Active substance and mechanisms of Actinidia chinensis Planch for the treatment of breast cancer was explored based on network pharmacology and in silico study.

In this paper, our objective was to investigate the potential mechanisms of Actinidia chinensis Planch (ACP) for breast cancer treatment with the application of network pharmacology, molecular docking, and molecular dynamics. "Mihoutaogen" was used as a key word to query the Traditional Chinese Medicine Systems Pharmacology database for putative ingredients of ACP and its related targets. DrugBank, GeneCards, Online Mendelian Inheritance in Man, and therapeutic target databases were used to search for genes associated with "breast cancer." Using Cytoscape 3.9.0 we then constructed the protein-protein interaction and drug-ingredient-target-disease networks. An enrichment analysis of Kyoto encyclopedia of genes and genomes pathway and gene ontology were performed to exploration of the signaling pathways associated with ACP for breast cancer treatment. Discovery Studio software was applied to molecular docking. Finally, the ligand-receptor complex was subjected to a 50-ns molecular dynamics simulation using the Desmond_2020.4 tools. Six main active ingredients and 176 targets of ACP and 2243 targets of breast cancer were screened. There were 118 intersections of targets for both active ingredients and diseases. Tumor protein P53 (TP53), AKT serine/threonine kinase 1 (AKT1), estrogen receptor 1 (ESR1), Erb-B2 receptor tyrosine kinase 2 (ERBB2), epidermal growth factor receptor (EGFR), Jun Proto-Oncogene (JUN), and Heat Shock Protein 90 Alpha Family Class A Member 1 (HSP90AA1) selected as the most important genes were used for verification by molecular docking and molecular dynamics simulation. The primary active compounds of ACP against breast cancer were predicted preliminarily, and its mechanism was studied, thereby providing a theoretical basis for future clinical studies.

Unveiling kiwifruit TCP genes: evolution, functions, and expression insights.

The TEOSINTE-BRANCHED1/CYCLOIDEA/PROLEFERATING-CELL-FACTORS (TCP) gene family is a plant-specific transcriptional factor family involved in leaf morphogenesis and senescence, lateral branching, hormone crosstalk, and stress responses. To date, a systematic study on the identification and characterization of the TCP gene family in kiwifruit has not been reported. Additionally, the function of kiwifruit TCPs in regulating kiwifruit responses to the ethylene treatment and bacterial canker disease pathogen (Pseudomonas syringae pv. actinidiae, Psa) has not been investigated. Here, we identified 40 and 26 TCP genes in Actinidia chinensis (Ac) and A. eriantha (Ae) genomes, respectively. The synteny analysis of AcTCPs illustrated that whole-genome duplication accounted for the expansion of the TCP family in Ac. Phylogenetic, conserved domain, and selection pressure analysis indicated that TCP family genes in Ac and Ae had undergone different evolutionary patterns after whole-genome duplication (WGD) events, causing differences in TCP gene number and distribution. Our results also suggested that protein structure and cis-element architecture in promoter regions of TCP genes have driven the function divergence of duplicated gene pairs. Three and four AcTCP genes significantly affected kiwifruit responses to the ethylene treatment and Psa invasion, respectively. Our results provided insight into general characters, evolutionary patterns, and functional diversity of kiwifruit TCPs.

Genome-wide analysis and expression profiling of the HD-ZIP gene family in kiwifruit.

The homeodomain-leucine zipper (HD-Zip) gene family plays a pivotal role in plant development and stress responses. Nevertheless, a comprehensive characterization of the HD-Zip gene family in kiwifruit has been lacking. In this study, we have systematically identified 70 HD-Zip genes in the Actinidia chinensis (Ac) genome and 55 in the Actinidia eriantha (Ae) genome. These genes have been categorized into four subfamilies (HD-Zip I, II, III, and IV) through rigorous phylogenetic analysis. Analysis of synteny patterns and selection pressures has provided insights into how whole-genome duplication (WGD) or segmental may have contributed to the divergence in gene numbers between these two kiwifruit species, with duplicated gene pairs undergoing purifying selection. Furthermore, our study has unveiled tissue-specific expression patterns among kiwifruit HD-Zip genes, with some genes identified as key regulators of kiwifruit responses to bacterial canker disease and postharvest processes. These findings not only offer valuable insights into the evolutionary and functional characteristics of kiwifruit HD-Zips but also shed light on their potential roles in plant growth and development.

Two NAC transcription factors regulated fruit softening through activating xyloglucan endotransglucosylase/hydrolase genes during kiwifruit ripening.

Kiwifruit is a climacteric fruit that is prone to ripening and softening. Understanding molecular regulatory mechanism of kiwifruit softening, is helpful to ensure long-term storage of fruit. In the study, two NAC TFs and two XTH genes were isolated from kiwifruit. Phylogenetic tree showed that both AcNAC1 and AcNAC2 belonged to NAP subfamily, AcXTH1 belong to I subfamily, and AcXTH2 belong to III subfamily. Bioinformatics analysis predicted that AcNAC1 and AcNAC2 possessed similar three-dimensional structural, and belonged to hydrophilic proteins. AcXTH1 and AcXTH2 were hydrophilic proteins and contained signal peptides. AcXTH1 had a transmembrane structure, but AcXTH2 did not. qRT-PCR results showed that AcNAC1, AcNAC2, AcXTH1 and AcXTH2 were increased during kiwifruit ripening. Correlation analysis showed that kiwifruit softening was closely related to endotransglucosylase/hydrolase genes and NAC TFs, as well as there was also a close relationship between AcXTHs and AcNACs. Moreover, both AcNAC1 and AcNAC2 were transcriptional activators located in nucleus, which bound to and activated the promoters of AcXTH1 and AcXTH2. In shortly, we proved that the roles of NAC TFs in mediating fruit softening during kiwifruit ripening. Altogether, our results clarified that AcNAC1 and AcNAC2 were transcriptional activators, and took part in kiwifruit ripening and softening through activating endotransglucosylase/hydrolase genes, providing a new insight of fruit softening network in kiwifruit ripening.

Short-term anaerobic treatment maintained the quality of Actinidia arguta by activating the antioxidant defense system.

BACKGROUND: This study aimed to investigate the effect of 6, 12, and 24 h short-term anaerobic treatment on kiwiberry quality and antioxidant properties at 5 °C. RESULTS: Short-term anaerobic treatment was found to delay ripening and softening in kiwiberries, evident from changes in ethylene release, total soluble solids, starch, protopectin, and fruit texture. The 24 h treatment group exhibited the lowest decay rate of 12% on day 49, a 38% reduction compared with the control group. Anaerobic treatment reduced flesh translucency and decay in the fruit. The 12 h and 24 h treatments enhanced the activities of superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase, and increased the level of total phenolics, flavonoids, anthocyanins, and ascorbic acid. Moreover, it lowered oxidative damage in cell membranes, evidenced by reduced malondialdehyde content and relative conductivity. CONCLUSION: These results indicate that anaerobic treatment maintains the fruit quality by stimulating its antioxidant defense system. Therefore, short-term anaerobic treatment emerges as a promising method for kiwiberry storage. © 2024 Society of Chemical Industry.

Transcriptomic analysis reveals ozone treatment delays kiwifruit postharvest softening by modulating cell wall metabolism.

Kiwifruit ripening and senescence after harvesting are closely related to its economic value. Transcriptome analysis and biochemical parameters were used to investigate the differences in gene expression levels and the potential regulation of cell wall metabolism in kiwifruit treated with ozone, thereby regulating fruit softening and prolonging postharvest life. Compared to the control group, the activities of the cell wall modification enzyme were lower under ozone treatment, the content of polysaccharide in the cell wall of primary pectin and cellulose was higher, and the content of soluble pectin was lower. Meanwhile, ozone treatment delayed the degradation of the cell wall mesosphere during storage. A total of 20 pectinesterase (PE)-related genes were identified by sequencing analysis. The data analysis and quantitative polymerase chain reaction results confirmed that cell wall modifying enzyme genes played an important role in softening and senescence after harvesting, which may reduce or induce the expression of certain genes affecting cell wall metabolism. Ozone treatment not only regulates active genes such as xyloglucan endo glycosyltransferase/hydrolase, cellulose synthase, polygalacturonase, and PE to maintain the quality of fruit after harvest but also acts synergically with cell wall modifying enzymes to inhibit the degradation of cell wall, resulting in changes in the ultrastructure of cell wall, thereby reducing the hardness of kiwifruit. In addition, according to the results of cis-acting elements, cell wall degradation is also related to downstream hormone signaling, especially PE-related genes. These results provide a theoretical basis for studying the mechanism of firmness and cell wall metabolism difference of kiwifruit and also lay a good foundation for further research.

Antibacterial synergy between a phage endolysin and citric acid against the Gram-negative kiwifruit pathogen Pseudomonas syringae pv. actinidiae.

Horticultural diseases caused by bacterial pathogens provide an obstacle to crop production globally. Management of the infection of kiwifruit by the Gram-negative phytopathogen Pseudomonas syringae pv. actinidiae (Psa) currently includes copper and antibiotics. However, the emergence of bacterial resistance and a changing regulatory landscape are providing the impetus to develop environmentally sustainable antimicrobials. One potential strategy is the use of bacteriophage endolysins, which degrade peptidoglycan during normal phage replication, causing cell lysis and the release of new viral progeny. Exogenous use of endolysins as antimicrobials is impaired by the outer membrane of Gram-negative bacteria that provides an impermeable barrier and prevents endolysins from accessing their target peptidoglycan. Here, we describe the synergy between citric acid and a phage endolysin, which results in a reduction of viable Psa below detection. We show that citric acid drives the destabilization of the outer membrane via acidification and sequestration of divalent cations from the lipopolysaccharide, which is followed by the degradation of the peptidoglycan by the endolysin. Scanning electron microscopy revealed clear morphological differences, indicating cell lysis following the endolysin-citric acid treatment. These results show the potential for citric acid-endolysin combinations as a possible antimicrobial approach in agricultural applications. IMPORTANCE: The phytopathogen Pseudomonas syringae pv. actinidiae (Psa) causes major impacts to kiwifruit horticulture, and the current control strategies are heavily reliant on copper and antibiotics. The environmental impact and increasing resistance to these agrichemicals are driving interest in alternative antimicrobials including bacteriophage-derived therapies. In this study, we characterize the endolysin from the Otagovirus Psa374 which infects Psa. When combined with citric acid, this endolysin displays an impressive antibacterial synergy to reduce viable Psa below the limit of detection. The use of citric acid as a synergistic agent with endolysins has not been extensively studied and has never been evaluated against a plant pathogen. We determined that the synergy involved a combination of the chelation activity of citric acid, acidic pH, and the specific activity of the ΦPsa374 endolysin. Our study highlights an exciting opportunity for alternative antimicrobials in agriculture.

Transcriptome analysis reveals the effect of propyl gallate on kiwifruit callus formation.

KEY MESSAGE: Exploring the potential action mechanisms of reactive oxygen species during the callus inducing, they can activate specific metabolic pathways in explants to regulate callus development. Reactive oxygen species (ROS) play an important role in the regulation of plant growth and development, but the mechanism of their action on plant callus formation remains to be elucidated. To address this question, kiwifruit was selected as the explant for callus induction, and the influence of ROS on callus formation was investigated by introducing propyl gallate (PG) as an antioxidant into the medium used for inducing callus. The results have unveiled that the inclusion of PG in the medium has disturbed the equilibrium of ROS during the formation of the kiwifruit callus. We selected the callus that was induced by the addition of 0.05 mmol/L PG to the MS medium. The callus exhibited a significant difference in the amount compared to the control medium without PG. The callus induced by the MS medium without PG was used as the control for comparison. KEGG enrichment indicated that PG exposure resulted in significant differences in gene expression in related pathways, such as phytohormone signaling and glutathione in kiwifruit callus. Weighted gene co-expression analysis indicated that the pertinent regulatory networks of both ROS and phytohormone signaling were critical for the establishment of callus in kiwifruit leaves. In addition, during the process of callus establishment, the ROS level of the explants was also closely related to the genes for transmembrane transport of substances, cell wall formation, and plant organ establishment. This investigation expands the theory of ROS-regulated callus formation and presents a new concept for the expeditious propagation of callus in kiwifruit.

Antioxidant Activity Analysis of Native Actinidia arguta Cultivars.

Kiwiberry (Actinidia arguta) is a perennial fruit tree belonging to the family Actinidiaceae. Kiwiberries are known to have an extremely high concentration of sugars, phenolics, flavonoids, and vitamin C, and possess delicious taste and health-promoting properties. Numerous studies have focused on kiwiberry fruits, demonstrating that they possess a higher phytochemical content and greater antioxidant activities than other berry fruits. The purpose of this study was to compare the phytochemical content and antioxidant potential of leaf, stem, root, and fruit extracts from twelve kiwiberry cultivars grown in Wonju, Korea, characterized by a Dwa climate (Köppen climate classification). In most kiwiberry cultivars, the total phenolic (TPC) and total flavonoid (TFC) phytochemical content was significantly higher in leaf and stem tissues, while the roots exhibited higher antioxidant activity. In fruit tissues, the TPC and TFC were higher in unripe and ripe kiwiberry fruits, respectively, and antioxidant activity was generally higher in unripe than ripe fruit across most of the cultivars. Based on our results, among the 12 kiwiberry cultivars, cv. Daebo and cv. Saehan have a significantly higher phytochemical content and antioxidant activity in all of the tissue types, thus having potential as a functional food and natural antioxidant.

E3 Ubiquitin Ligase PUB23 in Kiwifruit Interacts with Trihelix Transcription Factor GT1 and Negatively Regulates Immune Responses against Pseudomonas syringae pv. actinidiae.

Kiwifruit bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) is the most serious disease threatening kiwifruit production. Our previous study found genes encoding the U-box containing proteins were significantly regulated by Psa infection. Here, we report a U-box type E3 ubiquitin ligase PUB23 in kiwifruit which acts as a negative regulator of immune responses against Psa. PUB23 was found to physically interact with GT1, a trihelix transcription factor, in vitro and in vivo. The expression of GT1 was up-regulated in PUB23-silenced plants, indicating that interacting with PUB23 may directly or indirectly suppress GT1 expression. The silencing of PUB23 led to enhanced immune responses of PAMP-triggered immunity (PTI), including a higher expression level of defense marker genes PR1 and RIN4, and increased accumulation of hydrogen peroxide and superoxide anion. Our results reveal a negative role PUB23 plays in kiwifruit immune responses against Psa and may regulate gene expression by interacting with GT1.

Genome-Wide Identification of the IQM Gene Family and Their Transcriptional Responses to Abiotic Stresses in Kiwifruit (Actinidia eriantha).

IQM is a plant-specific calcium-binding protein that plays a pivotal role in various aspects of plant growth response to stressors. We investigated the IQM gene family and its expression patterns under diverse abiotic stresses and conducted a comprehensive analysis and characterization of the AeIQMs, including protein structure, genomic location, phylogenetic relationships, gene expression profiles, salt tolerance, and expression patterns of this gene family under different abiotic stresses. Based on phylogenetic analysis, these 10 AeIQMs were classified into three distinct subfamilies (I-III). Analysis of the protein motifs revealed a considerable level of conservation among these AeIQM proteins within their respective subfamilies in kiwifruit. The genomic distribution of the 10 AeIQM genes spanned across eight chromosomes, where four pairs of IQM gene duplicates were associated with segmental duplication events. qRT-PCR analysis revealed diverse expression patterns of these AeIQM genes under different hormone treatments, and most AeIQMs showed inducibility by salt stress. Further investigations indicated that overexpression of AeIQMs in yeast significantly enhanced salt tolerance. These findings suggest that AeIQM genes might be involved in hormonal signal transduction and response to abiotic stress in Actinidia eriantha. In summary, this study provides valuable insights into the physiological functions of IQMs in kiwifruit.

AcMYB10 Involved in Anthocyanin Regulation of 'Hongyang' Kiwifruit Induced via Fruit Bagging and High-Postharvest-Temperature Treatments.

Light and temperature are key factors influencing the accumulation of anthocyanin in fruit crops. To assess the effects of fruit bagging during development and high post-ripening temperature on 'Hongyang' kiwifruit, we compared the pigmentation phenotypes and expression levels of anthocyanin-related genes between bagged and unbagged treatments, and between 25 °C and 37 °C postharvest storage temperatures. Both the bagging and 25 °C treatments showed better pigmentation phenotypes with higher anthocyanin concentrations. The results of the qRT-PCR analysis revealed that the gene expression levels of LDOX (leucoanthocyanidin dioxygenase), F3GT (UDP-flavonoid 3-O-glycosyltransferase ), AcMYB10, and AcbHLH42 were strongly correlated and upregulated by both the bagging treatment and 25 °C storage. The results of bimolecular fluorescence complementation and luciferase complementation imaging assays indicated an interaction between AcMYB10 and AcbHLH42 in plant cells, whereas the results of a yeast one-hybrid assay further demonstrated that AcMYB10 activated the promoters of AcLODX and AcF3GT. These results strongly suggest that enhanced anthocyanin synthesis is caused by the promoted expression of AcLODX and AcF3GT, regulated by the complex formed by AcMYB10-AcbHLH42.

Physiological and transcriptional analyses reveal the resistance mechanisms of kiwifruit (Actinidia chinensis) mutant with enhanced heat tolerance.

High temperature is an environmental stressor that severely threatens plant growth, development, and yield. In this study, we obtained a kiwifruit mutant (MT) of 'Hongyang' (WT) through 60Co-γ irradiation. The MT possessed different leaf morphology and displayed prominently elevated heat tolerance compared to the WT genotype. When exposure to heat stress, the MT plants exhibited stabler photosynthetic capacity and accumulated less reactive oxygen species, along with enhanced antioxidant capacity and higher expression levels of related genes in comparison with the WT plants. Moreover, global transcriptome profiling indicated that an induction in genes related to stress-responsive, phytohormone signaling, and transcriptional regulatory pathways, which might contribute to the upgrade of thermotolerance in the MT genotype. Collectively, the significantly enhanced thermotolerance of MT might be mainly attributed to profitable leaf structure variations, improved photosynthetic and antioxidant capacities, as well as extensive transcriptome reprogram. These findings would be insightful in elucidating the sophisticated mechanisms of kiwifruit response to heat stress, and suggest the MT holds great potential for future kiwifruit improvement with enhanced heat tolerance.

Streptothricin-F Inhibition of FtsZ Function: A Promising Approach for Controlling Pseudomonas syringae pv. actinidiae.

Pseudomonas syringae pv. actinidiae (Psa) is a significant pathogenic bacterium affecting the kiwifruit industry. This study investigated the target sites of streptothricin-F (ST-F), produced by Streptomyces lavendulae gCLA4. The inhibition of ST-F on Psa was examined by the microscopic structural differences of Psa before and after treatment with ST-F, as well as the interaction between ST-F and cell division-related proteins. The results revealed filamentation of Psa after ST-F treatment, and fluorescence microscopy showed that ST-F inhibited the formation of the Z-ring composed of FtsZ protein. In vitro experiments and molecular docking demonstrated that ST-F can bind to FtsZ with a binding energy of 0.4 µM and inhibit FtsZ's GTP-dependent polymerization reaction. In addition, ST-F does not exert inhibitory effects on cell division in Psa strains overexpressing ftsZ. In conclusion, FtsZ is one of the target sites for ST-F inhibition of Psa, highlighting its potential as a therapeutic target for controlling Psa-induced kiwifruit bacterial canker.

An 18-day, 3 °C cold treatment effectively kills Ceratitis capitata (Diptera: Tephritidae) in kiwifruit (Actinidia spp.).

A series of experiments were carried out to develop a phytosanitary disinfestation protocol to kill Ceratitis capitata (Weidemann) (Mediterranean fruit fly, Diptera: Tephritidae) in 'Hayward' kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang and A.R. Ferguson) and 'Zesy002' kiwifruit (Actinidia chinensis Planch.). Experiments on 4 immature life stages (eggs and 3 larval instars) with treatment durations of between 5 and 18 days showed that third instars were the most tolerant to temperatures around 3 °C, with the lethal time to 99.9968% (probit 9) mortality (LT99.9968) estimated to be 17.3 days (95% confidence interval (CI) 16.4-18.2). Larvae reared and treated in 'Zesy002' were significantly more susceptible to cold treatment than those reared in 'Hayward'. A large-scale trial testing a disinfestation protocol of 3 ±â€…0.5 °C for 18 days treated over 500,000 third-instar C. capitata with no survivors. These results demonstrate that a cold treatment of 3.5 °C or below for 18 days induces C. capitata mortality in kiwifruit at a rate that exceeds 99.9968% with a degree of confidence greater than 99%.

Screening and identification of photoresponse factors in kiwifruit (Actinidia arguta) development.

BACKGROUND: Light is essential for kiwifruit development, in which photoresponse factors contributes greatly to the quality formation. 'Light sensitive hypocotyls, also known as light-dependent short hypocotyls' (LSH) gene family can participate in fruit development as photoresponse factor. However, the key LSH gene that determine kiwifruit development remains unclear. This study aim to screen and identify the key gene AaLSH9 in A. arguta. MATERIALS AND METHODS: Genome-wide identification of the LSH gene family was used to analyse LSH genes in kiwifruit. Homologous cloning was used to confirm the sequence of candidate LSH genes. qRT-PCR and cluster analysis of expression pattern were used to screen the key AaLSH9 gene. Subcellular localization of AaLSH9 in tobacco leaves and overexpression of AaLSH9 in Arabidopsis thaliana hy5 mutant plants were used to define the acting place in cell and identify molecular function, respectively. RESULTS: We identified 15 LSH genes, which were divided into two sub-families namely A and B. Domain analysis of A and B showed that they contained different domain organizations, which possibly played key roles in the evolution process. Three LSH genes, AaLSH2, AaLSH9, and AaLSH11, were successfully isolated from Actinidia arguta. The expression pattern and cluster analysis of these three AaLSH genes suggested AaLSH9 might be a key photoresponse gene participating in fruit development in A. arguta. Subcellular localization showed AaLSH9 protein was located in the nucleus. The overexpression of AaLSH9 gene in Arabidopsis thaliana hy5 mutant plants partially complemented the long hypocotyls of hy5 mutant, implying AaLSH9 played a key role as photoresponse factor in cells. In addition, the seed coat color of A. thaliana over-expressing AaLSH9 became lighter than the wide type A.thaliana. Finally, AaCOP1 was confirmed as photoresponse factor to participate in developmental process by stable transgenic A. thaliana. CONCLUSIONS: AaLSH9 can be involved in kiwifruit (A. arguta) development as key photoresponse factor. Our results not only identified the photoresponse factors AaLSH9 and AaCOP1 but also provided insights into their key role in fruit quality improvement in the process of light response.

Efficient three phase partitioning of actinidin from kiwifruit (Actinidia deliciosa) and its characterization.

Three phase partitioning (TPP) method was effectively utilized for the extraction and purification of milk clotting protease (actinidin) from the kiwifruit pulp. The different purification parameters of TPP such as ammonium sulfate saturation, ratio of the crude kiwifruit extract to tert-butanol, and the pH value of extract were optimized. The 40% (w/v) salt saturation having 1.0:0.75 (v/v) ratio of crude kiwifruit extract to tert-butanol at 6.0 pH value exhibited 3.14 purification fold along with 142.27% recovery, and the protease was concentrated exclusively at intermediate phase (IP). This fraction showed milk-clotting activity (MCA), but there was no such activity in lower aqueous phase (AP). The enzyme molecular weight was found to be 24 kDa from Tricine SDS-PAGE analysis. Recovered protease demonstrated greater stability at pH 7.0 and temperature 50 °C. The Vmax and Km values were 121.9 U/ml and 3.2 mg/ml respectively. Its cysteine nature was demonstrated by inhibition studies. This study highlighted that the TPP is an economic and effective method for extraction and purification of actinidin from kiwifruit, and it could be used as a vegetable coagulant for cheesemaking.

Eco-friendly managements and molecular mechanisms for improving postharvest quality and extending shelf life of kiwifruit: A review.

Kiwifruit (Actinidia spp.) is a commercially important horticultural fruit crop worldwide. Kiwifruit contains numerous minerals, vitamins, and dietary phytochemicals, that not only responsible for the flavor but can also serve as adjuncts in the treatment of diabetes, digestive disorders, cardiovascular system, cancer and heart disease. However, fruit quality and shelf life affect consumer's acceptance and production chain. Understanding the methods of fruit storage preservation, as well as their biochemical, physiological, and molecular basis is essential. In recent years, eco-friendly (comprehensive and environmentally friendly) treatments such as hot water, ozone, chitosan, quercetin, and antifungal additive from biocontrol bacteria or yeast have been applied to improve postharvest fruit quality with longer shelf life. This review provides a comprehensive overview of the latest advancements in control measures, applications, and mechanisms related to water loss, chilling injury, and pathogen diseases in postharvest kiwifruit. Further studies should utilize genome editing techniques to enhance postharvest fruit quality and disease resistance through site-directed bio-manipulation of the kiwifruit genome.

Adapting the inoculation methods of kiwifruit canker disease to identify efficient biocontrol bacteria from branch microbiome.

Pseudomonas syringae pv. actinidiae (Psa), the bacterium that causes kiwifruit bacterial canker, is a common field occurrence that is difficult to control globally. Currently, exploring the resources for efficient biocontrol bacteria is a hot spot in the field. The common strategy for isolating biocontrol bacteria is to directly isolate biocontrol bacteria that can secrete diffusible antibacterial substances, most of which are members of Bacillus, Pseudomonas and Streptomycetaceae, from disease samples or soil. Here, we report a new approach by adapting the typical isolation methods of kiwifruit canker disease to identify efficient biocontrol bacteria from the branch microbiome. Using this unique approach, we isolated a group of kiwifruit biocontrol agents (KBAs) from the branch microbiome of Psa-resistant varieties. Thirteen of these showed no antagonistic activity in vitro, which depends on the secretion of antibacterial compounds. However, they exhibited antibacterial activity via cell-to-cell contacts mimicked by co-culture on agar plates. Through biocontrol tests on plants, two isolates, KBA13 and KBA19, demonstrated their effectiveness by protecting kiwifruit branches from Psa infection. Using KBA19, identified as Pantoea endophytica, as a representative, we found that this bacterium uses the type VI secretion system (T6SS) as the main contact-dependent antibacterial weapon that acts via translocating toxic effector proteins into Psa cells to induce cell death, and that this capacity expressed by KBA19 is common to various Psa strains from different countries. Our findings highlight a new strategy to identify efficient biocontrol agents that use the T6SS to function in an antibacterial metabolite-independent manner to control wood diseases.