The growth and development of apricot flower organs are severely impacted by spring frosts. To better understand this process, apricot flowers were exposed to temperatures ranging from 0 °C to −8 °C, including a control at 18 °C, in artificial incubators to mimic diverse low-temperature environments. We aimed to examine their physiological reactions to cold stress, with an emphasis on changes in phenotype, membrane stability, osmotic substance levels, and antioxidant enzyme performance. Results reveal that cold stress induces significant browning and cellular damage, with a sharp increase in browning rate and membrane permeability below −5 °C. Soluble sugars and proteins initially rise as osmoprotectants, but their content decreases at lower temperatures. Proline content consistently increases, suggesting a protective role. Antioxidant enzyme activities, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX), exhibit a complex pattern, with initial increases followed by declines at more severe cold conditions. Correlation and principal component analyses highlight the interplay between these responses, indicating a multifaceted adaptation strategy. The findings contribute to the understanding of apricot cold tolerance and inform breeding efforts for improved crop resilience.

This study investigated the phylogenetic relationships in the pear calcium-dependent protein kinase (CDPK) pan-gene family and elucidated its role in the resistance to scab disease caused by Venturia nashicola. By integrating data from eight genomic sets from five cultivated pear species, Pyrus bretschneideri, P. ussuriensis, P. sinkiangensis, P pyrifolia, and P. communis, along with P. betulifolia and interspecific hybrids, 63 PyCDPK family members were identified. Among these, P. communis possessed the highest number of CDPK genes, whereas P. bretschneiderilia had the fewest. These genes encode proteins ranging from 459 to 810 amino acids in length, and are predominantly localized to the cell membrane. Six genes, PyCDPK9, PyCDPK11, PyCDPK12, PyCDPK14, PyCDPK16, and PyCDPK19, were classified as core members of the pan-genome, and PyCDPK19 showed evidence of positive selection pressure. Clustering analysis and transcriptomic expression profiling of disease-resistance-related CDPKs identified PyCDPK19 as a key candidate associated with scab resistance. Promoter analysis revealed that the regulatory region of PyCDPK19 contains multiple cis-acting elements involved in defense responses and methyl jasmonate signaling. Transient overexpression of PyCDPK19 in tobacco leaves induced hypersensitive cell necrosis, accompanied by significant increases in hydrogen peroxide (H₂O₂) accumulation and malondialdehyde (MDA) content. Similarly, overexpression in pear fruit callus tissue followed by pathogen inoculation resulted in elevated levels of both H₂O₂ and MDA. Collectively, these findings indicate that PyCDPK19 mediates defense responses through the activation of the reactive oxygen species pathway in both tobacco and pear plants, providing a promising genetic target for enhancing scab resistance in pears.

The cuticular wax of ‘Hupingzao,’ an important economic crop in China, not only constitutes a key factor in determining the appearance quality and gloss of the fruit but also plays a vital role in regulating water evaporation and resisting biotic and abiotic stresses. In this study, ‘Hupingzao’ fruit produced during the white−ripe (WR) and full−red (FR) periods were used as study materials. The key genes and components of wax development were screened using a combination of transcriptomics and metabolomics. Enrichment analysis was performed on the differential genes and metabolites, and the fatty acid biosynthesis and elongation pathways were selected for further study. A series of key candidate genes in the de novo synthesis, elongation, and subsequent modification pathways of fatty acids were identified, such as acetyl−CoA carboxylase (ACCase), fabF (β−Ketoacyl−ACP Synthase II), and β−ketoacyl−CoA synthase (KCS). To further explore the mechanism of jujube wax biosynthesis, GC−MS (gas chromatography–mass spectrometry) was used to determine and analyze the content and composition of the wax after it was treated with gibberellin and paclobutrazol. The results showed that spraying the plants with GA₃ significantly upregulated the expression of genes involved in fatty acid de novo synthesis and elongation such as accC (Acetyl−CoA Carboxylase, Biotin Carboxylase Subunit), fabD (Malonyl−CoA:ACP Transacylase), fabG (β−Ketoacyl−ACP Reductase), fabI (Enoyl−ACP Reductase), ACSL (Long−chain Acyl−CoA Synthetase), and KCS and increased the content of dodecanoic acid, behenic acid, lignoceric acid, and hexacosanoic acid. These results suggest that the GA signal may participate in the upregulation of fatty acid synthesis. In this study, we systematically constructed a molecular map of wax fatty acid metabolism during the fruit development stage of the ‘Hupingzao’ variety, providing an important theoretical basis and candidate genes for future directional regulation of wax components via molecular breeding or cultivation measures.

Apple is notoriously difficult to propagate by cuttings, which severely restricts the large-scale production of own-rooted dwarfing rootstocks. ‘Y-1’ is a promising apple dwarfing rootstock that has been newly bred in China, but its recalcitrant rooting limits its application as an own-rooted stock. In this study, three-year-old ‘Y-1’ stock plants were subjected to three shading rates (40%, 60% and 80%) for 7, 14 and 21 days before cutting collection, and the rooting performance, endogenous hormone and phenolic profiles, antioxidant enzyme activities, and transcriptomic responses of the shoots and cuttings were systematically investigated. Shading of stock plants significantly promoted adventitious rooting, with the combination of 60% shading for 14 days giving the highest rooting rate (39.74%), compared with 5.13% in the unshaded control at the same stage. During shading, leaf chlorophyll content increased with shading intensity and peaked at day 14; phloem indole-3-acetic acid (IAA) and gibberellin (GA₃) contents remained higher than the control, whereas abscisic acid (ABA) and major phenolics (phloridzin, chlorogenic acid, quercitrin and rutin) declined. Transcriptome analysis of the phloem (full light vs. 60% shading at days 7 and 14) identified up to 10,944 differentially expressed genes (DEGs), which were significantly enriched in plant hormone signal transduction, MAPK signaling and plant–pathogen interaction pathways. Shading up-regulated auxin biosynthesis and transport genes (YUCCA6, ARG7, LAX2/LAX3, PIN2) and SAUR genes (SAUR20/50/72/78) while down-regulating auxin signaling repressors and receptors (IAA3/13/14/16/17/26/29/30, TIR1, AFB2, ARF5/6/17/19, PIN3) and the ABA-responsive factor DPBF3. During subsequent rooting, shaded cuttings exhibited four rooting phases (callus formation, root primordium induction, root emergence and elongation); higher IAA and GA₃ and lower ABA and total phenols, together with earlier peaks of POD, PPO, and IAAO activities, characterized the shaded, easy-to-root cuttings. These results indicate that pre-cutting shading creates a “rooting-competent” physiological and transcriptional state in stock-plant shoots that is inherited by the cuttings, providing a practical protocol for ‘Y-1’ cutting propagation and mechanistic insight into light-mediated regulation of adventitious rooting in apple.