Page 86 - 《广西植物》2022年第10期
P. 86
1 7 0 4 广 西 植 物 42 卷
Abstract: Carpinus tientaiensis is an endangered plant species with sparse population densities and is endemic to
China. The distribution of this species is restricted to the territory of Zhejiang Province and its survival rate is very
low. Based on data of chloroplast genome (cpDNA) single nucleotide polymorphism (SNP) in six natural populations
(including the mother plants of all populations)ꎬ we investigated genealogical structure and systematic developmentꎬ
assessed how endangered C. tientaiensis is and put forward relevant conservation strategies. The genomic DNA of C.
tientaiensis was extracted using TIANGEN kit method and a library was constructed for high ̄throughput sequencing with
Illumina NovaSeq 6000. To obtain the sequence of chloroplast complete genomeꎬ cpDNA maps were constructed using the
online program OGDRAW. Nucleotide diversity was analyzed by DnaSP software while PopART was used for haploid
network construction and RAxML was adopted for maximum likelihood ( ML) tree construction. Finallyꎬ MrBayes
software was used for construction of Bayes tree. The results were as follows: (1) According to chloroplast complete
genome sequence analysis of C. tientaiensisꎬ most of the protein ̄coding genes and amino acid sequences showed obvious
codon preference. Moreoverꎬ chloroplast long ̄term relationship (cpLTR) revealed 32 forward repeatsꎬ 25 palindromic
repeats and 22 reverse repeats. We detected 87 simple sequence repeats (SSR) in different typesꎬ most of which were
A/ T rich and the number of single nucleotides was the largest. (2) A total of 314 SNPs was identified in the cpDNA of
C. tientaiensis. Single ̄nucleotide substitution indicated that C. tientaiensis was monophyletic and could be categorized into
Tiantai County ( THS) and Jingning County ( JST) populations. The evolution of the haplotypes of the population
manifested stellar radiation. (3) The variation of nucleotide diversity was low in all populations (P <0.005) and the
i
haplotype diversity of THS and JST populations was also low (H 0.5- 0.6). This indicated that C. tientaiensis had
d
undergone historically local expansions after experiencing bottlenecks across its evolution historyꎬ with lower genetic
variation within populations and higher level of diversity among populations. The results of SNP of the cpDNA reveal the
genetic diversity and lineage differentiation of C. tientaiensisꎬ and provide theoretical basis for conservation of the genetic
resources as well as rescue of this endangered plant species.
Key words: Carpinus tientaiensisꎬ chloroplast genome (cpDNA)ꎬ single nucleotide polymorphism (SNP)ꎬ genealogical
structureꎬ phylogeny
天台鹅耳枥( Carpinus tientaiensis) 属于桦木科 2008ꎻ Wei & Jiangꎬ2012)ꎮ 根据 IUCN 物种红色
(Betulaceae)鹅耳枥属( Carpinus)ꎬ为中国特有和 名录ꎬ天台鹅耳枥属于极危( critically endangeredꎬ
濒危的第三纪孑遗植物ꎬ是国家二级重点保护野 CR)等级ꎮ 天 台 鹅 耳 枥 染 色 体 为 14 倍 体 ( 2n =
生植物( 章绍尧等ꎬ1993)ꎮ 我国是鹅耳枥属植物 14x = 112)ꎬ是桦木科倍性最高的多倍体植物( 陈
的分布中心ꎬ约有 33 种 8 变种( 傅立国ꎬ2003)ꎬ其 模舜等ꎬ2020)ꎮ 天台鹅耳枥在研究桦木科分类、
中东南沿海是鹅耳枥属植物一个重要的分布区ꎬ 古植物区系、濒危机制等研究中具有很高的科研
天 台 鹅 耳 枥 ( C. tientaiensis ) 和 普 陀 鹅 耳 枥 价值( 章绍尧和丁炳扬ꎬ1993ꎻ王昌腾和叶春林ꎬ
(C. putoensis)等为浙江地区特有( 陈之端ꎬ1994)ꎮ 2007)ꎮ
中国植物志曾记载天台鹅耳枥产于浙江东部( 中 目前ꎬ仅对天台鹅耳枥组织解剖结构、光合特
国科学院中国植物志编辑委员会ꎬ1979)ꎬ浙江植 性对生长光强的响应、群落特征等方面进行了研
物志统计天台鹅耳枥仅存 5 株( 章绍尧等ꎬ1993)ꎬ 究(陈模舜和柯世省ꎬ2013ꎻ陈模舜等ꎬ2020)ꎮ 但
但近年来在磐安县和景宁县等地有所发现ꎬ仅间 天台鹅耳枥种群的进化机制与种内系统发育尚未
断分布于浙江省境内的天台县、磐安县、青田县和 明确ꎬ必须收集群体样本进行基因组学的分析ꎬ在
景宁畲族自治县ꎬ野外成年植株不足 50 株ꎬ幼年 基因组水平上加深对这一濒危物种居群动态的了
个体缺少ꎬ低于野外种群稳定存活界限ꎬ已处于极 解ꎮ 叶绿体基因组( chloroplast genomeꎬcpDNA) 由
危状态ꎮ 生境片断化使得野生居群变小及居群间 于其高基因含量和保守的基因组结构ꎬ可用于研
的隔离程度增加ꎬ这将会导致遗传变异丧失和近 究开 花 植 物 的 母 系 遗 传ꎬ 特 别 是 多 倍 体 植 物
交衰退ꎬ最终增加物种灭绝的风险( Aguilar et al.ꎬ (Birkyꎬ 1995ꎻSoltis & Soltisꎬ 2000)ꎮ cpDNA 通常