Silver nanoparticles (AgNPs), widely recognized for their nanoscale geometric size and unique properties, such as large specific surface area, high permeability, and high safety, were synthesized using the endophytic fungus Penicillium polonicum PG21 through a green approach. Four key synthesis factors—48 h, 45 °C, pH 9.0, and 80 mM AgNPs concentration—were optimized. Characterization via ultraviolet–visible spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction revealed the AgNPs as approximately 3–25 nm spherical particles with numerous functional groups ensuring stability. AgNPs were tested against various fungal and bacterial plant pathogens, including Botrytis cinerea (EB-1), Alternaria alternata (EB-2, EB-3), Fusarium solani (RG-1), Williamsia serinedens (SL-1), Sphingopyxis macrogoltabida (SL-2), Bacillus velezensis (SL-3), and Pseudomonas mediterranea (SL-4), causing agricultural challenges. PG21-synthesized AgNPs exhibited inhibition rates against all tested fungi, with 60 μg/mL AgNPs demonstrating optimal inhibition rates. Notably, EB-1 experienced a significant growth inhibition, reaching an inhibition rate reached of 74.22 ± 1.54%. Conversely, RG-1 exhibited the smallest inhibitory effect at 48.13 ± 0.92%. The effect of AgNPs on safflower seed germination and growth revealed notable increases in shoot length, fresh weight, stem length, and number of lateral roots—1.4, 1.4, 1.33, and 10.67 times higher than the control, respectively, at an AgNPs concentration of 80 μg/mL. In conclusion, green-synthesized AgNPs demonstrate pathogen toxicity, showcasing potential applications in disease management for industrial crops and promoting plant growth.

The hairy roots of Rehmannia glutinosa (Gaertn.) Libosch. ex Fisch. & C. A. Mey. are capable of producing active compounds such as iridoid glycoside, and phenylethanoid glycosides, which have potential applications in the pharmaceutical industry. Silver nanoparticles (AgNPs) have been used as novel elicitors in the induced cultivation of hairy roots, but there is a lack of research regarding their effects on R. glutinosa hairy roots. In the present study, silver nanoparticles (Pp-AgNPs) synthesized by the endophytic fungus Penicillium polandii PG21 were adopted to elicit hairy roots of R. glutinosa, to investigate their influences on the biomass, color, secondary metabolites, antioxidant activity, sucrose metabolism, and phytohormone-related gene expression. The results revealed that the dry weight and fresh weight of R. glutinosa hairy roots were both higher in the treated group than in the control group after addition of 2 mg/L Pp-AgNPs for 20 d. The content of verbascoside, total phenylethanol glycosides and total cycloartenoid in the treatment group reached the highest level at 20 d, which were 1.75, 1.51, 1.44 times more than those in the control group, respectively. Pp-AgNPs significantly stimulated the enzyme activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). The growth-promoting effect of Pp-AgNPs may be accomplished by increasing sucrose metabolism, and regulating the synthesis and signal transduction of gibberellin (GA) and indoleacetic acid (IAA). Moreover, expressed sequence tags-simple sequence repeat (EST-SSR)-based genetic diversity analyses indicated that there was little possibility of genetic variation among samples under different treatment conditions. In conclusion, the appropriate concentration of Pp-AgNPs can be used as an effective elicitor to improve the biomass and secondary metabolites content in R. glutinosa hairy roots.

The HD-Zip family of transcription factors is unique to the plant kingdom, and play roles in modulation of plant growth and response to environmental stresses. R. glutinosa is an important Chinese medicinal material. Its yield and quality are susceptible to various stresses. The HD-Zip transcription factors is unique to the plant, and roles in modulation of plant growth and response to environmental stresses. However, there is no relevant research on the HD-ZIP of R. glutinosa. In this study, 92 HD-Zip transcription factors were identified in R. glutinosa, and denominated as RgHDZ1-RgHDZ92. Members of RgHDZ were classified into four groups (HD-ZipI-IV) based on the phylogenetic relationship of Arabidopsis HD-Zip proteins, and each group contains 38, 18, 17, and 19 members, respectively. Expression analyses of RgHDZ genes based on transcriptome data showed that the expression of these genes could be induced by the endophytic fungus of R. glutinosa. Additionally, we showed that RgHDZ genes were differentially expressed in response to drought, waterlogging, temperature, and salinity treatments. This study provides important information for different expression patterns of stress-responsive HD-Zip and may contribute to the better understanding of the different responses of plants to biotic and abiotic stresses, and provide a molecular basis for the cultivation of resistant varieties of R. glutinosa.

Light is one of the most pivotal environmental factors in plant life activities and plays a crucial role in regulating the synthesis of plant secondary metabolites. However, there is no report on the response mechanism of F. multiflora to different light quality treatments. In this study, different light qualities were applied. Physiological characteristics and secondary metabolites of plants, including leaf area, chlorophyll, proline, physcion, emodi, THSG etc., were measured after 20-day light quality treatment. Subsequently, the FmARF gene family was identified and analyzed the expression under the impact of light quality. Results showed that the blue-light treatment group significantly increased the leaf area by 46.19% and chlorophyll content by 7.35%, decreased the plant height by 20.92%, and increased the THSG content in roots by 28.37% and in stems by 27.15%. The yellow-light treatment significantly increased the proline content by 94.47% and the soluble sugar content by 19.03%. The red-light treatment significantly increased the plant height by 83.56%. There are 37 FmARF genes in F. multiflora , which are classified into four sub-families. Whole-genome duplication and segmental duplication are the predominant expansion modes. The promoters are abundant in light and other response elements, and most genes show tissue-specific expression. Correlation prediction analysis revealed that in the stems, the content of stilbene glycoside was significantly negatively correlated with FmARF9 and 30 , and free anthraquinone components such as physcion and emodin were significantly negatively correlated with FmARF2 , 5 etc. In the roots, the content of stilbene glycoside was significantly negatively correlated with FmARF8 , 9, 29, and positively correlated with FmARF17 ; physcion was negatively correlated with FmARF2, 5 etc., and positively correlated with FmARF8, 9 etc.; emodin was negatively correlated with FmARF2, 5 etc., and positively correlated with FmARF9, 15 etc. This study demonstrates that there are significant differences in the growth and development of F. multiflora under different light quality treatments. The FmARF gene family may mediate light quality regulation and metabolic synthesis pathways. This research provides a theoretical basis for the functional identification of key candidate genes for light regulation and the study of the molecular mechanism of light regulation in F. multiflora .