Anthocyanin accumulation in vacuoles results in red coloration in pear peels. Glutathione S-transferase (GST) proteins have emerged as important regulators of anthocyanin accumulation. Here, a total of 57 PcGST genes were identified in the European pear ‘Bartlett’ (Pyrus communis) through comprehensive genomic analysis. Phylogenetic analysis showed that PcGST genes were divided into 10 subfamilies. The gene structure, chromosomal localization, collinearity relationship, cis-elements in the promoter region, and conserved motifs of PcGST genes were analyzed. Further research indicated that glutamic acid (Glu) can significantly improve anthocyanin accumulation in pear peels. RNA sequencing (RNA-seq) analysis showed that Glu induced the expression of most PcGST genes, among which PcGST57 was most significantly induced. Further phylogenetic analysis indicated that PcGST57 was closely related to GST genes identified in other species, which were involved in anthocyanin accumulation. Transcript analysis indicated that PcGST57 was expressed in various tissues, other than flesh, and associated with peel coloration at different developmental stages. Silencing of PcGST57 by virus-induced gene silencing (VIGS) inhibited the expression of PcGST57 and reduced the anthocyanin content in pear fruit. In contrast, overexpression of PcGST57 improved anthocyanin accumulation. Collectively, our results demonstrated that PcGST57 was involved in anthocyanin accumulation in pear and provided candidate genes for red pear breeding.

Pear (Pyrus L.) is one of the most important temperate fruit crops worldwide, with considerable economic value and significant health benefits. Red-skinned pears have an attractive appearance and relatively high anthocyanin accumulation, and are especially favored by customers. Abnormal weather conditions usually reduce the coloration of red pears. The application of exogenous sucrose obviously promotes anthocyanins accumulation in ‘Kuerle Xiangli’ (Pyrus sinkiangensis Yü); however, the underlying molecular mechanism of sucrose-mediated fruit coloration remains largely unknown. In this study, comprehensive transcriptome analysis was performed to identify the essential regulators and pathways associated with anthocyanin accumulation. The differentially expressed genes enriched in Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes items were analyzed. The transcript levels of some anthocyanin biosynthetic regulatory genes and structural genes were significantly induced by sucrose treatment. Sucrose application also stimulated the expression of some sugar transporter genes. Further RT-qPCR analysis confirmed the induction of anthocyanin biosynthetic genes. Taken together, the results revealed that sucrose promotes pear coloration most likely by regulating sugar metabolism and anthocyanin biosynthesis, and this study provides a comprehensive understanding of the complex molecular mechanisms underlying the coloration of red-skinned pear.

Chinese cherry (Cerasus pseudocerasus (Lindl.) G.Don) is an economically important tetraploid fruiting cherry species native to China. Simple sequence repeats (SSRs)—due to their codominance, polymorphism, and stability—have been widely applied in genetic identification and trait-association analysis. In this study, using comparative genomics strategy and the data of one high-quality whole genome and seven preliminarily assembled genome sequences, we constructed a database containing 25,779 polymorphic SSR loci to efficiently develop novel markers. Sixty-four SSR loci covering eight linkage groups were selected to design primer pairs. Sixty (93.75%) primer pairs yielded specific bands and 32 (50.00%) exhibited moderate-to-high levels of informativeness (PIC ranging from 0.264 to 0.728) in 94 Chinese cherry accessions. A total of 38 primer pairs exhibited high transferability across 13 Cerasus taxa. The marker SAUCps203 was species-specific in C. pseudocerasus by checking with 114 accessions from Cerasus and 16 relatives, suggesting its potential application in accurate identification of Chinese cherry or its interspecific hybrid. Moreover, 1081 out of 1122 individuals from three cross F₁ populations of Chinese cherry were identified as true hybrid offspring by using only five SSR markers. Trait association analysis suggested that 20 SSR loci were significantly associated with soluble solids and fruit size, with explained phenotypic variance ranging from 9.02% to 26.35%. This study will provide a basis for SSR-based germplasm identification and further marker-assisted selection (MAS) of Chinese cherry.

The subgenus Cerasus and its relatives include many crucial economic drupe fruits and ornamental plants. Repetitive elements make up a large part of complex genomes, and some of them play an important role in gene regulation that can affect phenotypic variation. However, the variation in their genomes remains poorly understood. This work conducted a comprehensive repetitive sequence identification across the draft genomes of eight taxa of the genus Prunus, including four of the Prunus subgenus Cerasus (Prunus pseudocerasus, P. avium, P. yedoensis and P. × yedoensis) as well as congeneric species (Prunus salicina, P. armeniaca, P. dulcis and P. persica). Annotation results showed high proportions of transposable elements in their genomes, ranging from 52.28% (P. armeniaca) to 61.86% (P. pseudocerasus). The most notable differences in the contents of long terminal repeat retrotransposons (LTR-RTs) and tandem repeats (TRs) were confirmed with de novo identification based on the structure of each genome, which significantly contributed to their genome size variation, especially in P. avium and P.salicina. Sequence comparisons showed many similar LTR-RTs closely related to their phylogenetic relationships, and a highly similar monomer unit of the TR sequence was conserved among species. Additionally, the predicted centromere-associated sequence was located in centromeric regions with FISH in the 12 taxa of Prunus. It presented significantly different signal intensities, even within the diverse interindividual phenotypes for Prunus tomentosa. This study provides insight into the LTR-RT and TR variation within Prunus and increases our knowledge about its role in genome evolution.

A precise, rapid and straightforward approach to chromosome identification is fundamental for cytogenetics studies. However, the identification of individual chromosomes was not previously possible for Chinese cherry or other Prunus species due to the small size and similar morphology of their chromosomes. To address this issue, we designed a pool of oligonucleotides distributed across specific pseudochromosome regions of Chinese cherry. This oligonucleotide pool was amplified through multiplex PCR with specific internal primers to produce probes that could recognize specific chromosomes. External primers modified with red and green fluorescence tags could produce unique signal barcoding patterns to identify each chromosome concomitantly. The same oligonucleotide pool could also discriminate all chromosomes in other Prunus species. Additionally, the 5S/45S rDNA probes and the oligo pool were applied in two sequential rounds of fluorescence in situ hybridization (FISH) localized to chromosomes and showed different distribution patterns among Prunus species. At the same time, comparative karyotype analysis revealed high conservation among P. pseudocerasus, P. avium, and P. persica. Together, these findings establish this oligonucleotide pool as the most effective tool for chromosome identification and the analysis of genome organization and evolution in the genus Prunus.

Fire blight, caused by Erwinia amylovora, is a devastating bacterial disease threatening apple, pear, and other Rosaceae species. In our prior study, transcriptome analysis identified a fire blight-resistant variety, Duli (Pyrus betulifolia Bunge), and highlighted the PR1 gene as a key resistance factor. Using Duli’s genomic data, we systematically identified and characterized the Pb-PR-1 gene family through bioinformatics analysis. A total of 31 Pb-PR-1 genes were found, encoding proteins of 123–341 amino acids. Phylogenetic analysis grouped these genes into four subfamilies, with 27 genes distributed across seven chromosomes, all contain a conserved CAP superfamily domain. Their promoter regions were enriched in hormone and stress-responsive elements. After inoculation with E. amylovora, susceptible Duli showed lesion development by day 2, with rapid disease progression, while resistant plants exhibited slower disease advancement and smaller lesions. Enzyme activity assays revealed that in resistant plants, PPO (polyphenol oxidase) and CAT (catalase) activities peaked on day 6, showing a 2.4-fold and 3.81-fold increase compared to susceptible Duli. At the same time, MDA (malondialdehyde) content decreased by 16.6%. The activities of SOD (superoxide dismutase) and PAL (phenylalanine ammonia-lyase) peaked on day 4, with increments of 34.32% and 47.1% over susceptible Duli. qRT-PCR showed significant differences in Pb-PR-1 gene family expression between resistant and susceptible plants post-inoculation. Notably, Pb-PR-1-11, Pb-PR-1-21, and Pb-PR-1-26 expression increased with infection duration, aligning with PPO and CAT activity trends. Other genes showed high early infection expression but declined by day 6. Pb-PR-1-3, Pb-PR-1-6, Pb-PR-1-8, Pb-PR-1-16, and Pb-PR-1-30 were upregulated 13.17-fold on average by day 2. In summary, the Pb-PR-1 family exhibited elevated expression during early infection and enhanced defense-related enzyme activities, improving plant resistance. This study provides a foundation for understanding the PR-1 family’s role in Duli and advancing fire blight resistance in Pyrus species.