Methyl jasmonate-loaded composite biofilm sustainably alleviates chilling lignification of loquat fruit during postharvest storage.

In this work, the MeJA-loaded gelatin/pullulan/chitosan composite biofilm was prepared to inhibit the chilling lignification of the loquat fruit during storage at 0 °C. The firmness and lignin content were decreased by 89 % and 81.77 % after MeJA-loaded biofilm treatment. Malondialdehyde (MDA) production was almost completely suppressed and chilling injury of loquat fruit was significantly reduced. Enzyme activity results show that the biofilm alleviated chilling lignification mainly by inhibiting peroxidase (POD) activity in the phenylpropanoid pathway (PCCs = 0.715, with lignin content). Also, the conventional MeJA vapor treatment only alleviated lignification on day 3, but the biofilm treatment had a better and more sustained effect throughout the whole storage due to its sustained release ability. Besides, the biofilm had good mechanical properties, transparency and water vapor transmission rate. This work indicates that loading preservatives into biofilms has a promising application prospect for inhibiting the postharvest quality deterioration of fruit and vegetables.

Application of atomic force microscopy in the characterization of fruits and vegetables and associated substances toward improvement in quality, preservation, and processing: nanoscale structure and mechanics perspectives.

Fruits and vegetables are essential horticultural crops for humans. The quality of fruits and vegetables is critical in determining their nutritional value and edibility, which are decisive to their commercial value. Besides, it is also important to understand the changes in key substances involved in the preservation and processing of fruits and vegetables. Atomic force microscopy (AFM), a powerful technique for investigating biological surfaces, has been widely used to characterize the quality of fruits and vegetables and the substances involved in their preservation and processing from the perspective of nanoscale structure and mechanics. This review summarizes the applications of AFM to investigate the texture, appearance, and nutrients of fruits and vegetables based on structural imaging and force measurements. Additionally, the review highlights the application of AFM in characterizing the morphological and mechanical properties of nanomaterials involved in preserving and processing fruits and vegetables, including films and coatings for preservation, bioactive compounds for processing purposes, nanofiltration membrane for concentration, and nanoencapsulation for delivery of bioactive compounds. Furthermore, the strengths and weaknesses of AFM for characterizing the quality of fruits and vegetables and the substances involved in their preservation and processing are examined, followed by a discussion on the prospects of AFM in this field.

The calcium-mediated homogalacturonan pectin complexation in cell walls contributes the firmness increase in loquat fruit during postharvest storage.

INTRODUCTION: Postharvest textural changes in fruit are mainly divided into softening and lignification. Loquat fruit could have severe lignification with increased firmness during postharvest storage. Pectin is mainly associated with the postharvest softening of fruit, but some studies also found that pectin could be involved in strengthening the mechanical properties of the plant. OBJECTIVES: This study focused on characterizing the dynamics of pectin and its complexation in the cell wall of lignified loquat fruit during postharvest storage, and how these changes could influence fruit firmness. METHODS: The homogalacturonan (HG) pectin in the cell wall of loquat fruit was identified using monoclonal antibodies. An oligogalacturonide (OG) probe was used to label the egg-box structure formed by Ca2+ cross-linking with low-methylesterified HG. An exogenous injection was used to verify the role of egg-box structures in the firmness increase in loquat fruit. RESULTS: The JIM5 antibody revealed that low-methylesterified HG accumulated in the tricellular junctions and middle lamella of loquat fruit that had severe lignification symptoms. The pectin methylesterase (PME) activity increased during the early stages of storage at 0 °C, and the calcium-pectate content and flesh firmness constantly increased during storage. The OG probe demonstrated the accumulation of egg-box structures at the cellular level. The exogenous injection of PME and Ca2+ into the loquat flesh led to an increase in firmness with more low-methylesterified HG and egg-box structure signals. CONCLUSION: PME-mediated demethylesterification generated large amounts of low-methylesterified HG in the cell wall. This low-methylesterified HG further cross-linked with Ca2+ to form egg-box structures. The pectin-involved complexations then contributed to the increased firmness in loquat fruit. Overall, besides being involved in fruit softening, pectin could also be involved in strengthening the mechanical properties of postharvest fruit. This study provides new ideas for obtaining a better texture of postharvest loquat fruits based on pectin regulation.

Virome of Rhipicephalus ticks by metagenomic analysis in Guangdong, southern China.

Tick-borne viruses (TBVs) have increasingly caused a global public health concern. This study collected Rhipicephalus ticks in Guangdong, southern China to identify RNA viruses. Meta-transcriptome analysis revealed the virome in Rhipicephalus ticks, resulting in the discovery of 10 viruses, including Lihan tick virus, Brown dog tick phlebovirus 1 and 2 in the family Phenuiviridae, Mivirus and Wuhan tick virus 2 in the family Chuviridae, Wuhan tick virus 1 in the family Rhabdoviridae, bovine hepacivirus in the family Flaviviridae, Guangdong tick quaranjavirus (GTQV) in the family Orthomyxoviridae, Guangdong tick orbivirus (GTOV) in the family Reoviridae, and Guangdong tick Manly virus (GTMV) of an unclassified family. Phylogenetic analysis showed that most of these TBVs were genetically related to the strains in countries outside China, and GTQV, GTOV, and GTMV may represent novel viral species. These findings provided evidence of the long-distance spread of these TBVs in Guangdong, southern China, suggesting the necessity and importance of TBV surveillance.

Hybrid Label-Free Molecular Microscopies for Simultaneous Visualization of Changes in Cell Wall Polysaccharides of Peach at Single- and Multiple-Cell Levels during Postharvest Storage.

Softening of fruit during the postharvest storage, which is mainly associated with both compositional and spatial changes of polysaccharides within cell wall, affects the texture and quality of fruit. Current research on the fruit softening mechanism lacks an understanding of the overall softening at the cell level. The objective of this work was to investigate the change in the spatial distribution of cell wall polysaccharides in peach flesh cells at both single- and multiple-cell levels in a label-free way during the postharvest storage. Nonmelting peaches (Prunus persica L. Batsch cv."Zhonghuashoutao") at commercial maturity were stored at 0 °C and 20 °C. Firmness measurement and chemical analysis were performed at each storage time. In addition, three molecular imaging techniques, namely confocal Raman microspectroscopy (CRM), Fourier transform infrared microspectroscopy (FTIRM), and stimulated Raman scattering microscopy (SRS) were used to visualize changes in the spatial distribution of cell wall polysaccharides of peach fruit in a label-free way during the postharvest storage. The combination of CRM and FTIRM provided complementary spectral information to visualize the spatial changes of cellulose, hemicellulose, and pectin in the cell wall of peach flesh during softening at the single-cell level, and found that the cell wall polysaccharides tended to be concentrated in the cell corner of parenchymal cells at the late stage. Furthermore, SRS, which is an ultrafast Raman imaging technique (approximately three or four orders of magnitude faster than CRM), was used for high-throughput cell wall phenotypes measurement. Different degradation degrees of parenchymal cells during fruit softening were found based on the gray-scale statistical analysis of SRS data. In general, cell wall polysaccharides decreased during softening and tended to be concentrated in the cell corner for most parenchymal cells at the late stage, but there were also some cells not in line with the whole softening trends. The results show that there were differences in the content and spatial changes of cell wall polysaccharides among parenchymal cells of peach fruit during the softening process, and the hybrid use of CRM, FTIRM, and SRS is a promising method for simultaneous visualization of changes in cell wall polysaccharides of peach.

Fabrication of lysozyme/κ-carrageenan complex nanoparticles as a novel carrier to enhance the stability and in vitro release of curcumin.

In this manuscript, lysozyme/κ-carrageenan (LYS-CRG) complexes were prepared and used to encapsulate curcumin. The LYS-CRG complexes demonstrate good encapsulation of curcumin (CUR), and the encapsulation efficiency (EE) and loading capacity (LC) reach 96.2% and 2.31%, respectively. The encapsulated CUR has high antioxidant activity, while the thermal stability and photostability of CUR are also increased. The LYS-CRG complexes could effectively improve the storage stability of CUR and increase its retention rate. In simulated gastric fluid, only 17.91% CUR in the CUR-LYS-CRG complex nanoparticles is released in 3 h, while in the simulated intestinal fluid, the CUR release rate quickly reaches 62.56% in 1.5 h. The release rate tends to be stable within 1.5 h to 3 h and the final release rate reaches 67.23%, suggesting that the formation of CUR-LYS-CRG complex nanoparticles does not affect CUR release in the simulated intestinal fluid.

6 Gbps real-time optical quantum random number generator based on vacuum fluctuation.

We demonstrate a 6 Gbps real-time optical quantum random number generator by measuring vacuum fluctuation. To address the common problem that speed gap exists between fast randomness generation and slow randomness extraction in most high-speed real-time quantum random number generator systems, we present an optimized extraction algorithm based on parallel implementation of Toeplitz hashing to reduce the influence of classical noise due to the imperfection of devices. Notably, the real-time rate of randomness extraction we have achieved reaches the highest speed of 12 Gbps by occupying less computing resources, and the algorithm has the ability to support hundreds of Gbps randomness extraction. By assuming that the eavesdropper with complete knowledge of the classical noise, our generator has a randomness generation speed of 6.83 Gbps and this supports the generation of 6 Gbps information-theoretically provable quantum random numbers, which are output in real-time through peripheral component interconnect express interface.

Quantitative visualization of pectin distribution maps of peach fruits.

Pectin content is an important quality index of fruits, as pectin content undergoes significant changes during the peach ripening process. The commonly used carbazole colorimetry method measures only the total content value of each kind of pectin for each pulp sample and cannot provide distribution maps of the pectin contents for the whole fruit pulp. This work used the hyperspectral imaging technique to quantitatively visualize the distribution maps of pectin contents inside peach pulp at the pixel level. The protopectin contents were well predicted, with the best residual predictive deviation of 2.264, whereas the predictions of the water-soluble pectin and the total pectin contents were not satisfied. On the basis of the best predictive model, the distribution maps of the protopectin contents were quantitatively visualized. A histogram of an example protopectin distribution revealed the existence of a wide range of protopectin contents in peach pulp. Our results show that hyperspectral imaging holds promise as a powerful alternative to the carbazole colorimetry method for measuring the spatial variations in the protopectin distribution inside peach pulp. The distribution maps could be used as a maturity indicator to understand and evaluate the ripening process of peach fruit in depth.

Fine mapping of the qLOP2 and qPSR2-1 loci associated with chilling stress tolerance of wild rice seedlings.

KEY MESSAGE: Using leaf osmotic potential and plant survival rate as chilling-tolerant trait indices, we identified two major quantitative trait loci qLOP2 and qPSR2 - 1 (39.3-kb region) and Os02g0677300 as the cold-inducible gene for these loci. Chilling stress tolerance (CST) at the seedling stage is an important trait affecting rice production in temperate climate and high-altitude areas. To identify quantitative trait loci (QTLs) associated with CST, a mapping population consisting of 151 BC(2)F(1) plants was constructed by using chilling-tolerant Dongxiang wild rice (Oryza rufipogon Griff.) as a donor parent and chilling-sensitive indica as a recurrent parent. With leaf osmotic potential (LOP) and plant survival rate (PSR) as chilling-tolerant trait indexes, two major QTLs, qLOP2 (LOD = 3.8) and qPSR2-1 (LOD = 3.3), were detected on the long arm of chromosome 2 by composite interval mapping method in QTL Cartographer software, which explained 10.1 and 12.3% of the phenotypic variation, respectively. In R/QTL analyzed result, their major effects were also confirmed. Using molecular marker RM318 and RM106, qLOP2 and qPSR2-1 have been introgressed into chilling-sensitive varieties (93-11 and Yuefeng) by marker-assisted selection procedure (MAS), which resulted in 16 BC(5)F(3) BILs that chilling tolerance have significantly enhanced compare with wild-type parents (P < 0.01). Therefore, two large segregating populations of 11,326 BC(4)F(2) and 8,642 BC(4)F(3) were developed to fine mapping of qLOP2 and qPSR2-1. Lastly, they were dissected to a 39.3-kb candidate region between marker RM221 and RS8. Expression and sequence analysis results indicated that Os02g0677300 was a cold-inducible gene for these loci. Our study provides novel alleles for improving rice CST by MAS and contributes to the understanding of its molecular mechanisms.

Fine mapping of qRC10-2, a quantitative trait locus for cold tolerance of rice roots at seedling and mature stages.

UNLABELLED: Cold stress causes various injuries to rice seedlings in low-temperature and high-altitude areas and is therefore an important factor affecting rice production in such areas. In this study, root conductivity (RC) was used as an indicator to map quantitative trait loci (QTLs) of cold tolerance in Oryza rufipogon Griff., Dongxiang wild rice (DX), at its two-leaf stage. The correlation coefficients between RC and the plant survival rate (PSR) at the seedling and maturity stages were -0.85 and -0.9 (P = 0.01), respectively, indicating that RC is a reliable index for evaluating cold tolerance of rice. A preliminary mapping group was constructed from 151 BC2F1 plants using DX as a cold-tolerant donor and the indica variety Nanjing 11 (NJ) as a recurrent parent. A total of 113 codominant simple-sequence repeat (SSR) markers were developed, with a parental polymorphism of 17.3%. Two cold-tolerant QTLs, named qRC10-1 and qRC10-2 were detected on chromosome 10 by composite interval mapping. qRC10-1 (LOD = 3.1, RM171-RM1108) was mapped at 148.3 cM, and qRC10-2 (LOD = 6.1, RM25570-RM304) was mapped at 163.3 cM, which accounted for 9.4% and 32.1% of phenotypic variances, respectively. To fine map the major locus qRC10-2, NJ was crossed with a BC4F2 plant (L188-3), which only carried the QTL qRC10-2, to construct a large BC5F2 fine-mapping population with 13,324 progenies. Forty-five molecular markers were designed to evenly cover qRC10-2, and 10 markers showed polymorphisms between DX and NJ. As a result, qRC10-2 was delimited to a 48.5-kb region between markers qc45 and qc48. In this region, Os10g0489500 and Os10g0490100 exhibited different expression patterns between DX and NJ. Our results provide a basis for identifying the gene(s) underlying qRC10-2, and the markers developed here may be used to improve low-temperature tolerance of rice seedling and maturity stages via marker-assisted selection (MAS). KEY MESSAGE: With root electrical conductivity used as a cold-tolerance index, the quantitative trait locus qRC10-2 was fine mapped to a 48.5-kb candidate region, and Os10g0489500 and Os10g0490100 were identified as differently expressed genes for qRC10-2.

[Effects of cadmium stress on photosynthetic functions of strawberry].

With pot experiment, this paper studied the effects of cadmium stress on the leaf chlorophyll content, photosynthetic rate, stomatal conductance, transpiration rate, and intercellular CO2 concentration of strawberry. The results showed that cadmium reduced the chlorophyll content, and changed the chlorophyll a/b ratio. Cadmium reduced the photosynthetic rate and stomatal conductance, though they were increased by low concentration cadmium at the initial stage of cadmium stress. Cadmium also reduced the transpiration rate and intercellular CO2 concentration, but the decrement of intercellular CO2 concentration was relatively less.

Some properties of the allantoate amidohydrolase from French bean seedlings.

Allantoate degradation was demonstrated in the extracts of ungerminated seeds and roots, stems and leaves in germinated seedlings of French bean (Phaseolus vulgaris L.). Activity of allantoate-degrading enzyme could only be measured when phenylhydrazine was included in the assay mixture. Partial purification of allantoate-degrading enzyme from seedlings was performed and two fractions with allantoate-degrading enzyme activity were obtained. The molecular mass of the first fraction was over 200 kD and that of the second one was 13.5 kD. The allantoate-degrading enzyme with small molecular weight contained no activity of either ureidoglycolate-degrading enzyme or urease. From the stoichiometry of the reaction catalyzed by the allantoate-degrading enzyme with small molecular weight it followed that the enzyme was allantoate amidohydrolase (EC 3.5.3.9). The optimal pH for the allantoate amidohydrolase was 8.5. Mn(2+) ions were essential for enzymatic activity. Glyoxylate and glycolate strongly inhibited the enzyme activity. The lysine and tryptophan residues were essential to the enzymatic catalysis; thiol group and tyrosyl residues were not involved in the enzyme catalysis.

[Content and extractability of heavy metals in cultivated soil in Fujian province].

The total and extractable contents of 7 heavy metals in cultivated soil in Fujian Province were determined. Statistical results indicated that the cultivated soil in Fujian Province was polluted by heavy metals, but different heavy metals caused different pollution levels. The extractable contents of heavy metals accounted for 10.0 to 52.2% of total contents, varying with different heavy metals. There was a significantly positive correlation between total and extractable content of Cu, Zn, Cd, Pb, and Ni. Besides, Zn, Cd, Pb and As had a significantly positive correlation to each other, while only Zn had a significantly positive correlation to Ni, and Cu and Hg were not significantly correlated to any of other heavy metals.