Ishiguro Sara, Taniguchi Shota, Schmidt Nicola, Jost Matthias, Wanke Stefan, Heitkam Tony, Ohmido Nobuko
Graduate School of Human Development and Environment, Kobe University, Nada-ku, Kobe, 657-8501, Japan.
Faculty of Biology, Technische Universität Dresden, D-01069 Dresden, Germany.
Ann Bot. 2025 Feb 19;135(3):549-564. doi: 10.1093/aob/mcae184.
Ornamental hortensias are bred from a reservoir of over 200 species in the genus Hydrangea s.l. (Hydrangeaceae), and are valued in gardens, households and landscapes across the globe. The phenotypic diversity of hortensia cultivars, hybrids and wild relatives is mirrored by their genomic variation, with differences in genome size, base chromosome numbers and ploidy level. We aim to understand the genomic and chromosomal basis of hortensia genome variation. Therefore, we analysed six hortensias with different origins and chromosomal setups for repeatome divergence, the genome fraction with the highest sequence turnover. This holds information from the hortensias' evolutionary paths and can guide breeding initiatives.
We compiled a hortensia genotype panel representing members of the sections Macrophyllae, Hydrangea, Asperae and Heteromallae and reconstructed a plastome-based phylogenetic hypothesis as the evolutionary basis for all our analyses. We comprehensively characterized the repeatomes by whole-genome sequencing and comparative repeat clustering. Major tandem repeats were localized by multicolour FISH.
The Hydrangea species show differing repeat profiles reflecting their separation into the two major Hydrangea clades: diploid Hydrangea species from Japan show a conserved repeat profile, distinguishing them from Japanese polyploids as well as Chinese and American hortensias. These results are in line with plastome-based phylogenies. The presence of specific repeats indicates that H. paniculata was not polyploidized directly from the common ancestor of Japanese Hydrangea species, but evolved from a distinct progenitor. Major satellite DNAs were detected over all H. macrophylla chromosomes.
Repeat composition among the Hydrangea species varies in congruence with their origins and phylogeny. Identified species-specific satDNAs may be used as cytogenetic markers to identify Hydrangea species and cultivars, and to infer parental species of old Hydrangea varieties. This repeatome and cytogenetics information helps to expand the genetic toolbox for tracing hortensia evolution and guiding future hortensia breeding.
观赏绣球花由广义绣球属（绣球科）200多个物种培育而来，在全球的花园、家庭和景观中都备受珍视。绣球花栽培品种、杂交品种和野生近缘种的表型多样性反映在其基因组变异上，包括基因组大小、基本染色体数和倍性水平的差异。我们旨在了解绣球花基因组变异的基因组和染色体基础。因此，我们分析了六个起源和染色体组成不同的绣球花，以研究重复序列组的差异，重复序列组是序列周转率最高的基因组部分。这包含了绣球花进化路径的信息，并可为育种计划提供指导。
我们编制了一个绣球花基因型面板，代表大叶组、绣球组、糙叶组和异叶组的成员，并重建了基于叶绿体基因组的系统发育假说，作为我们所有分析的进化基础。我们通过全基因组测序和比较重复序列聚类对重复序列组进行了全面表征。主要串联重复序列通过多色荧光原位杂交进行定位。
绣球属物种显示出不同的重复序列特征，反映了它们分为两个主要的绣球花分支：来自日本的二倍体绣球花物种显示出保守的重复序列特征，这使它们与日本多倍体以及中国和美国的绣球花区分开来。这些结果与基于叶绿体基因组的系统发育一致。特定重复序列的存在表明圆锥绣球并非直接从日本绣球花物种的共同祖先多倍体化而来，而是从一个独特的祖先进化而来。在所有大叶绣球染色体上都检测到了主要卫星DNA。
绣球属物种之间的重复序列组成与其起源和系统发育一致。已鉴定的物种特异性卫星DNA可作为细胞遗传学标记，用于鉴定绣球花物种和品种，并推断古老绣球花品种的亲本物种。这些重复序列组和细胞遗传学信息有助于扩展用于追踪绣球花进化和指导未来绣球花育种的遗传工具库。
