Drought is one of the main abiotic stress factors affecting yield of Paeonia ostii. In this study, we conducted bioinformatics and differential expression analyses of P. ostii ‘Feng Dan’ ptc-miR396g-5p in leaf samples under different drought stress. ptc-miR396g-5p belongs to the miR396 family. Among the 271 plant species registered in the miRBase database, at least one miR396 member was found in 48 Angiospermae species, 3 in Gymnospermae species, and 1 in Pteridophy. Mature sequence alignment showed that P. ostii ‘Feng Dan’ ptc-miR396g-5p had high sequence similarity with miR396 from other species. Secondary structure prediction showed that the precursor sequence of ‘Feng Dan’ ptc-miR396g-5p could form a stable stem-loop structure, and the mature sequence was located on the 5′ arm of the secondary structure. Phylogenetic tree analysis showed that ‘Feng Dan’ was closely related to 20 species such as Glycine max, Medicago truncatula, Populus trichocarpa, Citrus sinensis, Vitis vinifera, and Theobroma cacao. The predicted target gene of the ‘Feng Dan’ ptc-miR396g-5p encodes a Signal Transducer and Activator of Transcription (STAT) transcription factor. The negative correlation of expression between the miRNA and its target gene was confirmed by qRT-PCR. Our data indicate that ‘Feng Dan’ ptc-miR396g-5p′s expression decreases under drought, leading to an expression increase of the STAT transcription factor.

MiRNA plays an important role in plant growth and development and in response to various stresses. Quantitative real-time PCR (qRT-PCR) technology is often used to detect the expression level of miRNAs and genes by comparing with reference genes. In order to screen out the optimal reference miRNAs in different tree peony varieties, the petals of 42 different early- and late-flowering tree peony varieties were used as experimental materials, and geNorm, NormFinder, Bestkeeper, and RefFinder software were used to evaluate the stability of 16 candidate reference miRNAs. The results showed that the average Ct values of all candidate reference miRNAs were between 15.34 ± 0.29 and 32.64 ± 0.38. The optimal number of reference miRNAs was four, which were PsPC-5p-19095, PsPC-3p-51259, PsmiR159a, and PsPC-3p-6660 in geNorm. The stability of PsPC-3p-6660 was the highest in the analysis results of NormFinder software. Among the analysis results of Bestkeeper software, PsMIR319-p5 has the highest stability. Among the results of comprehensive evaluation and analysis of several software using RefFinder, the candidate reference miRNA with the highest stability was PsPC-3p-6660. When PsPC-3p-6660 was used as the reference miRNA, the expression of PomiR171 and PomiR414 in response to different flowering times of tree peony was relatively stable in 42 tree peony varieties, indicating that PsPC-3p-6660 was stable and reliable. The results of this study provide a reference miRNA for studying the expression changes of miRNA in different tree peony varieties and further exploring the regulatory mechanism of miRNA in different peony varieties.

The aim of this paper was to investigate the transcriptomic and metabolomic differences in Populus cathayana × canadasis ‘Xinlin1’ (P. cathayana × canadasis ‘Xinlin 1’) under varying irrigation and fertilization conditions. Ten-year-old P. cathayana × canadasis ‘Xinlin 1’ was selected as the test subject in this study; different irrigation and fertilization treatments were set up, and DEGs and DAMs in response to water and fertilizer regulation were identified. Transcriptomic and metabolomic profiles were analyzed from both leaves and roots. A total of 22,870 DEGs were identified in response to water and fertilizer treatments, predominantly belonging to 48 transcription factor families, including MYB, ERF, and MYB-related ones. Additionally, 2432 DAMs were detected and categorized into 18 metabolite classes, with flavonoids being the most abundant (342 metabolites), followed by terpenoids, lipids, and others. KEGG enrichment analysis revealed that DEGs and DAMs were significantly associated with pathways such as plant hormone signal transduction and starch and sucrose metabolism pathways. The levels of ABA exhibited an initial decrease followed by an increase, with several key genes, including PYR/PYL, PP2C, SnRK2, and ABF, also differentially expressed in the plant hormone signal transduction pathway. In the starch and sucrose metabolic pathways, sucrose was more hydrolyzed into D-fructose, which gradually translocated from roots to leaves. DEGs were significantly involved in sucrose synthesis and decomposition into D-fructose and 1,3-β-glucose, as well as starch synthesis and starch decomposition into cellulose dextrin, which underwent complete hydrolysis to glucose. In the starch hydrolysis process, 29 DEGs were involved, with 12 down-regulated and 17 up-regulated.