High-temperature inhibition of biosynthesis and transportation of anthocyanins results in the poor red coloration in red-fleshed Actinidia chinensis.

In plants, the role of anthocyanins trafficking in response to high temperature has been rarely studied, and therefore poorly understood. Red-fleshed kiwifruit has stimulated the world kiwifruit industry owing to its appealing color. However, fruit in warmer climates have been found to have poor flesh coloration, and the factors responsible for this response remain elusive. Partial correlation and regression analysis confirmed that accumulative temperatures above 25 °C (T25) was one of the dominant factors inhibiting anthocyanin accumulation in red-fleshed Actinidia chinensis, 'Hongyang'. Expression of structural genes, AcMRP and AcMYB1 in inner pericarp sampled from the two high altitudes (low temperature area), was notably higher than the low altitude (high temperature area) during fruit coloration. AcMYB1 and structural genes coordinate expression supported the MYB-bHLH (basic helix-loop-helix)-WD40 regulatory complex mediated downregulation of anthocyanin biosynthesis induced by high temperatures in kiwifruit. Moreover, cytological observations using the light and transmission electronic microscopy showed that there were a series of anthocyanic vacuolar inclusion (AVI)-like structures involved in their vacuolization process and dissolution of the pigmented bodies inside cells of fruit inner pericarp. Anthocyanin transport was inhibited by high temperature via retardation of vacuolization or reduction in AIV-like structure formation. Our findings strongly suggested that complex multimechanisms influenced the effects of high temperature on red-fleshed kiwifruit coloration.

Do sun- versus shade-grown kiwifruits perform differently upon storage? An overview of fruit maturity and nutraceutical properties of whole and fresh-cut produce.

Fresh-cut produce represents a good method to save about 25% of the kiwifruit not useful to meet the fresh fruit-marketing standard due to improper size and shape. For that reason, fresh-cut kiwifruit has been extensively studied. However, the comprehension of the influence of some aspects of cultivation might further increase the shelf life as well as the nutritional values of that fruit. This study explored the hypothesis that kiwifruits grown fully exposed to sunlight or partially shaded differently perform upon storage as whole fruit and as minimally processed produce. Flesh firmness (FF), total solids soluble (SSC), ascorbate (AAT), flavonoids (TFO), and phenols (TF) contents were evaluated in sliced and whole fruit upon 3 days of storage at 4 °C after 75 days of cold chamber storage at 0 °C. The activities of two enzymes related to the softening process, polygalacturonase (PG) and pectinmethylesterase (PME), were evaluated as well. FF and SSC were constitutively higher in sun-exposed fruit, and those characteristics remained higher during the storage as whole fruit. Greater constitutive content of AAT, TFO, and TP was found in sun-exposed whole fruit, although after cutting the reduction in their content was significantly lower in shaded fruits. PME and PG activities were higher only in whole shaded fruits, whereas no relevant differences occurred after cutting. In summary, sun-exposed fruits were more suitable for the fresh-fruit market, whereas the shaded counterpart displayed a good predisposition for use as fresh-cut produce, maintaining similar fruit maturity properties but higher nutraceutical values when sliced than fruit grown under full sun.

Expression patterns and promoter characteristics of the gene encoding Actinidia deliciosa L-galactose-1-phosphate phosphatase involved in the response to light and abiotic stresses.

The gene encoding L-galactose-1-phosphate phosphatase (GPP) plays a central role in ascorbic acid (AsA) biosynthesis in plants. Here, we report AsA contents, GPP expression, and functioning of its promoter in response to light, exogenous stress-signalling hormones, or abiotic stresses in kiwifruit (Actinidia deliciosa). To identify the upstream region of GPP required for promoter activity, we constructed a series of promoter deletion derivatives. Each construct was analyzed by Agrobacterium-mediated transient transformation in tobacco leaves after various treatments. Some correlation was observed between the relative levels of GPP mRNA and AsA contents when kiwi leaves were exposed to varying light conditions, treatment with ABA or SA, wounding, or a hypoxic environment. Analysis of a series of 5' deletions in tobacco leaves indicated that the proximal area 390 bp from the transcription initiation site was needed for establishing both the constitutive and the induced patterns of expression. This promoter was induced by light or one of our abiotic treatments. These results suggest that GPP is regulated by light or abiotic stress and that it plays an important role in controlling AsA contents in kiwifruit.

Shading the whole vines during young fruit development decreases ascorbate accumulation in kiwi.

We investigated how different lighting conditions affected the levels of ascorbate (AsA), sugar contents, the mRNA expression of genes involved in AsA biosynthesis and recycling and enzyme activity in kiwi fruits. Shaded leaves had dramatically less AsA as well as altered transcript levels and enzyme activities. In contrast, fruits that had been covered directly at various developmental stages showed no changes in those parameters. Fruits had significantly less AsA content before 40 days after anthesis (DAA) when whole vines were shaded only from 0 to 40 DAA, whereas transcript levels of most related genes (except those for GDP-L-galactose-1-phosphate phosphorylase and GDP-mannose pyrophosphorylase) followed a parallel trend. When the shading was removed after 40 DAA, values for the ripening fruits returned to those measured for the control. Such a response, however, was not observed when shading treatments were delayed until after 40 DAA. Fruits were also smaller at harvest when vines were shaded at the earliest time point. The present results suggest that lighting conditions can indirectly affect the capacity of biosynthesis and recycling of AsA in young fruits of kiwi, and this regulation might occur via the interaction of signal from leaves and development of fruit.

Artificial neural networks as an alternative to the traditional statistical methodology in plant research.

In this work, we compared the unique artificial neural networks (ANNs) technology with the usual statistical analysis to establish its utility as an alternative methodology in plant research. For this purpose, we selected a simple in vitro proliferation experiment with the aim of evaluating the effects of light intensity and sucrose concentration on the success of the explant proliferation and finally, of optimizing the process taking into account any influencing factors. After data analysis, the traditional statistical procedure and ANNs technology both indicated that low light treatments and high sucrose concentrations are required for the highest kiwifruit microshoot proliferation under experimental conditions. However, this particular ANNs software is able to model and optimize the process to estimate the best conditions and does not need an extremely specialized background. The potential of the ANNs approach for analyzing plant biology processes, in this case, plant tissue culture data, is discussed.

Morphological anomalies in pollen tubes of Actinidia deliciosa (kiwi) exposed to 50 Hz magnetic field.

The role of the pollen grain, with respect to the reproductive process of higher plants, is to deliver the spermatic cells to the embryo sac for egg fertilisation. Delivery occurs through the pollen tube, a self produced organ that is generated when the pollen grain reaches the stigma surface. The effect of magnetic fields on pollen tube growth was reported in a recent publication by Germanà et al. Pollen tube growth is an interesting candidate for the detailed study of the effects of electromagnetic fields on cytoplasmic structures and organelles. In this research Actinidia deliciosa (kiwifruit) pollen grains were germinated in the presence of an alternating magnetic field (50 Hz). Our results, although of preliminary nature, show that pollen tube growth is affected by magnetic fields. The analysis of the observed anomalies in the pollen tube appear to be the result of changes in the ionic charges within the pollen tube cytoplasm.

Weak extremely high frequency microwaves affect pollen-tube emergence and growth in kiwifruit: pollen grain irradiation and water-mediated effects.

OBJECTIVE: This study was designed to evaluate the effects of weak-intensity extremely high frequency (EHF) microwaves in a model system-the plant organism pollen grain-lacking the placebo effect, available in large populations, to ensure accurate statistical analysis, and whose sensitivity is closely relevant to animal and human biology. DESIGN: This study was blinded using an in vitro pollen germination technique. SUBJECTS AND STUDY INTERVENTIONS: Pollen of kiwifruit (Actinidia deliciosa) was either directly irradiated or grown in a medium prepared with irradiated water, using a CromoStim 2000, (PromoPharma, Republic of San Marino) designed for EHF microwave resonance therapy (MRT). It produces weak intensity EHF radiations (40-78 GHz), either continuous wave (cw) or modulated, at a 10 Hz-frequency, with infrared (IR) carried to 635-950 nm, and with an impedance (IPD) of 10(-21) W/Hz cm(2) and a power supply from 0 to 20 mW. OUTCOME MEASUREMENTS: Pollen-tube emergence was expressed as a percent of grains producing a tube and tube elongation was measured at 4 hours of incubation by a turbidimetric assay (A(500)) of cultures, expressed as the net absorbance increase over time 0. RESULTS: At days 2 and 4 during aging, both percent of germination and tube growth significantly and consistently improved over controls in kiwifruit pollen grains irradiated for 30 minutes at day 0 at 10 Hz frequency with the CromoStim 2000. Highly significant effects, either stimulant or inhibitory, were also observed on kiwifruit pollen (stressed or not) growing in a medium prepared with water previously irradiated either cw or modulated. Irradiated water affected pollen germination immediately and even after several days following EHF treatment. CONCLUSIONS: Either direct or indirect EHF irradiation performed by the CromoStim 2000 is effective on pollen growth processes. In both cases, water seemed to play a primary role. According to the quantum electrodynamical coherence theory, our work could also have implications for homeopathy, suggesting a key to explain the efficacy of high dilutions and succussion procedures.