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.

Weinan Huang,Di Wu,Minbiao Ji,Yating Nie,Yifan Yang,Changqing Zhu,Nan Zhu,Kunsong Chen

doi:10.3390/cells9030761

Weinan Huang, Di Wu + Show 6 more

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https://doi.org/10.3390/cells9030761

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Journal: Cells	Publication Date: Mar 20, 2020
Citations: 14	License type: CC BY 4.0

Affiliation: Zhejiang University

Abstract

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.

Highlights

Peach, as one of the most favored fruits among consumers worldwide, is rich in nutrition and good flavor
The chemical analysis found that the contents of three major cell wall polysaccharides, cellulose, hemicellulose, and total pectin, and two pectin fractions (CSP and diluted alkali soluble pectins (DASP)) decreased during the postharvest storage
Based on the complement of confocal Raman microspectroscopy (CRM) and Fourier transform infrared microspectroscopy (FTIRM) label-free hyperspectral molecular images, the content distribution of cellulose, hemicellulose, and pectin in the cell wall of peach flesh was visualized simultaneously during the softening process at the single-cell level, and the results show that the cell wall polysaccharides tended to be concentrated in the cell corner of parenchymal cells at the late stage

Summary

Introduction

As one of the most favored fruits among consumers worldwide, is rich in nutrition and good flavor. Like most other fruits and vegetables, peach fruit softens during the ripening process [1]. The softening of peach fruit affects its texture, and significantly influences consumer preference and acceptability [2]. The textural changes of fruit are closely related to the cell wall polysaccharides [3,4]. The structure and composition of the cell wall determines the mechanical properties of the fruit flesh, and further affects fruit texture. During the development and postharvest of a peach, polysaccharides change substantially, and this process is mainly related to structural and compositional changes of cellulose, hemicellulose, and pectin, i.e., as well as their spatial orientation [5]

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