Differential protein profiles of postharvest Gynura bicolor D.C leaf treated by 1-methylcyclopropene and ethephon

Effect of postharvest 1-methylcyclopropene application on reactive oxygen species scavenging and sucrose metabolism in Gynura bicolor DC

After harvest, the metabolism of Gynura bicolor DC (G. bicolor) is vigorous, resulting in sugar scarcity and reactive oxygen species (ROS) accumulation, thus aggravating the quality deterioration. 1-Methylcyclopropene (1-MCP) shows crucial effect in alleviating the postharvest metabolism of vegetables and fruits. This research aimed to evaluate the effect of 1-MCP on ROS scavenging and sucrose metabolism in G. bicolor. In this research, G. bicolor was treated with 10 μL L^-1 1-MCP for 12 h, followed by storage at 20 ± 2 °C and 90 ± 5% relative humidity in darkness for 7 days. During storage, the increases in the respiration rate, electrolytic leakage, weight loss rate, ROS levels, and membrane lipid oxidation were effectively inhibited by 1-MCP. Moreover, starch and hexose degradation was decreased in the 1-MCP group, as were sucrose synthesis and catabolism. Correlation analysis indicated that sugar starvation was associated with respiration, activities regulation of CAT, SOD, and enzymes involved in sucrose metabolism were associated with the levels of hydrogen peroxide at the early storage. In conclusion, 1-MCP delayed postharvest quality deterioration of G. bicolor by alleviating respiration, inducing oxidative stress to enhance ROS scavenging, and inhibiting sucrose metabolism.

1-Methylcyclopropene Preserves the Quality of Chive (Allium schoenoprasum L.) by Enhancing Its Antioxidant Capacities and Organosulfur Profile during Storage

The quality, antioxidant capacities, and organosulfur profile of chives (Allium schoenoprasum L.) treated with 1-methylcyclopropene (1-MCP) during storage were investigated in this study. The 1-MCP treatment (100 μL/L, fumigation 12 h at 20 °C) effectively inhibited tissue respiration and H₂O₂ production, enhanced the ascorbic acid (ASA) and glutathione (GSH) content, and promoted the activity of antioxidant enzymes (superoxide dismutase SOD, Catalase CAT, and ascorbic peroxidase APX) during the 5-day storage period at 20 °C. The result further showed that the 1-MCP treatment inhibited chlorophyll degradation, alleviated cell membrane damage, and delayed the chive senescence, with the yellowing rate being reduced by 67.8% and 34.5% in the 1-MCP treated chives on days 4 and 5 of storage at 20 °C, respectively. The free amino acid content of the chive was not affected by the 1-MCP treatment at 20 °C. However, the senescence rate of the chive was not reduced by the 1-MCP treatment when stored at 3 °C. The liquid chromatography data further showed that the 1-MCP treatment induced a 15.3% and 13.9% increase in the isoalliin and total S-alk(en)ylcysteine sulfoxides (ACSOs) content of the chive on day 2 at 20 °C, respectively. Furthermore, there was a strong positive correlation between ACSOs content and CAT/APX activity, indicating that ACSOs probably played a key role in enhancing the antioxidant capacities of the chive during storage at 20 °C. Thus the study efficiently demonstrates that 1-methylcyclopropene preserves the quality of chive (Allium schoenoprasum L.) by enhancing its antioxidant capacities and organosulfur profile during storage.

iTRAQ-based mitochondrial proteome analysis of the molecular mechanisms underlying postharvest senescence of Zizania latifolia

To explore the molecular mechanisms underlying postharvest senescence of Zizania latifolia, the changes in the mitochondrial proteome of plants treated with or without (control) 1-methyleyelopropene and ethylene during storage at room temperature for 0, 3 and 6 days were investigated using isobaric tags for relative and absolute quantitation (iTRAQ) labeling combined with two-dimensional liquid chromatography-tandem mass spectrometry. A total of 1,390 proteins with two or more peptides were identified, of which 211 showed a significant (p < .05) change (at least twofold) in relative abundance. Monitoring the parallel reaction validated the reliability and accuracy of the iTRAQ results. Bioinformatics and functional analysis of these differentially expressed proteins (DEPs) revealed that postharvest senescence of Z. latifolia could be attributed to (a) strengthened pentose phosphate pathway, (b) imbalanced protein, amino acid, organic acid, and fatty acid metabolism, (c) disordered energy homeostasis, (d) exacerbated oxidative damage, (e) RNA degradation, (f) activation of the Ca²⁺ , mitogen-activated protein kinase, and jasmonic acid signaling pathways, (g) programed cell death, (h) excessive biosynthesis of secondary metabolites, or (i) degradation of cell structure. Our findings provide integrated insight into the molecular mechanisms of postharvest senescence during storage as well as the DEPs that show promise as targets for controlling senescence-induced quality deterioration of Z. latifolia. PRACTICAL APPLICATIONS: Postharvest senescence is the most important factor that causes fast quality deterioration of Zizania latifolia. The understanding of the processes leading to postharvest senescence of Z. latifolia is essential in enhancing the commercial value and extending the shelf life of the product. It is currently believed that the mitochondrial metabolism is closely related to postharvest senescence. For this, the changes of proteome in Z. latifolia mitochondria treated with or without (control) 1-MCP and ETH during storage at room temperature were investigated. Results showed that a variety of physiobiochemical responses occur during postharvest senescence of Z. latifolia. 1-MCP treatment significantly inhibited the changes of these physiobiochemical processes, finally, retarding the postharvest senescence of Z. latifolia. ETH treatment had opposite effects on proteome changes compared with 1-MCP treatment. Taken together, these results enrich the understanding of the molecular mechanisms of postharvest senescence of Z. latifolia.

Unraveling the target genes of RIN transcription factor during tomato fruit ripening and softening

BACKGROUND

The RIN transcription factor is one of the MADS box family members and predominantly controls fruit ripening. In this study, effort was made to demonstrate the regulation network of RIN transcription factor during tomato fruit ripening and softening. Novel RIN target genes were identified by proteomics, electrophoresis mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) analysis.

RESULTS

Over 700 protein spots were achieved by two-dimensional gel electrophoresis, and 42 proteins were successfully identified. Among them, 1-aminocyclopropane-1-carboxylate oxidase (LeACO4, ethylene synthesis, spot 3) and α-galactosidase-like isoform 2 (α-Gal, cell wall metabolism, spot 26) exhibited varied expression levels in different tomato fruits. Particularly high expression levels of LeACO4 and α-Gal were observed in wild type but not in the rin mutant. Additionally, CArG box, a RIN-binding site, was discovered in the promoter regions of both LeACO4 and α-Gal genes, suggesting that RIN possibly directly regulates their transcriptions, and this assumption was further confirmed by EMSA and ChIP assay.

CONCLUSION

Functional annotations of RIN target genes demonstrated the specific role of RIN in the process of fruit ripening and softening, especially in cell wall degradation and ethylene biosynthesis. This study will further illuminate the mechanism of tomato ripening and softening. © 2016 Society of Chemical Industry.

Molecular Cloning and Expression Analysis of Cu/Zn SOD Gene from Gynura bicolor DC

Superoxide dismutase is an important antioxidant enzyme extensively existing in eukaryote, which scavenges reactive oxygen species (ROS) and plays an essential role in stress tolerance of higher plants. A full-length cDNA encoding Cu/Zn SOD was cloned from leaves of Gynura bicolor DC. by rapid amplification of cDNA ends (RACE). The full-length cDNA of Cu/Zn SOD is 924 bp and has a 681 bp open reading frame encoding 227 amino acids. Bioinformatics analysis revealed that belonged to the plant SOD super family. Cu/Zn SODs of the Helianthus annuus, Mikania micrantha, and Solidago canadensis var. scabra all have 86% similarity to the G. bicolor Cu/Zn SOD. Analysis of the expression of Cu/Zn SOD under different treatments revealed that Cu/Zn SOD was a stress-responsive gene, especially to 1-MCP. It indicates that the Cu/Zn SOD gene would be an important gene in the resistance to stresses and will be helpful in providing evidence for future research on underlying molecular mechanism and choosing proper postharvest treatments for G. bicolor.