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Virus-induced gene silencing (VIGS) is known as a powerful tool for identifying gene functions during plant growth and development. Tobacco rattle virus (TRV) based VIGS has been successfully employed in many plants. However, there have been few reports that VIGS can be used to study the function of gene at fruit level, especially the genes without visible silencing phenotype. Here we used miniature tomato cultivar Micro-Tom (Solanum lycopersicum L.) as material to silence phytoene desaturase (SlPDS) and SlARG2, an important gene encoding arginase in arginine metabolism, separately or simultaneously with TRV agroinoculated by sprout vacuum-infiltration to test the utility of concurrently silencing two genes. When SlPDS and SlARG2 were co-silenced in the same tissue at the same time, there are no compromises in silencing efficiency and silencing efficacy compared with SlPDS or SlARG2 silenced separately. Moreover, the silence of SlPDS and SlARG2 with TRV agroinoculated by sprout vacuum-infiltration occurred at the early stage of tomato plant, and the silence can extend to full red stage of fruit. Therefore, our results provide a means for functional analysis of genes, particularly the genes with no obvious visible phenotype after silencing, involved in all of the metabolic networks during fruit development and ripening.

The different sequential combined effect of carbon dioxide (CO2, 90%) and 1-methylcyclopropene (1-MCP, 0.5 μL L−1) on storage quality of persimmon fruit was investigated. In this study, the application of CO2 could induce the decrease of soluble tannin. But, the CO2-treated persimmon fruit soften rapidly, reducing their shelf life. Compared with CO2 treatment before cold storage, the treatment with CO2 deastringency after cold storage (air → CO2), CO2 deastringency followed by 1-MCP treatment before cold storage (CO2 → 1-MCP), and 1-MCP treatment followed cold storage before CO2 deastringency (1-MCP → CO2) were more effective in prolonging the storage time of persimmon fruit, especially the application of CO2 → 1-MCP, as indicated by higher firmness and soluble solids content, and the lower electrical conductivity and MDA content during most of the storage periods. Moreover, the treatment with CO2 → 1-MCP could induce the enhancement of antioxidant enzyme activities including superoxide dismutase, peroxidase and catalase. Meanwhile, the treatment with CO2 → 1-MCP could also maintain the lower lipoxygenase activity. These results suggest that the treatment of CO2 → 1-MCP may be an useful technique to decrease the soluble tannin content, maintain quality and prolong the storage time in postharvest persimmon fruit during storage.

Chilling acclimation and methyl jasmonate (MeJA) treatments are effective ways to alleviate chilling injury (CI) in postharvest fruit and vegetables. Soluble sugars can be used as an important energy substance, as well as an osmotic adjustment substance, participating in various stress responses in plants. However, the regulation mechanism of chilling acclimation and MeJA treatments on sugar metabolism remains unclear during the fruit response to chilling stress. In this study, tomato fruits were used to study the regulation of sugar metabolism during chilling resistance induced by 0.05 mM MeJA and 2 °C chilling acclimation treatments for 12 h and recovering at 25 °C for 6 h before being stored at 2 °C for up to 20 days. The results showed that both 2 °C and MeJA significantly induced chilling tolerance in tomato fruit, which was reflected by the decreased CI and malondialdehyde content, as well as the increased fruit color change and total antioxidant capacity. In addition, we found that 2 °C and MeJA promoted starch degradation and sucrose accumulation, but inhibited the increase of glucose and fructose contents. MeJA and 2 °C treatments enhanced the transcription levels of genes encoding amylase (AM), sucrose phosphate synthase (SPS), sucrose synthase (SuS) and neutral invertase (NI), while decreased the transcription level of gene encoding acid invertase (AI) during most of the storage periods. Further correlation analysis suggested that the chilling resistance of three groups of fruit was closely associated with sucrose content (r=−0.824 in control, r=−0.964 in 2 °C-treated fruit and r=−0.838 in MeJA-treated fruit); and the sucrose content of the fruit was positively correlated with SlSPS3 (r=0.681 in control, r=0.947 in 2 °C-treated fruit and r=0.889 in MeJA-treated fruit) and negatively correlated with SlAI (r=−0.954 in control, r=−0.921 in 2 °C-treated fruit and r=−0.637 in MeJA-treated fruit). In addition, in 2 °C-treated fruit, sucrose content was also correlated with the expression of a-AM (r=0.723), while in MeJA-treated fruit sucrose content was correlated with β-AM (r=0.694). These results suggested that 2 °C and MeJA treatments were both effective measures for enhancing the chilling resistance of tomato fruit by regulating sugar metabolism.

This study parsed the mechanism of SlMYC2 involving methyl jasmonate (MeJA)-mediated tomato fruit chilling tolerance. The data indicated that the application of MeJA significantly prevented chilling injury (CI) and inhibited the accumulation of hydrogen peroxide (H2O2) and superoxide anions (O2•−) in tomato fruit during cold storage. The accumulation of endogenous ascorbate (AsA) and glutathione (GSH) contents in fruit were enhanced by MeJA treatment resulting from increasing activities of enzymes related to AsA-GSH cycle. Meanwhile, the MeJA-treated fruit exhibited significantly higher expression levels of C-repeat-binding factor 1 (SlCBF1), cold regulated gene (SlCOR413) and inducer of SlCBF expression (SlICE1 and SlICEa), which belong to the SlICE-SlCBF-SlCOR (ICC) signaling pathway. However, the effects of MeJA were inhibited by the silence of SlMYC2. The expression levels of SlCBF1, SlCOR413, SlICE1 and SlICEa were reduced in SlMYC2-silenced fruits, and there was no significant difference in CI index and the indexes related to AsA-GSH cycle between (SlMYC2-silenced+MeJA)-treated fruit and control during most storage periods. In addition, correlation analysis indicated that the indexes involved in AsA-GSH cycle and ICC signaling pathway were closely related to the transcription of SlMYC2. Therefore, these results illustrated that SlMYC2 was involved in the regulation of ASA-GSH cycle and ICC signaling pathway mediated by MeJA during the cold tolerance of tomato fruit.

The main purpose of this study was to investigate the effects of preharvest regulation of ethylene on apple fruit carbohydrate metabolism and quality at harvest and during storage. The positive regulation of ethylene was achieved by Ethephon, and the negative regulation was by Harvista, a kind of sprayable 1-methylcyclopropylene (1-MCP). ‘Starkrimson’ apple were treated with Harvista or Ethephon 7 d before harvest, respectively, and then stored at 0 °C for 180 d. The contents of starch, sucrose, glucose, fructose, and related enzymes activities and gene expression levels of sucrose phosphate synthase (SPS), sucrose synthase (SUSY), acid invertase (AINV), neutral invertase (NINV), cell wall invertase (CWINV) and amylase (AMY) were determined. The results showed that Harvista inhibited the starch degradation, retarded the increase of soluble sugar, reducing sugar, sucrose, glucose and fructose contents before 120 d of fruit storage, while no obvious difference was observed in these sugar content after 120 d of storage among three treatments. The enzyme activities of SPS, AINV, CWINV and AMY were also inhibited by Harvista at the early period of storage, and the expression levels of MdSPS, MdAINV, MdCWINV and MdAMY were positively correlated with their enzyme activities. In addition, Harvista reduced the fruit dropping rate at harvest and maintained the fruit firmness, while Ethephon showed the opposite effect. These results indicated that the preharvest regulation of ethylene effectively altered the carbohydrate metabolism and the quality of ‘Starkrimson’ apple fruit, and Harvista may be a useful tool applied at preharvest to maintain fruit quality at harvest and during storage.

Endogenous hormones play significant roles in the storage quality of horticultural products. In the present study, the influence of diverse stalk lengths on hormones and storage quality of broccoli heads was investigated. Broccoli heads accompanied with stalk lengths (1, 3, 6, and 9 cm) were selected and stored at 10 °C and 85–90 % relative humidity. The results showed that the metabolism center was transferred from broccoli florets to stalk in broccoli heads with 9-cm stalks after 6 days. Compared to other treatments, the florets of broccoli heads with 6-cm stalks maintained the metabolism center via regulation of the consumption and distribution of endogenous hormones throughout the storage time, suppressing the reduction of water and protein content and hue angle H. Shorter stalk lengths accelerated the broccoli floret’s degradation during storage. The present results suggest that stalk/stem length should be considered for horticultural products during storage, especially for products with long stalk/stem.

Tomato ( Solanum lycopersicum cv. Messina) fruit, at five ripening stages (mature green, breaker, pink, light red and full red), have been analyzed for the expression of genes involved in arginine metabolism, polyamines and arginine-related amino acids content, as well as the nitric oxide synthase (NOS) activity and nitric oxide (NO) content. During ripening, the expression of LeARG1 and LeARG2 , two genes encoding arginase, and NOS activity, as well as NO content decreased and the highest levels of them were found in mature green fruit. The expression of gene encoding arginine decarboxylase (ADC) increased with fruit ripening and reached the highest value at pink stage, which possibly contributed to the increased polyamines concentration. While the ornithine decarboxylase (ODC) might play a minor role in polyamines biosynthesis during tomato fruit ripening, the gene expression pattern of which differed with that of polyamines accumulation. The expression of gene encoding ornithine aminotransferase (OAT) increased during the later ripening stages of tomato, which was accompanied by proline accumulation. From all the amino acids tested, glutamate content was the most abundant and showed a marked increase during the course of fruit ripening. In contrast, arginine and ornithine contents remain relatively uniform throughout fruit ripening. These results implicate that the unique physiological roles of arginine in fruit ripening may depend on the coordination of different pathways of arginine metabolism.

Fresh pollen grains of 37 species representing eight genera (Magnolia, Manglietia, Lirianthe, Houpoea, Talauma, Michelia, Woonyoungia, and Parakmeria) of the subfamily Magnolioideae, one of the most primitive families among the angiosperms, were investigated using scanning electron microscopy, and 31 of them are reported for the first time. The Magnoliaceae family is typically stenopalynous. Pollen grains are bilaterally symmetrical, heteropolar, boat-shaped and monosulcate, rounded or elliptical in distal view. They are medium to large in size, ranging from 41.6 ± 4.4 μm to 94.1 ± 5.6 μm in the longest axis. Most species examined have microperforate ornamentation. Uniform perforations of 0.2 μm or from 0.1 μm to 0.5 μm in diameter on the outer surface of the exine were detected in Manglietia and Lirianthe species. Pollen grains of some species had microgemmae or ring-like appurtenances on the outer surface of the exine. Six pollen types and three subtypes are proposed in the Magnoliaceae. This is one more than the five types proposed by Praglowski in 1974. A key for the identification of these pollen types and subtypes is presented and its taxonomic implications in the Magnolioideae are discussed.

The in vitro leaves of Valeriana jatamansi Jones were used as explants to induce adventitious shoots and somatic embryos from embryogenic callus. Both morphogenic processes could be induced on Murashige and Skoog (MS) basal medium supplemented with different concentrations and combinations of plant growth regulators. Embryogenic callus, which was induced exclusively in the presence of auxins, namely 1.0–7.5 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 5.0 μM α-naphthaleneacetic acid (NAA), differentiated into adventitious shoots and somatic embryos, respectively when left on the same medium. Callus, when placed on MS medium containing 5.0 μM indole-3-butyric acid (IBA), 5.0 μM NAA or 1.0–5.0 μM 2,4-D, induced adventitious roots. Cytokinins that were added singly to callus induction medium, including 6-benzyladenine, kinetin and thidiazuron, could not induce callus at 5.0 μM except when combined with 0.25–1.0 μM NAA.

To identify the most effective modified-atmosphere packaging (MAP) and/or 1-methylcyclopropene (1-MCP) treatment to maintain the fruit quality of ‘Laiyang’ pear ( Pyrus bretschneideri Reld cv. Laiyang) during 210 days of cold storage (0–2 °C), two kinds of low-density polyethylene (LDPE) packaging films with different O 2 and CO 2 permeabilities were evaluated with and without 1-MCP (0.5 μL/L or 1.0 μL/L). The results showed that 0.5 μL/L 1-MCP plus micro-perforated film packaging maintained the color, firmness, titratable acidity, and vitamin C content of the fruit flesh and was the most appropriate treatment for ‘Laiyang’ pear fruit during cold storage. Treatment with 0.5 μL/L 1-MCP plus micro-perforated film packaging inhibited respiration and ethylene production; maintained the activity levels of super oxidase dismutase, peroxidase, and catalase; decreased the cell-membrane permeability and malondialdehyde content; and inhibited the lipoxygenase and polyphenol oxidase activity of the fruit during cold storage.