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Cytotype classification and genetic diversity of Platostoma palustre revealed by rDNA localization and chloroplast genome.

Chunhui Zhao·Xinyi Li·Xiu Lan·Rupeng Zhao·Ruolan Huang·Lixia Ruan·Zhaoqin Cai·Zhenling Huang·Wanling Wei·Huixian Chen·Hengrui Li·Haixia Yang
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Abstract

BACKGROUND: Platostoma palustre A. J. Paton is an edible medicinal plant that plays a significant role in traditional food production and medicinal applications. However, the genetic basis of P. palustre remains unclear, thereby hampering research on its genome and polyploid evolution. RESULTS: To characterize the karyotype and ploidy of P. palustre, we performed fluorescence in situ hybridization (FISH) by using 35 S and 5 S rDNA probes in P. palustre. FISH results indicated that 35 S rDNA mapped to the end of the chromosome (chromosome satellite, heterochromatic region) and that 5 S rDNA was located close to the centromere of the chromosomes. Based on the rDNA sites, we identified three distinct cytotypes of P. palustre: diploid (2n = 2x = 30, x = 15), triploid (2n = 3x = 45, x = 15), and tetraploid (2n = 4x = 60, x = 15). To further explore the genetic evolutionary relationship among these P. palustre cytotypes, we conducted Illumina sequencing and assembled the chloroplast (CP) genome. The CP genomes of P. palustre accessions maintained a conserved single circular molecule with a length of 152,534 - 152,788 bp, comprising a large single-copy region (LSC) and small single-copy region (SSC) separated by two inverted repeat regions (IRs). Phylogenetic trees were also created based on CP and nuclear molecular markers, showing that most P. palustre accessions clustered together corresponding to their collection regions. Of these, GDZC2 (2n = 2x = 30) clustered with several triploid accessions, suggesting that it may share a common ancestor with these triploid accessions. CONCLUSIONS: This is the first study to characterize the karyotype, identify three cytotypes of P. palustre using FISH, and provide molecular evidence for an evolutionary relationship among different P. palustre accessions. These findings will be useful for further genomic studies and polyploid evolution of P. palustre.

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Genome, ChloroplastGenetic VariationDNA, RibosomalPhylogenyIn Situ Hybridization, FluorescenceEvolution, MolecularKaryotypeChromosomes, PlantChloroplast genomeFluorescence in situ hybridizationGenetic diversityGermplasm resourcesPlatostoma palustreJournal Article

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Chunhui Zhao, Xinyi Li, Xiu Lan, Rupeng Zhao, Ruolan Huang, Lixia Ruan, Zhaoqin Cai, Zhenling Huang, Wanling Wei, Huixian Chen, Hengrui Li, Haixia Yang. 2025-10-21. Cytotype classification and genetic diversity of Platostoma palustre revealed by rDNA localization and chloroplast genome.. https://doi.org/10.1186/s12864-025-12118-3

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