Hongbo Mi

Maturity-dependent chilling tolerance regulated by the antioxidative capacity in postharvest cucumber (Cucumis sativus L.) fruits

BACKGROUND The aim of the present study was to reveal the effect of fruit maturity on the chilling tolerance of cucumber (Cucumis sativus L.) fruit and the oxidative and antioxidative mechanisms involved. Chinese mini-cucumber (cv. Hangcui-1) fruits were harvested at four developmental stages: Immature (3-8 days after anthesis (DAA)), Mature (9-16 DAA), Breaker (17-22 DAA) and Yellow (35-40 DAA). All fruits were stored at 2 °C for 9 days and rewarmed at 20 °C for 2 days. RESULTS The chilling injury index declined with advancing fruit maturity. High superoxide anion radical production rate and hydrogen peroxide content were observed in Immature fruits after cold storage and rewarming. Under chilling stress, superoxide dismutase showed an early response. Fruits at earlier maturity stages exhibited higher catalase, ascorbate peroxidase and monodehydroascorbate reductase activities and glutathione content as well as its redox state, and lower peroxidase, dehydroascorbate reductase and glutathione reductase activities and ascorbate content as well as its redox state. CONCLUSION Fruits at the earlier developmental stage are more susceptible to chilling injury, which is related to increased oxidative stress. High peroxidase activity and ascorbate content and maintenance of the latters redox state appear critical to the chilling tolerance of cucumber fruits at later developmental stages.

Role of antioxidative system during the development and senescence of cucumber fruit

The oxidative processes and antioxidative system in cucumber (Cucumis sativus L.) fruit were determined during development and senescence. Four distinct developmental stages could be delineated during fruit maturation: immature (3–8 d after anthesis, DAA), mature (9–16 DAA), breaker (17–22 DAA), and yellow (35–40 DAA). The electrolyte leakage, malondialdehyde content, superoxide anion production rate, and hydrogen peroxide content increased continuously during fruit development and senescence. Superoxide dismutase and peroxidase activities consistently increased during fruit maturation, and the catalase activity displayed a single peak at the mature stage. Ascorbate peroxidase and glutathione reductase activities declined during fruit development, but both were activated in yellow fruit. Monodehydroascorbate reductase activity declined and dehydroascorbate reductase (DHAR) activity increased during fruit growth. DHAR was repressed in yellow fruit. Ascorbate dramatically accumulated and its redox state increased, whereas glutathione was degraded and its redox state declined, with fruit maturation.

Proteomic Analysis of Mechanisms Responsible for the Waterless Preservation of Fenneropenaeus chinensis Based on Cold-Forced Hibernation

ABSTRACT In this study, the comparative proteomic approach was used to identify the proteins that were changed significantly during the waterless preservation of Chinese white shrimp (Fenneropenaeus chinensis). Approximately 380–430 protein spots were observed in the two-dimensional protein electrophoresis (2-DE) gels. Among them, 14 altered proteins from hemolymph were excised and subjected to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis. Eleven protein spots were successfully identified—including hemocyanin, hemolymph clottable protein, myosin light chain, and sarcoplasmic calcium-binding protein. It could be speculated that the combined action of decreased hemocyanin, increased hemolymph clottable protein, and myosin light chain forced Chinese white shrimp into a temporary state of hibernation under cold temperature and could keep the hibernated shrimps alive during the waterless preservation. Moreover, increased expression of sarcoplasmic calcium-binding protein ensured that hibernated shrimps could be aroused at warm temperature. On the basis of these findings, it is believed that a protein-protein networking mechanism of hemocyanin, hemolymph clottable protein, myosin, and sarcoplasmic calcium-binding protein could interpret the cold-forced hibernation and warm-arousal of Chinese white shrimp.

Quality and Biochemical Influence of Eugenol to Anesthetize Crucian Carp (Carassius Auratus)

The aim of this study was to identify the influence of the anesthetic eugenol on crucian carp. The muscle quality and freshness were little influenced by anesthesia from the perspective of cooking loss (CL) and total volatile basic nitrogen (TVB-N). In contrast, lower redness, liquid loss (LL), and 2-thiobarbituric acid (TBA) values were observed in anesthetized fish. It was found that anesthesia increased serum cortisol content and reduced serum glucose concentration. There was little influence of eugenol on serum glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT), and alkaline phosphatase (AKP) activities, while serum and muscle acid phosphatase (ACP) activities significantly increased after the use of the anesthetic. Results suggested that the stress of eugenol to crucian carp was nontoxic and did not lead to hyperglycemia. On the basis of these findings, eugenol as an anesthetic is effective and safe for the transportation of crucian carp.

Cucumber BAX inhibitor-1, a conserved cell death suppressor and a negative programmed cell death regulator under cold stress

Programmed cell death (PCD) is a genetically controlled and conserved process in eukaryotes during development as well as in response to pathogens and other stresses. BAX inhibitor-1 (BI-1) has been implicated as an anti-PCD factor which is highly conserved in plants. Sequence of putative cucumber BI-1 protein exhibited 77.7 % identity and 91.2 % positive value with the homologue Blast BI-1 protein of Arabidopsis thaliana (AtBI-1). This highly homologous protein to the AtBI-1 protein was named CsBI-1. This protein contains an open reading frame (ORF) of 250 amino acids with a BAX inhibitor domain and five transmembrane regions conserved among members of the BI-1 family. Primers designed by the cDNA of CsBI-1gene were used for further sequencing. Cell death in cold-stored cucumber developed concomitantly with increased expression of the CsBI-1 gene and reached maximum at day 6. However, cell death accelerated significantly after 9 d when sharp decrease of the CsBI-1 expression occurred. After warming to 20 °C, expression of the CsBI-1 gene was the highest at day 3, decreased afterwards, and the lowest expression was detected at day 9 when PCD obviously appeared. The overall results indicate that CsBI-1 is cucumber homologue of Arabidopsis thaliana AtBI-1 gene. CsBI-1 is a conserved cell death suppressor induced by cold stress and a negative regulator of PCD.

Effect of chitosan coating enriched with 6-gingerol on red drum fillets quality and shelf-life during refrigerated storage

ABSTRACT The effect of chitosan coating enriched with 6-gingerol on the quality and shelf life of red drum fillets during refrigerated storage was investigated in this study. Samples were applied with chitosan coating (CH), 6-gingerol (GI), and chitosan coating with 6-gingerol (CH+GI) before storing at 4°C for 20 days. The data in this study showed that treatment with CH+GI could significantly decrease pH value, K-value, thiobarbituric acid value, and total volatile basic nitrogen in red drum fillets during refrigerated storage. The counts of microorganisms, such as Enterobacteriaceae, psychrotrophic, mesophilic bacteria, and lactic acid bacteria, were also significantly lower in the CH+GI group compared with those in the CH and GI groups. Moreover, the combination of chitosan coating and 6-gingerol was more effective in relieving the deterioration of tissue texture and sensory characteristics in the red drum fillets. In addition, the results suggested that chitosan coating and 6-gingerol had a synergistic effect on the quality improvement of red drum fillets. This work demonstrates that chitosan coating enriched with 6-gingerol may be a promising natural preservative for red drum during refrigerated storage.