Due to its ornamental and medicinal value, pear flower has been historically loved and used in China. However, the current understanding of their odor-active compounds and aroma profiles is rather limited. This work aimed to evaluate and compare the overall aroma profile of pear flowers; the volatiles in flowers of seven pear cultivars (Anli, Bayuesu, Golden, Brown peel, KorlaXiangli, Lyubaoshi, Xizilü) were analyzed using solid-phase microextraction–gas chromatography-mass spectrometry (SPME-GC-MS). A total of 93 volatile compounds were identified and quantified within the amount of volatiles in the range of 62.7–691.8 μg kg⁻¹ (FW) and showed high and significant variability in different cultivars. Anli and Brown peel flowers showed a relatively higher volatile abundance, while KorlaXiangli flowers were significantly lower than other cultivars. Although the composition of volatiles depended on the existence of different chemical classes, the odor activity values (OAVs) and odor descriptions showed some aldehydes were part of their main peculiarities and were considered as the basic active odorants that presented strong intensity of citrus and floral odor. Moreover, multivariate analysis showed the pear flower of different cultivars could be arranged in different clusters by the identified odorants. This study provides first-hand knowledge regarding pear flower aroma profiles, and that the cultivar differences were critical for the overall pattern.

The peach landrace ‘Liuyefeitao’ exhibits the unique reproductive trait of self-compatibility combined with cross-incompatibility, contrasting with typical Prunus species in this way. In preliminary studies involving controlled pollination assays, we showed complete pollen tube arrest in cross-pollinated styles, whereas self-pollination enabled full tube elongation. S-genotyping identified a homozygous S₂S₂ genotype with intact S₂-RNase but a truncated PpSFB2 due to a frameshift mutation. Transcriptome profiling of the styles revealed 7937 differentially expressed genes (DEGs) between self- and cross-pollination treatments, with significant enrichment in plant MAPK signaling, plant–pathogen interactions, and plant hormone signaling transduction pathways (|Fold Change| ≥ 2, FDR < 0.01). Notably, PpSLFL3 (a pollen F-box gene) showed down-regulation in cross-pollinated styles, as validated by means of qRT-PCR. Protein interaction assays revealed direct binding between PpSLFL3 and S₂-RNase via Y2H and BiFC analysis, suggesting its role in mediating SCF complex-dependent degradation. We propose that insufficient PpSLFL3 expression during cross-pollination disrupts SCF ubiquitin ligase complex-mediated degradation of non-self S₂-RNase, leading to the toxic degradation of RNA in pollen tubes by S₂-RNase. This mechanism is mechanistically similar to unilateral reproductive barriers in Solanaceae but represents a novel regulatory module in Rosaceae. Our findings provide critical insights into the evolution of cross-incompatibility systems and molecular breeding strategies for Prunus species.

Low temperatures are a major environmental factor limiting the growth and productivity of peaches (Prunuspersica). U-box E3 ubiquitin ligases (PUBs) are known to play a role in plant responses to abiotic stresses; however, their role in cold tolerance of peaches is unclear. In this study, transcriptome data revealed that a U-box E3 ubiquitin ligase gene, PpPUB20, was significantly activated by low temperatures. Expression analysis showed that PpPUB20 was rapidly upregulated under cold stress, with a more pronounced early response in cold-tolerant cultivars than in the cold-sensitive cultivars. Phylogenetic analysis revealed that PpPUB20 is evolutionarily conserved across plant species, and domain prediction identified a highly conserved U-box domain. Functional assays demonstrated that overexpressing PpPUB20 gene significantly enhanced low-temperature tolerance in Arabidopsis thaliana, whereas silencing it reduced low-temperature tolerance in peach calli. Physiological studies suggested that PpPUB20 positively regulates cold tolerance by enhancing antioxidant enzyme activity and minimizing membrane damage. Yeast two-hybrid screening identified sorbitol dehydrogenase (PpSDH) as a potential PpPUB20-interacting protein, which was further confirmed by luciferase complementation and co-immunoprecipitation assays. In vitro ubiquitination assays demonstrated that PpPUB20 functions as an E3 ubiquitin ligase mediating the polyubiquitination of PpSDH. This study found that an alternatively spliced transcript of PpPUB20 was present in the non-cold-resistant variety ‘21 Shiji’ but absent in the cold-resistant variety ‘Shijizhixing’. These splicing variants show functional deficiencies in their response to low-temperature stress and its substrate protein interaction due to an absent ARM domain. Full-length and structurally intact PpPUB20 was ubiquitinated by targeting PpSDH, thereby regulating sorbitol metabolism and enhancing the low-temperature tolerance of peaches. This study reveals a new molecular mechanism of peach response to low-temperature stress and further emphasizes the important role of ubiquitination-mediated post-translational regulation in the environmental adaptability of fruit trees.