, peroxidase, and microtubules, and thereby related to cell wall biosynthesis, are significantly contracted in F. hainanensis, potentially leading to its lower wood density relative to Hopea hainanensis. Overall, our study provides insights into the evolution of chromosome number, genome size, and the genetic basis of cell wall biosynthesis in Malvaceae species.

DOI: 10.1016/j.jgg.2024.12.009

Source: https://www.sciencedirect.com/science/article/abs/pii/S167385272400362X