Postharvest Broccoli Research Articles

Investigation of the preharvest arginine spraying mechanism on antioxidant system in postharvest broccoli via transcriptomics and metabolomics

According to our previous study, preharvest spraying of arginine for 1 day enhanced the antioxidant capacity of postharvest broccoli, but the underlying molecular mechanisms remain unclear. We here performed a comprehensive transcriptome and metabolome analysis to investigate the effects of arginine sprayed 1 day before harvest on the antioxidant capacity and yellowing of broccoli as well as the related action mechanisms. In total, 67 differentially expressed genes and 12 key differentially accumulated metabolites were identified in broccoli at 4 and 8 days during storage. Herein, the gene expression of superoxide dismutase, catalase, and the corresponding peroxisome protein Mpv17 (MPV17) was upregulated, consequently enhancing the scavenging of reactive oxygen species. Genes encoding glucosinolate synthesis- and metabolism-related enzymes were upregulated, and among them, the gene ST5b_c was upregulated by 8.23-fold, which promoted the accumulation of its metabolites. Expression of lignin- and flavonoid biosynthesis-related genes (CAD, POD, CHI, and CHS) was elevated. Flavonoid and lignin accumulation was promoted, with a greater antioxidant capacity at 4 and 8 days, respectively, in the arginine-sprayed broccoli. Additionally, the ascorbate–glutathione cycle was promoted in broccoli at 4 days, GLCAK and APX genes were upregulated by more than 2-fold, and broccoli exhibited a higher tolerance level because of the notably stimulated ascorbic acid and glutathione accumulation. This study offers new insights into the mechanisms through which preharvest spraying of arginine regulates the antioxidant capacity of postharvest broccoli.

Integrated transcriptomic and metabolomic analysis reveals the effects and potential mechanism of hydrogen peroxide on pigment metabolism in postharvest broccoli.

To understand the effects and related potential mechanism of H2O2 on pigment metabolism in postharvest broccoli, an integrated analysis of transcriptome and metabolome was performed. Results suggested that 65 differentially expressed genes and 26 differentially accumulated metabolites involved in chlorophyll, carotenoid, and flavonoid metabolism were identified. H2O2 treatment delayed the decrease of chlorophyll content by upregulating the expressions of chlorophyll synthetic genes, thylakoid synthetic genes, and 15 light-harvesting complex genes compared with the control and diphenylene iodonium treatments. H2O2 treatment decreased the accumulation of 11 flavonoids and 5 flavonols by downregulating the flavonoid synthetic genes. In addition, H2O2 treatment promoted carotenoid biosynthesis to eliminate reactive oxygen species in thylakoids, thereby protecting chlorophyll molecules from degradation. The inhibition of flavonoids and flavonols accumulation and chlorophyll decrease was the crucial reason for the delayed yellowing in H2O2 treatment. This study provides a new method and theoretical support for delaying the yellowing process in postharvest broccoli.

Exogenous melatonin delays yellowing in postharvest broccoli by regulation of ABA and carotenoid metabolite

Yellowing is the first visible sign of floret senescence and quality deterioration in broccoli, mainly caused by chlorophyll degradation and carotenoid accumulation. In this study, the impacts of melatonin (MLT) treatment on anabolism, catabolism and storage of carotenoid in postharvest broccoli associated with ABA regulation were investigated at transcript and metabolic levels. Results showed that MLT treatment effectively repressed yellowing and senescence along with a decrease in respiration rate and ethylene emission, enhancing endogenous MLT and abscisic acid (ABA) levels. A total of 925 metabolites were differentially expressed between the control and MLT treatment, which were mainly classified into amino acids, sugars, lipids, flavonoids and others. Specific analysis revealed that MLT treatment decreased sugars, lipids, flavonoids, and aromatic amino acids, but increased aliphatic amino acids. Meanwhile, MLT treatment suppressed the expression levels of genes related to carotenoid anabolism (BoPSY, BoPDS, BoZDS, BoCRTISO, BoLCYB, BoVDE, and BoZEP) and storage (BoOR), but the genes involved in carotenoid catabolism (BoNCED2, BoNCED6, BoCCD1 and BoCCD7) were up-regulated, which could collectively result in a decrease in the levels of β-carotene and lutein and an increase in ABA level. Moreover, correlation analysis indicated that lutein content was positively correlated with BoVDE, BoPDS and BoZDS, and negatively correlated with ABA level. Thus, MLT treatment slowed down the yellowing of broccoli during storage, which might be ascribed to inhibiting the anabolism and storage of carotenoid and promoting carotenoid catabolism and ABA biosynthesis.

Selenium Treatment Regulated the Accumulation of Reactive Oxygen Species and the Expressions of Related Genes in Postharvest Broccoli

This study aimed to investigate the impact of selenium (Se) treatment on the accumulation of reactive oxygen species (ROS) and the expressions of related genes in broccoli. To achieve this, one group of broccoli heads was treated with a selenite solution of 2 mg L−1, while another group was soaked in distilled water, serving as the control. The effects of these treatments were evaluated by analyzing the browning, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents, enzyme activity, and gene expression levels of WARK and RBOH. Our results show that the Se treatment effectively inhibited H2O2 accumulation in the broccoli and reduced harmful MDA levels. The inhibition of ROS accumulation following the Se treatment was associated with enhanced activity of the CAT and SOD enzymes, increased expression levels of BoCAT and BoSOD, and decreased expression levels of the WRKY and RBOH transcription factors. Our study provides insights into the mechanism of action of selenium and its potential application in vegetable storage.

Unique molecular mechanisms revealed for the effects of temperature, CA, ethylene exposure, and 1-MCP on postharvest senescence of broccoli

The management of postharvest broccoli (Brassica oleracea L. var. italica) exemplifies a crucial element in ensuring agricultural sustainability and food preservation. The main aim of our study was to investigate the physiological and molecular factors that influence the shelf life of broccoli by employing several technologies known to influence its deterioration, namely controlled atmosphere (CA), 1-methylcyclopropene (1-MCP), and ethylene interventions. Controlled atmosphere (CA) and 1-methylcyclopropene (1-MCP) delay the senescence process whereas ethylene promotes broccoli senescence. The study involved physiological assessments to investigate the broccoli senescence patterns as influenced by temperature, and the effects of CA, 1-MCP, and ethylene on the shelf life of broccoli. Concurrently, RNA sequencing and subsequent analysis improved our understanding of the intricate molecular mechanisms behind postharvest senescence. The application of 1-MCP and CA demonstrated significant delays in the senescence process, affirming their effectiveness in maintaining broccoli quality during postharvest storage. We found that the MAPK pathway during 1-MCP treatment was involved in stress and defense responses by expression of genes like WRKY33, WRKY29, EIN3, PYL4, Catalase 2-like (CAT2 like), and SRK2E. Furthermore, alterations in auxin-responsive genes like IAA, SAUR21, and SAUR36 highlight the differential modulation of ethylene and auxin signaling pathways. A subsequent experiment demonstrated that in postharvest broccoli, exogenous auxin promotes senescence and auxin inhibitors retard senescence. Downregulation of key enzymatic genes, including UTP-glucose-1-phosphate uridylyltransferases, during CA treatment points to inhibition of glycolysis, which might be one of the mechanisms to enhance the shelf life of harvested products and delay senescence. Senescence-associated gene expression patterns suggested stage-specific connections that need additional investigation. This study offers valuable insights into the field of postharvest management, providing practical knowledge by identifying target genes for enhancing broccoli storage life and mitigating food waste.

Exogenous leucine delayed the yellowing of postharvest broccoli by regulating strigolactone and abscisic acid signals based on multi-omics profiling

The yellowing of postharvest broccoli is the immediate manifestation of its quality deterioration, which can cause the loss of commodity value. This study employs a comprehensive analysis integrating transcriptomics and metabolomics to elucidate the effects and potential molecular mechanisms of exogenous leucine on pigment metabolism in postharvest broccoli stored at 10 ± 0.5 °C. Results demonstrate that leucine treatment significantly inhibited the decrease of chlorophyll content and the increase of carotenoid content. Leucine treatment also inhibited the respiration rate and maintained higher vitamin C content, total phenols content and DPPH radical scavenging activity of broccoli. Leucine treatment promoted chlorophyll biosynthesis by up-regulating UROD, PPOX, MC, CHLM, POR, DCVR, MT, and CAS expression while inhibiting chlorophyll liberation and degradation by up-regulating CABs expression and down-regulating NYC1, CLH2, PAO, and PPD expression. Additionally, exogenous leucine alleviated the damage of photosystem I, photosystem II, and photosynthetic electron transport chains in the thylakoid membrane. Furthermore, leucine treatment results in a lower transcriptional level of PDS, LCYB, crtZ, and ZEP, leading to reduced lycopene, zeaxanthin, and β-carotene content. Leucine treatment promotes the biosynthesis of carlactone, a strigolactone (SL) precursor, by up-regulating DWARF27, CCD7, and CCD8 expression. Additionally, leucine treatment down-regulated XDH expression and up-regulated CYP707A expression, inhibiting the biosynthesis and accumulation of abscisic acid (ABA). Consequently, our findings suggest that ABA and SLs may serve as crucial signaling factors in regulating chlorophyll and carotenoid metabolism in leucine-treated broccoli. This study introduces a novel method with theoretical support for delaying the yellowing process in postharvest broccoli.

Transcriptome revealed the wound-healing process of broccoli stem during SAS based on the hub of NADPH

Wound healing is a crucial metabolic process that occurs in fruit and vegetables within a short time after harvest, especially in cut-harvest ones. To reveal wound healing mechanisms in cut-harvest broccoli stems during the self-adaptive stage (SAS, 12 h after harvest), tissue samples from the stems at the incision were analyzed at the transcriptome level. With the extension of time, the expression levels of six differentially expressed genes (DEGs) in the pentose phosphate pathway (PPP) significantly increased in the stems after cut-harvest. Among the genes, the expression levels of PGLS and PGD, which are directly involved in nicotinamide adenine dinucleotide phosphate (NADPH) generation, were 2.62 and 5.82 times higher in the 12 h vs 0 h comparison group, respectively. The shikimate and phenylpropanoid pathways were significantly activated in the broccoli stems during SAS. Genes involved in NADPH degradation through the aforementioned two pathways, including DHQ-SDH1 (106323466), aroC1 (106295042), and PAL3 (106300639), were significantly upregulated. These findings certified that wound healing of cut-harvest broccoli stems was promoted by enhancing NADPH levels. Interestingly, glycolysis (EMP) was a non-significant change during SAS after cut-harvest that contributed to maintaining organic matter by suppressing respiration and acclimatizing the postharvest broccoli to become an independent unit. These results indicate that the focus should be on NADPH levels for promoting wound healing of fruit and vegetables during storage.

Multi-omics analysis revealed the effect of leucine treatment on nucleic acid metabolism and its potential mechanism in postharvest broccoli

To understand the effects and potential regulatory mechanism of leucine treatment on nucleic acid metabolism in yellowing and senescence process of postharvest broccoli, an integration profiling of transcriptome and metabolome was performed. Results showed that 5 mM leucine treatment delayed the increase in malondialdehyde content and inhibited the degradation of DNA and RNA, thus prolonging the shelf life of postharvest broccoli. A total of 92 differentially expressed genes and 9 differentially accumulated metabolites associated with nucleic acid metabolism were identified. Leucine treatment promoted DNA replication and enhanced DNA repair, thereby increasing the genome integrity and stability. Furthermore, leucine treatment augmented transcription and pre-mRNA processing by upregulating the expression of RNA polymerases, transcription factors, and splicing factors. The metabolomics results showed that the building blocks of DNA and RNA in leucine-treated broccoli were increased. In addition, exogenous leucine promoted mRNA translation and its subsequent recycling of mRNA, which upregulated the related protein biosynthesis and enhanced the energy utilization efficiency. Furthermore, leucine treatment enhanced the formation of small interfering RNA by upregulating the transcription of RNA polymerases V, 1, 5, and 6, thus increasing the resistance of broccoli against RNA viruses. The results of this study shed light on nucleic acid metabolism in postharvest broccoli and its regulatory mechanism and provide a theoretical basis for studying broccoli preservation.

The regulation of Cytochrome f by mannose treatment in broccoli and its relationship with programmed cell death in tobacco BY-2 cells

It is well established that programmed cell death (PCD) occurred in broccoli during postharvest senescence, but no studies have been conducted on the regulation of broccoli cytochrome f by mannose treatment and its relationship with PCD. In this study, we treated broccoli buds with mannose to investigate the changes in color, total chlorophyll content, gene expression related to chlorophyll metabolism, chloroplast structure, and cytochrome f determination during postharvest storage. In addition, to investigate the effect of cytochrome f on PCD, we extracted cytochrome f from broccoli and treated Nicotiana tabacum L. cv Bright Yellow 2 (BY-2) cells with extracted cytochrome f from broccoli at various concentrations. The results showed that cytochrome f can induce PCD in tobacco BY-2 cells, as evidenced by altered cell morphology, nuclear chromatin disintegration, DNA degradation, decreased cell viability, and increased caspase-3-like protease production. Taken together, our study indicated that mannose could effectively delay senescence of postharvest broccoli by inhibiting the expression of gene encoding cytochrome f which could induce PCD.

Effects and Regulatory Mechanism of Exogenous H2O2 on Amino Acid Metabolism in Post-harvest Broccoli: An Integrated Analysis of Transcriptomic and Metabolomic

Effects and Regulatory Mechanism of Exogenous H2O2 on Amino Acid Metabolism in Post-harvest Broccoli: An Integrated Analysis of Transcriptomic and Metabolomic

Multi-omics profiling reveals the effects of hydrogen peroxide treatment on carbohydrate and energy metabolism in postharvest broccoli

Energy status is a vital factor in the physiology of postharvest vegetables. An integration profiling of transcriptome and metabolome was used to examine the effects of hydrogen peroxide treatment on carbohydrate and energy metabolism in broccoli at 20 ℃ for 4 d. The results showed that hydrogen peroxide (H2O2) treatment maintained higher levels of ATP and energy charge during storage. The integration profiling of transcriptome and metabolome revealed that H2O2 treatment promoted the degradation of 1,3-β-glucan to D-glucose and inhibited sucrose, D-raffinose, maltose, and cellulose degradation, thereby maintaining a long-term and stable supply of glucose for glycolysis (EMP) and pentose phosphate pathway (PPP)·H2O2 treatment enhanced the EMP and PPP by upregulating the expression of related genes. Enhancing the tricarboxylic acid cycle and inhibiting alcohol fermentation in H2O2 treatment promoted energy production. Therefore, the long-term and stable energy supply might be crucial for the delayed senescence of postharvest broccoli via H2O2 treatment.

Pre and postharvest spraying of arginine enhanced the stress resistance and promoted wound healing in broccoli during storage

Broccoli rapidly yellows and dehydrates post-harvest, causing a short storage life. Although arginine post-harvest has been shown to enhance broccoli’s storage quality and shelf life, it remains unclear whether pre-harvest treatment yields similar benefits. The results showed that pre-harvest spraying of 5 mM arginine reduces the respiration rate and delays electrolyte leakage during broccoli’s storage period, minimizing weight loss and yellowing and chlorophyll degradation. It also inhibits the degradation of ascorbic acid (ASA) and promotes the synthesis of total phenols, thereby increasing the total antioxidant capacity. Further studies showed that pre-harvest arginine spraying enhanced the activity of arginine decarboxylase (ADC), ornithine decarboxylase (ODC), and nitric oxide synthase (NOS). This accelerated the nitric oxide (NO) and the polyamine (PA) accumulation. Additionally, arginine aids in reactive oxygen species (ROS) balance and wound healing. Notably, pre-harvest arginine spraying was found to inhibit the hydrogen peroxide (H2O2) accumulation and enhance the activities of superoxide dismutase (SOD) and catalase (CAT), while also activating the phenylalanine ammonia lyase (PAL) and cinnamic acid 4-hydroxylase (C4H) activities. In conclusion, pre-harvest arginine spraying extends the broccoli’s storage life and improves its storage quality by promoting endogenous arginine catabolism, ROS metabolism, and the wounds healing. Therefore, this study establishes a theoretical foundation for pre-harvest handling in post-harvest broccoli storage.

Transcriptome and metabolome integrated analysis revealed the effects and potential mechanism of hydrogen peroxide on antioxidant system in postharvest broccoli

To investigate the effects and potential mechanism of exogenous H2O2 on antioxidant metabolism and yellowing in postharvest broccoli, the transcriptome and metabolome integrated analysis were performed. A total of 61 differentially expressed genes and 6 differentially accumulated metabolites identified among of H2O2 and diphenylene iodonium (DPI) treatments on 2 and 4 d. Exogenous H2O2 promoted the accumulation of endogenous H2O2 within 1 d by activating RBOHs expressions·H2O2 treatment up-regulated the expressions of SOD, CAT and peroxiredoxin (Prx) genes and APX, DHAR and GPX genes involved in ascorbic acid-glutathione (AsA-GSH) cycle, thereby promoting the scavenging of O2-. and H2O2 and alleviating the oxidative damage. Additionally, H2O2 treatment promoted the biosynthesis of AsA and GSH, and increased the content of AsA, GSH, oxidized glutathione, and γ-glutamylcysteine·H2O2 treatment also promoted glucosinolate biosynthesis, the accumulation of 3-(6′-methylthio)hexylmalic acid, and the production of sulforaphane by up-regulating MYS expression, thereby enhancing the health-care function of postharvest broccoli. This study provided the new insights into regulatory mechanism of H2O2 on antioxidant system.

Effect of Potassium Permanganate, Ultraviolet Radiation and Titanium Oxide as Ethylene Scavengers on Preservation of Postharvest Quality and Sensory Attributes of Broccoli Stored with Tomatoes.

This study introduces an effective solution to enhance the postharvest preservation of broccoli, a vegetable highly sensitive to ethylene, a hormone produced by climacteric fruits such as tomatoes. The proposed method involves a triple combination of ethylene elimination techniques: potassium permanganate (KMnO4) filters combined with ultraviolet radiation (UV-C) and titanium oxide (TiO2), along with a continuous airflow to facilitate contact between ethylene and these oxidizing agents. The effectiveness of this approach was evaluated using various analytical techniques, including measurements of weight, soluble solids content, total acidity, maturity index, color, chlorophyll, total phenolic compounds, and sensory analysis conducted by experts. The results demonstrated a significant improvement in the physicochemical quality of postharvest broccoli when treated with the complete system. Notably, broccoli subjected to this innovative method exhibited enhanced organoleptic quality, with heightened flavors and aromas associated with fresh green produce. The implementation of this novel technique holds great potential for the food industry as it reduces postharvest losses, extends the shelf life of broccoli, and ultimately enhances product quality while minimizing waste. The successful development and implementation of this new technique can significantly improve the sustainability of the food industry while ensuring the provision of high-quality food to consumers.

Whole-transcriptome RNA sequencing reveals changes in amino acid metabolism induced in harvested broccoli by red LED irradiation

Whole-transcriptomic profiling combined with amino acid analysis were conducted in order to gain a better understanding of global changes in amino acid metabolism induced in broccoli by red LED irradiation. The results showed that the contents of almost all 16 amino acids in postharvest broccoli were maintained under red LED illumination. The red LED irradiation enhanced the anabolism of amino acid, including the biosynthesis of aromatic amino acids by upregulating the genes’ expression in the shikimate pathway, as well as by upregulating the genes’ expression which encoding biosynthetic enzymes in the branched-chain amino acid biosynthesis pathway. Red LED irradiation induced the expression of genes encoding aspartate aminotransferase, which plays a role in Asp synthesis, aspartate kinase, which functions in aspartate metabolism, and a cytoplasmic aspartate aminotransferase that converts 2-Oxoglutarate into Glu. Genes encoding imidazole glycerol-phosphate synthase and histidinol-phosphatase, which function in the His biosynthesis pathway, were also upregulated. According to our results, red LED irradiation delays broccoli’s yellowing and senescence by regulating amino acid metabolism. These results enhance our understanding of the role of amino acid metabolism in the senescence of broccoli and the mechanism of red LED irradiation to alter amino acid metabolism in harvested broccoli.

Integration profiling of transcriptome and metabolome reveals the effect of hydrogen peroxide on nucleic acid metabolism in postharvest broccoli during storage

To understand the effects and related molecular regulation mechanism of H2O2 on nucleic acid metabolism in yellowing and senescence process of postharvest broccoli, an integration profiling of transcriptome and metabolome was performed. Results showed that 2 mM H2O2 delayed the yellowing and increase of relative conductivity, whereas 3 μM diphenylene iodonium (DPI, an inhibitor of H2O2 production) accelerated these processes·H2O2 treatment promoted DNA replication and repair by up-regulating replication protein A, DNA polymerase, and DNA ligase 1 expressions and increasing the essential building blocks of DNA (e.g., cytosine, guanosine 5′-diphosphate, cytidine, and adenosine) contents, thereby ensuring the integrity of genome in broccoli·H2O2 treatment promoted transcription and pre-mRNA processing by up-regulating the expressions of RNA polymerases and spliceosome-related genes, which promoted the biosynthesis of mature mRNA·H2O2 treatment also up-regulated PABPs expression, and thus to promote translation process in broccoli. Additionally, H2O2 promoted the recycle of mRNA and accumulation of adenosine, which was beneficial to timely change own gene profile in response to complex postharvest environmental changes and alleviate the energy deficiency suffered by postharvest broccoli. These results suggested that H2O2 is involved in the positive regulation of nucleic acid metabolism and maintained higher contents of nucleic acid-related metabolites, DNA and RNA, ultimately delaying the senescence of postharvest broccoli, which provided new insight for the regulatory mechanism of the yellowing and senescence in broccoli.

Refrigeration, forchlorfenuron, and gibberellic acid treatments differentially regulate chlorophyll catabolic pathway to delay yellowing of broccoli

Postharvest broccoli has a high metabolic rate and senesces quickly. The most critical symptom of senescence is flower bud yellowing due to chlorophyll catabolism. Refrigeration and cytokinin treatment are effective means to retard broccoli yellowing; however, the mechanisms underlie are partially understood. Here, we examined the expression of NON-YELLOW COLORING1 (NYC1), CHLOROPHYLLASE1 (CLH1), CLH2, STAYGREEN1 (SGR1), SGR2, pheophytinase (PPH), pheophorbide a oxygenase (PAO), and other chlorophyll catabolic genes in broccoli and investigated the impact of refrigeration, forchlorfenuron (CPPU), and gibberellic acid (GA3) treatments on the expression of the genes. We found that SGR1 and PAO were most highly expressed, whereas expressions of CLH1 and CLH2 were low in fresh broccoli. Refrigeration and CPPU suppressed NYC1, SGR1, SGR2, and PAO while upregulating CLH1 or CLH2, whereas GA3 induced PPH and repressed CLH2. All 3 treatments retarded broccoli yellowing, and correlation analysis revealed that SGR1 and PAO were highly correlated with yellowing, while CLHs were inversely correlated with yellowing. Application of CPPU and GA3 stimulated mild but significant increases in ethylene production, suggesting cross-regulations between hormones during broccoli senescence. In conclusion, we elucidated the differential regulations of refrigeration, CPPU, and GA3 on chlorophyll catabolic genes and identified SGR1 and PAO as the most highly expressed and yellowing-related genes. These findings strengthen the understanding of broccoli senescence and may elicit new research and development of technologies to manipulate chlorophyll metabolism in postharvest crops.

Maintaining the quality of postharvest broccoli by inhibiting ethylene accumulation using diacetyl.

Broccoli (Brassica oleracea L. var. Italic) is rich in nutrition. However, it is susceptible to yellowing after harvest, leading to nutritional and economic losses. In this study, diacetyl, a natural food additive compound, was selected to inhibit the yellowing of broccoli florets and maintain the nutrient quality during storage time. It was found that 20 μl L-1 diacetyl treatment for 12 h could significantly delay the yellowing and decrease the weight loss and lignin content of broccoli florets. Meanwhile, diacetyl could maintain higher contents of chlorophyll, vitamin C and flavonoids and suppress the transcript levels of chlorophyll degradation-related genes in broccoli florets. Moreover, accumulations of reactive oxygen species (ROS) were inhibited by diacetyl treatment. Under diacetyl treatment, the generation of ethylene was prevented by inhibiting the activities and related-gene expressions of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase. Based on our findings, exogenous diacetyl could be employed as a novel bioactive molecule for retarding the yellowing and maintaining the quality of postharvest broccoli.

Proteomics revealed the effects of nucleic acid metabolism, transcription and translation on postharvest broccoli senescence under elevated O2 stress

Nucleic acids (DNA and RNA) play crucial roles in guiding protein synthesis and plant resistance to biotic and abiotic stresses, but our current available understanding concerning on the role and function of nucleic acid metabolism, transcription and translation processes in postharvest fruit and vegetables remains largely unclear. In this study, an iTRAQ-based proteomics was used to investigate changes of protein abundance in postharvest broccoli under 40% O2 + 5% CO2, 20% O2 + 5% CO2 and 5% O2 + 5% CO2 treatments. A total of 128 differentially expressed proteins (fold change ≥ 1.2) were identified. High O2 stress reduced the DNA level by down-regulating the expression of proteins involved in DNA replication and up-regulating the expression of proteins DNA degradation. The decrease of DNA content, inhibition of transcription and promotion of RNA degradation induced by high O2 stress further led to the mass loss of RNA content in postharvest broccoli. Additionally, high O2 stress suppressed RNA processing, transport and translation and activated the expression of 20 S and 26 S proteasome, thereby accelerating the decrease of protein levels in postharvest broccoli. The decrease of DNA and RNA content might be related to the early yellowing and senescence in postharvest broccoli. This study revealed that the effect and mechanism of high O2 stress on DNA and RNA metabolism, transcription and translation processes, and the role of these metabolic pathway on senescence in postharvest broccoli.

Metabolomic profiling and energy metabolism modulation unveil the mechanisms involved in enhanced disease resistance of postharvest broccoli by Meyerozyma guilliermondii

Postharvest diseases of broccoli resulted in quality deterioration and huge economic loss. This study investigated the biocontrol efficacy of Meyerozyma guilliermondii against natural decay of postharvest broccoli. Meanwhile, the mechanisms involved in the enhanced disease resistance of broccoli by M. guilliermondii were explored based on energy metabolism modulation and metabolomic analysis of broccoli. The results showed that M. guilliermondii could alleviate the disease index of postharvest broccoli. This yeast could potentially increase energy production and supply through inducing the activities of related enzymes and maintaining a higher ATP level. Metabolomic analysis illustrated that the treatment with M. guilliermondii significantly increased secondary metabolites synthesis, sugar alcohols accumulation, the level of unsaturated fatty acids and their metabolic intermediates, and glutathione level. In conclusion, M. guilliermondii improved the disease resistance of postharvest broccoli through enhancing energy production and supply, synthesis of resistant compounds, and thus reducing the natural decay disease index of broccoli.