LncRNAs represent a class of RNA transcripts of more than 200 nucleotides (nt) in length without discernible protein-coding potential. The expression levels of lncRNAs are significantly affected by stress or developmental cues. Recent studies have shown that lncRNAs participate in fruit development and ripening processes in tomato and strawberry; however, in other fleshy fruits, the association between lncRNAs and fruit ripening remains largely elusive. Here, we constructed 9 ssRNA-Seq libraries from three different peach (Prunus persica) fruit developmental stages comprising the first and second exponential stages and the fruit-ripening stage. In total, 1500 confident lncRNAs from 887 loci were obtained according to the bioinformatics analysis. The lncRNAs identified in peach fruits showed distinct characteristics compared with protein-coding mRNAs, including lower expression levels, lower complexity of alternative splicing, shorter isoforms and smaller numbers of exons. Expression analysis identified 575 differentially expressed lncRNAs (DELs) classified into 6 clusters, among which members of Clusters 1, 2, 4 and 5 were putatively associated with fruit development and ripening processes. Quantitative real-time PCR revealed that the DELs indeed had stage-specific expression patterns in peach fruits. GO and KEGG enrichment analysis revealed that DELs might be associated with fruit-ripening-related physiological and metabolic changes, such as flavonoid biosynthesis, fruit texture softening, chlorophyll breakdown and aroma compound accumulation. Finally, the similarity analysis of lncRNAs within different plant species indicated the low sequence conservation of lncRNAs. Our study reports a large number of fruit-expressed lncRNAs and identifies fruit development phase-specific expressed lncRNA members, which highlights their potential functions in fruit development and ripening processes and lays the foundations for future functional research.

The plant calcineurin B-like protein–CBL interacting protein kinase (CBL–CIPK) signaling pathway is a Ca2+-related signaling pathway that responds strongly to both biological and abiotic environmental stimuli. This study identified eight CBL and eighteen CIPK genes from peach for the first time. Their basic properties and gene structure were analyzed, and the CBL and CIPK members from Arabidopsis and apple were combined to study their evolutionary relationships. Using RT-qPCR and RNA-seq data, we detected the expression patterns of PprCBLs and PprCIPKs in different tissues and fruit development stages of peach. Among them, the expression levels of PprCBL1 and PprCIPK18 were stable in various tissues and stages. The expression patterns of other members showed specificity between cultivars and developmental stages. By treating shoots with drought and salt stress simulated using PEG6000 and NaCl, it was found that PprCIPK3, PprCIPK6, PprCIPK15 and PprCIPK16 were strongly responsive to salt stress, and PprCIPK3, PprCIPK4, PprCIPK10, PprCIPK14, PprCIPK15, PprCIPK16 and PprCIPK18 were sensitive to drought stress. Three genes, PprCIPK3, PprCIPK15 and PprCIPK16, were sensitive to both salt and drought stress. We cloned four PprCBL and several PprCIPK genes and detected their interaction by yeast two-hybrid assay (Y2H). The results of Y2H show not only the evolutionary conservation of the interaction network of CBL–CIPK but also the specificity among different species. In conclusion, CBL and CIPK genes are important in peach and play an important role in the response to various abiotic stresses.

Fruit development and ripening in peach (Prunus persica) involve complex transcriptional and post-transcriptional regulation. While short-read sequencing has advanced transcriptome studies, it often fails to accurately resolve complex transcript isoforms. This study employed Oxford Nanopore Technologies’ (ONT) full-length RNA-Seq to comprehensively characterize the transcriptomic landscape of peach fruits across three key developmental stages: the first exponential stage, the second exponential stage, and the ripening stage. Our analysis identified 44,042 non-redundant isoforms, including 1109 novel genes and 32,289 novel isoforms, significantly expanding the peach genome annotation. We further investigated alternative splicing (AS) events, revealing that intron retention (IR) and alternative 3′ splice site (A3′S) were the most prevalent types, with AS abundance peaking at the S1 stage. A total of 10,236 differentially expressed transcripts (DETs) were identified, highlighting dynamic expression patterns during fruit development. Functional characterization focused on a MADS-box gene, PpMADS6, which produced two isoforms via alternative splicing. Dual luciferase assays in tobacco leaves demonstrated that the full-length isoform, PpMADS6a, specifically activated the promoter of the fruit-softening gene PpPG1, while the truncated isoform, PpMADS6b, lost this transactivation ability. This study provides a valuable resource of full-length transcriptomes for peach and underscores the critical role of alternative splicing in generating functional diversity to fine-tune fruit development and ripening processes.