Page 6 - 《广西植物》2026年第9期
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1 4 4 2                                广  西  植  物                                         46 卷
              ( 1. School of Biological and Pharmaceutical Engineeringꎬ Lanzhou Jiaotong Universityꎬ Lanzhou 730070ꎬ Chinaꎻ 2. Chongqing Industry and
                  Trade Polytechnicꎬ Chongqing 408000ꎬ Chinaꎻ 3. College of Agronomyꎬ Gansu Agricultural Universityꎬ Lanzhou 730070ꎬ China )

                 Abstract: The recent revision of the Fabaceae classification system merged the Mimosoideae into a broadly defined
                 Caesalpinioideaeꎬ but its reliability still requires independent validation across multiple genetic systems. To clarify the
                 chloroplast genome characteristics and phylogenetic position of Pterolobium punctatumꎬ a representative species within
                 the Caesalpinioideaeꎬ the complete chloroplast genome of P. punctatum was assembled and annotated using Illumina
                 sequencing technologyꎬ and codon usage bias and performed comparative genomics with 19 related species were analyzed
                 in this study. Furthermoreꎬ phylogenetic reconstruction and divergence time estimation were conducted by integrating
                 genomic data from representative species of Caesalpinioideae. The results were as follows: (1) The chloroplast genome of
                 P. punctatum was 159 063 bp in lengthꎬ encoding 128 genesꎬ and exhibited a typical circular quadripartite structureꎬ
                 with significantly higher GC content in the inverted repeat ( IR) regions (42.61%) than in the single ̄copy ( SC)
                 regions. (2) Comparative genomic analysis revealed dynamic evolution at the IR/ SC boundaries between P. punctatum
                 and its close relativesꎬ and mono ̄nucleotide repeats dominated by A/ T bases were the most common SSR type. (3)
                 Analysis of codon usage bias indicated that natural selection was the primary driving forceꎬ and we screened highly
                 variable regions such as ycf1 as potential DNA barcodes. (4) Phylogenetic analysis strongly supported P. punctatum as a
                 sister group to Vachellia nilotica subsp. indicaꎬ providing critical chloroplast genomic validation for the new classification
                 system of Fabaceaeꎻ divergence time estimation suggested that the genus Pterolobium diverged during the Late Oligocene
                 (approx. 24.1 million years ago). This study systematically elucidates the chloroplast genome characteristics of P.
                 punctatum and confirms its phylogenetic position in Caesalpinioideaeꎬ providing a significant scientific basis for
                 understanding the structural evolution of the chloroplast genome as well as for the conservation and utilization of
                 Caesalpinioideae resources.
                 Key words: Pterolobium punctatumꎬ chloroplast genomeꎬ phylogenyꎬ codon usage biasꎬ sequence variation



                豆科(Fabaceae)作为被子植物第三大科ꎬ在陆                      重新界定、范围更广且保证单系性的云实亚科之
            地生态系统中占据重要地位ꎬ具有极高的生态功                              中ꎬ成为其中的一个分支ꎬ即含羞草分支( mimosoid
            能和经济价值ꎮ 长期以来ꎬ传统的分类系统将豆                             clade)( Azani et al.ꎬ2017)ꎮ 在此新框架下ꎬ老虎
            科分为 3 个亚科ꎬ即蝶形花亚科( Papilionoideae)、                 刺属(Pterolobium)被归入广义云实亚科的云实类
            含 羞 草 亚 科 ( Mimosoideae ) 和 云 实 亚 科                群(Caesalpinia group)ꎬ被视为非含羞草型云实类
            (Caesalpinioideae) ( Lin et al.ꎬ2014)ꎮ 其中ꎬ云实       群中较早分化的代表性谱系之一ꎮ 为了进一步解
            亚科作为基部类群ꎬ涵盖约 4 600 种和 163 个属ꎬ                      析各亚科间复杂的深层演化关系ꎬZhao 等(2021)
            展现出高度的形态多样性和生态适应性( Doyleꎬ                          利用大规模核基因转录组数据对豆科进行了系统
            2016ꎻBruneau et al.ꎬ2024)ꎮ 然而ꎬ随着分子系统               发育重建ꎬ进一步验证了六亚科划分的可靠性ꎮ
            学的兴起ꎬ传统分类体系的单系性受到了挑战ꎮ                              尽管这一宏观框架已基本确立ꎬ但由于传统的云
                 回 顾 早 期 分 子 系 统 学 进 展ꎬ Manzanilla 和           实亚科是一个并系群ꎬ而含羞草亚科则深嵌其中
            Bruneau (2012) 基于核基因与质体标记的系统发                      (Manzanilla & Bruneauꎬ2012)ꎬ因此云实类群内部
            育重建ꎬ通过详尽的取样揭示了传统的云实亚科                              属间关系错综复杂ꎬ特别是在属、种水平的精细发
            实质 上 是 一 个 由 蝉 翼 豆 属 ( Pterogyne)、 决 明 属           育关系上ꎬ仍有待更多基因组数据的验证与解析ꎮ
            (Cassia)等类群构成的并系群ꎮ 该研究表明ꎬ含羞                            叶绿体基因组因其结构保守、进化速率适中
            草类群并非独立起源ꎬ而是深嵌于这一并系群内                              等特点ꎬ是分子系统学研究和物种鉴定的重要工
            部ꎬ是由其中的一支衍生而来ꎮ 随后ꎬ豆科系统发                            具之一ꎬ在解析复杂类群系统发育关系中发挥着

            育 工 作 组 ( Legume Phylogeny Working Groupꎬ          重要作用( Moore et al.ꎬ2010ꎻ毕毓芳等ꎬ2020ꎻLi
            LPWG)于 2017 年正式提出了新的分类系统ꎬ该系                        X P et al.ꎬ2021)ꎮ 特别是在豆科植物中ꎬ叶绿体
            统将传统的含羞草亚科整体降级ꎬ并入一个经过                              基因组表现出高度的结构动态性ꎬ频繁发生倒位、
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