Page 20 - 广西植物2024年1期
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1 6 广 西 植 物 44 卷
( 1. School of Ecology and Nature Conservationꎬ Beijing Forestry Universityꎬ Beijing 100083ꎬ Chinaꎻ
2. Museum of Beijing Forestry Universityꎬ Beijing 100083ꎬ China )
Abstract: Diospyros sutchuensis is a national protected wild plant species with narrow distribution and extremely small
population in southwestern China. At presentꎬ the genomic information of this species is lacking and its phylogenetic
relationships among Diospyros remain unclear. In this studyꎬ the chloroplast genome of D. sutchuensis was sequenced by
Illumina platformꎬ assembled and annotated by Getorganelle v1.7.3.4 and PGAꎬ and analyzed by DnaSP 6.12.03 for
sequence comparisonꎬ REPuterꎬ Tandem Reapeats Finderꎬ MISA for repetitive sequencesꎬ CodonW1.4 for codon usage
biasꎬ and EasyCodemL for selection pressure. Meanwhileꎬ based on four different chloroplast genome sequence datasetsꎬ the
phylogenetic relationships between D. sutchuensis and 11 Diospyros species were analyzed using IQtree. The results were as
follows: (1) The chloroplast genome of D. sutchuensis was 157 917 bp in lengthꎬ including two inverted repeats (IRs) of
26 111 bpꎬ which was separated by large single copy (LSC) and short single copy (SSC) of 87 303 bp and 18 392 bpꎬ
respectively. The GC content was 37.4%. (2) The genome contained 113 genesꎬ including 79 protein ̄coding genesꎬ 30
tRNA genesꎬ and 4 rRNA genes. A total of 49 long repeatsꎬ 27 tandem repeatsꎬ and 34 simple sequence repeats were
identified. There were 31 high ̄frequency codons in protein ̄coding genesꎬ most of them ended in A or Uꎬ and the most used
codons were the ones encoding leucine. The coding regions were more conserved than the non ̄coding onesꎬ and 10 regions
were identified as most divergent hotspots for potential molecular markers. There had been positive selection on ndhBꎬ
ndhGꎬ ndhIꎬ rbcLꎬ rpoBꎬ petBꎬ petD and rps12 among protein ̄coding genes. (3) Phylogenetic analyses showed that
D. sutchuensis was closely related to D. rhombifolia and D. cathayensis. Together with D. hainanensisꎬ these four species
formed a monophyletic group. The phylogenetic tree constructed from the chloroplast genomes had the highest support
valuesꎬ indicating that the chloroplast genomes with most variable and informative sites are more suitable for phylogenetic
studies of Diospyros. The results provide useful chloroplast genomic resources for germplasm identificationꎬ genetic diversity
conservationꎬ repopulationꎬ and phylogenetic analysis of D. sutchuensis as well as Diospyros.
Key words: Diospyros sutchuensisꎬ chloroplast genomeꎬ repeat sequenceꎬ selection pressureꎬ phylogenetic analysis
柿科(Ebenaceae) 是一个主要分布于热带和亚 布极为狭窄ꎬ川柿( Diospyros sutchuensis ) 即为分布
热带的 木 本 植 物 科ꎬ 包 含 3 ~ 4 个 属 ( Wallnöferꎬ 范围狭窄的种类之一ꎮ
2001ꎻ Duangjai et al.ꎬ 2006)ꎮ 柿属(Diospyros)是柿 川柿由森林植物学家杨衔晋于 1945 年在« 华
科内种类最多、分布最广的属ꎬ也是柿科在中国唯 西边疆研究学会杂志» 上命名发表ꎬ 模式标本于
一的属ꎮ 同时ꎬ柿属很多种类也是重要的经济树 1941 年采自四川盆地东部华蓥山海拔 1 300 m 的杂
种ꎬ在食用、药用、木材、园艺等方面用途广泛(左大 木林中(Yangꎬ 1945)ꎮ 但是ꎬ自川柿发表后ꎬ几十年
勋等ꎬ 1984ꎻ Rauf et al.ꎬ 2017)ꎮ 柿属的系统分类 来一直未在野外见到ꎮ 研究人员曾去模式原产地
研究主要集中在形态学和孢粉学(Utsunomiya et al.ꎬ 调查ꎬ也未采到(方文培ꎬ 1985)ꎮ 2017 年ꎬ科研人
1998ꎻ Venkatasamy et al.ꎬ 2006ꎻ Akinsulire et al.ꎬ 员在重庆市江津区四面山林区再次调查到川柿ꎬ目
2018ꎻ 胡超琼等ꎬ 2018ꎻ 邹璞等ꎬ 2022)ꎮ 近年来ꎬ 前共发现 6 株个体ꎬ分散在 3 个分布点(刘燕琴等ꎬ
有学者陆续对柿属不同类群开展了分子系统学和 2021aꎬb)ꎮ 川柿在野外分布范围狭窄ꎬ种群数量极
基因组学研究(Yonemori et al.ꎬ 2008ꎻ Turner et al.ꎬ 少ꎬ生 境 受 威 胁 严 重ꎬ 根 据 极 小 种 群 野 生 植 物
2013ꎻ 梁晋军ꎬ 2014ꎻ 傅建敏等ꎬ 2015ꎻ 傅建敏等ꎬ (PSESP) 的 定 义 ( 孙 卫 邦 等ꎬ 2015ꎻ 杨 文 忠 等ꎬ
2017)ꎮ 在国内ꎬ柿属包含的物种数量一直存有争 2015)ꎬ该种应属于极小种群野生植物ꎮ 在 2021 年
议ꎬ很 多 种 类 的 系 统 地 位 也 不 明 确 ( 左 大 勋 等ꎬ 公布的« 国家重点保护野生植物名录» 中( http:/ /
1984ꎻ 吴征镒和崔鸿宾ꎬ 1987ꎻ Li et al.ꎬ 1996)ꎮ www.gov.cn/ zhengce/ zhengceku/ 2021-09/ 09/ content_
Tang 等(2019) 通过资料分析、标本查阅和实地调 5636409.htm)ꎬ柿科共有 2 种被列为国家二级保护
查ꎬ确认了 45 种中国特有的柿属种类ꎬ其中 18 种分 植物ꎬ分别为川柿和小萼柿( D. minutisepala)ꎮ 目