Carlo Andreotti

Transcriptional regulation of flavonoid biosynthesis in nectarine ( Prunus persica ) by a set of R2R3 MYB transcription factors

BackgroundFlavonoids such as anthocyanins, flavonols and proanthocyanidins, play a central role in fruit colour, flavour and health attributes. In peach and nectarine (Prunus persica) these compounds vary during fruit growth and ripening. Flavonoids are produced by a well studied pathway which is transcriptionally regulated by members of the MYB and bHLH transcription factor families. We have isolated nectarine flavonoid regulating genes and examined their expression patterns, which suggests a critical role in the regulation of flavonoid biosynthesis.ResultsIn nectarine, expression of the genes encoding enzymes of the flavonoid pathway correlated with the concentration of proanthocyanidins, which strongly increases at mid-development. In contrast, the only gene which showed a similar pattern to anthocyanin concentration was UDP-glucose-flavonoid-3-O-glucosyltransferase (UFGT), which was high at the beginning and end of fruit growth, remaining low during the other developmental stages. Expression of flavonol synthase (FLS1) correlated with flavonol levels, both temporally and in a tissue specific manner. The pattern of UFGT gene expression may be explained by the involvement of different transcription factors, which up-regulate flavonoid biosynthesis (MYB10, MYB123, and bHLH3), or repress (MYB111 and MYB16) the transcription of the biosynthetic genes. The expression of a potential proanthocyanidin-regulating transcription factor, MYBPA1, corresponded with proanthocyanidin levels. Functional assays of these transcription factors were used to test the specificity for flavonoid regulation.ConclusionsMYB10 positively regulates the promoters of UFGT and dihydroflavonol 4-reductase (DFR) but not leucoanthocyanidin reductase (LAR). In contrast, MYBPA1 trans-activates the promoters of DFR and LAR, but not UFGT. This suggests exclusive roles of anthocyanin regulation by MYB10 and proanthocyanidin regulation by MYBPA1. Further, these transcription factors appeared to be responsive to both developmental and environmental stimuli.

Induction of antimicrobial 3-deoxyflavonoids in pome fruit trees controls fire blight.

Abstract Fire blight, a devastating bacterial disease in pome fruits, causes severe economic losses worldwide. Hitherto, an effective control could only be achieved by using antibiotics, but this implies potential risks for human health, livestock and environment. A new approach allows transient inhibition of a step in the flavonoid pathway, thereby inducing the formation of a novel antimicrobial 3-deoxyflavonoid controlling fire blight in apple and pear leaves. This compound is closely related to natural phytoalexins in sorghum. The approach does not only provide a safe method to control fire blight: Resistance against different pathogens is also induced in other crop plants.

Enhancement of the bioactive compound content in strawberry fruits grown under iron and phosphorus deficiency

BACKGROUND Among berries, strawberry fruits are one of the richest natural sources of health-beneficial components such as micronutrients, antioxidants and phytochemicals. Strawberry quality depends greatly upon genotype, environmental factors, cultivation techniques and nutrient supply. This study aimed to assess the influence of phosphorus and iron deficiency on the bioactive compound content in strawberry fruits grown under hydroponic conditions. RESULTS Different nutrient supplies clearly influenced the qualitative parameters of strawberry fruits. Principal component analysis (PCA) showed that three homogeneous clusters could be identified. The three treatments (control, iron deficiency and phosphorus deficiency) differed especially because of their phenolic compounds and antioxidant potential, the strawberry fruits grown under Fe and P deficiency being richer in pelargonidin-3-glucoside, benzoic acids and flavonols than the control fruits. CONCLUSION Nutrient deficiency had a positive effect on nutritional parameters of strawberry fruits without impairing fruit yield and quality parameters such as acidity, firmness and total soluble solid content. The shaping of nutrient availability in the growing medium could thus be of help in producing an edible yield with the desired qualitative aspects and nutritional value.

Peach (Prunus persica L. Batsch) allergen-encoding genes are developmentally regulated and affected by fruit load and light radiation.

The fruits of Rosaceae species may frequently induce allergic reactions in both adults and children, especially in the Mediterranean area. In peach, true allergens and cross-reactive proteins may cause hypersensitive reactions involving a wide diversity of symptoms. Three known classes of allergenic proteins, namely, Pru p 1, Pru p 3, and Pru p 4, have been reported to be mostly involved, but an exhaustive survey of the proteins determining the overall allergenic potential, their biological functions, and the factors affecting the expression of the related genes is still missing. In the present study, the expression profiles of some selected genes encoding peach allergen isoforms were studied during fruit growth and development and upon different fruit load and light radiation regimens. The results indicate that the majority of allergen-encoding genes are expressed at their maximum during the ripening stage, therefore representing a potential risk for peach consumers. Nevertheless, enhancing the light radiation and decreasing the fruit load achieved a reduction of the transcription rate of most genes and a possible decrease of the overall allergenic potential at harvest. According to these data, new growing practices could be set up to obtain hypoallergenic peach fruits and eventually combined with the cultivation of hypoallergenic genotypes to obtain a significant reduction of the allergenic potential.

Indirect effect of glyphosate on wine fermentation studied by microcalorimetry

The use of herbicide such as glyphosate is a common practice in viticulture to limit nutrients and water competition between vine/weed plants. However, the impact of such herbicide on the resulting grapes juice quality and, later, on wine fermentation has not yet been proven. In this work, grapes of Vitis vinifera L. cv Gewürztraminer harvested from plants subjected to the weed control with glyphosate were analysed for their fermenting capacity by isothermal microcalorimetry after inoculation with Saccharomyces cerevisae. The resulting heat flow traces were fitted by two additive Gompertz functions and used to describe the yeast growth rate. The comparison of the fitting parameters showed that glyphosate decreased the heat generated by yeast growth. This effect was consistent with a change in the amino acids and sugars contents in grapes. However, the results also show that the impact of the herbicide on yeast fermentation can be partly overcome with an additional N fertilization (i.e. urea) in the vine. Microcalorimetry has revealed for the first time these effects on the fermenting process of grapes.

Use of Biostimulants for Organic Apple Production: Effects on Tree Growth, Yield, and Fruit Quality at Harvest and During Storage

The experiment was conducted during two consecutive seasons (years 2016 and 2017) in an organic apple orchard of the cultivar Jonathan. Several biostimulants were tested (10 in total), including humic acids, macro and micro seaweed extracts, alfalfa protein hydrolysate, amino acids alone or in combination with zinc, B-group vitamins, chitosan and a commercial product containing silicon. Treatments were performed at weekly intervals, starting from the end of May until mid-August. The macroseaweed extract was effective in stimulate tree growth potential in both years, as shown by a significantly larger leaf area (+20% as compared to control) and by an higher chlorophyll content and leaf photosynthetic rate in year 2016. As for the yield performances and apples quality traits at harvest (average fruit weight, soluble solids content, titratable acidity, and flesh firmness), they were generally affected by the different climatic conditions that characterized the two growing seasons (year 2017 being characterized by higher maximal and average temperatures and by limited rainfalls at the beginning of the season). Treatments with macroseaweed extract, B-group vitamins and alfalfa protein hydrolysate were able to significantly improve the intensity and extension of the red coloration of apples at harvest. Correspondingly, the anthocyanin content in the skin of apples treated with the same biostimulants resulted significantly higher than control, highlighting the potential influence of these substances on the synthesis of secondary metabolites in apple. The incidence of physiological disorders was also monitored during apple storage period. Amino acids plus zinc application was effective in reducing (more than 50%) the incidence of the “Jonathan spot,” the main post-harvest disorder for this cultivar.

Innovative light management to improve production sustainability, overall quality, and the phenolics composition of nectarine (Prunus persica cv. Stark Red Gold).

Summary This research was conducted under the framework of the ISAFRUIT Project and aimed to investigate the effects of different light micro-environments on the final overall quality of nectarine fruit production. Experiments were conducted in a commercial orchard of the nectarine (Prunus persica) ‘Stark Red Gold’ during 2006 and 2007. Reflective mulches were laid down in the inter-row spaces in mid-May. Those environmental conditions affected by mulching such as temperature and reflected light were monitored until fruit harvest. Fruit production per tree was enhanced by mulch-treatment in both years, but the differences were statistically significant only in 2006, when the average fruit weight was also enhanced. Nectarines became more ripe in the 2006 season, whereas no differences in the main fruit quality indices were detected in 2007.The concentrations of phenolic compounds in ripe nectarines were positively enhanced in both years. The increase in concentration of overall phenolic compounds (in mg 100 g−1 fresh weight) was calculated to be approx. 60% in 2006 and 2007, indicating an interesting improvement of the nutraceutical and anti-oxidant potential of nectarines. Experiments were also conducted using UV plus white light irradiation under controlled conditions. The accumulation of phenolic compounds, specifically anthocyanin concentrations, in nectarines previously screened using paper bags were determined at different times after irradiation. The results clearly indicated an inducing effect of UV plus white light irradiation on the synthesis and accumulation of anthocyanins in fruit skin. The consequences for the colour and health potential of nectarines are discussed.