Effect of bi-enzyme hydrolysis on the properties and composition of hydrolysates of Manchurian walnut dreg protein

Walnut dreg (WD) active peptides are an important source of dietary antioxidants; however, the products of conventional hydrolysis have limited industrial output owing to poor flavour and low bioactivity. To this end, in this study, we aimed to employ bvLAP, an aminopeptidase previously identified in our research, as well as commercially available Alcalase for bi-enzyme digestion. The flavour, antioxidant activity, and structures of products resulting from various digestion methods were compared. The results showed that the bi-enzyme digestion products had enhanced antioxidant activity, increased β-sheet content, and reduced bitterness intensity from 9.65 to 6.93. Moreover, bi-enzyme hydrolysates showed a more diverse amino acid composition containing 1640 peptides with distinct sequences. These results demonstrate that bi-enzyme hydrolysis could be a potential process for converting WD into functional food ingredients. Additionally, our results provide new concepts that can be applied in waste processing and high-value utilisation of WD.

Nutritional upgrade of olive mill stone waste, walnut shell and their mixtures by applying solid state fermentation initiated by Pleurotus ostreatus

Present study concerns the transformation of the agro-industrial by-products olive mill stone waste (OMSW) and walnut shell (WS) to a protein-enriched animal feedstuff utilizing the solid state fermentation (SSF) technique. For this purpose, various mixtures of these by-products were exploited as substrates of the SSF process which was initiated by the P. ostreatus fungus. The respective results indicated that the substrate consisted of 80% WS and 20% OMSW afforded the product with the highest increase in protein content, which accounted the 7.57% of its mass (69.35% increase). In addition, a 26.13% reduction of lignin content was observed, while the most profound effect was observed for their 1,3-1,6 β-glucans profile, which was increased by 3-folds reaching the 6.94% of substrate's mass. These results are indicative of the OMSW and WS mixtures potential to act as efficient substrate for the development of novel proteinaceous animal feed supplements using the SSF procedure. Study herein contributes to the reintegration of the agro-industrial by-products aiming to confront the problem of proteinaceous animal feed scarcity and reduce in parallel the environmental footprint of the agro-industrial processes within the context of circular economy.

Transcriptomic Analyses Reveal the Effects of Walnut Kernel Cake on Adipose Deposition in Pigs

With the rising cost of animal feed protein, finding affordable and effective substitutes is crucial. Walnut kernel cake, a polyphenol-, fiber-, protein- and fat-rich byproduct of walnut oil extraction, has been underexplored as a potential protein replacement in pig feed. In this study, we found that feeding large Diqing Tibetan pigs walnut kernel cake promoted adipose deposition and improved pork quality during pig growth. Transcriptome analysis revealed the upregulation of genes ANGPTL8, CCNP, ETV4, and TRIB3, associated with adipose deposition. Pathway analysis highlighted enrichment in adipose deposition-related pathways, including PPAR, insulin, PI3K-Akt, Wnt, and MAPK signaling. Further analysis identified DEGs (differentially expressed genes) positively correlated with adipose-related traits, such as PER2 and PTGES. Single-cell transcriptome data pointed to the specific expression of CD248 and PTGES in adipocyte progenitor/stem cells (APSCs), pivotal for adipocyte differentiation and adipose deposition regulation. This study demonstrates walnut kernel cake's potential to substitute soybean cake in pig feed, providing high-quality protein and promoting adipose deposition. It offers insights into feed protein replacement, human functional food, fat metabolism, and related diseases, with marker genes and pathways supporting pig breeding and pork quality improvement.

Genome-Wide Analysis of Transcription Factor R2R3-MYB Gene Family and Gene Expression Profiles during Anthocyanin Synthesis in Common Walnut (Juglans regia L.)

The R2R3-MYB gene family, encoding plant transcriptional regulators, participates in many metabolic pathways of plant physiology and development, including flavonoid metabolism and anthocyanin synthesis. This study proceeded as follows: the JrR2R3-MYB gene family was analyzed genome-wide, and the family members were identified and characterized using the high-quality walnut reference genome "Chandler 2.0". All 204 JrR2R3-MYBs were established and categorized into 30 subgroups via phylogenetic analysis. JrR2R3-MYBs were unevenly distributed over 16 chromosomes. Most JrR2R3-MYBs had similar structures and conservative motifs. The cis-acting elements exhibit multiple functions of JrR2R3-MYBs such as light response, metabolite response, and stress response. We found that the expansion of JrR2R3-MYBs was mainly caused by WGD or segmental duplication events. Ka/Ks analysis indicated that these genes were in a state of negative purifying selection. Transcriptome results suggested that JrR2R3-MYBs were widely entangled in the process of walnut organ development and differentially expressed in different colored varieties of walnuts. Subsequently, we identified 17 differentially expressed JrR2R3-MYBs, 9 of which may regulate anthocyanin biosynthesis based on the results of a phylogenetic analysis. These genes were present in greater expression levels in 'Zijing' leaves than in 'Lvling' leaves, as revealed by the results of qRT-PCR experiments. These results contributed to the elucidation of the functions of JrR2R3-MYBs in walnut coloration. Collectively, this work provides a foundation for exploring the functional characteristics of the JrR2R3-MYBs in walnuts and improving the nutritional value and appearance quality of walnuts.

Influence of Cold Stress on Physiological and Phytochemical Characteristics and Secondary Metabolite Accumulation in Microclones of Juglans regia L

The current study investigated the impact of cold stress on the morphological, physiological, and phytochemical properties of Juglans regia L. (J. regia) using in vitro microclone cultures. The study revealed significant stress-induced changes in the production of secondary antioxidant metabolites. According to gas chromatography-mass spectrometry (GC-MS) analyses, the stress conditions profoundly altered the metabolism of J. regia microclones. Although the overall spectrum of metabolites was reduced, the production of key secondary antioxidant metabolites significantly increased. Notably, there was a sevenfold (7×) increase in juglone concentration. These findings are crucial for advancing walnut metabolomics and enhancing our understanding of plant responses to abiotic stress factors. Additionally, study results aid in identifying the role of individual metabolites in these processes, which is essential for developing strategies to improve plant resilience and tolerance to adverse conditions.

The regulating mechanism of salt tolerance of black walnut seedlings was revealed by the physiological and biochemical integration analysis

Salt stress is an important abiotic stress that seriously affects plant growth. In order to research the salt tolerance of walnut rootstocks so as to provide scientific basis for screening salt-tolerant walnut rootstocks, two kinds of black walnut seedlings, Juglans microcarpa L. (JM) and Juglans nigra L. (JN), were treated under salt stress with different concentrations of NaCl (0, 50, 100, and 200 mM) and the growth situation of seedlings were observed. The physiological indexes of JM and JN seedlings were also measured in different days after treatment. Our study showed salt stress inhibited seedlings growth and limited biomass accumulation. Walnut mainly increased osmotic adjustment ability by accumulation Pro and SS. Furthermore, with the duration of treatment time increased, SOD and APX activities decreased, TPC and TFC contents increased. Walnut accumulated Na mostly in roots and transported more K and Ca to aboveground parts. The growth and physiological response performance differed between JM and JN, specifically, the differences occurred in the ability to absorb minerals, regulate osmotic stress, and scavenge ROS. Salt tolerance of JM and JN was assessed by principal component analysis (PCA) and resulted in JN > JM. In conclusion, our results indicated that JN has higher salt tolerance than JM, and JN might be used as a potential germplasm resource for the genetic breeding of walnuts.

Antioxidant and Anti-Obesity Effects of Juglans mandshurica in 3T3-L1 Cells and High-Fat Diet Obese Rats

Juglans mandshurica Maxim. walnut (JMW) is well-known for the treatment of dermatosis, cancer, gastritis, diarrhea, and leukorrhea in Korea. However, the molecular mechanism underlying its anti-obesity activity remains unknown. In the current study, we aimed to determine whether JMW can influence adipogenesis in 3T3-L1 preadipocytes and high-fat diet rats and determine the antioxidant activity. The 20% ethanol extract of JMW (JMWE) had a total polyphenol content of 133.33 ± 2.60 mg GAE/g. Considering the antioxidant capacity, the ABTS and DPPH values of 200 μg/ml of JMWE were 95.69 ± 0.94 and 79.38 ± 1.55%, respectively. To assess the anti-obesity activity of JMWE, we analyzed the cell viability, fat accumulation, and adipogenesis-related factors, including CCAAT-enhancer-binding protein alpha (C/EBPα), sterol regulatory element-binding protein-1c (SREBP1c), peroxisome proliferator-activated receptor-gamma (PPARγ), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC). We found that total lipid accumulation and triglyceride levels were reduced, and the fat accumulation rate decreased in a dose-dependent manner. Furthermore, JMWE suppressed adipogenesis-related factors C/EBPα, PPARγ, and SREBP1c, as well as FAS and ACC, both related to lipogenesis. Moreover, animal experiments revealed that JMWE could be employed to prevent and treat obesity-related diseases. Hence, JMWE could be developed as a healthy functional food and further explored as an anti-obesity drug.

Screening and Constructing of Novel Angiotensin I-Converting Enzyme Inhibiting Peptides from Walnut Protein Isolate and Their Mechanisms of Action: A Merged In Silico and In Vitro Study

Angiotensin I-converting enzyme (ACE)-inhibiting peptides were isolated from walnut protein isolate (WPI) using ultrasound-assisted extraction. This study aimed to assess the impact of ultrasonic pretreatment on the physicochemical properties of WPI. The optimal extraction conditions for WPI were determined as a 15-min ultrasonic treatment at 400 W. Subsequently, the hydrolysate exhibiting the highest in vitro ACE-inhibiting activity underwent further processing and separation steps, including ultrafiltration, ion exchange chromatography, liquid chromatography-tandem mass spectrometry, ADMET screening, and molecular docking. As a result of this comprehensive process, two previously unidentified ACE-inhibiting peptides, namely Tyr-Ile-Gln (YIQ) and Ile-Tyr-Gln (IYQ), were identified. In addition, a novel peptide, Ile-Lys-Gln (IKQ), was synthesized, demonstrating superior ACE-inhibiting activity and temperature stability. In silico analysis estimated an in vivo utilization rate of 21.7% for IKQ. These peptides were observed to inhibit ACE through an anti-competitive mechanism, with molecular docking simulations suggesting an interaction mechanism involving hydrogen bonding. Notably, both IYQ and IKQ peptides exhibited no discernible toxicity to HUVECs cells and promoted nitric oxide (NO) generation. These findings underscore the potential of ultrasonicated WPI in the separation of ACE-inhibiting peptides and their utility in the development of novel ACE inhibitors for functional food applications.

Therapeutic effects of a walnut-derived peptide on NLRP3 inflammasome activation, synaptic plasticity, and cognitive dysfunction in T2DM mice

NLRP3 inflammasome activation plays a key role in the development of diabetes-induced cognitive impairment. However, strategies to inhibit NLRP3 inflammasome activation remain elusive. Herein, we evaluated the impact of a walnut-derived peptide, TWLPLPR (TW-7), on cognitive impairment in high-fat diet/streptozotocin-induced type 2 diabetes mellitus (T2DM) mice and explored its underlying mechanisms in high glucose-induced HT-22 cells. In the Morris water maze test, TW-7 alleviated cognitive deficits in mice; this was confirmed at the level of synaptic structure and dendritic spine density in the mouse hippocampus using transmission electron microscopy and Golgi staining. TW-7 increased the expression of synaptic plasticity-related proteins and suppressed the NEK7/NLRP3 inflammatory pathway, as determined by western blotting and immunofluorescence analysis. The mechanism of action of TW-7 was verified in an HT-22 cell model of high glucose-induced insulin resistance. Collectively, TW-7 could regulate T2DM neuroinflammation and synaptic function-induced cognitive impairment by inhibiting NLRP3 inflammasome activation and improving synaptic plasticity.

The Gastroprotective Effect of Walnut Peptides: Mechanisms and Impact on Ethanol-Induced Acute Gastric Mucosal Injury in Mice

The objective of this research was to explore the protective impact of walnut peptides (WP) against ethanol-induced acute gastric mucosal injury in mice and to investigate the underlying defense mechanisms. Sixty male BALB-c mice were divided into five groups, and they were orally administered distilled water, walnut peptides (200 and 400 mg/kg bw), and omeprazole (20 mg/kg bw) for 24 days. Acute gastric mucosal injury was then induced with 75% ethanol in all groups of mice except the blank control group. Walnut peptides had significant protective and restorative effects on tissue indices of ethanol-induced gastric mucosal damage, with potential gastric anti-ulcer effects. Walnut peptides significantly inhibited the excessive accumulation of alanine aminotransferase (ALT), aspartate transferase (AST), and malondialdehyde (MDA), while promoting the expression of reduced glutathione (GSH), total antioxidant capacity (T-AOC), glutathione disulfide (GSSG), and mouse epidermal growth factor (EGF). Furthermore, the Western blot analysis results revealed that walnut peptides significantly upregulated the expression of HO-1 and NQO1 proteins in the Nrf2 signaling pathway. The defensive impact of walnut peptides on the gastric mucosa may be achieved by mitigating the excessive generation of lipid peroxides and by boosting cellular antioxidant activity.

Overexpression of JsFLS5 in calli improves salinity tolerance by maintaining active oxygen balance and reducing Na+ toxicity in Juglans sigillata

The escalating global climate change significantly threatens plant growth, development, and production through salinity stress. Flavonoids, a crucial category of secondary metabolites, have been extensively studied for their role in modulating plant growth and development mechanisms in the face of biological and abiotic stress. The flavonol synthetase (FLS) gene plays a key role in the biosynthesis and accumulation of flavonoids. To investigate the correlation between salt tolerance and flavonol synthesis, JsFLS5 was overexpressed in the callus of Juglans sigillata cv. "Qianhe-7." This study shows that the upregulation of JsFLS5 significantly elevates the overall flavonoid content by modulating the expression of genes associated with flavonoid synthesis under salinity stress conditions. Additionally, the overexpressing callus exhibited enhanced resistance to salt stress compared to the wild-type callus, as evidenced by reduced levels of reactive oxygen species accumulation, electrolyte leakage, and malondialdehyde content in the overexpressing callus relative to the wild type (WT). Moreover, the overexpressing callus showed higher antioxidant enzyme activity and a more efficient ascorbic acid-glutathione cycle. Furthermore, the concentration of Na+ in the overexpressing callus was lower than WT, resulting in a decreased Na+ /K+ ratio. These findings suggest that JsFLS5 overexpression in calli effectively mitigates the oxidative damage induced by osmotic stress and reduces Na+ toxicity by enhancing flavonoid synthesis under salt stress conditions. Consequently, this study offers a novel perspective for comprehending the role of JsFLS5 in the response to abiotic stress in J. sigillata.

Effects of dietary walnut (Juglans regia) leaves extract on immunity, gene expression responses, and disease resistance in Oreochromis niloticus

The dietary effects of walnut leaf extract (WLE) on the growth, immunity, and resistance of Oreochromis niloticus to bacterial infection have been investigated. Five diets were prepared with various WLE doses of 0, 250, 500, 750, and 1000 mg/kg, termed as Con (control), WLE250, WLE500, WLE750, and WLE1000, respectively. Fish (11.67 ± 0.21 g) were fed these diets for 60 days and then challenged with Plesiomonas shigelloides. Before the challenge, it was observed that dietary WLE did not significantly affect the growth, blood proteins (globulin, albumin, and total protein), and liver function enzymes (ALT and AST) activities. The WLE250 group significantly increased serum SOD and CAT activities more than other groups. The serum immunological indices (lysozyme and myeloperoxidase activities) and hematological parameters (phagocytic activity %, phagocytic index, respiratory burst activity, and potential activity) were significantly increased in the WLE groups compared with the Con group. The expression of IgM heavy chain, IL-1β, and IL-8 genes were significantly upregulated in all WLE-supplemented groups in comparison with the Con group. The fish survival rates (SR; %) post challenge in the Con, WLE250, WLE500, WLE750 and WLE1000 groups were 40.0%, 49.3%, 86.7%, 73.3%, and 70.7%, respectively. The Kaplan-Meier survivorship curves illustrated that the highest SR% was found in the WLE500 group (86.7%) amongst the other groups. Accordingly, we can suggest that feeding O. niloticus with a diet supplied with WLE at a dose rate of 500 mg/kg over 60 days could enrich haemato-immune responses and increase the fish survival against the challenge with P. shigelloides. These results recommend using WLE as a herbal dietary supplement to substitute antibiotic use in aquafeed.

Walnut-Derived Peptides Promote Autophagy via the Activation of AMPK/mTOR/ULK1 Pathway to Ameliorate Hyperglycemia in Type 2 Diabetic Mice

Autophagy flux plays a significant protective role in type 2 diabetes mellitus (T2DM). However, the mechanisms by which autophagy mediates insulin resistance (IR) to ameliorate T2DM remain unclear. This study explored the hypoglycemic effects and mechanisms of walnut-derived peptides (fraction 3-10 kDa and LP5) in streptozotocin and high-fat-diet-induced T2DM mice. Findings revealed that walnut-derived peptides reduced the levels of blood glucose and FINS and ameliorated IR and dyslipidemia. They also increased SOD and GSH-P_X activities and inhibited the secretion of TNF-α, IL-6, and IL-1β. Additionally, they increased the levels of ATP, COX, SDH, and MMP of liver mitochondria. Western blotting indicated that walnut-derived peptides up-regulated LC3-II/LC3-I and Beclin-1 expression, while they down-regulated p62 expression, which may be associated with the activation of the AMPK/mTOR/ULK1 pathway. Finally, the AMPK activator (AICAR) and inhibitor (Compound C) were used to verify that LP5 could activate autophagy through the AMPK/mTOR/ULK1 pathway in IR HepG2 cells.

Genome-wide identification, characterization, and expression pattern of the late embryogenesis abundant (LEA) gene family in Juglans regia and its wild relatives J. mandshurica

BACKGROUND

Late Embryogenesis Abundant (LEA) proteins are a class of proteins associated with plant stress resistance. Two Juglans species, Juglans regia and J. mandshurica, are both diploid (2n = 32), monoecious perennial economic tree species with high edible, pharmaceutical, and timber value. The identification, characterization, and expression patterns of LEA proteins in J. regia and its wild relative, J. mandshurica, would not only provide the genetic basis of this gene family, but it would also supply clues for further studies of the evolution and regulating mechanisms of LEA proteins in other tree species.

RESULTS

In this study, we identified 25 and 20 members of the LEA gene family in Juglans regia and its wild relative, Juglans mandshurica, respectively. The results of phylogenetic analysis showed that the LEA members were divided into eight main subgroups. Predictions of their physicochemical properties showed the variable characteristics of LEA proteins, and the subcellular localization analysis indicated that most LEA proteins are localized in the nucleus. Chromosomal localization analysis and gene replication pattern prediction indicated that WGD is the predominant duplication mode of LEA genes. The results of the comparative analysis indicated a high level of collinearity between the two Juglans species. Analysis of cis-acting elements indicated that LEA genes had a relatively wide range of responses to abiotic stresses and phytohormonal processes, particularly in two phytohormones, methyl jasmonate and abscisic acid. Transcriptome profiling and qRT-PCR experiments showed that JrLEAs are commonly expressed in leaves, green husks, and male and female flowers, and most JmLEAs are more highly expressed in male flowers. We also hypothesized that JrLEAs are involved in the process of anthracnose resistance. Anthracnose-resistant varieties of JrLEAs presented relatively high expression levels at later stages.

CONCLUSION

In this study, we provide a theoretical basis for the functional study of LEA genes in J. regia and J. mandshurica. Analysis of cis-acting elements and gene expression indicated that JrLEAs and JmLEAs play important roles in resistance to biotic stresses in these species.

Protocatechuic acid, ferulic acid and relevant defense enzymes correlate closely with walnut resistance to Xanthomonas arboricola pv. juglandis

BACKGROUND

Juglans regia L. is an important nut tree that has a wide range of distribution in temperate regions of the world. In some walnut orchards, walnut blight can become a problematic disease that affects the growth of walnut trees. To explore the correlation between biochemical response and walnut resistance, we inoculated four walnut cultivars with Xanthomonas arboricola pv. juglandis (Xaj). The walnut cultivars were, namely, 'Xiangling', 'Xiluo 2', 'Yuanfeng' and 'Xifu 2'. Total phenol content (TPC) and total flavonoid content (TFC) were measured, whereby nine major phenolic compounds and several relevant enzymes were identified.

RESULTS

The results showed that the most resistant and susceptible walnut varieties were 'Xiluo 2' and 'Xifu 2' respectively. The reaction of walnut to Xaj was characterized by the early accumulation of phenolic compounds in the infected site. After inoculation with Xaj, we found that the resistant variety 'Xiluo 2' show the significant differences with other varieties at different time points through the determination of related antioxidant enzymes such as catalase (CAT) and peroxidase (POD). Meanwhile, the phenylalanine ammonia lyase (PAL) of 'Xiluo 2' increased significantly at 8 day post infection (dpi) and made differences from the control samples, while other varieties changed little. And the polyphenol oxidase (PPO) was significantly higher than in the control at 16 dpi, maintaining the highest and the lowest activity in 'Xiluo 2' and 'Xifu 2' respectively. It was also found that the content of protocatechuic acid in all cultivars increased significantly at 4 dpi, and 'Xiluo 2' was significantly higher than that of the control. In the early stage of the disease, ferulic acid content increased significantly in 'Xiluo 2'.

CONCLUSION

Our findings confirmed that the metabolism of phenolic compounds and related defense enzymes are of great significance in the response of walnut to Xaj.

Broiler meat fatty acids composition, lipid metabolism, and oxidative stability parameters as affected by cranberry leaves and walnut meal supplemented diets

A randomized complete block with a 2 × 3 factorial arrangement was used to design a nutrition experiment conducted for the evaluation of the relation between walnut meal (WM-6% inclusion rate) and cranberry leaves (CL-1% and 2% inclusion rate) supplements and their effects on tissue lipid profile, lipid metabolism indices and oxidative stability of meat. Semi-intensive system conditions were simulated for 240 Ross 308 broilers and the animals were reared on permanent shave litter in boxes of 3 m2 (40 broilers / each group, housed in a single box). The current study results showed that the diets enriched in linolenic acid (LNA) (WM diets) led to broilers meat enriched in LNA, but the synthesis of long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA) was stimulated when the diets were supplemented with a natural antioxidants source (CL diets). The CL diet also exhibited the most powerful effect in counteracting the oxidative processes of meat.

Genome-Wide Identification of AP2/ERF Superfamily Genes in Juglans mandshurica and Expression Analysis under Cold Stress

Juglans mandshurica has strong freezing resistance, surviving temperatures as low as -40 °C, making it an important freeze tolerant germplasm resource of the genus Juglans. APETALA2/ethylene responsive factor (AP2/ERF) is a plant-specific superfamily of transcription factors that regulates plant development, growth, and the response to biotic and abiotic stress. In this study, phylogenetic analysis was used to identify 184 AP2/ERF genes in the J. mandshurica genome, which were classified into five subfamilies (JmAP2, JmRAV, JmSoloist, JmDREB, and JmERF). A significant amount of discordance was observed in the 184 AP2/ERF genes distribution of J. mandshurica throughout its 16 chromosomes. Duplication was found in 14 tandem and 122 segmental gene pairs, which indicated that duplications may be the main reason for JmAP2/ERF family expansion. Gene structural analysis revealed that 64 JmAP2/ERF genes contained introns. Gene evolution analysis among Juglandaceae revealed that J. mandshurica is separated by 14.23 and 15 Mya from Juglans regia and Carya cathayensis, respectively. Based on promoter analysis in J. mandshurica, many cis-acting elements were discovered that are related to light, hormones, tissues, and stress response processes. Proteins that may contribute to cold resistance were selected for further analysis and were used to construct a cold regulatory network based on GO annotation and JmAP2/ERF protein interaction network analysis. Expression profiling using qRT-PCR showed that 14 JmAP2/ERF genes were involved in cold resistance, and that seven and five genes were significantly upregulated under cold stress in female flower buds and phloem tissues, respectively. This study provides new light on the role of the JmAP2/ERF gene in cold stress response, paving the way for further functional validation of JmAP2/ERF TFs and their application in the genetic improvement of Juglans and other tree species.

Phosphorylated walnut protein isolate as a nanocarrier for enhanced water solubility and stability of curcumin

BACKGROUND

The low solubility and poor dispersion of alkaline-extracted walnut protein isolate (AWPI) limit its application as a protein-based carrier for the delivery of poorly soluble nutraceuticals, including curcumin. This work investigated the physicochemical characteristics of phosphorylated walnut protein isolate (PWPI) extracted using sodium tripolyphosphate (STP) and evaluated its encapsulation ability.

RESULTS

The results of phosphorus determination, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy confirmed the phosphorylation of the extracted PWPI. Circular dichroism (CD) analysis indicated that PWPI contained higher α-helix and lower β-sheet contents than AWPI. The PWPI prepared at pH 9.0 and 11.0 showed significantly improved solubility, similar surface hydrophobicity, and increased surface charges compared to the AWPI. Fluorescence quenching experiments indicated that the binding affinity of curcumin to PWPI was significantly higher than that of AWPI. When bound to PWPI, the solubility of curcumin in aqueous solution was greatly enhanced, with an 8700-fold increase at a nanocomplex concentration of 10 mg mL^-1 . The complexation of curcumin with PWPI significantly improved the storage stability of curcumin. Additionally, the PWPI-curcumin nanocomplexes showed significantly increased antioxidant capacity.

CONCLUSION

Phosphorylated walnut protein isolate showed greatly improved solubility and strong encapsulation ability, making it a promising nanocarrier for curcumin. © 2022 Society of Chemical Industry.

Multi-mode S-type ultrasound-assisted protein extraction from walnut dregs and in situ real-time process monitoring

This study aimed to investigate the impact of multi-mode S-type ultrasound treatment on the protein extraction level of walnut dregs. The structural properties of the walnut protein (WP) were characterized, and the correlation between protein structure and extraction level was analyzed. The in situ real-time monitoring model for the ultrasound-assisted WP extraction process was established by a miniature fiber near-infrared (NIR) spectrometer. Results showed that the protein yield, purity, and comprehensive extraction index (CEI) of extracted WP were 71.07 %, 72.69 %, and 71.72, respectively, under optimal conditions (dual-frequency 20/28 kHz, ultrasonic treatment duration 30 min, and ultrasound power density 120 W/L). The secondary structure of extracted WP displayed that the proportion of α-helix and β-sheet reduced, while the contents of β-turn and random coil increased after ultrasonic treatment. Besides, sonication decreased the disulfide bond content and increased free sulfhydryl (-SH) and surface hydrophobicity compared to the control. The microstructures of WP confirmed that appropriate sonication could unfold the protein aggregates and reduce the particle size. The extraction level of WP is positively correlated with the -SH content (p < 0.01). The quantitative prediction model of Si-PLS for -SH content in the ultrasound-assisted WP extraction process was established and performed a good correction and prediction performance (Rc = 0.9736; RMSECV = 0.446 μmol/L; Rp = 0.9342; RMSEP = 0.807 μmol/L). This study exploited a high-efficiency way for the WP extraction industry, and provided theoretical support for the development of the intelligent system in industrial protein extraction process.

Production, bioactivities and bioavailability of bioactive peptides derived from walnut origin by-products: a review

Walnut-origin by-products obtained from walnut oil extraction industry are high in proteins with various physiological functions and pharmacological properties and an extensive potential for usage in producing bioactive peptides. This review presents the current research status of bioactive peptides derived from walnut by-products, including preparation, separation, purification, identification, bioactivities, and bioavailability. A plethora of walnut peptides with multiple biological activities, including antioxidative, antihypertensive, neuroprotective, antidiabetic, anticancer, and antihyperuricemia activities, were obtained from walnut-origin by-products by enzymatic hydrolysis, fermentation, and synthesis. Different bioactive peptides show various structural characteristics and amino acid composition due to their diverse mechanism of action. Furthermore, walnut protein and its hydrolysate present a high bioavailability in human gastrointestinal digestive system. Improving the bioavailability of walnut peptides is needful in the development of walnut industry. However, future research still needs to exploit energy conservation, high efficiency, environmentally friendly and low-cost production method of walnut bioactive peptide. The molecular mechanisms of different bioactive walnut peptides still need to be explored at the cell and gene levels. Additionally, the digestion, absorption, and metabolism processes of walnut peptides are also the focus of future research.

Walnut-Derived Peptide Enhances Mitophagy via JNK-Mediated PINK1 Activation to Reduce Oxidative Stress in HT-22 Cells

Mitophagy has a neuroprotective effect on reactive oxygen species (ROS)-induced neurodegenerative diseases. The walnut-derived polypeptide (TW-7) has antioxidant activity and protects nerves by promoting autophagy. However, its action mechanism against oxidative stress through mitophagy remains obscure. Therefore, we aimed to assess the effects of TW-7 on HT-22 cells under oxidative stress. Mitochondrial ultrastructure and cristae number were observed by transmission electron microscopy. The results showed that TW-7 (100 μM) restored the fluorescence intensity of the mitochondrial membrane potential to 0.99 ± 0.04 (P < 0.05), decreased H₂O₂-induced opening of mitochondrial permeability transition pores, and inhibited mitochondrial bioenergetic deficits. Moreover, it significantly increased activities of antioxidant enzymes to 186.88 ± 5.40 U/mgprot, 40.08 ± 0.87 mU/mgprot, and 23.57 ± 0.77 U/mgprot (P < 0.05), based on superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) assay results, respectively. Consistently, it decreased cellular and mitochondrial ROS levels by 51.71 ± 0.81 and 49.75 ± 0.69% (P < 0.05). TW-7 also downregulated C-Jun N-terminal kinase (JNK) phosphorylation and activated PTEN-induced putative kinase 1 (PINK1)-mediated mitophagy in H₂O₂-induced HT-22 cells treated with JNK activator (anisomycin) and inhibitor (SP600125). Furthermore, TW-7 inhibited the mitochondrial apoptosis pathway by downregulation of the cytoplasmic cytochrome C, caspase-9, and cleaved-caspase-3 expression. Additionally, BDNF and SNAP-25 levels significantly increased to protect the synaptic function. Collectively, TW-7 improved oxidative stress-mediated nerve cell injury via JNK-regulated PINK1-mediated mitophagy.

Screening and functional prediction of differentially expressed genes in walnut endocarp during hardening period based on deep neural network under agricultural internet of things

The deep neural network is used to establish a neural network model to solve the problems of low accuracy and poor accuracy of traditional algorithms in screening differentially expressed genes and function prediction during the walnut endocarp hardening stage. The paper walnut is used as the research object to analyze the biological information of paper walnut. The changes of lignin deposition during endocarp hardening from 50 days to 90 days are observed by microscope. Then, the Convolutional Neural Network (CNN) and Long and Short-term Memory (LSTM) network model are adopted to construct an expression gene screening and function prediction model. Then, the transcriptome and proteome sequencing and biological information of walnut endocarp samples at 50, 57, 78, and 90 days after flowering are analyzed and taken as the training data set of the CNN + LSTM model. The experimental results demonstrate that the endocarp of paper walnut began to harden at 57 days, and the endocarp tissue on the hardened inner side also began to stain. This indicates that the endocarp hardened laterally from outside to inside. The screening and prediction results show that the CNN + LSTM model’s highest accuracy can reach 0.9264. The Accuracy, Precision, Recall, and F1-score of the CNN + LSTM model are better than the traditional machine learning algorithm. Moreover, the Receiver Operating Curve (ROC) area enclosed by the CNN + LSTM model and coordinate axis is the largest, and the Area Under Curve (AUC) value is 0.9796. The comparison of ROC and AUC proves that the CNN + LSTM model is better than the traditional algorithm for screening differentially expressed genes and function prediction in the walnut endocarp hardening stage. Using deep learning to predict expressed genes’ function accurately can reduce the breeding cost and significantly improve the yield and quality of crops. This research provides scientific guidance for the scientific breeding of paper walnut.

Effect of oral and intraperitoneal administration of walnut-derived pentapeptide PW5 on cognitive impairments in APPSWE/PS1ΔE9 mice

Food-derived bioactive peptides, encrypted in native protein sequence, have attracted enormous research attention due to its potential in the prevention and/or treatment of a broad range of diseases. However, administration route poses a great challenge to their development and commercial applications. Patient-friendly delivery of bioactive peptides which also enhances its efficacy urgently remain to be addressed. Here we compared the effects of oral administration (PO) to intraperitoneal injection (IP) of a walnut-derived bioactive pentapeptide PW5 (Pro-Pro-Lys-Asn-Trp) in cognitive improvement capacity in APP_SWE/PS1_ΔE9 transgenic mice. Strikingly, we found that only PO administration of PW5 could effectively ameliorate cognitive impairments and reduce the β-amyloid deposits in the brain compared to the IP administration. This may be attributable to alterations in the gut microbiota communities, including alterations in microbial α- and β-diversities after PO treatment, leading to the reversal of the relative abundances of ten differential genera (e.g. Acinetobacter, Lactobacillus, Akkermansia, Allobaculum, Adlercreutzia, Coriobacteriaceae, unclassified_p_ Firmicutes, Desulfovibrionaceae, Oscillospira and Anaeroplasma) which are highly correlated with disease progression. Thus, this study has leveraged on PW5 to proof the superior efficacy of oral delivery to injection delivery in improving cognitive impairments in vivo, suggesting that oral delivery might be highly recommended as a prioritized delivery route in the development of food-derived peptides.

Identification and Characterization of Wall-Associated Kinase (WAK) and WAK-like (WAKL) Gene Family in Juglans regia and Its Wild Related Species Juglans mandshurica

Wall-associated kinase (WAK) and WAK-like kinase (WAKL) are receptor-like kinases (RLKs), which play important roles in signal transduction between the cell wall and the cytoplasm in plants. WAK/WAKLs have been studied in many plants, but were rarely studied in the important economic walnut tree. In this study, 27 and 14 WAK/WAKL genes were identified in Juglans regia and its wild related species Juglans mandshurica, respectively. We found tandem duplication might play a critical role in the expansion of WAK/WAKL gene family in J. regia, and most of the WAK/WAKL homologous pairs underwent purified selection during evolution. All WAK/WAKL proteins have the extracellular WAK domain and the cytoplasmic protein kinase domain, and the latter was more conserved than the former. Cis-acting elements analysis showed that WAK/WAKL might be involved in plant growth and development, plant response to abiotic stress and hormones. Gene expression pattern analysis further indicated that most WAK/WAKL genes in J. regia might play a role in the development of leaves and be involved in plant response to biotic stress. Our study provides a new perspective for the evolutionary analysis of gene families in tree species and also provides potential candidate genes for studying WAK/WAKL gene function in walnuts.

The role of JrLACs in the lignification of walnut endocarp

BACKGROUND

The walnut shell, which is composed of a large number of sclereids originating from the lignified parenchyma of the endocarp, plays an important role in fruit development and during harvesting and storage. The physical and chemical properties of walnut shells are closely related to the lignin content. Laccase is the key enzyme responsible for lignin biosynthesis by the polymerization of monolignols and plays crucial roles in secondary cell wall formation in plants. In this study, we screened and identified laccase family genes from the walnut genome and investigated the expression of laccase during endocarp lignification in walnut.

RESULTS

A total of 37 laccase genes were screened from the walnut genome and distributed on nine chromosomes and classified into 6 subfamilies, among which subfamily IV showed distinct expansion. We observed that endocarp lignification started 44 days after flowering (DAF), and at later periods, the lignin content increased rapidly, with growth peaks at 44-50 DAF and 100-115 DAF. The lignification of the endocarp proceeded from the outside to the inside, as demonstrated by section staining in combination with endocarp staining. Furthermore, the changes in the expression of laccase family genes in the endocarp at different developmental stages were studied, and JrLACs showed different expression trends. The expression of nine genes showed significant increase after 44 DAF, and among these, JrLAC12-1, JrLAC12-2 and JrLAC16 showed a significant change in expression at the lignification stage. A study of the expression of JrLACs in different tissues and at various endocarp developmental stages revealed, that most JrLACs were expressed at low levels in mature tissues and at high levels in young tissues, in particular, JrLAC12-1 showed high expression in the young stems. A significant positive correlation was found between the expression of JrLAC12-1 and the variation in the lignin content in the endocarp.

CONCLUSION

Laccase genes play an important role in the lignification of the walnut endocarp, and JrLACs play different roles during fruit development. This study shows that JrLAC12-1 may play a key role in the lignification of endocarp.