Diversity of flavour characteristics of table grapes and their contributing volatile compounds analysed by the solvent-assisted flavour evaporation method.

To identify the compounds that contribute to the diverse flavours of table grapes, the flavours and volatile compounds of 38 grape cultivars harvested over 3 years are evaluated through sensory analysis and solvent-assisted flavour evaporation (SAFE). The cultivars are characterized and grouped into seven clusters by hierarchical cluster analysis (HCA) using sensory evaluation data with a flavour wheel specific to table grapes. These clusters were similar to conventional flavour classifications, except that the foxy and neutral cultivars form multiple clusters, highlighting the flavour diversity of table grapes. The SAFE method provides a comprehensive profile of the volatile compounds, including slightly volatile compounds whose profiles are lacking in hybrid grapes and Vitis rotundifolia. The sensory evaluation is supported by the volatile compound profiles, and relationships between the datasets are clarified by multivariate analysis. Specific accumulations and combinations of compounds (α-pinene, ß-pinene, phenylethyl alcohol, furaneol, mesifurane, methyl N-formylanthranilate, and mixed ethyl ester and monoterpenoid) were also identified that contribute to the diversity of flavours (fresh green, floral, fruity, fatty green, sweet, fermented/sour) in table grapes, including linalool and linalool analogues (muscat flavour) along with ethyl ester and hydroxyethyl esters (foxy flavour). The accumulation of these compounds was positively related to a higher flavour intensity. Their specific accumulation and combination supported the flavour diversity of table grapes. This study identified novel flavour-associated compound profiles in table grapes through in-depth volatile compound analysis and non-conventional multivariate analysis.

Influence of Postharvest Temperatures on Carotenoid Biosynthesis and Phytochemicals in Mature Green Chili (Capsicum annuum L.).

An intense red color appearance in hot chili is what industry commonly demands. The harvested mature green "Takanotsume" chili, a popular cultivar in Japan, incubated at 20 and 30 °C is investigated. At 30 °C, the chili rapidly degraded chlorophylls and obtained an intense red color, but presented an orange-red color at 20 °C. The sample showed higher carotenoid accumulations at 30 °C, along with significantly upregulated carotenoid biosynthesis-related genes-phytoene synthase (Psy), lycopene-ß-cyclase (Lcyb), ß-carotene hydroxylase (CrtZ), and capsanthin/capsorubin synthase (Ccs)-during the experiment. While the expression of the Ccs gene was reduced, there was a 5.5-fold upregulation of the Psy gene at the end of incubation. At 20 °C, the Psy gene was downregulated. These observations suggest that the expression of individual genes is temperature-dependent, and these would affect specific carotenoid compounds. The antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl; DPPH and ferric-reducing antioxidant power; FRAP) values had no difference between temperatures; the higher content of total phenolics and vitamin C presented in the chili at 30 °C probably corresponds to the advanced ripening process. Thus, 30 °C is the recommended incubation temperature for mature green chili to achieve the industry-demanded intense red color and high accumulation of phytochemicals.

Color Development and Phytochemical Changes in Mature Green Chili (Capsicum annuum L.) Exposed to Red and Blue Light-Emitting Diodes.

Exposure of mature green "Takanotsume" chili fruit to blue and red light-emitting diodes (LEDs) was investigated. The red LED accelerated the red color development of chili as indicated by higher a* and chroma values, as well as lower hue angle and total chlorophyll compared to the blue LED and darkness (control). These were linked to increases in ß-carotene, free-capsanthin, and total carotenoids. The carotenoid biosynthesis-related genes, lycopene-ß-cyclase (Lcyb), ß-carotene hydroxylase (CrtZ), and capsanthin/capsolubin synthase (Ccs), were up-regulated by the red LED after 2 days of the experiment. The blue LED was more effective in increasing the expression of the phytoene synthase (Psy) gene at day 1 of experiment. The total phenolic, vitamin C content, and antioxidant capacity were also higher in the blue LED-treated chili. Results suggest that the responses of each carotenoid-related gene to the light wavelengths and the accumulation of phytochemicals are specific characteristics of this chili cultivar.

Metabolomics analysis of 'Housui' Japanese pear flower buds during endodormancy reveals metabolic suppression by thermal fluctuation.

Dormancy is a complex phenomenon that allows plants to survive the winter season. Studies of dormancy have recently attracted more attention due to the expansion of temperate fruit production in areas under mild winters and due to climate changes. This study aimed to identify and characterize the metabolic changes induced by chilling temperatures, as well as during thermal fluctuation conditions that simulate mild winter and/or climate change scenarios. To do this, we compared the metabolic profile of Japanese pear flower buds exposed to constant chilling at 6 °C and thermal fluctuations of 6 °C/18 °C (150 h/150 h) during endodormancy. We detected 91 metabolites by gas chromatography paired with time-of-flight mass spectrometry (GC-TOF-MS) that could be classified into eight groups: amino acids, amino acid derivatives, organic acids, sugars and polyols, fatty acids and sterols, phenol lipids, phenylpropanoids, and other compounds. Metabolomics analysis revealed that the level of several amino acids decreased during endodormancy. Sugar and polyol levels increased during endodormancy during constant chilling and might be associated with chilling stress tolerance and providing an energy supply for resuming growth. In contrast, thermal fluctuations produced low levels of metabolites related to the pentose phosphate pathway, energy production, and tricarboxylic acid (TCA) cycle in flower buds, which may be associated with failed endodormancy release. This metabolic profile contributes to our understanding of the biological mechanism of dormancy during chilling accumulation and clarifies the metabolic changes during mild winters and future climate change scenarios.

Abscisic acid metabolism and anthocyanin synthesis in grape skin are affected by light emitting diode (LED) irradiation at night.

The effects of blue and red light irradiation at night on abscisic acid (ABA) metabolism and anthocyanin synthesis were examined in grape berries. The expressions of VlMYBA1-2, VlMYBA2, UDP-glucose-flavonoid 3-O-glucosyltransferase (VvUFGT), 9-cis-epoxycarotenoid dioxygenase (VvNCED1), and ABA 8'-hydroxylase (VvCYP707A1) were also investigated. Endogenous ABA, its metabolite phaseic acid (PA), and the expressions of VvNCED1 and VvCYP707A1 were highest in red light-emitting diode (LED)-treated skin. In contrast, anthocyanin concentrations were highest in blue LED-treated skin, followed by red LED treatment. However, the expressions of VlMYBA1-2, VlMYBA2, and VvUFGT did not necessarily coincide with anthocyanin concentrations. The quality of coloring may depend on the amount of malvidin-based anthocyanin, which increased toward harvest in blue and red LED-treated skin, unlike in untreated controls. An increase in sugars was also observed in blue and red LED-treated skin. These results suggest that blue LED irradiation at night may be effective in increasing anthocyanin and sugar concentrations in grape berries. However, there is evidence that another factor may influence anthocyanin concentrations in grape berry skin significantly more than endogenous ABA: ABA concentrations were highest in red LED-treated skin, which had lower anthocyanin concentrations than blue LED-treated skin.

Dehydration tolerance in apple seedlings is affected by an inhibitor of ABA 8'-hydroxylase CYP707A.

The effects of an abscisic acid (ABA) 8'-hydroxylase inhibitor (Abz-F1) on ABA catabolism, stomatal aperture, and water potential were examined in apple seedlings under dehydration and rehydration conditions. In this study, 9-cis-epoxycarotenoid dioxigenase (MdNCED) and ABA 8'-hydroxylase (MdCYP707A) genes were isolated and their expressions were investigated under dehydration and rehydration conditions. The stomatal aperture decreased up to 4 h after spraying with Abz-F1 and the stomatal aperture in the Abz-F1-treated leaves was generally lower than that in the untreated control-leaves during the dehydration condition. Although the water potential in untreated control-leaves decreased with the progress of dehydration, it was maintained at a higher level in the Abz-F1 treated-leaves than in the untreated control-leaves during dehydration. Endogenous ABA concentrations increased with dehydration in both the Abz-F1 treated- and untreated-control-leaves, but the ABA levels in the Abz-F1 treated-leaves were higher than those in the untreated control-leaves throughout dehydration. In contrast, the phaseic acid (PA) concentrations in the Abz-F1 treated-leaves were lower than those in the untreated control-leaves during dehydration. The expressions of MdNCEDs in the Abz-F1 treated-leaves were lower than those in the untreated control-leaves regardless of the higher endogenous ABA concentrations. Moreover, the expressions of MdCYP707As in the Abz-F1 treated-leaves were also lower than those in the untreated control-leaves. Higher 50% effective concentrations (EC(50)) and ascorbic acid concentrations were observed in the Abz-F1 treated-leaves, which show that the oxidative damage under dehydration may be reduced by Abz-F1 application. These results suggest that prompt stomata closure is required for survival under dehydration, and Abz-F1 application may therefore be of practical use. The increase of endogenous ABA, which induced prompt stomata closure in Abz-F1 treated-leaves may depend on inhibition of the expression of MdCYP707As. Furthermore, the results showed the close relationship between MdNCEDs and MdCYP707As on ABA catabolism.

Salinity induces carbohydrate accumulation and sugar-regulated starch biosynthetic genes in tomato (Solanum lycopersicum L. cv. 'Micro-Tom') fruits in an ABA- and osmotic stress-independent manner.

Salinity stress enhances sugar accumulation in tomato (Solanum lycopersicum) fruits. To elucidate the mechanisms underlying this phenomenon, the transport of carbohydrates into tomato fruits and the regulation of starch synthesis during fruit development in tomato plants cv. 'Micro-Tom' exposed to high levels of salinity stress were examined. Growth with 160 mM NaCl doubled starch accumulation in tomato fruits compared to control plants during the early stages of development, and soluble sugars increased as the fruit matured. Tracer analysis with (13)C confirmed that elevated carbohydrate accumulation in fruits exposed to salinity stress was confined to the early development stages and did not occur after ripening. Salinity stress also up-regulated sucrose transporter expression in source leaves and increased activity of ADP-glucose pyrophosphorylase (AGPase) in fruits during the early development stages. The results indicate that salinity stress enhanced carbohydrate accumulation as starch during the early development stages and it is responsible for the increase in soluble sugars in ripe fruit. Quantitative RT-PCR analyses of salinity-stressed plants showed that the AGPase-encoding genes, AgpL1 and AgpS1 were up-regulated in developing fruits, and AgpL1 was obviously up-regulated by sugar at the transcriptional level but not by abscisic acid and osmotic stress. These results indicate AgpL1 and AgpS1 are involved in the promotion of starch biosynthesis under the salinity stress in ABA- and osmotic stress-independent manners. These two genes are differentially regulated at the transcriptional level, and AgpL1 is suggested to play a regulatory role in this event.

Differential adaptation of high- and low-chill dormant peaches in winter through aquaporin gene expression and soluble sugar content.

Plants have their own mechanisms for overcoming various stresses. In cold regions, plants are subject to stress and must enter an inherent dormancy, through several complex mechanisms, if they are to continue to exist. In winter, regulation of tonoplast and plasma membrane aquaporin genes differed in the bud cushions of the high-chill peach (Prunus persica L. Batsch) cv. Kansuke Hakuto and the low-chill peach cv. Coral. In December and January, when the temperature was lowest (around 2 degrees C), the increased expression of Pp-gammaTIP1 and Pp-PIP1 seen in the bud cushions of Kansuke Hakuto may have been related to the concomitant high-soluble sugar content of the cushions of this cultivar. This relationship may have made the cells highly stable and relatively unaffected by low-temperature stress owing to the presence of "glasses" that prevented ice nucleation. However, a simpler form of cold protection regulation seemed to occur in Coral, in which there was no winter increase in Pp-gammaTIP1 and Pp-PIP1 mRNA and a slow decline in total soluble sugar content in December and January. These results suggested that Pp-gammaTIP1 and Pp-PIP1, respectively, play important roles in intra- and intercellular membrane transport, enhancing cold resistance in the bud cushions of high-chill cultivars. In addition, Pp-deltaTIP1 and Pp-PIP2 mRNA increased at the end of endodormancy in both cultivars. This change may be induced by endodormancy-release signals and the resumption of bud activity in both cultivars.

Changes in aquaporin gene expression and magnetic resonance imaging of water status in peach tree flower buds during dormancy.

The movement of cellular water accompanies changes in growth within dormant buds. To further understand this process, accumulation of tonoplast deltaTIP1 and plasma membrane PIP2 aquaporin transcripts was measured by quantitative reverse transcriptase-polymerase chain reaction and the water dynamics in dormant peach (Prunus persica L.) flower buds was studied by magnetic resonance imaging. Proton density (PD), spin-spin relaxation time (T(2)) and apparent diffusion coefficient (ADC) were used to observe water dynamics during dormancy. The expression of deltaTIP1 and PIP2 aquaporins, PD and T(2) in the upper part of the bud including primordia, in the basal part of the bud and the bud trace increased earlier in the low-chill cultivar 'Coral' than in the high-chill cultivar 'Kansuke Hakuto,' reflecting the difference in timing for the end of endodormancy in the two cultivars. deltaTIP1 mRNA accumulated mainly in the basal part of the bud, whereas PIP2 mRNA was detected mainly in the upper part. These findings may reflect the activation of inter- and intracell communication through membrane transport properties of aquaporins resulting in a gradual increase in water content to that required for bud activity at the end of endodormancy. An apparent decrease in the expression of deltaTIP1 and PIP2 mRNAs was, however, observed in late winter in some portions of the buds of both cultivars just before sprouting.

Agrobacterium-mediated transformation of the dwarf pomegranate (Punica granatum L. var. nana).

The dwarf pomegranate (Punica granatum L. var. nana) is a dwarf ornamental plant that has the potential to be the model plant of perennial fruit trees because it bears fruits within 1 year of seedling. We established an Agrobacterium-mediated transformation system for the dwarf pomegranate. Adventitious shoots regenerated from leaf segments were inoculated with A. tumefaciens strain EHA105 harboring the binary vector pBin19-sgfp, which contains neomycin phosphotransferase (npt II) and green fluorescent protein (gfp) gene as a selectable and visual marker, respectively. After co-cultivation, the inoculated adventitious shoots were cut into small pieces to induce regeneration, and then selected on MS medium supplemented with 0.5 muM alpha-naphthaleneacetic acid (NAA), 5 muM N(6)-benzyladenine (BA), 0.3% gellan gum, 50 mg/l kanamycin, and 10 mg/l meropenem. Putative transformed shoots were regenerated after 6-8 months of selection. PCR and PCR-Southern blot analysis revealed the integration of the transgene into the plant genome. Transformants bloomed and bore fruits within 3 months of being potted, and the inheritance of the transgene was confirmed in T(1) generations. The advantage of the transformation of dwarf pomegranate was shown to be the high transformation rate. The establishment of this transformation system is invaluable for investigating fruit-tree-specific phenomena.