Paeonia ostii is a worldwide ornamental flower and an emerging oil crop. Zyotic embryogenesis is a critical process during seed development, and it can provide a basis for improving the efficiency of somatic embryogenesis (SE). In this study, transcriptome sequencing of embryo development was performed to investigate gene expression profiling in P. ostii and identified Differentially expressed genes (DEGs) related to transcription factors, plant hormones, and antioxidant enzymes. The results indicated that IAA (Indole-3-acetic acid), GA (Gibberellin), BR (Brassinosteroid) and ETH (Ethylene) were beneficial to early embryonic morphogenesis, while CTK (Cytokinin) and ABA (Abscisic Acid) promoted embryo morphogenesis and maturation. The antioxidant enzymes’ activity was the highest in early embryos and an important participant in embryo formation. The high expression of the genes encoding fatty acid desaturase was beneficial to fast oil accumulation. Representative DEGs were selected and validated using qRT-PCR. Protein-protein interaction network (PPI) was predicted, and six central node proteins, including AUX1, PIN1, ARF6, LAX3, ABCB19, PIF3, and PIF4, were screened. Our results provided new insights into the formation of embryo development and even somatic embryo development in tree peonies.

Tree peony (Paeonia suffruticosa Andr.), which is a traditional flower cultivated in China, is rapidly becoming an important species in the cut flower industry. Thus, extending the vase life of tree peony cut flowers is a major goal in the cut flower industry. Melatonin, which is a new type of antioxidant, plays an important regulatory role in the preservation of cut flowers. Therefore, this study employed the cut flower of tree peony “Diguan” as the test material to investigate the preservative effects of the antioxidant melatonin on the cut flower of tree peony “Diguan”. We examined tree peony cut flowers in terms of their morphology, lifespan, relative fresh weight, relative diameter, and water balance value after treatments with different melatonin concentrations (0.2, 0.3, 0.4, and 0.5 mg·L⁻¹) to select the optimal treatment concentration. Considered together, these analyses clarified the effects of melatonin on the preservation of “Diguan” tree peony cut flowers. Specifically, the exogenous application of melatonin positively affected the preservation of tree peony cut flowers by improving the water balance value and increasing the soluble protein content and antioxidant enzyme activities, thereby prolonging the ornamental period of tree peony cut flowers. The fresh weight of flower branches is significantly positively correlated with soluble protein, and cut flower lifespan increases with the values of soluble protein and the fresh weight of flower branches, with a large correlation coefficient. It can be used as an important indicator to measure cut flower lifespan in subsequent research. The 0.4 mg L⁻¹ melatonin treatment was optimal for preserving tree peony cut flowers because of its positive effects on the duration of the ornamental period and ornamental quality.

Tree peony (Paeonia ostii T. Hong et J. X. Zhang) is an important medicinal and ornamental plant. It would be useful to propagate this plant in tissue culture, but it is difficult to induce root formation. Auxin plays a pivotal role in adventitious root formation, and ABCB transporter proteins are involved in auxin transport. To elucidate the function of the ABCB transporter family in P. ostii, we identified members of the ABCB gene family in the P. ostii genome and analyzed the functional characteristics of the putative proteins. In total, 29 ABCB genes were identified in P.ostii, distributed on five chromosomes. In a phylogenetic analysis, the PoABCBs were grouped into four subfamilies, with the largest being Subfamily I, characterized by their MDR structure. PoABCB genes in the same subfamily exhibited similar intron/exon arrangements and motif composition. The promoters of PoABCBs contained cis-acting elements associated with the photoresponse and hormone signaling. qRT-PCR analyses showed that, after treatment of tissue-cultured P. ostii seedlings with auxin, five PoABCB gene family members (PoABCB6, PoABCB10, PoABCB11, PoABCB12, and PoABCB16) were significantly upregulated during adventitious root development. These genes may play roles in the auxin response and adventitious root development of P. ostii in vitro.

Light-emitting diodes (LEDs) can be programmed to provide specialized light sources and spectra for plant growth. UV-A (397.6 nm), blue (460.6 nm), green (520.7 nm), and red (661.9 nm) LED light sources were used to study the effects of different monochromatic lights on the growth, antioxidant system, and photosynthetic characteristics of Spathiphyllum floribundum ‘Tian Jiao’ (a shade-loving species) and Chrysanthemum morifolium ‘Huang Xiu Qiu’ (a sun-loving species). This research revealed that green and blue light could enhance the morphological indicators, Chl a/b, photosynthetic electron transfer chain performance, and photosystem activity of S. floribundum, blue and red light could enhance the solution protein, Chl a, and photosynthetic electron transfer chain performance of C. morifolium, red and UV-A light viewed the highest SOD and CAT activities of S. floribundum (275.56 U·min·g⁻¹; 148.33 U·min·g⁻¹) and C. morifolium (587.03 U·min·g⁻¹; 98.33 U·min·g⁻¹), respectively. Blue and green light were more suitable for the growth and development of the shade-loving plant S. floribundum, while red and blue light were more suitable for the sun-loving plant C. morifolium. UV-A light could be used for their stress research. The research revealed the different adaptation mechanism of different plants to light environmental conditions.

The adventitious rooting−related oxygenase (ARRO−1) gene is specifically expressed in the early rooting stage and is considered a molecular marker of rooting. In this study, a PsARRO−1 gene (GenBank accession number KJ620008) was identified from a pre−constructed transcriptome database of root development of Paeonia suffruticosa under sandy loam cultivation. The expression was verified by RT−qPCR, and it was found that the expression trend was consistent with the expression in the transcriptome database. The PsARRO−1 gene was specifically highly expressed during the root primordium germination phase. In addition, the RT−qPCR analysis indicated that the expression of PsARRO−1 in roots was significantly higher than in stems and leaves, its peak expression in vitro was 5 days earlier than in soil, and its expression was higher than that of tree peony in soil. Subcellular localization analysis showed that PsARRO−1 was localized in the plasma membrane. Moreover, the transient silent expression of the PsARRO−1 gene was found in the roots of peony seedlings grown using VIGS technology. The root activity was significantly reduced after transient silencing of the expression of the PsARRO−1 gene. These results indicate that PsARRO−1 has a positive regulatory effect on tree peony root development.

SERK is a marker gene for early somatic embryogenesis. We screened and functionally verified a SERK-interacting protein to gain insights into tree-peony somatic embryogenesis. Using PoSERK as bait, we identified PorbcL (i.e., the large subunit of Rubisco) as a SERK-interacting protein from a yeast two-hybrid (Y2H) library of cDNA from developing tree-peony somatic embryos. The interaction between PorbcL and PoSERK was verified by Y2H and bimolecular fluorescence complementation analyses. PorbcL encodes a 586-amino-acid acidic non-secreted hydrophobic non-transmembrane protein that is mainly localized in the chloroplast and plasma membrane. PorbcL was highly expressed in tree-peony roots and flowers and was up-regulated during zygotic embryo development. PorbcL overexpression caused the up-regulation of PoSERK (encoding somatic embryogenesis receptor-like kinase), PoAGL15 (encoding agamous-like 15), and PoGPT1 (encoding glucose-6-phosphate translocator), while it caused the down-regulation of PoLEC1 (encoding leafy cotyledon 1) in tree-peony callus. PorbcL overexpression led to increased indole-3-acetic acid (IAA) content but decreasing contents of abscisic acid (ABA) and 6-benzyladenosine (BAPR). The changes in gene expression, high IAA levels, and increased ratio of IAA to ABA, BAPR, 1-Aminocyclopropanecarboxylic acid (ACC), 5-Deoxystrigol (5DS), and brassinolide (BL) promoted embryogenesis. These results provide a foundation for establishing a tree-peony embryogenic callus system.