Meta-analysis of RNA-Seq studies reveals genes with dominant functions during flower bud endo- to eco-dormancy transition in Prunus species.

In deciduous fruit trees, entrance into dormancy occurs in later summer/fall, concomitantly with the shortening of day length and decrease in temperature. Dormancy can be divided into endodormancy, ecodormancy and paradormancy. In Prunus species flower buds, entrance into the dormant stage occurs when the apical meristem is partially differentiated; during dormancy, flower verticils continue their growth and differentiation. Each species and/or cultivar requires exposure to low winter temperature followed by warm temperatures, quantified as chilling and heat requirements, to remove the physiological blocks that inhibit budburst. A comprehensive meta-analysis of transcriptomic studies on flower buds of sweet cherry, apricot and peach was conducted, by investigating the gene expression profiles during bud endo- to ecodormancy transition in genotypes differing in chilling requirements. Conserved and distinctive expression patterns were observed, allowing the identification of gene specifically associated with endodormancy or ecodormancy. In addition to the MADS-box transcription factor family, hormone-related genes, chromatin modifiers, macro- and micro-gametogenesis related genes and environmental integrators, were identified as novel biomarker candidates for flower bud development during winter in stone fruits. In parallel, flower bud differentiation processes were associated to dormancy progression and termination and to environmental factors triggering dormancy phase-specific gene expression.

Metabolic features underlying the response of sweet cherry fruit to postharvest UV-C irradiation.

The impact of ultraviolet-C (UV-C) irradiation on sweet cherry fruit was studied. Following harvest, fruits (cv. Sweetheart) were exposed to different doses of UV-C (0, 1.2, 3.0 or 6.0 kJ m-2) and then cold stored (0 °C) for 10 days. Treatments with UV-C delayed most ripening features and reduced pitting symptoms, particularly following prolonged UV-C application. Also, application of the highest UV-C dose inhibited pectin degradation and delayed skin resistance to penetration. An activation of antioxidants capacity and bioactive compounds, such as flavonoids and phenolics was observed. Illumination with UV-C diminished respiration and altered metabolite profile in whole fruit and skin samples. Several amino acids (eg., threonine and aspartate), sugars, (eg., glucose and fructose) and alcohols (e.g., inositol and mannitol) were modulated by long-term UV-C treatment in whole cherry fruit. Various metabolites, including malate, galacturonate, oxoproline and glutamine were also modulated by UV-C skin tissue. These data enhance our understanding of UV-C function in fruit biology.

Transcriptomic analysis of light-dependent anthocyanin accumulation in bicolored cherry fruits.

Sweet cherry (Prunus avium L.) fruits are classified into dark-red and bicolored cultivars based on their anthocyanin contents; however, the mechanisms regulating the accumulation of these pigments are unclear. Here, we reveal that anthocyanin accumulation is highly dependent on light in bicolored 'Rainier' cherries, while it is only slightly light dependent in the dark-red 'Hongdeng' fruits. To reveal the transcriptional mechanisms regulating light-dependent anthocyanin accumulation in bicolored 'Rainier' cherries, we sequenced the transcriptomes of fruits grown in light or in darkness. Genes encoding the anthocyanin biosynthesis enzymes chalcone synthase, chalcone isomerase, flavanone 3-hydroxylase, and flavonoid 3'-hydroxylase were significantly upregulated by light in the bicolored fruits. Most of the differentially expressed regulatory genes were known to be involved in the light or hormone signal transduction pathways, such as those encoding protein phosphatase 2Cs, PHYTOCHROME INTERACTING FACTOR 3, phytochromes, and ELONGATED HYPOCOTYL 5. The expression levels of 32 highly expressed transcription factors were found to be significantly altered by light in the bicolored fruits, including members of the basic leucine zipper, R2R3-MYB, and WRKY transcription factor families. A co-expression network analysis further revealed that many of the light-regulated genes were co-expressed with genes involved in the abscisic acid and gibberellic acid signaling pathways, suggesting that these phytohormones play important roles in light-dependent anthocyanin biosynthesis. Together, our data reveal multiple roles for light in regulating anthocyanin biosynthesis in differently colored cherries.

Effect of UV-C Radiation, Ultra-Sonication Electromagnetic Field and Microwaves on Changes in Polyphenolic Compounds in Chokeberry (Aronia melanocarpa).

Chokeberry fruits are highly valued for their high content of polyphenolic compounds. The use of such abiotic stress factors as UV-C radiation, an electromagnetic field, microwave radiation, and ultrasound, at different operation times, caused differentiation in the contents of anthocyanins, phenolic acids, flavonols, and flavan-3-ols. Samples were analyzed for contents of polyphenolics with ultra-performance liquid chromatography and photodiode detector-quadrupole/time-of-flight mass spectrometry (UPLC-PDA-MS/MS). The analysis showed that after exposure to abiotic stress factors, the concentration of anthocyanins ranged from 3587 to 6316 mg/100 g dry matter (dm) that constituted, on average, 67.6% of all identified polyphenolic compounds. The second investigated group included phenolic acids with the contents ranging between 1480 and 2444 mg/100 g dm (26.5%); then flavonols within the range of 133 to 243 mg/100 g dm (3.7%), and finally flavan-3-ols fluctuated between 191 and 369 mg/100 g dm (2.2%). The use of abiotic stress factors such as UV-C radiation, microwaves and ultrasound field, in most cases contributed to an increase in the content of the particular polyphenolic compounds in black chokeberry. Under the influence of these factors, increases were observed: in anthocyanin content, of 22%; in phenolic acids, of 20%; in flavonols, of 43%; and in flavan-3-ols, of 30%. Only the use of the electromagnetic field caused a decrease in the content of the examined polyphenolic compounds.

The sweet cherry (Prunus avium) FLOWERING LOCUS T gene is expressed during floral bud determination and can promote flowering in a winter-annual Arabidopsis accession.

KEY MESSAGE: FT gene is expressed in leaves and buds and is involved in floral meristem determination and bud development in sweet cherry. In woody fruit perennial trees, floral determination, dormancy and bloom, depends on perception of different environmental and endogenous cues which converge to a systemic signaling gene known as FLOWERING LOCUS T (FT). In long-day flowering plants, FT is expressed in the leaves on long days. The protein travels through the phloem to the shoot apical meristem, where it induces flower determination. In perennial plants, meristem determination and flowering are separated by a dormancy period. Meristem determination takes place in summer, but flowering occurs only after a dormancy period and cold accumulation during winter. The roles of FT are not completely clear in meristem determination, dormancy release, and flowering in perennial plants. We cloned FT from sweet cherry (Prunus avium) and analyzed its expression pattern in leaves and floral buds during spring and summer. Phylogenetic analysis shows high identity of the FT cloned sequence with orthologous genes from other Rosaceae species. Our results show that FT is expressed in both leaves and floral buds and increases when the daylight reached 12 h. The peak in FT expression was coincident with floral meristem identity genes expression and morphological changes typical of floral meristem determination. The Edi-0 Arabidopsis ecotype, which requires vernalization to flower, was transformed with a construct for overexpression of PavFT. These transgenic plants showed an early-flowering phenotype without cold treatment. Our results suggest that FT is involved in floral meristem determination and bud development in sweet cherry. Moreover, we show that FT is expressed in both leaves and floral buds in this species, in contrast to annual plants.

Effect of spatial coherence of light on the photoregulation processes in cells.

The effect of the statistical properties of light on the value of the photoinduced reaction of the biological objects, which differ in the morphological and physiological characteristics, the optical properties, and the size of cells, was studied. The fruit of apple trees, the pollen of cherries, the microcuttings of blackberries in vitro, and the spores and the mycelium of fungi were irradiated by quasimonochromatic light fluxes with identical energy parameters but different values of coherence length and radius of correlation. In all cases, the greatest stimulation effect occurred when the cells completely fit in the volume of the coherence of the field, while both temporal and spatial coherence have a significant and mathematically certain impact on the physiological activity of cells. It was concluded that not only the spectral, but also the statistical (coherent) properties of the acting light play an important role in the photoregulation process.

Effect of phytosanitary irradiation and methyl bromide fumigation on the physical, sensory, and microbiological quality of blueberries and sweet cherries.

BACKGROUND: The objective of this study was to determine whether irradiation could serve as a suitable phytosanitary treatment alternative to methyl bromide (MB) fumigation for blueberries and sweet cherry and also to determine the effect of phytosanitary irradiation treatment on survival of Salmonella spp. and Listeria monocytogenes on these fruit. 'Bluecrop' blueberries (Vaccinium corymbosum) and 'Sweetheart' cherries (Prunus avium) were irradiated at 0.4 kGy or fumigated with methyl bromide and evaluated for quality attributes during storage. RESULTS: Irradiation caused an immediate decrease in firmness of both fruit without further significant change during storage. Fumigated fruit, in contrast, softened by 11-14% during storage. Irradiation did not adversely affect blueberry and cherry shelf-life. MB fumigation did not impact blueberry and cherry quality attributes initially; however, fumigated fruit exhibited greater damage and mold growth than the control and irradiated samples during storage. Irradiation at 400 Gy resulted in a ∼1 log CFU g(-1) reduction in Salmonella spp. and Listeria monocytogenes counts, indicating that this treatment cannot significantly enhance safety. CONCLUSION: This study indicates that irradiation at a target dose of 0.4 kGy for phytosanitary treatment does not negatively impact blueberry and cherry quality and can serve as an alternative to methyl bromide fumigation. © 2016 Society of Chemical Industry.