Oligonucleotide (Oligo)-based fluorescence in situ hybridization (FISH) represents a highly effective methodology for identifying plant chromosomes. Longan is a commercially significant fruit species, yet lacking basic chromosomal markers has hindered its cytogenetic research. In this study, we developed a cost-effective oligo-based system for distinguishing chromosomes of longan (Dimocarpus longan Lour., 2n = 2x = 30). For this system, each synthesized oligo contained two chromosome-specific sequences that spanned a distance of over 200 kb, and a PCR-based flexible amplification method coupled with nested primers was used for probe labeling. The use of these oligo-based barcodes enabled the marking of 36 chromosomal regions, which allowed for the unambiguous distinction of all 15 chromosomes in both longan and lychee (Litchi chinensis Sonn., 2n = 2x = 30) species. Based on the identification of individual chromosomes, we constructed karyotypes and detected genome assembly errors involving the 35S ribosomal RNA gene (35S rDNA) in longan and lychee. Developing oligo-based barcodes offers considerable promise for advancing cytogenetic research in longan, lychee, and their related species. Furthermore, this cost-effective synthesis system can be referred to the development of new oligo libraries among other species.

Smooth cordgrass (Spartina alterniflora) is a native salt marsh plant along the Atlantic coast but has become an invasive species in coastal regions in China, as well as other areas. Utilizing it for resources has become a control measure in reducing the spread of S. alterniflora. This study assesses the nutritional and phytochemical properties of the edible stems of S. alterniflora collected from three locations in Fujian province, China. The tender stems of S. alterniflora exhibit a rich nutritional profile, with high levels of protein, carbohydrates, and fats, and significant amounts of essential vitamins, minerals, and antioxidants, indicating their potential as a nutritious addition to the diet or forage. In addition, the levels of potential contaminants, including nitrate, nitrite, cadmium, lead, and chromium, are below the established safe thresholds for consumption. Our results provide valuable information for the sustainable utilization of S. alterniflora resources and will contribute to the integrated control of S. alterniflora.

Satellite DNA is a fundamental component of eukaryotic genomes, playing critical roles in chromosome organization and genome stability. Nevertheless, its e

In eukaryotes, tandem repeats are often unstable, leading to rapid evolutionary changes. However, the evolutionary dynamics of these repeats in allopolyploids like the water hyacinth remain (Eichhornia crassipes or Pontederia crassipes) poorly understood. In our study, we analyzed five typ-ical tandem repeats in the allotetraploid water hyacinth using genomic and cytogenetic methods. We found non-random distribution and copy number variation across the genome. The highly abundant centromeric tandem repeat, putative CentEc, co-localized with the centromeric re-trotransposon CREc, indicating conserved centromeric features. Putative CentEc sequences showed high conservation (91%-100%), suggesting ongoing concerted evolution post-subgenome divergence. Fluorescence in situ hybridization (FISH) analysis showed telomere sequences on all chromosomes, with tandem repeat of interstitial chromosome regions (ICREc) only on certain chromosomes, both exhibiting copy number variation. Moreover, 5S rDNA was detected on one chromosome pair, and 35S rDNA on multiple chromosomes with varying intensities. Examination of the genome assembly also revealed sequence heterogeneity in copies of 5S and 35S rDNA from the two subgenomes, implying divergent evolution of these two rDNA families within their re-spective subgenomes. Our findings highlight the role of tandem repeats in the water hyacinth genome's structure and evolution, with implications for understanding the genomic dynamics of invasive species.

Drastic karyotype changes are a major evolutionary force, potentially involving centromere position, number, distribution, or strength alterations. Yet, the genetic and epigenetic landscape of centromeres, especially in allopolyploid plants during subgenome reshuffling, remains poorly understood. Here, we present a near-complete chromosome-scale genome assembly of the allotetraploid Pennisetum purpureum ‘Purple’, resolving all 14 centromeres. We find that subgenome-biased expansion of six LTR retrotransposons drives architectural divergence between subgenomes. Centromeric satellite repeats (CentPs) show rapid sequence divergence across subgenomes and chromosomes, with CENH3 preferentially binding conserved higher order repeats. Intriguingly, centromeric retrotransposons in Pennisetum (CRPs) are evolutionarily younger compared to their noncentromeric counterparts, coupled with marked subgenome B-biased amplification. Notably, CRP insertions flanking CentP satellites correlate with elevated satellite DNA polymorphism, supporting a model wherein CentP homogenization processes actively purge retrotransposons from centromeric arrays. Despite rapid sequence diversification of centromeric repeats, the epigenetic landscapes remain evolutionarily conserved in the centromeres of two subgenomes. Additionally, comparative analyses across Pennisetum species demonstrate rapid species- and chromosome-level turnover of CentPs and CRPs. Overall, our study illuminates the genetic and epigenetic plasticity of centromeres in allopolyploids, revealing how centromeric repeats adapt post-subgenome reshuffling.