Chitosan nano-biopolymer/Citrus paradisi peel oil delivery system enhanced shelf-life and postharvest quality of cherry tomato.

Grapefruit peel essential oil (CpEO) was loaded on chitosan (Cs) nano-biopolymer by ionic gelation method and its effect on physicochemical properties of cherry tomatoes was evaluated during 18 days of storage at 10 °C. The highest loading capacity and encapsulation efficiency were obtained from the weight ratio of 1:0.25 Cs to oil. TEM, DLS and FTIR were used to characterize the nanoparticles. The release of the oil from the nanoparticles followed the Fickian diffusion model. CpEO-CsNPs-CO and CpEO-CsNPs-RE treatments reduced ethylene production and respiration rate and indicated a significant and promising effect on increasing the level of antioxidant enzymes (CAT and POD), slowing down the loss of ascorbic acid and total phenolic content and consequently, maintaining antioxidant capacity. These treatments prevented a rapid decline in TSS and TA and an increase in lycopene and MDA level, and maintained the firmness, weight, and color of the fruits throughout storage period.

Pinpointing genomic regions associated with root system architecture in rice through an integrative meta-analysis approach.

KEY MESSAGE: Applying an integrated meta-analysis approach led to identification of meta-QTLs/ candidate genes associated with rice root system architecture, which can be used in MQTL-assisted breeding/ genetic engineering of root traits. Root system architecture (RSA) is an important factor for facilitating water and nutrient uptake from deep soils and adaptation to drought stress conditions. In the present research, an integrated meta-analysis approach was employed to find candidate genes and genomic regions involved in rice RSA traits. A whole-genome meta-analysis was performed for 425 initial QTLs reported in 34 independent experiments controlling RSA traits under control and drought stress conditions in the previous twenty years. Sixty-four consensus meta-QTLs (MQTLs) were detected, unevenly distributed on twelve rice chromosomes. The confidence interval (CI) of the identified MQTLs was obtained as 0.11-14.23 cM with an average of 3.79 cM, which was 3.88 times narrower than the mean CI of the original QTLs. Interestingly, 52 MQTLs were co-located with SNP peak positions reported in rice genome-wide association studies (GWAS) for root morphological traits. The genes located in these RSA-related MQTLs were detected and explored to find the drought-responsive genes in the rice root based on the RNA-seq and microarray data. Multiple RSA and drought tolerance-associated genes were found in the MQTLs including the genes involved in auxin biosynthesis or signaling (e.g. YUCCA, WOX, AUX/IAA, ARF), root angle (DRO1-related genes), lateral root development (e.g. DSR, WRKY), root diameter (e.g. OsNAC5), plant cell wall (e.g. EXPA), and lignification (e.g. C4H, PAL, PRX and CAD). The genes located within both the SNP peak positions and the QTL-overview peaks for RSA are suggested as novel candidate genes for further functional analysis. The promising candidate genes and MQTLs can be used as basis for genetic engineering and MQTL-assisted breeding of root phenotypes to improve yield potential, stability and performance in a water-stressed environment.

Chitosan nanoparticles-loaded Citrus aurantium essential oil: a novel delivery system for preserving the postharvest quality of Agaricus bisporus.

BACKGROUND: One of the main problems in the button mushroom industry is the rapid deterioration of fruit bodies after harvest. Today, nanotechnology has become a more reliable technique to improve the quality of products in food packaging. In the present study, the effectiveness of chitosan nanoparticles containing Citrus aurantium essential oil on postharvest quality of white button mushroom was examined and compared to essential oil fumigation and control treatments. RESULTS: Based on high-resolution transmission electron microscopy and dynamic light scattering, nanoparticles exhibited a spherical shape of 20-60 nm diameter. The results revealed that the application of chitosan nanoparticles loaded with C. aurantium oil significantly decelerated the rate of color change, weight loss and firmness compared to fumigation with essential oil and control treatments. Treatment of fruit bodies with chitosan nanoparticles loaded with C. aurantium oil promoted the accumulation of phenolic compounds and ascorbic acid, and resulted in increases in catalase and superoxide dismutase and a decrease in polyphenol oxidase activities, as the highest antioxidant capacity was observed after 15 days of cold storage. CONCLUSION: This present research demonstrates that gradual release of C. aurantium essential oil from chitosan nanoparticles could be an effective and practical method for extending the shelf life of white button mushroom up to 15 days without significant decrease in antioxidant capacity. © 2018 Society of Chemical Industry.

Development and characterization of nano biopolymer containing cumin oil as a new approach to enhance antioxidant properties of button mushroom.

The aim of present study was to design a controlled release system using Cuminum cyminum essential oil loaded chitosan nanoparticles (CEO-CSNPs) and evaluate its effect on catalase (CAT), glutathione reductase (GR), peroxidase (POD) activity and ascorbic acid content of Agaricus bisporus fruit bodies during 20days of storage at 4°C. The success of encapsulation was evaluated through TEM, DLS, FT-IR and spectrophotometry and its release behavior was studied in buffer solutions with different pH. The CEO-CSNPs exhibited an average size of 30 to 80nm with a spherical shape. Encapsulation efficiency (EE) and loading capacity (LC) were 4.46 to 17.89% and 2.47 to 6.68%, respectively. The highest CAT and GR activity was observed in samples packed with CEO-CSNPs after 15days of storage. In contrast, POD activity reached a peak at the end of storage in control samples. Interestingly, after 20days the level of POD increased 17.13% in CEO-CSNPs treatment, as compared with the initial level of the mentioned enzyme. At the end of storage, ascorbic acid content in samples treated with CEO-CSNPs was significantly higher than that detected in the control samples. In brief, application of CEO loaded chitosan nanoparticles in packages effectively increased the antioxidant activity in white button mushroom and showed promising results for extending the shelf life of treated samples.

Metal oxides as a biostimulator for upregulation of genes involved in the biosynthesis of Rebaudioside- A.

Stevia rebaudiana Bertoni is a kind of perennial medicinal plant with sweetening properties which belongs to Asteraceae family. Its leaves with fundamental glycoside compounds consist of both a sugar part and a non-sugar sector. One of the glycoside compounds is Rebaudioside- A which has a greater importance in business. This experiment was conducted to evaluate the effects of Ag2O, CrO3, PbO, Fe2O3, BaO and TiO2 on the expression pattern of these genes in the Stevia rebaudiana. Rebaudioside- A biosynthesis was repeated 3 times with concentrations of 50, 100 and 200µM. Also, the results of the study pertaining to the expression pattern of these genes showed that metal oxides have led to an increase in the expression of the regulatory genes involved in biosynthesis of Rebaudioside- A. According to the expression profile, it was found that its effect on DXR, HDS, HDR, IDI and CPPS genes is more than other genes. The peak HPLC indicated for stevioside and Rebaudioside- A represents an increase in the production of this active ingredient under the influence of all treatments. In general, the expression profile of these genes and the results of HPLC show that whatever going to the end of the pathway of production of Rebaudioside- A, the activity of the enzymes increases under the influence of these treatments, and eventually a greater amount of Rebaudioside- A will be produced. This process shows that metal oxides will have a significant effect on the biosynthesis of Rebaudioside- A.

Genome scanning for identification and mapping of receptor-like kinase (RLK) gene superfamily in Solanum tuberosum.

Receptor-like kinases (RLKs) are a key class of genes that contribute to diverse phenomena from plant development to defense responses. The availability of completed potato genome sequences provide an excellent opportunity to identify and characterize RLK gene superfamily in this lineage. We identified 747 non-redundant RLK genes in the potato genome that were classified into 52 subfamilies, of which 58% members organized into tandem repeats. Nine of potato RLK subfamilies organized into tandem repeats. Also, six subfamilies exhibited lineage-specific expansion compared to Arabidopsis. The majority of RLK genes were physically organized within heterogeneous and homogeneous clusters on chromosomes and were unevenly distributed on the genome. Chromosome 2, 3 and 7 contained the highest number of RLK genes and the most underrepresented chromosomes were chromosome 8, 10 and 11. Taken together, our results provide a framework for future efforts on comparative, evolutionary and functional studies of the members of RLK superfamily.

Biochemical characterization of the tomato phosphatidylinositol-specific phospholipase C (PI-PLC) family and its role in plant immunity.

Plants possess effective mechanisms to quickly respond to biotic and abiotic stresses. The rapid activation of phosphatidylinositol-specific phospholipase C (PLC) enzymes occurs early after the stimulation of plant immune-receptors. Genomes of different plant species encode multiple PLC homologs belonging to one class, PLCζ. Here we determined whether all tomato homologs encode active enzymes and whether they can generate signals that are distinct from one another. We searched the recently completed tomato (Solanum lycopersicum) genome sequence and identified a total of seven PLCs. Recombinant proteins were produced for all tomato PLCs, except for SlPLC7. The purified proteins showed typical PLC activity, as different PLC substrates were hydrolysed to produce diacylglycerol. We studied SlPLC2, SlPLC4 and SlPLC5 enzymes in more detail and observed distinct requirements for Ca(2+) ions and pH, for both their optimum activity and substrate preference. This indicates that each enzyme could be differentially and specifically regulated in vivo, leading to the generation of PLC homolog-specific signals in response to different stimuli. PLC overexpression and specific inhibition of PLC activity revealed that PLC is required for both specific effector- and more general "pattern"-triggered immunity. For the latter, we found that both the flagellin-triggered response and the internalization of the corresponding receptor, Flagellin Sensing 2 (FLS2) of Arabidopsis thaliana, are suppressed by inhibition of PLC activity. Altogether, our data support an important role for PLC enzymes in plant defence signalling downstream of immune receptors. This article is part of a Special Issue entitled: Plant Lipid Biology edited by Kent D. Chapman and Ivo Feussner.

Novel applications of motif-directed profiling to identify disease resistance genes in plants.

BACKGROUND: Molecular profiling of gene families is a versatile tool to study diversity between individual genomes in sexual crosses and germplasm. Nucleotide binding site (NBS) profiling, in particular, targets conserved nucleotide binding site-encoding sequences of resistance gene analogs (RGAs), and is widely used to identify molecular markers for disease resistance (R) genes. RESULTS: In this study, we used NBS profiling to identify genome-wide locations of RGA clusters in the genome of potato clone RH. Positions of RGAs in the potato RH and DM genomes that were generated using profiling and genome sequencing, respectively, were compared. Largely overlapping results, but also interesting discrepancies, were found. Due to the clustering of RGAs, several parts of the genome are overexposed while others remain underexposed using NBS profiling. It is shown how the profiling of other gene families, i.e. protein kinases and different protein domain-coding sequences (i.e., TIR), can be used to achieve a better marker distribution. The power of profiling techniques is further illustrated using RGA cluster-directed profiling in a population of Solanum berthaultii. Multiple different paralogous RGAs within the Rpi-ber cluster could be genetically distinguished. Finally, an adaptation of the profiling protocol was made that allowed the parallel sequencing of profiling fragments using next generation sequencing. The types of RGAs that were tagged in this next-generation profiling approach largely overlapped with classical gel-based profiling. As a potential application of next-generation profiling, we showed how the R gene family associated with late blight resistance in the SH*RH population could be identified using a bulked segregant approach. CONCLUSIONS: In this study, we provide a comprehensive overview of previously described and novel profiling primers and their genomic targets in potato through genetic mapping and comparative genomics. Furthermore, it is shown how genome-wide or fine mapping can be pursued by choosing different sets of profiling primers. A protocol for next-generation profiling is provided and will form the basis for novel applications. Using the current overview of genomic targets, a rational choice can be made for profiling primers to be employed.