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<p><i>Penthorum chinense</i> Push and <i>Penthorum sedoides</i> L. are the only two species in <i>Penthorum</i> L. (<i>Penthoraceae</i>) with an eastern Asian-eastern North American disjunction, and their systematic placement remains uncertain with respect to <i>Saxifragaceae</i>, <i>Crassulaceae</i>, <i>Haloragaceae</i>, <i>Caryophyllaceae</i>, <i>Polygonaceae</i>, and <i>Phytolaccaceae</i> based on previous molecular, morphological, and anatomical data. To clarify the phylogeny and evolutionary history of <i>Penthorum</i>, new primers were designed to amplify exons 11–14 and intervening introns of the nuclear gene RNA polymerase II second largest subunit (<i>RPB2</i>). Exons 12–13 sequences were analyzed using maximum parsimony (MP), maximum likelihood (ML), and Bayesian inference (BI) methods for 35 species of 21 genera in seven families. Intron analysis revealed two <i>RPB2</i> paralogues, <i>RPB2-I</i> copy (introns 11–13 presence) and <i>RPB2-D</i> copy (introns 11–12 deleted; intron 13 absent only in <i>P. chinense</i>). The MP, ML, and BI phylogenetic trees showed that species of <i>Saxifragaceae</i>, <i>Crassulaceae</i>, <i>Haloragaceae</i>, and <i>Penthoraceae</i> (<i>P. sedoides</i> and <i>P. chinense</i>) clustered into a strongly supported <i>RPB2-I</i> clade. <i>Caryophyllaceae</i>, <i>Penthoraceae</i> (<i>P. chinense</i>), and <i>Phytolaccaceae</i> species formed one well-supported <i>RPB2-D</i> clade, and <i>Polygonaceae</i> species formed another robust <i>RPB2-D</i> clade. In <i>RPB2-I</i> clade, <i>P. chinense</i> and <i>P. sedoides</i> were clustered with <i>Myriophyllum spicatum</i> L. (<i>Haloragaceae</i>). In <i>RPB2-D</i> clade, <i>P. chinense</i> and <i>Myosoton aquaticum</i> (L.) Moench (<i>Caryophyllaceae</i>) formed a single monophyletic lineage. Thus, <i>Penthorum</i> is closely related to taxa in <i>Myriophyllum</i> L. and <i>Myosoton</i>, Moench with their common ancestor experiencing <i>RPB2</i> duplication and paralog sorting. Considering morphological and anatomical characters, the molecular results from this study support the retention of <i>Penthorum</i> within the monogeneric <i>Penthoraceae.</i></p>

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RPB2 gene phylogeny of species in Penthorum L. and related genera

  • 期刊论文

  • 发表日期：

    2026年3月27日

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  • Yan Wang,
  • Sha Yi,
  • Bin Wang,
  • Weiya Wang,
  • Haiqing Yu,
  • Xin Shu

摘要

Penthorum chinense Push and Penthorum sedoides L. are the only two species in Penthorum L. (Penthoraceae) with an eastern Asian-eastern North American disjunction, and their systematic placement remains uncertain with respect to Saxifragaceae, Crassulaceae, Haloragaceae, Caryophyllaceae, Polygonaceae, and Phytolaccaceae based on previous molecular, morphological, and anatomical data. To clarify the phylogeny and evolutionary history of Penthorum, new primers were designed to amplify exons 11–14 and intervening introns of the nuclear gene RNA polymerase II second largest subunit (RPB2). Exons 12–13 sequences were analyzed using maximum parsimony (MP), maximum likelihood (ML), and Bayesian inference (BI) methods for 35 species of 21 genera in seven families. Intron analysis revealed two RPB2 paralogues, RPB2-I copy (introns 11–13 presence) and RPB2-D copy (introns 11–12 deleted; intron 13 absent only in P. chinense). The MP, ML, and BI phylogenetic trees showed that species of Saxifragaceae, Crassulaceae, Haloragaceae, and Penthoraceae (P. sedoides and P. chinense) clustered into a strongly supported RPB2-I clade. Caryophyllaceae, Penthoraceae (P. chinense), and Phytolaccaceae species formed one well-supported RPB2-D clade, and Polygonaceae species formed another robust RPB2-D clade. In RPB2-I clade, P. chinense and P. sedoides were clustered with Myriophyllum spicatum L. (Haloragaceae). In RPB2-D clade, P. chinense and Myosoton aquaticum (L.) Moench (Caryophyllaceae) formed a single monophyletic lineage. Thus, Penthorum is closely related to taxa in Myriophyllum L. and Myosoton, Moench with their common ancestor experiencing RPB2 duplication and paralog sorting. Considering morphological and anatomical characters, the molecular results from this study support the retention of Penthorum within the monogeneric Penthoraceae.