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Stony hard (SH) peach (Prunus persica L. Batsch) fruit does not release ethylene and has very firm and crisp flesh at ripening, both on- and off-tree. Long-term cold storage can induce ethylene production and a serious risk of chilling injury in SH peach fruit, however, the regulatory mechanism underlying ethylene production in stony hard peach is relatively unclear. In this study, we analyzed the phytohormone levels, fruit firmness, transcriptome, and lipidome changes in SH peach ‘Zhongtao 9’ (CP9) during cold storage (4 °C). The expression level of the ethylene biosynthesis gene PpACS1 and the content of ethylene in SH peach fruit were found to be upregulated during cold storage. A peak in ABA release was observed before the release of ethylene and the genes involved in ABA biosynthesis and degradation, such as zeaxanthin epoxidase (ZEP) and 8’-hydroxylase (CYP707A) genes, were specifically induced in response to low temperatures. Fruit firmness decreased fairly slowly during the first 20 d of refrigeration, followed by a sharp decline. Furthermore, the expression level of genes encoding cell wall metabolic enzymes, such as polygalacturonase, pectin methylesterase, expansin, galactosidase, and β-galactosidase, were upregulated only upon refrigeration, as correlated with the decrease in fruit firmness. Lipids belonging to 23 sub-classes underwent differential rearrangement during cold storage, especially ceramide (Cer), monoglycosylceramide (CerG1), phosphatidic acid (PA), and diacyglyceride (DG), which may eventually lead to ethylene production. Exogenous PC treatment provoked a higher rate of ethylene production. We suspected that the abnormal metabolism of ABA and cell membrane lipids promotes the production of ethylene under low temperature conditions, causing the fruit to soften. In addition, ERF transcription factors also play an important role in regulating lipid, hormone, and cell wall metabolism during long-term cold storage. Overall, the results of this study give us a deeper understanding of the molecular mechanism of ethylene biosynthesis during the postharvest storage of SH peach fruit under low-temperature conditions.

Members of the GOLVEN (GLV) gene family encode small secreted peptides involved in important plant developmental programs, including meristem maintenance and gravitropic responses. However, research on the functions of peptide hormones has mainly focused on various model plants, and little is known about their possible roles in peach fruit. Here, we identified eight PpGLV genes and analyzed their expression patterns in peach. PpGLV family genes share some similarities with Arabidopsis GLV family genes. PpGLV4 is responsive to 1-MCP and naphthalene acetic acid treatment. To investigate the role of PpGLV4 in detail, we treated peach callus with a synthetic PpGLV4 peptide. The upregulation of auxin and ethylene biosynthesis and signal transduction pathway genes in response to these treatment and the expression patterns of PpGLV family genes suggest that PpGLV4 may be involved in the crosstalk between auxin and ethylene signaling. The comprehensive data generated in this study improve our understanding of the roles of PpGLV peptides in peach.

The plant hormone ethylene regulates ripening in climacteric fruits. The phytohormone abscisic acid (ABA) affects ethylene biosynthesis, but whether ethylene influences ABA biosynthesis is unknown. To explore this possibility, we investigated the interactions between the ABA biosynthesis genes PpNCED2/3 and the ethylene response transcription factor PpERF3 in peach fruit. The ABA content increased during fruit maturation and reached a peak at stage S4 III. The increase was greatly inhibited by the ethylene inhibitor 1-MCP, which also suppressed PpERF3 expression. PpERF3 shared a similar expression profile with PpNCED2/3, encoding a rate-limiting enzyme involved in ABA biosynthesis, during fruit ripening. A yeast one-hybrid assay suggested that the nuclear-localized PpERF3 might bind to the promoters of PpNCED2/3. PpERF3 increased the expression of PpNCED2/3 as shown by dual-luciferase reporters, promoter-GUS assays and transient expression analyses in peach fruit. Collectively, these results suggest that ethylene promotes ABA biosynthesis through PpERF3’s regulation of the expression of ABA biosynthesis genes PpNCED2/3., Fruit ripening: Hormones go hand in hand Two hormones that regulate fruit ripening are more closely linked than previously thought, according to a study of ripening in peaches. Ethylene is a key ripening hormone in many fruits, and high ethylene levels turn on ethylene response factors (ERFs), genes that trigger production of sugars, pigments, and flavor compounds associated with ripening. Another hormone, abscisic acid (ABA), has recently been found to affect ripening, but its interaction with ethylene is unclear. Zhiqiang Wang and Guohuai Li at the Chinese Academy of Agricultural Sciences and coworkers investigated how ethylene and ABA interact during ripening. They found that as ethylene levels increased, ABA production was stimulated. Further investigation showed that ethylene directly triggered the ABA increase via ERFs. These results illuminate the fruit ripening process, and may help in finding ways to prolong fruit shelf life.

Background The green peach aphid (GPA), Myzus persicae (Sülzer), is a widespread phloem-feeding insect that significantly influences the yield and visual quality of peach [Prunus persica (L.) Batsch]. Single dominant gene (Rm3)-based resistance provides effective management of this invasive pest, although little is known about the molecular responses of plants to GPA feeding. Results To illustrate the molecular mechanisms of monogenic resistance in peach to young tissue-infecting GPAs, aphid-resistant/aphid-susceptible peach lines from a segregating population with Rm3/rm3 and rm3/rm3 genotypes were infested with GPAs for 3 to 72 h. Transcriptome analysis of the infested tissues identified 3854 differentially expressed genes (DEGs). Although the majority of the DEGs in the resistant line also responded to aphid attack in the susceptible line, the overall magnitude of change was greater in the resistant line than in the susceptible line. The enriched gene ontology of the 3854 DEGs involved in plant defence responses included redox situation, calcium-mediated signalling, transcription factor (e.g., WRKY, MYB, and ERF), MAPK signalling cascade, phytohormone signalling, pathogenesis-related protein, and secondary metabolite terms. Of the 53 genes annotated in a 460 kb interval of the rm3 locus, seven genes were differentially expressed between the aphid-resistant and aphid-susceptible peach lines following aphid infestation. Conclusions Together, these results suggest that the Rm3-dependent resistance relies mainly on the inducible expression of defence-related pathways and signalling elements within hours after the initiation of aphid feeding and that the production of specific secondary metabolites from phenylpropanoid/flavonoid pathways can have major effects on peach-aphid interactions. Electronic supplementary material The online version of this article (10.1186/s12864-018-5215-7) contains supplementary material, which is available to authorized users.

Flower and fruit colors are important agronomic traits. To date, there is no forward genetic evidence that the glutathione S-transferase (GST) gene is responsible for the white flower color in peach (Prunus persica). In this study, genetic analysis indicated that the white-flower trait is monogenetic, is recessive to the non-white allele, and shows pleiotropic effects with non-white-flowered types. The genetic locus underpinning this trait was mapped onto chromosome 3 between 0.421951 and 3.227115 Mb by using bulked segregant analysis in conjunction with whole-genome sequencing, and was further mapped between 0 and 1.178149 Mb by using the backcross 1 (BC1 ) population. Finally, the locus was fine-mapped within 535.974- and 552.027-kb intervals by using 151 F2 individuals and 75 individuals from a BC1 self-pollinated (BC1 S1 ) population, respectively. Pp3G013600, encoding a GST that is known to transport anthocyanin, was identified within the mapping interval. The analysis of genome sequence data showed Pp3G013600 in white flowers has a 2-bp insertion or a 5-bp deletion in the third exon. These variants likely render the GST non-functional because of early stop codons that reduce the protein length from 215 amino acids to 167 and 175 amino acids, respectively. Genetic markers based on these variants validated a complete correlation between the GST loss-of-function alleles and white flower in 128 peach accessions. This correlation was further confirmed by silencing of Pp3G013600 using virus-induced gene silencing technology, which reduced anthocyanin accumulation in peach fruit. The new knowledge from this study is useful for designing peach breeding programs to generate cultivars with white flower and fruit skin.

Peach (Prunus persica) is a typical climacteric fruit that produces ethylene rapidly during ripening, and its fruit softens quickly. Stony hard peach cultivars, however, do not produce large amounts of ethylene, and the fruit remains firm until fully ripe, thus differing from melting flesh peach cultivars. To identify the key proteins involved in peach fruit ripening, an antibody-based proteomic analysis was conducted. A mega-monoclonal antibody (mAb) library was generated and arrayed on a chip (mAbArray) at a high density, covering ~4950 different proteins of peach. Through the screening of peach fruit proteins with the mAbArray chip, differentially expressed proteins recognized by 1587 mAbs were identified, and 33 corresponding antigens were ultimately identified by immunoprecipitation and mass spectrometry. These proteins included not only important enzymes involved in ethylene biosynthesis, such as ACO1, SAHH, SAMS, and MetE, but also novel factors such as NUDT2. Furthermore, protein–protein interaction analysis identified a metabolon containing SAHH and MetE. By combining the antibody-based proteomic data with the transcriptomic and metabolic data, a mathematical model of ethylene biosynthesis in peach was constructed. Simulation results showed that MetE is an important regulator during peach ripening, partially through interaction with SAHH.

The auxin/indole acetic acid (Aux/IAA) genes encode a large family of short-lived proteins that regulate auxin signaling in plants. Previous attempts to understand the role of auxin during fruit development in peach (Prunus persica) found that expression of the Aux/IAA gene PpIAA19 was upregulated during fruit ripening, but the biological significance of the PpIAA19 protein is still unknown. The current study detected PpIAA19 transcripts in all peach plant tissues but found higher levels of accumulation in fruit S1 and S4II stages. During fruit ripening, the expression level of the PpIAA19 gene in melting flesh (MF) peach fruit was unsurprisingly higher than in stony hard (SH) peach fruit. Tomato (Solanum lycopersicum cv. ‘Micro-Tom’) was used as a model for investigating the phenotypic and molecular changes associated with over-expression of PpIAA19. This revealed that PpIAA19 was involved in regulating tomato lateral root number, stem elongation, parthenocarpy, and fruit shape. Molecular analyses of transgenic tomato plants over-expressing PpIAA19 indicated that the observed phenotypic changes were partially mediated by regulating the expression of auxin response genes. This result extends the functional characterization of PpIAA19 in tomato, and broadens our understanding of the role of auxin signaling in regulating plant growth and development.

The signaling pathways of both auxin and ethylene regulate peach fruit ripening via the Aux/IAA and ERF transcription factors, respectively. However, the molecular mechanisms that coordinate both auxin and ethylene signals during peach fruit ripening remain unclear. In this study, we show that PpIAA1 and PpERF4 act as key players in a positive feedback loop, and promote peach fruit ripening by directly binding to and enhancing the activity of target gene promoters. PpIAA1 increased the expression of the ethylene biosynthesis gene PpACS1. Furthermore, PpERF4 enhanced the transcription of PpACO1 and PpIAA1 genes by binding to their promoters. Additionally, PpIAA1 and PpERF4 bound to each other to form a complex, which then enhanced the transcription of abscisic acid biosynthesis genes (PpNCED2 and PpNCED3) and the fruit softening gene (PpPG1) to levels higher than those achieved by each transcription factor individually. Moreover, overexpression of PpIAA1 in tomato accelerated fruit ripening and shortened the fruit shelf-life by increasing the production of ethylene and the expression levels of ripening regulator genes. Collectively, these results advance our understanding of the molecular mechanisms underlying peach fruit ripening and softening via auxin and ethylene signaling pathways.

Ethylene is an essential regulator of fruit development. However, the role of this phytohormone in the development and maturation of peach (Prunus persica L. Batsch) fruit has not been systematically examined. In this study, through BLAST analysis of tomato (Solanum lycopersicum) protein sequences against the peach genome database and transcriptome analysis of all APETALA2/Ethylene Responsive Factor (AP2/ERF) genes in peach, we identified 15 ethylene signal transduction genes and 15 AP2/ERF genes and examined their expression levels in SH (stony hard) peaches and MF (melting flesh) peaches during fruit maturation. We investigated the expression patterns of six genes, including one ETR-like gene (Prupe.1G034300) and five AP2/ERF genes (Prupe.1G037700, Prupe.2G289500, Prupe.3G240000, Prupe.5G061800, and Prupe.7G194400), through quantitative RT-PCR expression analysis. The transcript levels of these genes were lower at the early stages of fruit development and increased dramatically at stage S4 in MF peaches, while they remained low in SH peaches, which mirrors the pattern of changes observed in ethylene production. Treatment of MF (‘Zhongyoutao 13’, ‘CN13’) fruit at stage S4 II with 1-MCP was ineffective in blocking ethylene production, and the expression of these genes was inhibited by 1-MCP treatment in ‘CN13’ on day 1, further demonstrating that these genes are closely related to fruit ripening. We detected a slight change in fruit firmness in ‘CN13’ after 1-MCP treatment, whereas ethylene production was not affected. By contrast, the transcript profile of gene Prupe.5G090800 exhibited the opposite trend. The comprehensive data generated in this study will improve our understanding of the ethylene receptor genes and ERF genes in peach and lay the foundation for further exploring the mechanisms underlying peach fruit ripening and softening.

Pectins are synthesized and secreted to the cell wall as highly methyl-esterified polymers and demethyl-esterified by pectin methylesterases (PMEs), which are regulated by pectin methylesterase inhibitors (PMEIs). PMEs and PMEIs are involved in pectin degradation during fruit softening; however, the roles of the PME and PMEI gene families during fruit softening remain unclear. Here, 71 PME and 30 PMEI genes were identified in the peach (Prunus persica) genome and shown to be unevenly distributed on all eight chromosomes. The 71 PME genes comprised 36 Type-1 PMEs and 35 Type-2 PMEs. Transcriptome analysis showed that 11 PME and 15 PMEI genes were expressed during fruit ripening in melting flesh (MF) and stony-hard (SH) peaches. Three PME and five PMEI genes were expressed at higher levels in MF than in SH fruit and exhibited softening-associated expression patterns. Upstream regulatory cis elements of these genes related to hormone response, especially naphthaleneacetic acid and ethylene, were investigated. One PME (Prupe.7G192800) and two PMEIs (Prupe.1G114500 and Prupe.2G279800), and their promoters were identified as potential targets for future studies on the biochemical metabolism and regulation of fruit ripening. The comprehensive data generated in this study will improve our understanding of the PME and PMEI gene families in peach. However, further detailed investigation is necessary to elucidate the biochemical function and regulation mechanism of the PME and PMEI genes during peach fruit ripening.

Cultivated peach (Prunus persica) is an important fruit species worldwide. The wild relatives in Prunus, such as P. mira, P. davidiana, P. kansuensis, P. ferganensis, and P. persica, are valuable for peach breeding, and early and accurate identification of parental and hybrid genotypes is critical. In this study, 20 representative accessions of peach germplasm from the National Germplasm Repository of Peach in China were used to select a set of 18 simple sequence repeat (SSR) markers for accurate species discrimination. Eight unknown peach samples were successfully identified using the SSR panel and species genotype database. Interspecific hybrid genotypes of P. persica × P. davidiana, P. persica × P. kansuensis, and P. persica × P. ferganensis were also analyzed reliably. The markers were amenable to high-throughput fluorescent labeling and capillary electrophoresis (CE) analysis, allowing rapid and efficient species identification. The practical method described in this study will facilitate peach breeding and germplasm management.

Ethylene response factors (ERFs) are known to regulate fruit ripening. However, the ERF regulatory networks are not clear. In this study, we have shown that peach (Prunus persica) PpeERF2 regulates fruit ripening through suppressing the expression of two ABA biosynthesis genes (PpeNCED2, PpeNCED3) and a cell wall degradation gene (PpePG1). The transcript levels of PpeERF2 in fruit were opposite to that of PpeNCED2, PpeNCED3 and PpePG1 during ripening and in response to various ripening treatments. PpeERF2 was found to bind to the PpeNCED2, PpeNCED3 and PpePG1 promotors as demonstrated by yeast one-hybrid (Y1H) and EMSA assays; and further found to repress the promoter activities of the three genes in tobacco leaf tissues after Agrobacterium infiltration. Taken together, these results provide new information for a better understanding of the crosstalk network between ethylene signaling, cell wall degradation and ABA biosynthesis during fruit ripening.

In fleshy fruits, sugars (glucose, fructose, sucrose and sorbitol) are most important for fruit growth and development but also play a central role in fruit quality. In Peach (Prunus persica), we observed the sugars content at six developmental stages through high pressure liquid chromatography (HPLC). There was variation during fruit development and ripening, sucrose first increased then decreased; glucose and fructose first decreased, and then increased while sorbitol always decreased. In past, understanding about the mechanisms which control the sugar metabolism and accumulation in peach remains quite limited. We studied the transcript profiles of total 30 genes encoding key enzymes and transporters, which were involved in sucrose metabolism, resynthesis and transport. 13 putative genes including sucrose phosphatase synthase (PpSPS4 and PpSPS2), Hexokinases (PpHK1 and PpHK3), neutral/natural invertase (PpNINV1and PpNINV2), vacuolar acid invertase (PpVAINV2), sucrose transporter (PpSUT2), vacuolar glucose transporters (PpVGT1, PpVGT2 and PpVGT3) and tonoplast monosaccharides transporters (PpTMT1 and PpTMT2) highly expressed during peach fruit ripening. PpSPS4 had significantly positive correlation with glucose and fructose. Our results suggested that more sucrose accumulated in cytosol because of upregulation of (PpSPS4 and PpSPS2), that sucrose imported into vacuole through upregulation of PpSUT2, PpVGT1, PpVGT2, PpVGT3, PpTMT1 and PpTMT2 transporters, where cleaving of sucrose is done by upregulation of PpVAINV2. Hence, level of sucrose decreased as fruit ripe. As a result, the concentration of glucose and fructose increased at ripening stage (S4 II to S4 III). So, these marker genes can be involved in peach fruit ripening. This study will improve our understanding and lay foundation to explore the function of these genes and improvement of peach fruit quality.

Highlight PpYUC11 is a strong candidate gene for the control of the stony hard phenotype in peach., High concentrations of indole-3-acetic acid (IAA) are required for climacteric ethylene biosynthesis to cause fruit softening in melting flesh peaches at the late ripening stage. By contrast, the fruits of stony hard peach cultivars do not soften and produce little ethylene due to the low IAA concentrations. To investigate the regulation of IAA accumulation during peach ripening [the transition from stage S3 to stage S4 III (climacteric)], a digital gene expression (DGE) analysis was performed. The expression patterns of auxin-homeostasis-related genes were compared in fruits of the melting flesh peach ‘Goldhoney 3’ and the stony hard flesh peach ‘Yumyeong’ during the ripening stage. It is revealed here that a YUCCA flavin mono-oxygenase gene (PpYUC11, ppa008176m), a key gene in auxin biosynthesis, displayed an identical differential expression profile to the profiles of IAA accumulation and PpACS1 transcription: the mRNA transcripts increased at the late ripening stage in melting flesh peaches but were below the limit of detection in mature fruits of stony hard peaches. In addition, the strong association between intron TC microsatellite genotypes of PpYUC11 and the flesh texture (normal or stony hard) is described in 43 peach varieties, indicating that this locus may be responsible for the stony hard phenotype in peach. These findings support the hypothesis that PpYUC11 may play an essential role in auxin biosynthesis during peach fruit ripening and is a candidate gene for the control of the stony hard phenotype in peach.