Piriformospora indica, an endophytic fungus of Sebacinales, has a wide host range and promotes the performance of mono- and eudicot plants. Here, we compare the interaction of P. indica with the roots of seven host plants (Anthurium andraeanum, Arabidopsis thaliana, Brassica campestris, Lycopersicon esculentum, Oncidium orchid, Oryza sativa, and Zea mays). Microscopical analyses showed that the colonization time and the mode of hyphal invasion into the roots differ in the symbiotic interactions. Substantial differences between the species were also observed for the levels and accumulation of jasmonate (JA) and gibberellin (GA) and the transcript levels for genes involved in their syntheses. No obvious correlation could be detected between the endogenous JA and/or GA levels and the time point of root colonization in a given plant species. Our results suggest that root colonization strategies and changes in the two phytohormone levels are highly host-specific.

Callus browning is a significant problem that hinders plant tissue regeneration in Paeonia ostii “Fengdan” by causing cell death and inhibiting growth. However, the molecular mechanism underlying callus browning in P. ostii remains unclear. In this study, we investigated the metabolites and potential regulatory genes involved in callus browning of P. ostii using metabolomic and transcriptomic analyses. We found a significant accumulation of phenolic compounds in the browned callus, represented by flavonoid compounds. Notably, the accumulations of luteotin and disomentin were higher in browning calli compared to non-browning calli. Transcriptomic analysis identified that candidate genes associated with flavonoid biosynthesis, including flavonoid 3-hydroxylase (PoF3H) and flavone synthase II (PoFNSII), were highly expressed in the browned callus of P. ostii “Fengdan”. Weighted gene co-expression network analysis (WGCNA) further highlighted that polyphenol oxidase (PoPPO) which encoded polyphenol oxidase, together with flavonoid biosynthesis-related genes such as flavanone 3-hydroxylase (PoF3H) and flavonone Synthase II (PoFNSII), as well as cellular totipotency-related genes wuschel-related homeobox 4 (PoWOX4), were involved in callus browning. Based on these findings, we proposed the molecular mechanism by which flavonoid accumulation, polyphenol oxidation, and cellular totipotency pathways contribute to callus browning in P. ostii. Our study provides new insights into the molecular mechanism underlying callus browning and offers the foundations to facilitate the establishment of an efficient plant tissue regeneration system in P. ostii.

Paeonia lactiflora Pall. (herbaceous peony) is a high-value ornamental and medicinal plant in China with considerable market potential. However, conventional propagation methods are limited by low multiplication rates and long production cycles, making it difficult to meet the demand for large-scale planting materials. As a key approach for rapid propagation, tissue culture techniques for P. lactiflora have achieved significant progress in recent years. This review summarizes advances in the tissue culture system for P. lactiflora over the past decade, focusing on major in vitro regeneration pathways (organogenesis and somatic embryogenesis) and crucial technical stages, including explant selection and culture environment optimization. Distinct from previous reviews that only introduce partial technical aspects of P. lactiflora tissue culture, this review comprehensively outlines the overall tissue culture system, analyses the current species-specific bottlenecks (browning, vitrification, rooting and acclimatization) with their underlying causes and proposes targeted strategies. Furthermore, future development trends are prospected by integrating emerging research directions, including molecular regulatory mechanisms and eco-adaptive breeding. This review aims to provide a theoretical foundation and technical support for obtaining propagule for commercial plantations and achieving multi-functional utilization of P. lactiflora.

High-temperature stress severely limits the cultivation and ornamental quality of herbaceous peony, especially in low-latitude regions. The objective of this study was to reveal the potential mechanism involved in regulation of jasmonates on herbaceous peony heat tolerance through crosstalk between phytohormones and the reactive oxygen species (ROS) scavenging system. The study found that exogenous methyl jasmonate (MeJA) significantly improved thermotolerance of the low-latitude cultivar ‘Hang Baishao’ by enhancing antioxidase activities and modulating endogenous phytohormone levels. The MeJA-treated group exhibited markedly higher ratios of MeJA to zeatin riboside (ZR), gibberellic acid (GA₃), brassinolide (BR), and indole-3-acetic acid (IAA) compared with the control group; catalase (CAT) and superoxide dismutase (SOD) activities were significantly elevated relative to hydrogen peroxide (H₂O₂) content, with both ratios peaking at 36 h post-heat treatment. Transcriptomic results revealed that MeJA reshaped the expression of genes involved in jasmonic acid (JA) signaling and ROS scavenging, such as FAD4, MED25, and JAZ2 and CSD2/3, FSD1, and CAT3. Four modules including the hub genes CIPK5/6, WRKY19/40 and CYPs were identified from the weighted gene co-expression network analysis (WGCNA), which may be key players in coordinating JA signaling and antioxidant defense. This study demonstrates that MeJA enhanced herbaceous peony thermotolerance by orchestrating a regulatory network involving phytohormonal crosstalk and activation of the ROS scavenging system, and offers candidate genes for future exploration of function and interactions.

Paeonia suffruticosa cv. ‘Yu Luo Chun’ is an important representative of the peony groups from the Jiangnan region of China. However, little is known about the genetic basis of chloroplast genome phylogeny and the adaptive evolution of this group. In this study, high-throughput sequencing technology was used to sequence the complete chloroplast genome of leaves, and sequence assembly, annotation and feature analysis were performed by bioinformatics analysis methods. The results showed that the chloroplast genome of P. suffruticosa cv. ‘Yu Luo Chun’ exhibited a typical tetrad structure with a total length of 152,596 bp, including a large single-copy (LSC) region, a small single-copy (SSC) region, and two inverted repeats (IRs) whose lengths were 84,272 bp, 17,044 bp and 25,640 bp, respectively. A total of 126 genes were annotated, including 85 protein-coding genes, 37 tRNA genes and 4 rRNA genes. Bioinformatics analysis showed that a total of 71 simple sequence repeats (SSRs) were searched in the chloroplast genome, of which the numbers of mononucleotide, dinucleotide, trinucleotide and tetranucleotide repeat motifs were 47, 12, 7 and 5, respectively, and no pentanucleotide or hexanucleotide repeat motifs were found. The chloroplast genome prefers to end in A/T, among which leucine (Leu) is the most frequently used, while cysteine ​​(Cys) is the least frequently used. Highly differentiated regions, such as rpoC1, petB, rsp16, rps19, clpP, ccsA, ycf1, ndhF-trnL, ndhD-psaC and trnV-rps12, were identified as DNA barcodes and potential genetic markers for interspecies relationships. We compared the gene selection pressure and identified 5 genes, ndhF, petB, petD, rpoA and ycf2 that were positively selected, and these genes have important contributions to the adaptive evolution. The chloroplast genome sequences of 18 species, including P. suffruticosa cv. ‘Yu Luo Chun’, were clustered by the nearest neighbour combination method and the maximum likelihood method. Both methods gave the same result and indicated that this cultivar has a relatively close kinship with P. qiui and P. rockii. The results provide important references for species identification, genetic diversity analysis and systematic taxonomic research between P. suffruticosa cv. ‘Yu Luo Chun’ and other Paeonia species.