Identification of miRNA858 long-loop precursors in seed plants.

MicroRNAs (miRNAs) are a class of nonprotein-coding short transcripts that provide a layer of post-transcriptional regulation essential to many plant biological processes. MiR858, which targets the transcripts of MYB transcription factors, can affect a range of secondary metabolic processes. Although miR858 and its 187-nt precursor have been well studied in Arabidopsis (Arabidopsis thaliana), a systematic investigation of miR858 precursors and their functions across plant species is lacking due to a problem in identifying the transcripts that generate this subclass. By re-evaluating the transcript of miR858 and relaxing the length cut-off for identifying hairpins, we found in kiwifruit (Actinidia chinensis) that miR858 has long-loop hairpins (1,100 to 2,100 nt), whose intervening sequences between miRNA generating complementary sites were longer than all previously reported miRNA hairpins. Importantly, these precursors of miR858 containing long-loop hairpins (termed MIR858L) are widespread in seed plants including Arabidopsis, varying between 350 and 5,500 nt. Moreover, we showed that MIR858L has a greater impact on proanthocyanidin and flavonol levels in both Arabidopsis and kiwifruit. We suggest that an active MIR858L-MYB regulatory module appeared in the transition of early land plants to large upright flowering plants, making a key contribution to plant secondary metabolism.

Chromosome-level genome of putative autohexaploid Actinidia deliciosa provides insights into polyploidisation and evolution.

Actinidia ('Mihoutao' in Chinese) includes species with complex ploidy, among which diploid Actinidia chinensis and hexaploid Actinidia deliciosa are economically and nutritionally important fruit crops. Actinidia deliciosa has been proposed to be an autohexaploid (2n = 174) with diploid A. chinensis (2n = 58) as the putative parent. A CCS-based assembly anchored to a high-resolution linkage map provided a chromosome-resolved genome for hexaploid A. deliciosa yielded a 3.91-Gb assembly of 174 pseudochromosomes comprising 29 homologous groups with 6 members each, which contain 39 854 genes with an average of 4.57 alleles per gene. Here we provide evidence that much of the hexaploid genome matches diploid A. chinensis; 95.5% of homologous gene pairs exhibited >90% similarity. However, intragenome and intergenome comparisons of synteny indicate chromosomal changes. Our data, therefore, indicate that if A. deliciosa is an autoploid, chromosomal rearrangement occurred following autohexaploidy. A highly diversified pattern of gene expression and a history of rapid population expansion after polyploidisation likely facilitated the adaptation and niche differentiation of A. deliciosa in nature. The allele-defined hexaploid genome of A. deliciosa provides new genomic resources to accelerate crop improvement and to understand polyploid genome evolution.

The kiwifruit amyloplast proteome (kfALP): a resource to better understand the mechanisms underlying amyloplast biogenesis and differentiation.

The biogenesis and differentiation (B&D) of amyloplasts contributes to fruit flavor and color. Here, remodeling of starch granules, thylakoids and plastoglobules was observed during development and ripening in two kiwifruit (Actinidia spp.) cultivars - yellow-fleshed 'Hort16A' and green-fleshed 'Hayward'. A protocol was developed to purify starch-containing plastids with a high degree of intactness, and amyloplast B&D was studied using label-free-based quantitative proteomic analyses in both cultivars. Over 3000 amyloplast-localized proteins were identified, of which >98% were quantified and defined as the kfALP (kiwifruit amyloplast proteome). The kfALP data were validated by Tandem-Mass-Tag (TMT) labeled proteomics in 'Hort16A'. Analysis of the proteomic data across development and ripening revealed: 1) a conserved increase in the abundance of proteins participating in starch synthesis/degradation during both amyloplast B&D; 2) up-regulation of proteins for chlorophyll degradation and of plastoglobule-localized proteins associated with chloroplast breakdown and plastoglobule formation during amyloplast differentiation; 3) constitutive expression of proteins involved in ATP supply and protein import during amyloplast B&D. Interestingly, two different pathways of amyloplast B&D were observed in the two cultivars. In 'Hayward', significant increases in abundance of photosynthetic- and tetrapyrrole metabolism-related proteins were observed, but the opposite trend was observed in 'Hort16A'. In conclusion, analysis of the kfALP provides new insights into the potential mechanisms underlying amyloplast B&D with relevance to key fruit quality traits in contrasting kiwifruit cultivars.

Comprehensive assessment of drought resistance and recovery in kiwifruit genotypes using multivariate analysis.

As global climate change persists, ongoing warming exposes plants, including kiwifruit, to repeated cycles of drought stress and rewatering, necessitating the identification of drought-resistant genotypes for breeding purposes. To better understand the physiological mechanisms underlying drought resistance and recovery in kiwifruit, moderate (40-45% field capacity) and severe (25-30% field capacity) drought stresses were applied, followed by rewatering (80-85% field capacity) to eight kiwifruit rootstocks in this study. We then conducted a multivariate analysis of 20 indices for the assessment of drought resistance and recovery capabilities. Additionally, we identified four principal components, each playing a vital role in coping with diverse water conditions. Three optimal indicator groups were pinpointed, enhancing precision in kiwifruit drought resistance and recovery assessment and simplifying the evaluation system. Finally, MX-1 and HW were identified as representative rootstocks for future research on kiwifruit's responses to moderate and severe drought stresses. This study not only enhances our understanding of the response mechanisms of kiwifruit rootstocks to progressive drought stress and recovery but also provides theoretical guidance for reliable screening of drought-adaptive kiwifruit genotypes.

Restricted responses of AcMYB68 and AcERF74/75 enhanced waterlogging tolerance in kiwifruit.

Most of kiwifruit cultivars (e.g. Actinidia chinensis cv. Donghong, "DH") were sensitive to waterlogging, thus, waterlogging resistant rootstocks (e.g. Actinidia valvata Dunn, "Dunn") were widely used for kiwifruit industry. Those different species provided ideal materials to understand the waterlogging responses in kiwifruit. Compared to the weaken growth and root activities in "DH", "Dunn" maintained the relative high root activities under the prolonged waterlogging. Based on comparative analysis, transcript levels of pyruvate decarboxylase (PDCs) and alcohol dehydrogenase (ADHs) showed significantly difference between these two species. Both PDCs and ADHs had been significantly increased by waterlogging in "DH", while they were only limitedly triggered by 2 days stress and subsided during the prolonged waterlogging in "Dunn". Thus, 19 differentially expressed transcript factors (DETFs) had been isolated using weighted gene co-expression network analysis combined with transcriptomics and transcript levels of PDCs and ADHs in waterlogged "DH". Among these DETFs, dual luciferase and electrophoretic mobility shift assays indicated AcMYB68 could bind to and trigger the activity of AcPDC2 promoter. The stable over-expression of AcMYB68 significantly up-regulated the transcript levels of PDCs but inhibited the plant growth, especially the roots. Moreover, the enzyme activities of PDC in 35S::AcMYB68 were significantly enhanced during the waterlogging response than that in wild type plants. Most interestingly, comparative analysis indicated that the expression patterns of AcMYB68 and the previously characterized AcERF74/75 (the direct regulator on ADHs) either showed no responses (AcMYB68 and AcERF74) or very limited response (AcERF75) in "Dunn". Taken together, the restricted responses of AcMYB68 and AcERF74/75 in "Dunn" endow its waterlogging tolerance.

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.

An efficient genetic transformation system mediated by Rhizobium rhizogenes in fruit trees based on the transgenic hairy root to shoot conversion.

Genetic transformation is a critical tool for gene editing and genetic improvement of plants. Although many model plants and crops can be genetically manipulated, genetic transformation systems for fruit trees are either lacking or perform poorly. We used Rhizobium rhizogenes to transfer the target gene into the hairy roots of Malus domestica and Actinidia chinensis. Transgenic roots were generated within 3 weeks, with a transgenic efficiency of 78.8%. Root to shoot conversion of transgenic hairy roots was achieved within 11 weeks, with a regeneration efficiency of 3.3%. Finally, the regulatory genes involved in stem cell activity were used to improve shoot regeneration efficiency. MdWOX5 exhibited the most significant effects, as it led to an improved regeneration efficiency of 20.6% and a reduced regeneration time of 9 weeks. Phenotypes of the overexpression of RUBY system mediated red roots and overexpression of MdRGF5 mediated longer root hairs were observed within 3 weeks, suggesting that the method can be used to quickly screen genes that influence root phenotype scores through root performance, such as root colour, root hair, and lateral root. Obtaining whole plants of the RUBY system and MdRGF5 overexpression lines highlights the convenience of this technology for studying gene functions in whole plants. Overall, we developed an optimized method to improve the transformation efficiency and stability of transformants in fruit trees.

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.

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.

Comparative chloroplast-specific SNP and nSCoT markers analysis and population structure study in kiwifruit plants.

BACKGROUND: Kiwifruit (Actinidiaceae family) is an economically important fruit tree in China and New Zealand. It is a typical dioecious plant that has undergone frequent natural hybridization, along with chromosomal ploidy diversity within the genus Actinidia, resulting in higher genetic differences and horticultural diversity between interspecific and intraspecific traits. This diversity provides a rich genetic base for breeding. China is not only the original center of speciation for the Actinidia genus but also its distribution center, housing the most domesticated species: A. chinensis var. chinensis, A. chinensis var. deliciosa, A. arguta, and A. polygama. However, there have been relatively few studies on the application of DNA markers and the genetic basis of kiwifruit plants. By combining information from chloroplast-specific SNPs and nuclear SCoT (nSCoT) markers, we can uncover complementary aspects of genetic variation, population structure, and evolutionary relationships. In this study, one chloroplast DNA (cpDNA) marker pair was selected out of nine cpDNA candidate pairs. Twenty nSCoT markers were selected and used to assess the population structure and chloroplast-specific DNA haplotype diversity in 55 kiwifruit plants (Actinidia), including 20 samples of A. chinensis var. chinensis, 22 samples of A. chinensis var. deliciosa, 11 samples of A. arguta, and two samples of A. polygama, based on morphological observations collected from China. RESULTS: The average genetic distance among the 55 samples was 0.26 with chloroplast-specific SNP markers and 0.57 with nSCoT markers. The Mantel test revealed a very small correlation (r = 0.21). The 55 samples were categorized into different sub-populations using Bayesian analysis, the Unweighted Pair Group Method with the Arithmetic Mean (UPGMA), and the Principal Component Analysis (PCA) method, respectively. Based on the analysis of 205 variable sites, a total of 15 chloroplast-specific DNA haplotypes were observed, contributing to a higher level of polymorphism with an Hd of 0.78. Most of the chloroplast-specific DNA haplotype diversity was distributed among populations, but significant diversity was also observed within populations. H1 was shared by 24 samples, including 12 of A. chinensis var. chinensis and 12 of A. chinensis var. deliciosa, indicating that H1 is an ancient and dominant haplotype among the 55 chloroplast-specific sequences. H2 may not have evolved further.The remaining haplotypes were rare and unique, with some appearing to be exclusive to a particular variety and often detected in single individuals. For example, the H15 haplotype was found exclusively in A. polygama. CONCLUSION: The population genetic variation explained by chloroplast-specific SNP markers has greater power than that explained by nSCoTs, with chloroplast-specific DNA haplotypes being the most efficient. Gene flow appears to be more evident between A. chinensis var. chinensis and A. chinensis var. deliciosa, as they share chloroplast-specific DNA haplotypes, In contrast, A.arguta and A. polygama possess their own characteristic haplotypes, derived from the haplotype of A. chinensis var. chinensis. Compared with A. chinensis, the A.arguta and A. polygama showed better grouping. It also seems crucial to screen out, for each type of molecular marker, especially haplotypes, the core markers of the Actinidia genus.

Genome-Wide Identification and Expression Analysis of Kiwifruit Leucine-Rich Repeat Receptor-Like Proteins Reveal Their Roles in Biotic and Abiotic Stress Responses.

Leucine-rich repeat receptor-like proteins (LRR-RLPs), a major group of receptor-like proteins in plants, have diverse functions in plant physiology, including growth, development, signal transduction, and stress responses. Despite their importance, the specific roles of kiwifruit LRR-RLPs in response to biotic and abiotic stresses remain poorly understood. In this study, we performed family identification, characterization, transcriptome data analysis, and differential gene expression analysis of kiwifruit LRR-RLPs. We identified totals of 101, 164, and 105 LRR-RLPs in Actinidia chinensis 'Hongyang', Actinidia eriantha 'Huate', and Actinidia chinensis 'Red5', respectively. Synteny analysis revealed that the expansion of kiwifruit LRR-RLPs was primarily attributed to segmental duplication events. Based on RNA-seq data from pathogen-infected kiwifruits, we identified specific LRR-RLP genes potentially involved in different stages of pathogen infection. Additionally, we observed the potential involvement of kiwifruit LRR-RLPs in abiotic stress responses, with upstream transcription factors possibly regulating their expression. Furthermore, protein interaction network analysis unveiled the participation of kiwifruit LRR-RLP in the regulatory network of abiotic stress responses. These findings highlight the crucial roles of LRR-RLPs in mediating both biotic and abiotic stress responses in kiwifruit, offering valuable insights for the breeding of stress-resistant kiwifruit varieties.

Ethylene induced AcNAC3 and AcNAC4 take part in ethylene synthesis through mediating AcACO1 during kiwifruit (Actinidia chinensis) ripening.

BACKGROUND: Ethylene plays a vital role in the ripening process of kiwifruit. A terrific amount of transcription factors (TFs) have been shown to regulate ethylene synthesis in various fruits. RESULTS: In this research, two new NAC TFs, named AcNAC3 and AcNAC4, were isolated from kiwifruit, which belonged to NAM subfamily. Bioinformatics analysis showed that both AcNAC3 and AcNAC4 were hydrophilic proteins with similar three-dimensional structures. The expression levels of AcNAC3, AcNAC4 and AcACO1 increased during kiwifruit ripening, as well as were induced by ethylene and repressed by 1-methylcyclopropene (1-MCP). Correlation analysis exhibited that ethylene production was positively correlated with the expression levels of AcNAC3, AcNAC4 and AcACO1. Moreover, both AcNAC3 and AcNAC4 acted as transcriptional activators and could bind to and activate AcACO1 promoter. CONCLUSION: All results unveiled that the ethylene-induced AcNAC3 and AcNAC4 were transcriptional activators, and might participate in kiwifruit ripening and ethylene biosynthesis through activating AcACO1, providing a new insight of ethylene synthetic regulation during kiwifruit ripening. © 2024 Society of Chemical Industry.

Mechanisms of Actinidia chinensis Planch in treating colon cancer based on the integration of network pharmacology, molecular docking, and experimental verification.

BACKGROUND: As an anticancer Chinese herbal medicine, the effective components and mechanism of Actinidia chinensis Planch (ACP, Tengligen) in the treatment of colon cancer are still unclear. In the present study, the integration of network pharmacology, molecular docking, and cell experiments was employed to study the effective mechanism of ACP against colon cancer. METHODS: The Venn diagram and STRING database were used to construct the protein-protein interaction network (PPI) of ACP-colon cancer, and further topological analysis was used to obtain the key target genes of ACP in colon cancer. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to visualize the related functions and pathways. Molecular docking between key targets and compounds was determined using software such as AutoDockTools. Finally, the effect of ACP on CT26 cells was observed in vitro. RESULTS: The study identified 40 ACP-colon key targets, including CASP3, CDK2, GSK3B, and PIK3R1. GO and KEGG enrichment analyses found that these genes were involved in 211 biological processes and 92 pathways, among which pathways in cancer, PI3K-Akt, p53, and cell cycle might be the main pathways of ACP against colon cancer. Molecular docking verified that the key components of ACP could stably bind to the corresponding targets. The experimental results showed that ACP could inhibit proliferation, induce apoptosis, and downregulate the phosphorylation of PIK3R1, Akt, and GSK3B in CT26 cells. CONCLUSION: ACP is an anti-colon cancer herb with multiple components, and involvement of multiple target genes and signaling pathways. ACP can significantly inhibit proliferation and induce apoptosis of colon cancer cells, which may be closely related to the regulation of PI3K/AKT/GSK3B signal transduction.

A 4D Proteome Investigation of the Potential Mechanisms of SA in Triggering Resistance in Kiwifruit to Pseudomonas syringae pv. actinidiae.

Kiwifruit bacterial cankers caused by Pseudomonas syringae pv. actinidiae (Psa) are a serious threat to the kiwifruit industry. Salicylic acid (SA) regulates plant defense responses and was previously found to enhance kiwifruit's resistance to Psa. However, the underlying mechanisms of this process remain unclear. In this study, we used 4D proteomics to investigate how SA enhances kiwifruit's resistance to Psa and found that both SA treatment and Psa infection induced dramatic changes in the proteomic pattern of kiwifruit. Psa infection triggered the activation of numerous resistance events, including the MAPK cascade, phenylpropanoid biosynthesis, and hormone signaling transduction. In most cases, the differential expression of a number of genes involved in the SA signaling pathway played a significant role in kiwifruit's responses to Psa. Moreover, SA treatment upregulated numerous resistance-related proteins, which functioned in defense responses to Psa, including phenylpropanoid biosynthesis, the MAPK cascade, and the upregulation of pathogenesis-related proteins. We also found that SA treatment could facilitate timely defense responses to Psa infection and enhance the activation of defense responses that were downregulated in kiwifruit during infection with Psa. Thus, our research deciphered the potential mechanisms of SA in promoting Psa resistance in kiwifruit and can provide a basis for the use of SA to enhance kiwifruit resistance and effectively control the occurrence of kiwifruit bacterial cankers.

Kiwifruit Monodehydroascorbate Reductase 3 Gene Negatively Regulates the Accumulation of Ascorbic Acid in Fruit of Transgenic Tomato Plants.

Ascorbic acid is a potent antioxidant and a crucial nutrient for plants and animals. The accumulation of ascorbic acid in plants is controlled by its biosynthesis, recycling, and degradation. Monodehydroascorbate reductase is deeply involved in the ascorbic acid cycle; however, the mechanism of monodehydroascorbate reductase genes in regulating kiwifruit ascorbic acid accumulation remains unclear. Here, we identified seven monodehydroascorbate reductase genes in the genome of kiwifruit (Actinidia eriantha) and they were designated as AeMDHAR1 to AeMDHAR7, following their genome identifiers. We found that the relative expression level of AeMDHAR3 in fruit continued to decline during development. The over-expression of kiwifruit AeMDHAR3 in tomato plants improved monodehydroascorbate reductase activity, and, unexpectedly, ascorbic acid content decreased significantly in the fruit of the transgenic tomato lines. Ascorbate peroxidase activity also increased significantly in the transgenic lines. In addition, a total of 1781 differentially expressed genes were identified via transcriptomic analysis. Three kinds of ontologies were identified, and 106 KEGG pathways were significantly enriched for these differently expressed genes. Expression verification via quantitative real-time PCR analysis confirmed the reliability of the RNA-seq data. Furthermore, APX3, belonging to the ascorbate and aldarate metabolism pathway, was identified as a key candidate gene that may be primarily responsible for the decrease in ascorbic acid concentration in transgenic tomato fruits. The present study provides novel evidence to support the feedback regulation of ascorbic acid accumulation in the fruit of kiwifruit.

Genome assembly of autotetraploid Actinidia arguta highlights adaptive evolution and enables dissection of important economic traits.

Actinidia arguta, the most widely distributed Actinidia species and the second cultivated species in the genus, can be distinguished from the currently cultivated Actinidia chinensis on the basis of its small and smooth fruit, rapid softening, and excellent cold tolerance. Adaptive evolution of tetraploid Actinidia species and the genetic basis of their important agronomic traits are still unclear. Here, we generated a chromosome-scale genome assembly of an autotetraploid male A. arguta accession. The genome assembly was 2.77 Gb in length with a contig N50 of 9.97 Mb and was anchored onto 116 pseudo-chromosomes. Resequencing and clustering of 101 geographically representative accessions showed that they could be divided into two geographic groups, Southern and Northern, which first diverged 12.9 million years ago. A. arguta underwent two prominent expansions and one demographic bottleneck from the mid-Pleistocene climate transition to the late Pleistocene. Population genomics studies using paleoclimate data enabled us to discern the evolution of the species' adaptation to different historical environments. Three genes (AaCEL1, AaPME1, and AaDOF1) related to flesh softening were identified by multi-omics analysis, and their ability to accelerate flesh softening was verified through transient expression assays. A set of genes that characteristically regulate sexual dimorphism located on the sex chromosome (Chr3) or autosomal chromosomes showed biased expression during stamen or carpel development. This chromosome-level assembly of the autotetraploid A. arguta genome and the genes related to important agronomic traits will facilitate future functional genomics research and improvement of A. arguta.

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.

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.

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.

Bioactive compounds from Actinidia arguta fruit as a new strategy to fight glioblastoma.

In recent years, there has been a significant demand for natural products as a mean of disease prevention or as an alternative to conventional medications. The driving force for this change is the growing recognition of the abundant presence of valuable bioactive compounds in natural products. On recent years Actinia arguta fruit, also known as kiwiberry, has attracted a lot of attention from scientific community due to its richness in bioactive compounds, including phenolic compounds, organic acids, vitamins, carotenoids and fiber. These bioactive compounds contribute to the fruit's diverse outstanding biological activities such as antioxidant, anti-inflammatory, neuroprotective, immunomodulatory, and anti-cancer properties. Due to these properties, the fruit may have the potential to be used in the treatment/prevention of various types of cancer, including glioblastoma. Glioblastoma is the most aggressive form of brain cancer, displaying 90 % of recurrence rate within a span of 2 years. Despite the employment of an aggressive approach, the prognosis remains unfavorable, emphasizing the urgent requirement for the development of new effective treatments. The preclinical evidence suggests that kiwiberry has potential impact on glioblastoma by reducing the cancer self-renewal, modulating the signaling pathways involved in the regulation of the cell phenotype and metabolism, and influencing the consolidation of the tumor microenvironment. Even though, challenges such as the imprecise composition and concentration of bioactive compounds, and its low bioavailability after oral administration may be drawbacks to the development of kiwiberry-based treatments, being urgent to ensure the safety and efficacy of kiwiberry for the prevention and treatment of glioblastoma. This review aims to highlight the potential impact of A. arguta bioactive compounds on glioblastoma, providing novel insights into their applicability as complementary or alternative therapies.