Background: Soil heavy metal pollution by chromium (Cr) and copper (Cu) is a global environmental concern. Methods: This study evaluated Cr/Cu accumulation in Paulownia fortunei tissues and analyzed its root transcriptome under Cr and Cu stress to elucidate molecular response mechanisms. Results: Findings revealed significantly higher Cr and Cu accumulation capacity in roots compared to stems and leaves. Transcriptome sequencing identified 6017 and 2265 differentially expressed genes (DEGs) under Cr and Cu stress, respectively. These DEGs were primarily involved in redox reactions, stress responses, transcriptional regulation, transmembrane transport, and metabolism. Quantitative PCR of 20 selected genes validated dynamic expression changes under stress. Weighted Gene Co-expression Network Analysis (WGCNA) identified distinct co-expression modules associated with Cr and Cu. Hub gene analysis implicated Pfo_020668 and Pfo_019190 in Cr response, while Pfo_010312 and Pfo_000197 may enhance Cu tolerance via cell wall polysaccharide synthesis regulation. Pathways related to pyruvate metabolism and proteasome were significantly enriched under Cr stress, whereas amino acid metabolism pathways were prominent under Cu stress. Conclusions: Differentially expressed transporter genes suggest potential roles in heavy metal uptake and transport. This transcriptomic analysis provides novel insights into P. fortunei’s molecular responses to Cr and Cu stress, offering a foundation for utilizing this species in soil phytoremediation efforts.

The genus Paphiopedilum (Orchidaceae) has high ornamental value due to its long flowering period, brilliant flower color, and peculiar floral morphology. Guangxi is the center of ecological diversity of Paphiopedilum, and therefore it is urgent to conduct rescue studies on the genetic resources and genetic structure of this genus in Guangxi. In this study, the genetic diversity of 39 populations from eight Paphiopedilum species in Guangxi was analyzed using ten selected EST-SSR primer pairs and fluorescent PCR amplification. The results show that genetic diversity varied among species, with large differences in expected heterozygosity (He). The highest genetic diversity was observed in P. barbigerum (I = 0.923; He = 0.480), while P. dianthum (I = 0.179; He = 0.098) showed the lowest diversity. From the genus perspective, molecular variance analysis (AMOVA) revealed that 57% of the genetic variation occurred among populations and 43% within populations, with inter-population variation being the main source of genetic variation. From a species perspective, genetic differentiation varied, with inter-individual differentiation ranging from 79% to 95%. The percentage of molecular variance indicated that genetic variation mainly occurred among individuals, which was the main source of total variation. According to the principle of maximum likelihood, the optimal K value was determined to be 6, and 760 Paphiopedilum samples were divided into six subgroups. The results of this study not only identify priority populations for conservation and establish a germplasm repository to preserve existing resources, but also provide references for research on asexual reproduction, seed propagation, and hybrid breeding of Paphiopedilum, thereby promoting the conservation and sustainable utilization of Paphiopedilum germplasm resources.

Three viruses, Telosma mosaic virus (TeMV), East Asian passiflora virus (EAPV), and Cucumber mosaic virus (CMV), are widespread in Chinese passion fruit growing regions. Co-infection by these three viruses was confirmed in symptomatic field samples collected from Guilin. To evaluate the effectiveness of shoot tip culture alone for virus elimination, in vitro organogenesis was examined, and both direct (DOR) and indirect (IOR) regeneration pathways were observed. In the DOR pathway, organogenic buds and nodules were induced at a rate of 40.83%, and 14.86% of explants produced adventitious buds longer than 1 cm. In the IOR pathway, callus was induced at a rate of 26.67%, and callus-derived meristemoids yielded a bud induction rate of 7.46%. Semi-quantitative PCR analysis showed that only a few virus-free plantlets were obtained, and no regenerated plantlets were found to simultaneously eliminate two or three viruses. No significant difference in median virus elimination efficiency was detected between the DOR and IOR pathways (TeMV: 0% vs. 16.67%; EAPV: 16.67% vs. 0%; CMV: 33.33% vs. 16.67%). SSR analysis confirmed genetic stability in the DOR pathway, whereas a polymorphism rate of 27.27% was observed in the IOR pathway. These findings indicate that the DOR pathway maintains genetic stability while achieving elimination of certain viruses in a small number of co-infected plantlets, providing a basis for subsequent secondary virus elimination and combined treatments.

Three viruses, Telosma mosaic virus (TeMV), East Asian passiflora virus (EAPV), and Cucumber mosaic virus (CMV), were found to be widespread in Chinese purple passion fruit (Passiflora edulis Sims) growing regions, with co-infection by these three viruses confirmed in symptomatic field samples collected from Guilin. To evaluate the effectiveness of single shoot tip culture for virus elimination, in vitro organogenesis was examined, and both direct (DOR) and indirect (IOR) organogenesis pathways were observed. In the DOR pathway, organogenic buds and nodules were induced at a rate of 40.83%, and adventitious buds longer than 1 cm were produced by 14.86% of explants. In the IOR pathway, callus was induced at a rate of 26.67%, and a bud induction rate of 7.46% was obtained from callus-derived meristemoids. Semi-quantitative reverse transcription polymerase chain reaction (semi-qPCR) analysis revealed that viral RNA was undetectable in only a few regenerated plantlets, and none of the plantlets tested negative for two or three viruses simultaneously. The proportion of plantlets with detectable virus loss was comparable between the DOR and IOR pathways (TeMV: 5.56% vs. 11.11%; EAPV: 16.67% vs. 5.56%; CMV: 27.78% vs. 16.67%). All tested Simple Sequence Repeat (SSR) loci were monomorphic in the DOR pathway, whereas a polymorphism rate of 27.27% was observed in the IOR pathway. These findings indicate that the DOR pathway yielded only monomorphic bands at the assessed SSR loci while enabling the production of a small number of plantlets with viral RNA levels below the semi-qPCR detection limit, providing a basis for the subsequent application of more sensitive detection methods and combined treatment strategies.