Page 104 - 《广西植物》2025年第7期
P. 104

1 2 9 6                                广  西  植  物                                         45 卷
                   ( 1. School of Life Sciencesꎬ Qinghai Normal Universityꎬ Xining 810008ꎬ Chinaꎻ 2. Key Laboratory of Biodiversity Formation
                              Mechanism and Comprehensive Utilization of the Qinghai ̄Xizang Plateau in Qinghai Provinceꎬ
                                           Qinghai Normal Universityꎬ Xining 810008ꎬ China )


                 Abstract: In order to comprehensively investigate the characteristics of the chloroplast genome and phylogenetic location
                 of Sophora alopecuroidesꎬ we sequenced the chloroplast genome of S. alopecuroides using Illumina platformꎬ and
                 performed assemblyꎬ annotation and characteristic analysis by bioinformatics methodsꎬ conducting phylogenetic studies
                 and divergence time estimation of S. alopecuroides based on chloroplast genomes and single ̄copy orthologous genes. The
                 results were as follows: (1) The chloroplast genome of S. alopecuroides was 154 399 bp in lengthꎬ with a typical
                 quadripartite structure and 36.6% GC contentꎬ which contained 84 protein ̄coding genesꎬ 37 tRNA genes and eight
                 rRNA genes. (2)A total of 94 simple sequence repeat (SSR) sites were detected in the chloroplast genomeꎬ which were
                 mainly distributed in the intergenic regions and dominated by single nucleotide A/ T repeats. (3)Simultaneouslyꎬ codon
                 bias analysis indicated that leucine (Leu) was the most frequent amino acid used (10.39%). There were 21 codons
                 whose relative synonymous codon usage (RSCU) was greater than 1 and ΔRSCU≥0.08ꎬ all of which mainly ended in
                 A/ U. Their preferences are influenced by the combined effects of mutation and natural selection. (4)We also found that
                 the ycf2 gene of the chloroplast genome in S. alopecuroides were under positive selection through selective pressure
                 analysis. (5)Additionallyꎬ due to the different evolutionary rates of organelle genes and nuclear genesꎬ the topological
                 structures of phylogenetic trees constructed based on chloroplast genome sequences and single ̄copy orthologous gene
                 sequences screened from transcriptome/ genome were not exactly the sameꎬ but the results showed that S. alopecuroides
                 and S. davidii were closely related. Estimates of divergence times indicated that the estimated differentiation time of
                 S. alopecuroides based on chloroplast genome (8.05 Mya) was much smaller than that based on single ̄copy of orthologous
                 gene (18.28 Mya). This study clarified the chloroplast genome characteristics and obtained reasonable phylogenetic
                 position and differentiation time of S. alopecuroide. It provides fundamental data and reference value for subsequent
                 discussions on the phylogenyꎬ genetic diversityꎬ and selection and utilization of germplasm resources of Sophora in the
                 future.
                 Key words: Sophora alopecuroidesꎬ chloroplast genomeꎬ codon usage biasꎬ phylogenyꎬ selective pressure



                叶绿体是植物光合作用的主要场所ꎬ是植物                            体基因的适应性进化ꎬ结果发现参试物种的叶绿
            细胞特有的半自主性细胞器ꎮ 作为相对独立的遗                             体基因均受到不同程度的正选择作用ꎮ 此外ꎬ田
            传物质ꎬ叶绿体基因组( chloroplast genome) 包含完                春育等 ( 2021) 研 究 认 为 密 码 子 在 遗 传 信 息 从
            整且丰富的蛋白编码信息( Howe et al.ꎬ 2003)ꎬ一                  mRNA 传递至蛋白过程中发挥着重要作用ꎮ 在 20
            般呈环状四分体结构ꎬ包括 1 个大单拷贝( large                        种编码 氨 基 酸 中ꎬ 除 甲 硫 氨 酸 ( Met) 和 色 氨 酸
            single ̄copyꎬ LSC )、 1 个 小 单 拷 贝 ( small single ̄    (Trp)由一种密码子编码外ꎬ其余 18 种氨基酸均
            copyꎬ SSC) 及 2 个反 向 重 复 序 列 ( inverted repeat      由多种密码子编码( 田春育等ꎬ2021)ꎮ 编码同种
            sequenceꎬ IRs)ꎮ 大多被子植物的叶绿体基因组为                     氨基酸的不同密码子被称为同义密码子( 田春育
            母系遗传、高度保守ꎬ因其结构稳定、进化速率慢                             等ꎬ2021)ꎮ 同义密码子使用频率不同的现象ꎬ即
            及分子 量 小 而 被 广 泛 应 用 于 物 种 鉴 定 ( Yang et            同义密码子使用偏好性ꎮ Chakraborty 等(2020) 认
            al.ꎬ 2013)、系统进化( Cattolicoꎬ 1986)、遗传多样             为由于密码子使用偏好性主要受突变和选择压力
            性( Allender et al.ꎬ 2007) 及 基 因 工 程 ( Daniell et   影响ꎬ因此密码子使用偏好性在物种进化研究时
            al.ꎬ 2016) 等研究ꎮ 在分子进化、比较基因组学、                      能预测基因的表达水平ꎬ可以在分子水平上深层
            系统发育重建等领域具有重要作用ꎬ可为揭示分                              理解物种的进化过程(Leffler et al.ꎬ 2012)ꎮ
            子序列的进化过程及基因组进化的分子机制提供                                  苦 豆 子 ( Sophora alopecuroides ) 是 豆 科
            理 论 依 据 ( Li & Jackꎬ 1998 )ꎮ 例 如ꎬ 王 博 等            (Fabaceae)苦参属(Sophora) 一种多年生草本植物
            (2012)利用叶绿体全基因组分析了真叶植物叶绿                           (中国科学院中国植物志编辑委员会ꎬ1984)ꎬ广泛
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