Wintersweet (Chimonanthus praecox) is a well-known traditional fragrant plant and a winter-flowering deciduous shrub that originated in China. The five different developmental stages of wintersweet, namely, flower-bud period (FB), displayed petal stage (DP), open flower stage (OF), later blooming period (LB), and wilting period (WP) were studied using a scanning electron microscope (SEM) to determine the distribution characteristics of aroma-emitting nectaries. Results showed that the floral scent was probably emitted from nectaries distributed on the adaxial side of the innermost and middle petals, but almost none on the abaxial side. The nectaries in different developmental periods on the petals differ in numbers, sizes, and characteristics. Although the distribution of nectaries on different rounds of petals showed a diverse pattern at the same developmental periods, that of the nectaries on the same round of petals showed some of regularity. The nectary is concentrated on the adaxial side of the petals, especially in the region near the axis of the lower part of the petals. Based on transcriptional sequence and phylogenetic analysis, we report one nectary development related gene CpCRC (CRABS CLAW), and the other four YABBY family genes, CpFIL (FILAMENTOUS FLOWER), CpYABBY2, CpYABBY5-1, and CpYABBY5-2 in C. praecox (accession no. MH718960-MH718964). Quantitative RT-PCR (qRT-PCR) results showed that the expression characteristics of these YABBY family genes were similar to those of 11 floral scent genes, namely, CpSAMT, CpDMAPP, CpIPP, CpGPPS1, CpGPPS2, CpGPP, CpLIS, CpMYR1, CpFPPS, CpTER3, and CpTER5. The expression levels of these genes were generally higher in the lower part of the petals than in the upper halves in different rounds of petals, the highest being in the innermost petals, but the lowest in the outer petals. Relative expression level of CpFIL, CpCRC, CpYABBY5-1, and CpLIS in the innermost and middle petals in OF stages is significant higher than that of in outer petals, respectively. SEM and qRT-PCR results in C. praecox showed that floral scent emission is related to the distribution of nectaries.

Lily is one of the world’s important ornamental flowers. Potted Asiatic lily is a further selected dwarf cultivar suitable for indoor or garden planting. However, there is a lack of relevant research on the cultivation adaptability of potted Asiatic lilies cultivars in the Chongqing region which in the southwest of China. This study selected five potted Asiatic lily cultivars, and the phenological period, stem and leaf characteristics, and flowering traits were assessed through statistical observation. The Asiatic lily ‘Tiny Ghost’ and ‘Tiny Double You’ are well-suited for both spring and autumn planting in Chongqing, while ‘Sugar Love’ and ‘Curitiba’ are best planted in the spring. The ‘Tiny Diamond’ is more appropriate for autumn planting due to its low tolerance to high temperature. The application of exogenous substances, including calcium chloride (CaCl₂), potassium fulvic acid (PFA) and melatonin (MT), can mitigate the detrimental effects of high-temperature stress on ‘Tiny Diamond’ by regulating photosynthesis, antioxidant systems, and osmotic substance content. A comprehensive evaluation using the membership function showed that the effect of exogenous CaCl₂ treatment is the best, followed by exogenous PFA treatment. CaCl₂ acts as a positive regulator of heat stress tolerance in Asian lilies, with potential applications in Asian lily cultivation. This study provides reference for cultivation and application of Asian lily varieties in Chongqing region, and also laid the foundation for further research on the mechanism of exogenous substances alleviating heat stress in lilies.

NAC (NAM, ATAF1/2, and CUC2) transcription factors regulate plant growth and development and response to various stresses. However, there is still limited insight into the NAC family in Chimonanthus praecox. This study performed a genome-wide characterization of the NAC transcription factor family members in C. praecox. A total of 105 NAC family members were identified from the C. praecox genome. The phylogenetic tree categorized the CpNACs into nine groups and the accuracy of this classification was confirmed by the analysis results of conserved motifs, conserved domain, and gene structure. Cis-acting element analysis revealed that the promoters of CpNACs were abundant in elements responsive to various hormones and stresses, implying the functional diversity and complexity of CpNACs. Furthermore, we investigated the function of the CpNAC30. The expression level of CpNAC30 could be significantly induced by abiotic stress and the CpNAC30 was the highest expressed in mature leaves of C. praecox. Overexpression of CpNAC30 reduced salt stress tolerance of transgenic Arabidopsis. Nevertheless, the drought stress tolerance of transgenic plants was enhanced. This study lays a foundation for further understanding the function of CpNACs genes and provides insights for abiotic stress tolerance breeding of C. praecox and other woody plants.

Phenylalanine ammonia-lyase (PAL) is the rate-limiting enzyme in the phenylpropane metabolic pathway, which is crucial for plant disease resistance. However, the functional roles of specific PAL members in lily defense against gray mold (Botrytis elliptica) remain unclear. Using the resistant lily cultivar ‘Sorbonne’, metabolomics analysis revealed that phenylpropane metabolites were significantly induced upon pathogen infection. Combined second- and third-generation transcriptome sequencing identified eight PAL family members. Among them, LhSorPAL1 and LhSorPAL2 were strongly induced by B. elliptica and were selected for further analysis. Both recombinant proteins exhibited PAL enzymatic activity catalyzing cinnamic acid production from L-phenylalanine. Overexpression of LhSorPAL1 or LhSorPAL2 in lily via Agrobacterium-mediated transformation had no obvious effect on plant growth but significantly increased the accumulation of lignin, flavonoids, and total phenols upon pathogen challenge, leading to enhanced resistance to gray mold. Conversely, antisense expression of LhSorPAL1 or LhSorPAL2 reduced the accumulation of these metabolites. Promoter analysis revealed that both LhSorPAL1pro and LhSorPAL2pro contain methyl jasmonate (MeJA)-, abscisic acid (ABA)-, and transcription factor-binding cis-elements. Collectively, these results demonstrate that LhSorPAL1 and LhSorPAL2 positively regulate lily resistance to B. elliptica by promoting phenylpropane metabolism, providing candidate genes for molecular breeding.