Label-free visualization of lignin deposition in loquats using complementary stimulated and spontaneous Raman microscopy

Structural characteristics of wheat bran insoluble dietary fiber with various particle size distributions and their influences on the kinetics of gastrointestinal emptying in mice

Wheat bran is an abundant yet underutilized agricultural byproduct. Herein, the insoluble dietary fiber from wheat bran (WBIDF) was ultra-milled to investigate its impact on physicochemical properties and gastrointestinal emptying. SEM and CLSM showed that the laminar structure of WBIDF was disrupted as the particle size was significantly reduced. In the similar characteristic peaks appearing at 3410, 2925, 1635, 1041, and 895 cm-1 in the FT-IR spectra and at 2940, 1593, 1080, and 526 cm-1 in the Raman spectra, the peak intensity was increased as the particle size decreased. It may be that the hydrogen bonding between cellulose, hemicellulose, or other macromolecules was enhanced. X-ray diffraction showed cellulose type I results for all five samples. Correspondingly, the water-holding, swelling, and oil-holding capacities increased by 75.33 %, 52.62 %, and 75.00 %, respectively, in WBIDF-CW1.8 compared with WBIDF-CWy. Additionally, smaller particle sizes had lower viscosity, thereby enhancing intestinal propulsion and gastric emptying rates. Enhanced contact of the cecal tissue growth factor with the intestinal mucosa delayed ghrelin secretion and stimulated the secretion of motilin, gastrin, and cholecystokinin. In conclusion, the particle sizes of WBIDF were reduced through ultramicro-grinding, leading to altered structure, enhanced hydration and oil-holding capacities, decreased viscosity, and improved gastrointestinal emptying capacity.

Multiscale microscopy to decipher plant cell structure and dynamics

New imaging methodologies with high contrast and molecular specificity allow researchers to analyze dynamic processes in plant cells at multiple scales, from single protein and RNA molecules to organelles and cells, to whole organs and tissues. These techniques produce informative images and quantitative data on molecular dynamics to address questions that cannot be answered by conventional biochemical assays. Here, we review selected microscopy techniques, focusing on their basic principles and applications in plant science, discussing the pros and cons of each technique, and introducing methods for quantitative analysis. This review thus provides guidance for plant scientists in selecting the most appropriate techniques to decipher structures and dynamic processes at different levels, from protein dynamics to morphogenesis.

Maintaining the quality of postharvest broccoli by inhibiting ethylene accumulation using diacetyl

Broccoli (Brassica oleracea L. var. Italic) is rich in nutrition. However, it is susceptible to yellowing after harvest, leading to nutritional and economic losses. In this study, diacetyl, a natural food additive compound, was selected to inhibit the yellowing of broccoli florets and maintain the nutrient quality during storage time. It was found that 20 μl L^-1 diacetyl treatment for 12 h could significantly delay the yellowing and decrease the weight loss and lignin content of broccoli florets. Meanwhile, diacetyl could maintain higher contents of chlorophyll, vitamin C and flavonoids and suppress the transcript levels of chlorophyll degradation-related genes in broccoli florets. Moreover, accumulations of reactive oxygen species (ROS) were inhibited by diacetyl treatment. Under diacetyl treatment, the generation of ethylene was prevented by inhibiting the activities and related-gene expressions of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase. Based on our findings, exogenous diacetyl could be employed as a novel bioactive molecule for retarding the yellowing and maintaining the quality of postharvest broccoli.

Morphological and Developmental Features of Stone Cells in Eriobotrya Fruits

Some members of the Rosaceae family, particularly pear, contain stone cells in their fruits. Although stone cells in pear fruits are well studied, relatively little attention has been given to loquat stone cells. Only a few reports have suggested a relationship between stone cell traits and storage and transport tolerance of loquat fruits. Previously, we generated the variety JT8 from the interspecific hybrid of the loquat cultivar Jiefangzhong (JFZ; Eriobotrya japonica Lindl. cv. Jiefangzhong, female parent) and wild Taiwanese loquat (TL; E. deflexa Nakai, male parent). The JT8 fruits had a granular feel, similar to that of pear fruits, due to the presence of stone cells. In this study, the shape, size, development, and distribution dynamics of stone cells of Eriobotrya plants were thoroughly investigated. The results showed that loquat stone cells are brachysclereids and often contain typical branching pits. Loquat stone cells were distributed as both single stone cells and in stone cell clusters (SCCs), and the density of the stone cells near the core was higher than that near the peel. Stone cell density first increased and then decreased during fruit development. These traits noted in Eriobotrya were very similar to those observed in pear, indicating a close relationship between loquat and pear. Moreover, the contents, density dynamics, and aggregation traits of stone cells of the interspecific hybrid JT8 were derived from the male parent (TL). Transgressive segregation was likely exhibited in the content of stone cells and the size of the SCCs. More specifically, the content of stone cells reached 1.61% (w/w). In extreme cases, SCCs of JT8 exceeded 1,000 μm in length and 500 μm in width. This demonstrated that stone cell traits could be transmitted from parent to progeny through interspecific hybridization. The density dynamics of stone cells in two loquat cultivars with different storage and transport tolerances were also investigated, which indicated that the cultivar with more stone cells was more tolerant to storage and transport. We suggest that wild loquat genetic resources containing stone cells in Eriobotrya plants can be used to gradually improve the storage and transport tolerance of loquat fruits.

Biosynthetic labeling with 3-O-propargylcaffeyl alcohol reveals in vivo cell-specific patterned lignification in loquat fruits during development and postharvest storage

Lignification is a major cell wall modification that often results in the formation of sophisticated subcellular patterns during plant development or in response to environmental stresses. Precise localization of the spatiotemporal deposition of lignin is of great importance for revealing the lignification regulatory mechanism of individual cells. In loquat fruits, lignification typically increases the flesh lignin content and firmness, reducing their edibility and processing quality. However, the precise localization of the spatiotemporal active zones of lignification inside loquat fruit flesh remains poorly understood, and little is known about the contribution of patterned lignification to cell wall structure dynamics and the subsequent fruit-quality deterioration. Here, we performed an emerging bioorthogonal chemistry imaging technique to trace the in vivo patterned lignification dynamics in cells of loquat fruit flesh during development and storage. In developing fruits, lignified cells (LCs) and vascular bundles (VBs) were the zones of active lignification, and ring-like LCs deposited lignin at both the inner wall layer and the outer periphery sides. The domino effect of the generation of LCs was preliminarily visualized. In mature fruits, the newly formed lignin in the flesh of fruits during storage was specifically deposited in the corners and middle lamellae of parenchyma cells surrounding the VBs, resulting in the development of a reticular structure. Based on the findings, distinct spatiotemporal patterned lignification modes for different flesh cells in loquat fruits were proposed. These findings provide loquat lignification dynamics together with spatiotemporal data that can improve our understanding of the lignification process in planta.

Multicolour chemical imaging of plant tissues with hyperspectral stimulated Raman scattering microscopy

Recent development of stimulated Raman scattering (SRS) microscopy allows for label-free biological imaging with chemical specificity based on molecular-vibrational signatures. In particular, hyperspectral SRS imaging can acquire a molecular-vibrational spectrum at each pixel, allowing us not only to investigate the spectral difference of various biological molecules but also to discriminate different constituents based on their spectral difference. However, the number of constituents discriminated in previous label-free SRS imaging was limited to four because of the subtleness of spectral difference. Here, we report hyperspectral SRS imaging of plant tissues including leaves of Camellia japonica, roots of Arabidopsis thaliana, and thalli of a liverwort Marchantia polymorpha L. We show that SRS can discriminate as many as six components in Marchantia polymorpha L. without labeling. Our results demonstrate the effectiveness of hyperspectral SRS imaging as a tool for label-free multicolour imaging analysis of various biomolecules in plant tissues.

Investigating Effects of Bordered Pit Membrane Morphology and Properties on Plant Xylem Hydraulic Functions-A Case Study from 3D Reconstruction and Microflow Modelling of Pit Membranes in Angiosperm Xylem

Pit membranes in between neighboring conduits of xylem play a crucial role in plant water transport. In this review, the morphological characteristics, chemical composition and mechanical properties of bordered pit membranes were summarized and linked with their functional roles in xylem hydraulics. The trade-off between xylem hydraulic efficiency and safety was closely related with morphology and properties of pit membranes, and xylem embolism resistance was also determined by the pit membrane morphology and properties. Besides, to further investigate the effects of bordered pit membranes morphology and properties on plant xylem hydraulic functions, here we modelled three-dimensional structure of bordered pit membranes by applying a deposition technique. Based on reconstructed 3D pit membrane structures, a virtual fibril network was generated to model the microflow pattern across inter-vessel pit membranes. Moreover, the mechanical behavior of intervessel pit membranes was estimated from a single microfibril's mechanical property. Pit membranes morphology varied among different angiosperm and gymnosperm species. Our modelling work suggested that larger pores of pit membranes do not necessarily contribute to major flow rate across pit membranes; instead, the obstructed degree of flow pathway across the pit membranes plays a more important role. Our work provides useful information for studying the mechanism of microfluid flow transport across pit membranes and also sheds light on investigating the response of pit membranes both at normal and stressed conditions, thus improving our understanding on functional roles of pit membranes in xylem hydraulic function. Further work could be done to study the morphological and mechanical response of bordered pit membranes under different dehydrated conditions, as well as the related microflow behavior, based on our constructed model.

Plant Growth-Promoting Fungi (PGPF) Instigate Plant Growth and Induce Disease Resistance in Capsicum annuum L. upon Infection with Colletotrichum capsici (Syd.) Butler & Bisby

In the current study, a total of 70 fungi were isolated from the rhizosphere soil of chilli collected from six different districts of south Karnataka, India. All the rhizospheric fungi were evaluated for its antagonistic nature against Colletotrichum capsici-the causal agent of anthracnose disease-and eight isolates were found positive. The antagonistic fungi were further characterized for the production of plant growth-promoting traits wherein five isolates were recorded positive for all the traits tested and were also positive for root colonization. All five plant growth-promoting fungi (PGPF) were subjected to molecular characterization for identification up to the species level and the accession numbers were obtained from NCBI. The five isolates, namely NBP-08, NBP-45, NBP-61, NBP-66 and NBP-67, were further experimented with on susceptible seeds to evaluate its efficacy on seed and plant growth parameters along with induction of resistance against the anthracnose disease. The evaluated PGPF offered significant enhancement in seed and plant growth parameters with maximum improvement observed in seeds treated with NBP-61. Among the PGPF isolates, NBP-61 showed the maximum protection of 78.75%, while all the other isolates also showed significant protection against anthracnose disease compared to untreated plants. The higher accumulation of lignin and callose deposition along with enhanced defense enzyme activities in the PGPF-treated challenge-inoculated seedlings authenticated the protection offered by PGPF. The study evidenced the immense ability of PGPF in eliciting disease protection and enhancement of plant growth in chilli, which may act as a possible substitute for harmful chemicals.