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Kiwifruit bacterial canker is a devastating disease threatening kiwifruit production. To clarify the defense mechanism in response to Pseudomonas syringae pv. actinidiae (Psa), we observed phenotypic changes in resistant Huate (HT) and susceptible Hongyang (HY) kiwifruit varieties at 0, 12, 24, 48, 96, and 144 hour after inoculation (hai) with Psa. Brown lesions appeared in the inoculation areas 12 hai in HY shoots, and the lesion length gradually increased from 24 to 144 h. In contrast, no lesions were found in HT shoots at any time points. Furthermore, RNA-seq analysis showed significantly more differentially expressed genes between HT and HY at 12 hai than at any other time point. According to weighted gene co-expression network analysis, five modules were notably differentially expressed between HT and HY; pathway mapping using the Kyoto Encyclopedia of Gene and Genomes database was performed for the five modules. In MEgreenyellow and MEyellow modules, pathways related to\"plant-pathogen interaction\", \"Endocytosis\", \"Glycine, serine and threonine metabolism\", and \"Carbon fixation in photosynthetic organisms\" were enriched, whereas in the MEblack module, pathways related to \"protein processing in endoplasmic reticulum\", \"plant-pathogen interaction\", and \"Glycolysis / Gluconeogenesis\" were enriched. In particular, the Pti1 and RPS2 encoding effector receptors, and the NPR1, TGA, and PR1 genes involved in the salicylic acid signaling pathway were significantly up-regulated in HT compared with HY. This indicates that the effector-triggered immunity response was stronger and that the salicylic acid signaling pathway played a pivotal role in the Psa defense response of HT. In addition, we identified other important genes, involved in phenylpropanoid biosynthesis and Ca2+ internal flow, which were highly expressed in HT. Taken together, these results provide important information to elucidate the defense mechanisms of kiwifruit during Psa infection.

Cold stress poses a serious treat to cultivated kiwifruit since this plant generally has a weak ability to tolerate freezing tolerance temperatures. Surprisingly, however, the underlying mechanism of kiwifruit’s freezing tolerance remains largely unexplored and unknown, especially regarding the key pathways involved in conferring this key tolerance trait. Here, we studied the metabolome and transcriptome profiles of the freezing-tolerant genotype KL ( Actinidia arguta ) and freezing-sensitive genotype RB ( A. arguta ), to identify the main pathways and important metabolites related to their freezing tolerance. A total of 565 metabolites were detected by a wide-targeting metabolomics method. Under (−25°C) cold stress, KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway annotations showed that the flavonoid metabolic pathways were specifically upregulated in KL, which increased its ability to scavenge for reactive oxygen species (ROS). The transcriptome changes identified in KL were accompanied by the specific upregulation of a codeinone reductase gene, a chalcone isomerase gene, and an anthocyanin 5-aromatic acyltransferase gene. Nucleotides metabolism and phenolic acids metabolism pathways were specifically upregulated in RB, which indicated that RB had a higher energy metabolism and weaker dormancy ability. Since the LPCs (LysoPC), LPEs (LysoPE) and free fatty acids were accumulated simultaneously in both genotypes, these could serve as biomarkers of cold-induced frost damages. These key metabolism components evidently participated in the regulation of freezing tolerance of both kiwifruit genotypes. In conclusion, the results of this study demonstrated the inherent differences in the composition and activity of metabolites between KL and RB under cold stress conditions.

Understanding canopy nitrogen (N) and phosphorus (P) differences is crucial for optimizing plant nutrient distribution and management. This study evaluated leaf N and P content in citrus trees across three cultivation modes: traditional mode (TM), wide-row and narrow-plant mode (WRNPM), and fenced mode (FM). We used hyperspectral data for non-destructive quantification and compared 1080 leaf samples from upper, middle, and lower canopy layers. Four models—Random Forest (RF), Backpropagation Neural Network (BPNN), Partial Least Squares (PLS), and Support Vector Machine (SVM)—were employed for leaf N and P estimation. Results showed that the TM had significantly lower N content compared to the WRNPM and FM, while the WRNPM exhibited higher P content. The canopy layer had minimal impact on N and P in the FM, and leaves in the upper layer had higher nutrient content in the WRNPM and TM. RF provided the best estimation accuracy, with R2 values of 0.66 for N and 0.72 for P. The cultivation mode and canopy layer significantly influenced the estimation accuracy, with the TM yielding the highest R2, followed by the WRNPM and FM obtaining the lowest accuracy. The labor-saving cultivation mode had different nutrient utilization efficiency compared to the TM. The cultivation mode and canopy layer should be considered when hyperspectral data were used for estimating the leaf N and P content. The study can offer new insights for precise fertilization strategies in fruit trees.

Beta-amylase (BAM) plays an important role in plant resistance to cold stress. However, the specific role of the BAM gene in freezing tolerance is poorly understood. In this study, we demonstrated that a cold-responsive gene module was involved in the freezing tolerance of kiwifruit. In this module, the expression of AaBAM3.1, which encodes a functional protein, was induced by cold stress. AaBAM3.1-overexpressing kiwifruit lines showed increased freezing tolerance, and the heterologous overexpression of AaBAM3.1 in Arabidopsis thaliana resulted in a similar phenotype. The results of promoter GUS activity and cis-element analyses predicted AaCBF4 to be an upstream transcription factor that could regulate AaBAM3.1 expression. Further investigation of protein-DNA interactions by using yeast one-hybrid, GUS coexpression, and dual luciferase reporter assays confirmed that AaCBF4 directly regulated AaBAM3.1 expression. In addition, the expression of both AaBAM3.1 and AaCBF4 in kiwifruit responded positively to cold stress. Hence, we conclude that the AaCBF-AaBAM module is involved in the positive regulation of the freezing tolerance of kiwifruit.

To address the demands of precision agriculture and the measurement of plant photosynthetic response and nitrogen status, it is necessary to employ advanced methods for estimating chlorophyll content quickly and non-destructively at a large scale. Therefore, we explored the utilization of both linear regression and machine learning methodology to improve the prediction of leaf chlorophyll content (LCC) in citrus trees through the analysis of hyperspectral reflectance data in a field experiment. And the relationship between phenology and LCC estimation was also tested in this study. The LCC of citrus tree leaves at five growth seasons (May, June, August, October, and December) were measured alongside measurements of leaf hyperspectral reflectance. The measured LCC data and spectral parameters were used for evaluating LCC using univariate linear regression (ULR), multivariate linear regression (MLR), random forest regression (RFR), K-nearest neighbor regression (KNNR), and support vector regression (SVR). The results revealed the following: the MLR and machine learning models (RFR, KNNR, SVR), in both October and December, performed well in LCC estimation with a coefficient of determination (R2) greater than 0.70. In August, the ULR model performed the best, achieving an R2 of 0.69 and root mean square error (RMSE) of 8.92. However, the RFR model demonstrated the highest predictive power for estimating LCC in May, June, October, and December. Furthermore, the prediction accuracy was the best with the RFR model with parameters VOG2 and Carte4 in October, achieving an R2 of 0.83 and RMSE of 6.67. Our findings revealed that using just a few spectral parameters can efficiently estimate LCC in citrus trees, showing substantial promise for implementation in large-scale orchards.

Actinidia arguta is the most basal species in a phylogenetically and economically important genus in the family Actinidiaceae. To better understand the molecular basis of the Actinidia arguta chloroplast (cp), we sequenced the complete cp genome from A. arguta using Illumina and PacBio RS II sequencing technologies. The cp genome from A. arguta was 157,611 bp in length and composed of a pair of 24,232 bp inverted repeats (IRs) separated by a 20,463 bp small single copy region (SSC) and an 88,684 bp large single copy region (LSC). Overall, the cp genome contained 113 unique genes. The cp genomes from A. arguta and three other Actinidia species from GenBank were subjected to a comparative analysis. Indel mutation events and high frequencies of base substitution were identified, and the accD and ycf2 genes showed a high degree of variation within Actinidia. Forty-seven simple sequence repeats (SSRs) and 155 repetitive structures were identified, further demonstrating the rapid evolution in Actinidia. The cp genome analysis and the identification of variable loci provide vital information for understanding the evolution and function of the chloroplast and for characterizing Actinidia population genetics.

Background Kiwifruit ( Actinidia Lindl.) is considered an important fruit species worldwide. Due to its temperate origin, this species is highly vulnerable to freezing injury while under low-temperature stress. To obtain further knowledge of the mechanism underlying freezing tolerance, we carried out a hybrid transcriptome analysis of two A. arguta ( Actinidi arguta ) genotypes, KL and RB, whose freezing tolerance is high and low, respectively. Both genotypes were subjected to − 25 °C for 0 h, 1 h, and 4 h. Results SMRT (single-molecule real-time) RNA-seq data were assembled using the de novo method, producing 24,306 unigenes with an N50 value of 1834 bp. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEGs showed that they were involved in the ‘starch and sucrose metabolism’, the ‘mitogen-activated protein kinase (MAPK) signaling pathway’, the ‘phosphatidylinositol signaling system’, the ‘inositol phosphate metabolism’, and the ‘plant hormone signal transduction’. In particular, for ‘starch and sucrose metabolism’, we identified 3 key genes involved in cellulose degradation, trehalose synthesis, and starch degradation processes. Moreover, the activities of beta-GC (beta-glucosidase), TPS (trehalose-6-phosphate synthase), and BAM (beta-amylase), encoded by the abovementioned 3 key genes, were enhanced by cold stress. Three transcription factors (TFs) belonging to the AP2/ERF, bHLH (basic helix-loop-helix), and MYB families were involved in the low-temperature response. Furthermore, weighted gene coexpression network analysis (WGCNA) indicated that beta-GC , TPS5 , and BAM3.1 were the key genes involved in the cold response and were highly coexpressed together with the CBF3 , MYC2 , and MYB44 genes. Conclusions Cold stress led various changes in kiwifruit, the ‘phosphatidylinositol signaling system’, ‘inositol phosphate metabolism’, ‘MAPK signaling pathway’, ‘plant hormone signal transduction’, and ‘starch and sucrose metabolism’ processes were significantly affected by low temperature. Moreover, starch and sucrose metabolism may be the key pathway for tolerant kiwifruit to resist low temperature damages. These results increase our understanding of the complex mechanisms involved in the freezing tolerance of kiwifruit under cold stress and reveal a series of candidate genes for use in breeding new cultivars with enhanced freezing tolerance.

The vibration controlled transient elastography (VCTE) technique was used to assess the effectiveness of a Biejia Decoction pill in combination with Entecavir in the treatment of hepatitis B liver fibrosis/cirrhosis. We randomly selected 120 patients to receive entecavir and 119 patients to receive both entecavir and Biejia Decoction Pill, which both with hepatitis B liver fibrosis/cirrhosis visited the Second Affiliated Hospital of Nanchang University between January 2019 and February 2022. The observation group got ETV (entecavir) and Biejia Decoction pills, whereas the control group received only standard ETV antiviral medication. Based on the grading of the VCTE detection value (LSM) initially diagnosed for patients with hepatitis B liver fibrosis/cirrhosis, we divided the patients into two subgroups of liver fibrosis and cirrhosis. In addition, patients with liver fibrosis were divided into mild and moderate subgroups according to their VCTE values. Patients were measured for liver hardness after three, six, nine, and twelve months of treatment with VCTE. Biejia Decoction Pill combined with ETV on HBV liver fibrosis/cirrhosis was evaluated by comparing patients' changes in liver hardness and HBV-DNA negative conversion rates before and after treatment in each group at the same baseline. The LSM (liver elasticity value) of the observation group and the control group after treatment was lower than that before treatment, and the difference was statistically significant (P < 0.0001); The LSM of the observation group after treatment was significantly lower than that of the control group, and the difference was also statistically significant (P = 0.0005 < 0.05). In the subgroup of liver fibrosis, the number of patients with moderate and severe liver fibrosis who completely reversed liver fibrosis after treatment in the treatment group was far more than that in the control group, and the difference between the two groups was statistically significant (χ 2  = 4.82 P = 0.028 < 0.05) 。 When the treatment course was more than 9 months, the negative conversion rate of patients in the observation group reached 87.4%, which was higher than that in the control group (70.8%), and the difference was statistically significant (P = 0.002 < 0.05); After 12 months of treatment, the negative conversion rate of patients in the observation group was as high as 95%, which was significantly higher than 76.67% in the control group (P < 0.001). The degree of liver fibrosis was significantly improved when Biejia Decoction Pill was combined with ETV in patients with liver fibrosis/cirrhosis due to hepatitis B. The virological response rate to HBV-DNA increased with the prolongation of treatment, and the Biejia Decoction Pill assists with entecavir in antiviral therapy.

Fruit skin color is an important characteristic of fruit quality. The light-mediated regulation on fruit skin coloration in Actinidia arguta remains unclear. To better understand the role of light in fruit skin coloration, we performed bagging treatments in both on-tree and off-tree ‘Hongbaoshixing’, which is a kind of all-red-typed A. arguta cultivar. Non-bagging kiwifruits were used as control. For off-tree fruits, there was no difference between non-bagging and bagging treatments. For on-tree fruits, physiological and molecular changes were investigated during fruit development in non-bagging and bagging treatments. Phenotypic identification and the hue angle measurement showed that the stage of most significant color difference between non-bagging and bagging treatments was 130 days (after full bloom). Determination of five anthocyanin components suggested cyanidin-3-O-galactoside and cyanidin-3-O-xylose-galactoside made a main contribution to the fruit skin coloration. Gene expression profiles and cluster analysis showed AaLDOX and AaUFGT were highly expressed at 130 days and obviously clustered into the same class in non-bagging treatment, respectively. Correlation analysis suggested only AaLDOX expression was significantly correlated with anthocyanin content in non-bagging treatment while no correlation in bagging treatment. Similar results was observed for MYB1 transcription factor. The result of subcellular localization showed that AaLDOX was located in the cytoplasm, indicating AaLDOX is indeed structural gene that encodes leucoanthocyanidin dioxygenase participated in anthocyanin biosynthesis. All results were used to establish a possible working model, showing that light is indispensable for normal fruit skin coloration, and bagging treatment suppresses anthocyanin biosynthesis and accumulation mainly by inhibiting AaMYB1 and AaLDOX expression in A. arguta.

Among the genus Actinidia, Actinidia arguta possesses the strongest cold resistance and produces fresh fruit with an intense flavor. To investigate genomic variation that may contribute to variation in phenotypic traits, we performed whole-genome re-sequencing of four A. arguta genotypes originating from different regions in China and identified the polymorphisms using InDel markers. In total, 4,710,650, 4,787,750, 4,646,026, and 4,590,616 SNPs and 1,481,002, 1,534,198, 1,471,304, and 1,425,393 InDels were detected in the 'Ruby-3', 'Yongfeng male', 'Kuilv male', and 'Hongbei male' genomes, respectively, compared with the reference genome sequence of cv 'Hongyang'. A subset of 120 InDels were selected for re-sequencing validation. Additionally, genes related to non-synonymous SNPs and InDels in coding domain sequences were screened for functional analysis. The analysis of GO and KEGG showed that genes involved in cellular responses to water deprivation, sucrose transport, decreased oxygen levels and plant hormone signal transduction were significantly enriched in A. arguta. The results of this study provide insight into the genomic variation of kiwifruit and can inform future research on molecular breeding to improve cold resistance in kiwifruit.