The double flower is an important trait with substantial ornamental value. While mutations in PETALOSA TOE-type or AG (AGAMOUS) genes play a crucial role in enhancing petal number in ornamental plants, the complete mechanism underlying the formation of double flowers remains to be fully elucidated. Through the application of bulked segregant analysis (BSA), we identified a novel gene, APETALA2-like (PmAP2L), characterized by a 49-bp deletion in double-flowered Prunus mume. β-Glucuronidase (GUS) staining and luciferase reporter assays confirmed that the 49-bp deletion in PmAP2L reduced its binding with Pmu-miRNA172a. Phylogenetic analysis and microsynteny analysis suggested that PmAP2L was not a PETALOSA TOE-type gene, and it might be a new gene controlling the formation of double flower in P. mume. Subsequently, overexpression of PmAP2L-D in tobacco led to a significant rise in the number of stamens and the conversion of stamens to petals. Furthermore, silencing of the homologue of RC5G0530900 in rose significantly reduced the number of petals. Using transient gene expression in P. mume flower buds, we determined the functional differences between PmAP2L-D and PmAP2-S in controlling flower development. Meanwhile, DNA-affinity purification sequencing (DAP-seq), yeast hybrid assays and luciferase reporter assays indicated that PmAP2L negatively regulated the floral organ identity genes by forming a repressor complex with PmTPL and PmHDA6/19. Overall, these findings indicate that the variation in PmAP2L is associated with differences in the regulation of genes responsible for floral organ identity, providing new insights into the double-flower trait and double-flower breeding in plants.

Trehalose and its key synthase (trehalose-6-phosphate synthase, TPS) can improve the drought tolerance of plants. However, little is known about the roles of trehalose and the TPS family in Prunus mume response to drought. In our study, we discovered that the trehalose content in leaf, root, and stem tissues significantly increased in P. mume in response to drought. Therefore, the characteristics and functions of the TPS family are worth investigating in P. mume. We identified nine TPS family members in P. mume, which were divided into two sub-families and characterized by gene structure, promoter elements, protein conserved domains, and protein motifs. We found that the Hydrolase_3 domain and several motifs were highly conserved in Group II instead of Group I. The distinctions between the two groups may result from selective constraints, which we estimated by the d_N/d_S (ω) ratio. The ω values of all the PmTPS family gene pairs were evaluated as less than 1, indicating that purity selection facilitated their divergence. A phylogenetic tree was constructed using 92 TPSs from 10 Rosaceae species, which were further divided into five clusters. Based on evolutionary analyses, the five clusters of TPS family proteins mainly underwent varied purity selection. The expression patterns of PmTPSs under drought suggested that the TPS family played an important role in the drought tolerance of P. mume. Combining the expression patterns of PmTPSs and the trehalose content changes in leaf, stem, and root tissues under normal conditions and drought stress, we found that the PmTPS2 and PmTPS6 mainly function in the trehalose biosynthesis in P. mume. Our findings not only provide valuable information about the functions of trehalose and TPSs in the drought response of P. mume, but they also contribute to the future drought breeding of P. mume.

Cyclins, a prominent class of cell division regulators, play an extremely important role in plant growth and development. D-type cyclins (CYCDs) are the rate-limiting components of the G1 phase. In plants, studies of CYCDs are mainly concerned with herbaceous plants, yet little information is available about these genes in perennial woody plants, especially ornamental plants. Here, twelve Prunus mume CYCD (PmCYCDs) genes are identified and characterized. The PmCYCDs were named on the basis of orthologues in Arabidopsis thaliana and Oryza sativa. Gene structure and conserved domains of each subgroup CYCDs was similar to that of their orthologues in A. thaliana and O. sativa. However, PmCYCDs exhibited different tissue-specific expression patterns in root, stem, leaf, bud, and fruit organs. The results of qRT-PCR showed that all PmCYCDs, except PmCYCD5;2 and PmCYCD7;1, were primarily highly expressed in leaf buds, shoots, and stems. In addition, the transcript levels of PmCYCD genes were analyzed in roots under different treatments, including exogenous applications of NAA, 6-BA, GA3, ABA, and sucrose. Interestingly, although PmCYCDs were induced by sucrose, the extent of gene induction among PmCYCD subgroups varied. The induction of PmCYCD1;2 by hormones depended on the presence of sucrose. PmCYCD3;1 was stimulated by NAA, and induction was strengthened when sugar and hormones were applied together. Taken together, our study demonstrates that PmCYCDs are functional in plant stem development and provides a basis for selecting members of the cyclin gene family as candidate genes for ornamental plant breeding.

Soil salinization is a crucial factor that impacts plant distribution and growth. Apocynum venetum, an ornamental plant with medicinal value, has shown remarkable salt tolerance. However, the specific mechanisms through which A. venetum responds to salt stress are not yet fully understood. To address this gap, we conducted a study where 10-week-old A. venetum seedlings were subjected to salt stress by irrigating them with a nutrient solution containing varying concentrations of NaCl (0, 100, 200, and 350 mmol·L⁻¹). After the salt stress treatment, various growth indicators (such as plant height, root length, root fresh weight, root dry weight, leaf fresh weight, leaf dry weight, root water content, leaf water content, and root–leaf ratio) as well as physiological indicators (including SOD and CAT activities in both leaves and roots, soluble protein contents in leaves and roots, and chlorophyll and carotene contents in leaves) were determined. In addition, the gene expression profile of roots under salt stress was examined by transcriptome sequencing to explore the mechanism of salt response in A. venetum. Our results show that salt stress led to yellowing and wilting of A. venetum seedling leaves. Furthermore, the chlorophyll and carotenoid contents in the leaves of the 350 mmol·L⁻¹ NaCl-treated group were significantly reduced. Although the leaf and root biomass gradually decreased with an increase in the salt concentration, the root–leaf ratio exhibited a decreasing trend. NaCl stress also caused significant changes in physiological indices in the A. venntum leaves and roots. The activities of superoxide dismutase (SOD) and catalase (CAT) increased in both leaves and roots of the 100 mmol·L⁻¹ NaCl-treated group. The soluble protein content in both leaves and roots increased under the 200 mmol·L⁻¹ NaCl stress. To screen changes in root gene expression, transcriptome sequencing and qRT-PCR were performed. GO and KEGG enrichment analyses revealed that salt stress primarily affects carbohydrate metabolism, MAPK signaling transduction, phytohormone signaling pathways, glyoxylate and dicarboxylate metabolism, and other pathways. This study provides a novel understanding of the growth and physiological response of A. venetum leaf and root to NaCl stress, as well as the changes in the transcription levels in A. venetum root. The results serve as a reference for future research on salt-tolerant mechanisms and molecular breeding of A. venetum.

Dehydration response element binding factor (DREB) is a family of plant-specific transcription factors, whose members participate in the regulation of plant responses to various abiotic stresses. Prunus nana, also known as the wild almond, is a member of the Rosaceae family that is rare and found to grow in the wild in China. These wild almond trees are found in hilly regions in northern Xinjiang, and exhibit greater drought and cold stress resistance than cultivated almond varieties. However, the response of P. nana DREBs (PnaDREBs) under low temperature stress is still unclear. In this study, 46 DREB genes were identified in the wild almond genome, with this number being slightly lower than that in the sweet almond (Prunus dulcis cultivar ‘Nonpareil’). These DREB genes in wild almond were separated into two classes. All PnaDREB genes were located on six chromosomes. PnaDREB proteins that were classified in the same groups contained specific shared motifs, and promoter analyses revealed that PnaDREB genes harbored a range of stress-responsive elements associated with drought, low-temperature stress, light responsivity, and hormone-responsive cis-regulatory elements within their promoter regions. MicroRNA target site prediction analyses also suggested that 79 miRNAs may regulate the expression of 40 of these PnaDREB genes, with PnaDREB2. To examine if these identified PnaDREB genes responded to low temperature stress, 15 of these genes were selected including seven homologous to Arabidopsis C-repeat binding factor (CBFs), and their expression was assessed following incubation for 2 h at 25 °C, 5 °C, 0 °C, −5 °C, or −10 °C. In summary, this analysis provides an overview of the P. nana PnaDREB gene family and provides a foundation for further studies of the ability of different PnaDREB genes to regulate cold stress responses in almond plants.

The Homeodomain leucine zipper (HD-Zip) family of transcription factors is crucial in helping plants adapt to environmental changes and promoting their growth and development. Despite research on the HD-Zip family in various plants, studies in Lagerstroemia (crape myrtle) have not been reported. This study aimed to address this gap by comprehensively analyzing the HD-Zip gene family in crape myrtle. This study identified 52 HD-Zip genes in the genome of Lagerstroemia indica, designated as LinHDZ1-LinHDZ52. These genes were distributed across 22 chromosomes and grouped into 4 clusters (HD-Zip I-IV) based on their phylogenetic relationships. Most gene structures and motifs within each cluster were conserved. Analysis of protein properties, gene structure, conserved motifs, and cis-acting regulatory elements revealed diverse roles of LinHDZs in various biological contexts. Examining the expression patterns of these 52 genes in 6 tissues (shoot apical meristem, tender shoot, and mature shoot) of non-dwarf and dwarf crape myrtles revealed that 2 LinHDZs (LinHDZ24 and LinHDZ14) and 2 LinHDZs (LinHDZ9 and LinHDZ35) were respectively upregulated in tender shoot of non-dwarf crape myrtles and tender and mature shoots of dwarf crape myrtles, which suggested the important roles of these genes in regulate the shoot development of Lagerstroemia. In addition, the expression levels of 2 LinHDZs (LinHDZ23 and LinHDZ34) were significantly upregulated in the shoot apical meristem of non-dwarf crape myrtle. These genes were identified as key candidates for regulating Lagerstroemia plant height. This study enhanced the understanding of the functions of HD-Zip family members in the growth and development processes of woody plants and provided a theoretical basis for further studies on the molecular mechanisms underlying Lagerstroemia plant height.