Ze Yun

Proteomic analysis of differentially expressed proteins involved in ethylene-induced chilling tolerance in harvested banana fruit

To better understand the mechanism involved in ethylene-induced chilling tolerance in harvested banana fruit, a gel-based proteomic study followed by MALDI-TOF-TOF MS was carried out. Banana fruit were treated with 500 ppm ethylene for 12 h and then stored at 6°C. During cold storage, the chilling tolerance was assessed and the proteins from the peel were extracted for proteomic analysis. It was observed that ethylene pretreatment significantly induced the chilling tolerance in harvested banana fruit, manifesting as increases in maximal chlorophyll fluorescence (Fv/Fm) and decreased electrolyte leakage. Sixty-four proteins spots with significant differences in abundance were identified, most of which were induced by ethylene pretreatment during cold storage. The up-regulated proteins induced by ethylene pretreatment were mainly related to energy metabolism, stress response and defense, methionine salvage cycle and protein metabolism. These proteins were involved in ATP synthesis, ROS scavenging, protective compounds synthesis, protein refolding and degradation, and polyamine biosynthesis. It is suggested that these up-regulated proteins might play a role in the ethylene-induced chilling tolerance in harvested banana fruit.

Comparative transcriptome and metabolome provides new insights into the regulatory mechanisms of accelerated senescence in litchi fruit after cold storage

Litchi is a non-climacteric subtropical fruit of high commercial value. The shelf life of litchi fruit under ambient conditions (AC) is approximately 4–6 days. Post-harvest cold storage prolongs the life of litchi fruit for up to 30 days with few changes in pericarp browning and total soluble solids. However, the shelf life of litchi fruits at ambient temperatures after pre-cold storage (PCS) is only 1–2 days. To better understand the mechanisms involved in the rapid fruit senescence induced by pre-cold storage, a transcriptome of litchi pericarp was constructed to assemble the reference genes, followed by comparative transcriptomic and metabolomic analyses. Results suggested that the senescence of harvested litchi fruit was likely to be an oxidative process initiated by ABA, including oxidation of lipids, polyphenols and anthocyanins. After cold storage, PCS fruit exhibited energy deficiency, and respiratory burst was elicited through aerobic and anaerobic respiration, which was regulated specifically by an up-regulated calcium signal, G-protein-coupled receptor signalling pathway and small GTPase-mediated signal transduction. The respiratory burst was largely associated with increased production of reactive oxygen species, up-regulated peroxidase activity and initiation of the lipoxygenase pathway, which were closely related to the accelerated senescence of PCS fruit.

Comparative proteomic approaches to analysis of litchi pulp senescence after harvest

Litchi fruit (Litchi chinensis Sonn.) is highly perishable after harvest. The shelf life is only 4-6days under ambient temperature storage conditions, which has restricted the development of the litchi industry to a considerable extent. To investigate the molecular mechanisms of litchi fruit senescence, comparative proteomic analysis was carried out on litchi pulp. After two-dimensional gel electrophoresis (2-DE), 64 spots were significantly differentially expressed, 61 of which were successfully identified using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). All of the identified proteins were classified according to biological process, molecular function, and cellular component using Blast2GO. Results showed that those proteins were mainly involved in signal transduction, cell wall metabolism, primary and secondary metabolism, energy metabolism. Specifically, many up-regulated proteins were involved in auxin/ethylene regulation, which suggested that auxin and ethylene might cooperate to regulate litchi pulp senescence. Histone deacetylase and DNA methyltransferase might involve the down-regulation of proteins related to reactive oxygen species (ROS) scavenging, glycolysis, tricarboxylic acid cycle, and ATP synthesis in litchi senescence. A higher proportion of differentially expressed proteins were up-regulated and these were involved in a range of processes including cell wall organization or biogenesis, anaerobic respiration, protein degradation, lipid degradation. All of those proteins might accelerate fruit softening, deterioration and senescence. This study is the first to carry out proteomic analysis of the regulation of litchi fruit senescence.

Salicylic acid treatment reduces the rot of postharvest citrus fruit by inducing the accumulation of H2O2, primary metabolites and lipophilic polymethoxylated flavones.

To comprehensively analyze the effects of salicylic acid (SA) on the storability of Satsuma mandarin (Citrus unshiu), fruits were treated with 2mM SA. The disease incidence of control/SA-treated fruit at 50d and 120d after treatment was 23.3%/10% and 67.3%/23.3%, respectively, suggesting that SA treatment can significantly reduce the rot rate of postharvest citrus fruit. Fruit quality assays revealed that the treatment can maintain fruit firmness without affecting the inner quality. Furthermore, the contents of H2O2 and some defense-related metabolites, such as ornithine and threonine, in citrus pericarp, were significantly increased by SA treatment. Moreover, it was lipophilic polymethoxylated flavones, rather than flavanone glycosides, that accumulated in SA-treated fruits and these can directly inhibit pathogen development. These results suggest that the effects of SA on postharvest citrus fruit may be attributed to the accumulation of H2O2 and defense-related metabolites.

Comparison of miRNA Evolution and Function in Plants and Animals

MicroRNAs (miRNAs), as a major player in post-transcriptional regulation of gene expression, have been reported to regulate a broad variety of key biological processes, including growth, development and stress responses in both plants and animals. While the biogenesis and regulatory abilities of miRNAs have been extensively studied, the evolutionary history of miRNAs still needs more exploration. So far, several models explain the origination of plant and animal MIRNA (MIR) genes. Both inter-species and intra-species conservation and divergence of miRNAs exhibits functional adaptation to changing environments in evolution. Here we summarize recent progress in how these similarities and differences contribute to the characteristic features of miRNA evolution in the two kingdoms.

Application of Proteomics for the Investigation of the Effect of Initial pH on Pathogenic Mechanisms of Fusarium proliferatum on Banana Fruit

Fusarium proliferatum is an important pathogen and causes a great economic loss to fruit industry. Environmental pH-value plays a regulatory role in fungi pathogenicity, however, the mechanism needs further exploration. In this study, F. proliferatum was cultured under two initial pH conditions of 5 and 10. No obvious difference was observed in the growth rate of F. proliferatum between two pH-values. F. proliferatum cultured under both pH conditions infected banana fruit successfully, and smaller lesion diameter was presented on banana fruit inoculated with pH 10-cultured fungi. Proteomic approach based on two-dimensional electrophoresis (2-DE) was used to investigate the changes in secretome of this fungus between pH 5 and 10. A total of 39 differential spots were identified using matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF/TOF-MS) and liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Compared to pH 5 condition, proteins related to cell wall degrading enzymes (CWDEs) and proteolysis were significantly down-regulated at pH 10, while proteins related to oxidation-reduction process and transport were significantly up-regulated under pH 10 condition. Our results suggested that the downregulation of CWDEs and other virulence proteins in the pH 10-cultured F. proliferatum severely decreased its pathogenicity, compared to pH 5-cultured fungi. However, the alkaline environment did not cause a complete loss of the pathogenic ability of F. proliferatum, probably due to the upregulation of the oxidation-reduction related proteins at pH 10, which may partially compensate its pathogenic ability.

Proteomic profiling of 24-epibrassinolide-induced chilling tolerance in harvested banana fruit

The mechanism of 24-epibrassinolide (EBR)-induced chilling tolerance in harvested banana fruit was investigated. Results showed that EBR pretreatment remarkably suppressed the development of chilling injury (CI) in harvested banana fruit during 12 days of cold storage at 8 °C, as indicated by lower CI index in treated fruit. Physiological measurements exhibited that EBR treatment reduced the relative electrolyte leakage and malondialdehyde (MDA) content while increased the chlorophyll fluorescence (Fv/Fm), total soluble solids (TSS) and ratio of TSS and titratable acidity. Furthermore, the differentially accumulated proteins of banana fruit in response to EBR and cold treatment were investigated by employing gel-based proteomic in combination with MALDI-TOF-TOF MS and LC-ESI-MS/MS analyses. There were fifty five protein spots to be successfully identified. Notably, most of up-regulated proteins by EBR treatment were related to energy biosynthesis, stress response and cell wall modification. In contrast, proteins involved in protein degradation and energy consumption were down-regulated by EBR treatment. These results suggest that EBR treatment could enhance the defense ability, promote the synthesis and utilization of energy, as well as maintain the protein function via enhancing protein biosynthesis and inhibiting protein degradation, consequently contributing to improvement of cold tolerance in harvested banana fruit. SIGNIFICANCE To extend our understanding of chilling injury (CI) of harvested banana fruit, we reported the effect of 24-epibrassinolide (EBR) on CI of banana fruit when stored at 8 °C. It was the first report on the comprehensive proteomic analysis of banana fruit in response to EBR treatment at low temperature. EBR pretreatment significantly reduced CI in harvested banana fruit. Fifty five protein spots were successfully identified. Notably, the most of up-regulated proteins by EBR treatment were related to energy biosynthesis, stress response and cell wall modification. In contrast, proteins involved in protein degradation and energy consumption were down-regulated. These results suggest that exogenous EBR treatment could enhance the defense ability and maintain high energy status. Meanwhile, EBR treatment maintained protein function via enhancing protein biosynthesis and inhibiting protein degradation. These results may help us to understand the molecular mechanism of the chilling tolerance induced by EBR treatment and broaden the current knowledge of the mechanism of CI of harvested banana fruit.