Terpene synthases (TPSs) are crucial for the diversification of terpenes, catalyzing the formation of a wide variety of terpenoid compounds. However, genome-wide systematic characterization of TPS genes in Cymbidium ensifolium has not been reported. Within the genomic database of C. ensifolium, we found 30 CeTPS genes for this investigation. CeTPS genes were irregularly distributed throughout the seven chromosomes and primarily expanded through tandem duplications. The CeTPS proteins were classified into three TPS subfamilies, including 17 TPS-b members, 8 TPS-a members, and 5 TPS-c members. Conserved motif analysis showed that most CeTPSs contained DDxxD and RRX₈W motifs. Cis-element analysis of CeTPS gene promoters indicated regulation primarily by plant hormones and stress. Transcriptome analysis revealed that CeTPS1 and CeTPS18 had high expression in C. ensifolium flowers. qRT-PCR results showed that CeTPS1 and CeTPS18 were predominantly expressed during the flowering stage. Furthermore, CeTPS1 and CeTPS18 proteins were localized in the chloroplasts. These results lay the theoretical groundwork for future research on the functions of CeTPSs in terpenoid biosynthesis.

Background: Paulownia, an ecologically and economically valuable plant species native to China, is notable for its excellent timber quality and strong adaptability. Among them, Paulownia catalpifolia displays the ability to survive in cold climate, a trait associated with northern China. Yet, the molecular information for its cold-tolerance has not been explored. This study was to investigate the changes in physiological indices and transcript levels of P. catalpifolia following cold exposure, which could provide evidence for revealing whether there were differences in the genetic basis of inducing physiological perturbations between moderate low temperature (MLT) and extreme low temperature (ELT). Results: The detection of physiological indices under diverse degrees of chilling stress showed similar patterns of alteration. Enhanced accumulation of osmoregulatory substances, such as soluble sugar and soluble protein, were more conducive under ELT compared to MLT in P. catalpifolia. Moreover, we observed leaf wilting symptoms distinctly after exposure to ELT for 48 h, while this effect was not obvious after MLT exposure for 48 h. Comparative transcriptomic analysis between MLT and ELT demonstrated 13,688 differentially expressed genes (DEGs), most of them appeared after 12 h and 48 h of treatment. GO and KEGG analyses elucidated prominent enrichment in aromatic-L-amino-acid decarboxylase activity term and carbohydrate metabolism pathways. Therefore, it was speculated that the DEGs involved in the above processes might be related to the difference in the contents of soluble protein and soluble sugar between MLT and ELT. Time series clustering analyses further highlighted several key genes engaged in the ‘Glycosyltransferases’, ‘Galactose metabolism’ and ‘Starch and sucrose metabolism’ pathways as well as the ‘tyrosine decarboxylase activity’ term. For instance, cellulose synthase-like A (CLSA2/9), raffinose synthase (RafS2), β-amylase (BAM1) and tyrosine/DOPA decarboxylase (TYDC1/2/5) genes, diverging in their expression trends between MLT and ELT, might significantly affect the soluble sugar and soluble protein abundance within P. catalpifolia. Conclusion: Between MLT and ELT treatments, partial overlaps in response pathways of P. catalpifolia were identified, while several genes regulating the accumulation of osmotic adjustment substances had disparate expression patterns. These findings could provide a novel physiological and molecular perspective for P. catalpifolia to adapt to complex low temperature habitats.

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.

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.