Effects of high-temperature stress on gene expression related to photosynthesis in two jujube (Ziziphus jujuba Mill.) varieties.

Elevated temperatures critically impact crop growth, development, and yield, with photosynthesis being the most temperature-sensitive physiological process in plants. This study focused on assessing the photosynthetic response and genetic adaptation of two different heat-resistant jujube varieties 'Junzao' (J) and 'Fucuimi' (F), to high-temperature stress (42°C Day/30°C Night). Comparative analyses of leaf photosynthetic indices, microstructural changes, and transcriptome sequencing were conducted. Results indicated superior high-temperature adaptability in F, evidenced by alterations in leaf stomatal behavior - particularly in J, where defense cells exhibited significant water loss, shrinkage, and reduced stomatal opening, alongside a marked increase in stomatal density. Through transcriptome sequencing 13,884 differentially expressed genes (DEGs) were identified, significantly enriched in pathways related to plant-pathogen interactions, amino acid biosynthesis, starch and sucrose metabolism, and carbohydrate metabolism. Key findings include the identification of photosynthetic pathway related DEGs and HSFA1s as central regulators of thermal morphogenesis and heat stress response. Revealing their upregulation in F and downregulation in J. The results indicate that these genes play a crucial role in improving heat tolerance in F. This study unveils critical photosynthetic genes involved in heat stress, providing a theoretical foundation for comprehending the molecular mechanisms underlying jujube heat tolerance.

Characteristics of ZjCIPKs and ZjbHLH74-ZjCIPK5 regulated cold tolerance in jujube.

CIPKs are kind of serine/threonine (Ser/Thr) protein kinases which play important roles in response to biotic and abiotic stresses, and in plant growth and development. However, CIPKs in jujube (Ziziphus jujuba Mill.) had limited information, especially regarding their response to cold stress. In the current study, a total of 18 ZjCIPKs were identified in jujube genome which unevenly distributed on seven chromosomes. Conserved motif and gene structural analysis depicted them with conserved DEGLSA and APE motifs and similar structures. Phylogenetic analysis indicated that CIPKs were classified into five subgroups (I-V). In addition, three pairs of ZjCIPKs exhibited tandem duplication while the segmental duplication of ZjCIPKs was not identified. Study on the cis-acting elements indicted that stress or hormone related cis-acting elements were distributed unevenly on ZjCIPKs promoters and most ZjCIPKs were down- or up-regulated by the cold stress. VIGS induced silencing of ZjCIPK5 decreased the cold tolerance of sour jujube. Subcellular location analysis showed ZjCIPK5 located in nucleus. Moreover, transcription factor ZjbHLH74 which was induced at 6 h under cold stress could interact with the promoter of ZjCIPK5 to regulate jujube cold tolerance. These findings provided insights to a molecular basis of CIPK5 in jujube cold tolerance breeding for future.

The 'Candidatus Phytoplasma ziziphi' effectors SJP1/2 negatively control leaf size by stabilizing the transcription factor ZjTCP2 in jujube.

Phytoplasmas manipulate host plant development to benefit insect vector colonization and their own invasion. However, the virulence factors and mechanisms underlying small-leaf formation caused by jujube witches' broom (JWB) phytoplasmas remain largely unknown. Here, effectors SJP1 and SJP2 from JWB phytoplasmas were identified to induce small-leaf formation in jujube (Ziziphus jujuba). In vivo interaction and expression assays showed that SJP1 and SJP2 interacted with and stabilized the transcription factor ZjTCP2. Overexpression of SJP1 and SJP2 in jujube induced ZjTCP2 accumulation. In addition, the abundance of miRNA319f_1 was significantly reduced in leaves of SJP1 and SJP2 transgenic jujube plants and showed the opposite pattern to the expression of its target, ZjTCP2, which was consistent with the pattern in diseased leaves. Overexpression of ZjTCP2 in Arabidopsis promoted ectopic leaves arising from the adaxial side of cotyledons and reduced leaf size. Constitutive expression of the miRNA319f_1 precursor in the 35S::ZjTCP2 background reduced the abundance of ZjTCP2 mRNA and reversed the cotyledon and leaf defects in Arabidopsis. Therefore, these observations suggest that effectors SJP1 and SJP2 induced small-leaf formation, at least partly, by interacting with and activating ZjTCP2 expression both at the transcriptional and the protein level, providing new insights into small-leaf formation caused by phytoplasmas in woody plants.

DNA barcoding identification of grafted Semen Ziziphi Spinosae and transcriptome study of wild Semen Ziziphi Spinosae.

Semen Ziziphi Spinosae (SZS) is the dried and ripe seeds of Ziziphus jujuba var. spinosa. Currently, the yield of naturally grown SZS is unstable owing to environmental factors. Grafting high-quality sour jujube scions onto sour jujube or jujube tree stocks can result in a greater yield. However, the effects of grafting on the quality and gene expression of SZS have rarely been reported. This study used a DNA barcoding technique, high-performance liquid phase-evaporative luminescence detector (HPLC-ELSD), and transcriptomics to investigate the origin and genetic differences between grafted and wild jujube seeds. DNA barcoding identified all samples as Ziziphus jujuba var. spinosa. HPLC-ELSD analysis revealed a higher content of grafted SZS compared to that of the wild SZS. Transcriptome analysis of the metabolic pathways in SZS showed that 22 and 19 differentially expressed gene sequences encoded enzymes related to flavonoids and saponin synthesis, respectively. Weighted correlation network analysis (WGCNA) identified 15 core genes governing the differences in medicinal components between grafted and wild SZS. This study demonstrated the use of DNA barcoding and fingerprint methods to identify jujube seed species and effectively capture ingredient information of medicinal materials. Additionally, transcriptome technology provided data for identifying core differential genes, facilitating studies on quality differences between grafted and wild SZS.

ZjWRKY23 and ZjWRKY40 Promote Fruit Size Enlargement by Targeting and Downregulating Cytokinin Oxidase/Dehydrogenase 5 Expression in Chinese Jujube.

Fruit size is crucial for fruit trees, as it contributes to both quality and yield. However, the underlying mechanism of fruit size regulation remains largely unknown. Taking advantage of using a fruit double-sized bud mutant of Chinese jujube, "Jinkuiwang" and its wild type, "Jinsixiaozao", we carried out a comprehensive study on the mechanism of fruit size development in jujube. Using weighted gene coexpression network analyses, a number of candidate regulators for fruit size including those involved in hormonal signaling pathways, transcription factors, and heat shock proteins were identified. A hub gene named cytokinin oxidase/dehydrogenase 5 (ZjCKX5), responsible for cytokinin degradation, was found to play a negative role in regulating fruit size development, and overexpressing ZjCKX5 in tomato and Arabidopsis resulted in much smaller fruits and dwarf plants. Furthermore, another two hub genes, ZjWRKY23 and ZjWRKY40 transcription factors, were found to participate in fruit size regulation by targeting and downregulating the ZjCKX5 expression. Overexpressing ZjWRKY23 or ZjWRKY40 in tomato led to much larger fruits and promoted plant architecture. Based on these results, a molecular framework for jujube fruit size regulation, namely, ZjWRKY-ZjCKX5 module, was proposed. This study provides a new insight into the molecular networks underlying fruit size regulation.

Genome-wide analysis of ALDH gene family in jujube and identification of ZjALDH3F3 for its important role in high-temperature tolerance.

Aldehyde dehydrogenases (ALDHs) are NAD(P)-dependent enzymes that oxidize aliphatic and aromatic aldehydes. They play crucial roles in various biological processes and plant responses to stress. The impact of high temperatures on jujube quality and yield has been well documented. Nevertheless, the involvement of ALDHs in the response to heat stress remains poorly understood. This study aimed to identify ZjALDHs in the jujube genome (Ziziphus jujuba var. spinosa) and conducted in silico analyses. Phylogenetic analyses indicated that ALDHs in plants, including jujube, can be divided into ten families, and members from the same family share conserved gene and protein structures. Quantitative real-time PCR (qRT-PCR) and ß-glucuronidase (GUS) histochemical staining were used to analyze the expression patterns of ZjALDHs in response to elevated temperatures. We identified a ZjALDH (ZjALDH3F3) gene displaying a significant upregulation and down-regulation, respectively in heat-resistant (HR) and heat-sensitive (HS) jujube in response to heat treatments. Such specific responses are probably attributed to the different heat-responsive cis-elements of ZjALDH3F3 in HR and HS jujubes. ZjALDH3F3 over-expressed in tobacco increased heat tolerance, as evidenced by the reduced accumulation of reactive oxygen species (ROS) and elevated activity of antioxidant enzymes. The qRT-PCR results indicated that the expression of antioxidant enzymes, abscisic acid (ABA), and stress-responsive genes was enhanced in transgenic tobacco. This study sheds novel light on the function of ZjALDHs in heat resistance of jujube.

Morphological characterization and interspecific variation among five species of Ziziphus genus to select superiors in Iran.

BACKGROUND: Several species of the genus Ziziphus are used worldwide for their medicinal and therapeutic properties. The present study aimed to investigate the phenotypic variation of five species of the Ziziphus genus, including Z. jujuba Mill. (25 accessions), Z. mauritiana Lam. (25 accessions), Z. spina-christi L. (25 accessions), Z. nummularia L. (10 accessions), and Z. xylopyrus Willd. (10 accessions) from Markazi, Sistan-va-Baluchestan, and Khuzestan provinces, Iran. RESULTS: The investigated accessions have significant differences in terms of all the measured as revealed using analysis of variance (ANOVA, P < 0.01). The range of fruit weight was 0.43-1.29 g in Z. jujuba, 17.85-29.87 g in Z. mauritiana, 0.94-3.44 g in Z. spina-christi, 0.93-2.02 g in Z. nummularia, and 0.91-3.02 g in Z. xylopyrus. All the measured traits showed significant and positive correlations with each other. Multiple regression analysis (MRA) results showed that fruit length, stone width, stone weight, stone length, and fruit width have significant effects on fruit weight, and thus their fluctuations have a significant effect on increasing or decreasing fruit weight. The accessions were grouped into two main clusters using hierarchical cluster analysis. The first cluster (I) included all the accessions of Z. mauritiana, while the second cluster (II) contained the accessions of the rest species forming two sub-clusters. CONCLUSION: Based on the commercial characters, accessions no. 12, 13, 17, 23, and 24 in Z. jujuba, accessions no. 3, 9, 17, 18, 20, 22, and 23 in Z. mauritiana, accessions no. 5, 6, 8, 13, 19, 22, and 24 in Z. spina-christi, accessions no. 3, 7, and 9 in Z. nummularia, and accessions no. 2, 4, 7, and 10 in Z. oxyphylla showed the highest fruit weight and thus can be suggested as superior for cultivation or use in breeding programs due to having larger fruits.

Biological Characteristics and Functional Analysis of the Linoleic Acid Synthase Gene ZjFAD2 in Jujube.

Jujube fruit is rich in linoleic acid and other bioactive components and has great potential to be used for the development of functional foods. However, the roles of FAD2 genes in linoleic acid biosynthesis in jujube fruit remain unclear. Here, we identified 15 major components in jujube and found that linoleic acid was the main unsaturated fatty acid; major differences in the content and distribution of linoleic acid in the pulp and seeds were observed, and levels of linoleic acid decreased during fruit maturation. Analysis of the fatty acid metabolome, genome, and gene expression patterns of cultivated and wild-type jujube revealed five ZjFAD2 family members highly related to linoleic acid biosynthesis. The heterologous expression of these five ZjFAD2 family members in tobacco revealed that all five of these genes increased the content of linoleic acid. Additionally, transient expression of these genes in jujube fruit and the virus-induced gene silencing (VIGS) test further confirmed the key roles of ZjFAD2-11 and ZjFAD2-1 in the biosynthesis of linoleic acid. The results of this research provide valuable insights into the molecular mechanism underlying linoleic acid synthesis in jujube and will aid the development of quality-oriented breeding strategies.

Anatomical observation and transcriptome analysis of branch-twisted mutations in Chinese jujube.

BACKGROUND: Plant organs grow in a certain direction and organ twisted growth, a rare and distinctive trait, is associated with internal structure changes and special genes. The twisted branch mutant of Chinese jujube jujube, an important fruit tree native to China and introduced to nearly 50 countries, provides new typical materials for exploration of plant twisted growth. RESULTS: In this study, the cytological characteristics and related genes of twisted branches in Chinese jujube were revealed by microscopy observation and transcriptome analysis. The unique coexistence of primary and secondary structures appeared in the twisted parts of branches, and special structures such as collateral bundle, cortical bundles, and internal phloem were formed. Ninety differentially expressed genes of 'Dongzao' and its twisted mutant were observed, in which ZjTBL43, ZjFLA11, ZjFLA12 and ZjIQD1 were selected as candidate genes. ZjTBL43 was homologous to AtTBL43 in Arabidopsis, which was involved in the synthesis and deposition of cellular secondary wall cellulose. The attbl43 mutant showed significant inflorescence stem bending growth. The transgenic lines of attbl43 with overexpression of ZjTBL43 were phenotypically normal.The branch twisted growth may be caused by mutations in ZjTBL43 in Chinese jujube. AtIQD10, AtFLA11 and AtFLA12 were homologous to ZjIQD1, ZjFLA11 and ZjFLA12, respectively. However, the phenotype of their function defect mutants was normal. CONCLUSION: In summary, these findings will provide new insights into the plant organ twisted growth and a reference for investigation of controlling mechanisms of plant growth direction.

Analysis of the Glycoside Hydrolase Family 1 from Wild Jujube Reveals Genes Involved in the Degradation of Jujuboside A.

Jujubosides are the major medicinal ingredients of Ziziphi Spinosae Semen (the seed of wild jujube). To date, a complete understanding of jujuboside's metabolic pathways has not been attained. This study has systematically identified 35 ß-glucosidase genes belonging to the glycoside hydrolase family 1 (GH1) using bioinformatic methods based on the wild jujube genome. The conserved domains and motifs of the 35 putative ß-glucosidases, along with the genome locations and exon-intron structures of 35 ß-glucosidase genes were revealed. The potential functions of the putative proteins encoded by the 35 ß-glucosidase genes are suggested based on their phylogenetic relationships with Arabidopsis homologs. Two wild jujube ß-glucosidase genes were heterologously expressed in Escherichia coli, and the recombinant proteins were able to convert jujuboside A (JuA) into jujuboside B (JuB). Since it has been previously reported that JuA catabolites, including JuB and other rare jujubosides, may play crucial roles in the jujuboside's pharmacological activity, it is suggested that these two proteins can be used to enhance the utilization potential of jujubosides. This study provides new insight into the metabolism of jujubosides in wild jujube. Furthermore, the characterization of ß-glucosidase genes is expected to facilitate investigations involving the cultivation and breeding of wild jujube.

Influences of Jujube Witches' Broom (JWB) Phytoplasma Infection and Oxytetracycline Hydrochloride Treatment on the Gene Expression Profiling in Jujube.

Jujube witches' broom disease (JWB), caused by Candidatus Phytoplasma ziziphi, is the most destructive phytoplasma disease threatening the jujube industry. Tetracycline derivatives treatments have been validated to be capable of recovering jujube trees from phytoplasma infection. In this study, we reported that oxytetracycline hydrochloride (OTC-HCl) trunk injection treatment could recover more than 86% of mild JWB-diseased trees. In order to explore the underlying molecular mechanism, comparative transcriptomic analysis of healthy control (C group), JWB-diseased (D group) and OTC-HCl treated JWB-diseased (T group) jujube leaves was performed. In total, 755 differentially expressed genes (DEGs), including 488 in 'C vs. D', 345 in 'D vs. T' and 94 in 'C vs. T', were identified. Gene enrichment analysis revealed that these DEGs were mainly involved in DNA and RNA metabolisms, signaling, photosynthesis, plant hormone metabolism and transduction, primary and secondary metabolisms, their transportations, etc. Notably, most of the DEGs identified in 'C vs. D' displayed adverse change patterns in 'D vs. T', suggesting that the expression of these genes was restored after OTC-HCl treatment. Our study revealed the influences of JWB phytoplasma infection and OTC-HCl treatment on gene expression profiling in jujube and would be helpful for understanding the chemotherapy effects of OTC-HCl on JWB-diseased jujube.

The genome of Candidatus phytoplasma ziziphi provides insights into their biological characteristics.

Phytoplasmas are obligate cell wall-less prokaryotic bacteria that primarily multiply in plant phloem tissue. Jujube witches' broom (JWB) associated with phytoplasma is a destructive disease of jujube (Ziziphus jujuba Mill.). Here we report the complete 'Candidatus Phytoplasma ziziphi' chromosome of strain Hebei-2018, which is a circular genome of 764,108-base pairs with 735 predicted CDS. Notably, extra 19,825 bp (from 621,995 to 641,819 bp) compared to the previously reported one complements the genes involved in glycolysis, such as pdhA, pdhB, pdhC, pdhD, ackA, pduL and LDH. The synonymous codon usage bias (CUB) patterns by using comparative genomics analysis among the 9 phytoplasmas were similar for most codons. The ENc-GC3s analysis among the 9 phytoplasmas showed a greater effect under the selection on the CUBs of phytoplasmas genes than mutation and other factors. The genome exhibited a strongly reduced ability in metabolic synthesis, while the genes encoding transporter systems were well developed. The genes involved in sec-dependent protein translocation system were also identified.The expressions of nine FtsHs encoding membrane associated ATP-dependent Zn proteases and Mn-SodA with redox capacity in the Ca. P. ziziphi was positively correlated with the phytoplasma concentration. Taken together, the genome will not only expand the number of phytoplasma species and provide some new information about Ca. P. ziziphi, but also contribute to exploring its pathogenic mechanism.

Comparative transcriptome profiling analysis provides insight into the mechanisms for sugar change in Chinese jujube (Ziziphus jujuba Mill.) under rain-proof cultivation.

Chinese jujube (Ziziphus jujuba Mill.) is a globally popular and economically important fruit that is rich in bioactive compounds with strong anti-cancer effects. Rain-proof cultivation is widely used to cultivate Chinese jujube, as it helps avoid rainfall damage during fruit harvest. Although the sugar content of jujube fruits differs between rain-proof and open-field cultivation, the underlying molecular mechanisms are unknown. Here, we analyzed the levels of sugar content, sugar accumulation pattern, and transcriptome profiles of jujube fruits at five developmental stages grown under rain-proof and open-field cultivation modes. The sugar content of jujube fruits was significantly higher under rain-proof cultivation than under open-field cultivation, although the sugar composition and sugar accumulation patterns were comparable. Comparative analysis of transcriptomic profiles showed that rain-proof cultivation enhanced the intrinsic metabolic activity of fruit development. Gene expression and correlation analyses suggested that ZjSPS, ZjSS, ZjHXK, and ZjINV regulate the development-related changes in sugar content in jujube fruits grown under rain-proof cultivation. Temperature, humidity, and moisture conditions were key climatic factors affecting sugar accumulation. Our results provide insights into the molecular mechanisms regulating sugar content and sugar accumulation in Chinese jujube fruits grown under rain-proof cultivation, and we provide genetic resources for studying the development mechanism of Chinese jujube fruit.

Solitalea agri sp. nov., a new member of the genus Solitalea isolated from rhizospheric soil of a jujube tree.

A Gram-stain negative, aerobic, rod-shaped and creamy pink-coloured bacterium, designated MAHUQ-68T, was isolated from rhizospheric soil of a jujube tree. Colonies grew at 10-40 °C (optimum, 28 °C), pH 6.0-9.0 (optimum pH, 7.0) and in the presence of 0-1.5 % NaCl (optimum 0-0.5 %). Positive for both catalase and oxidase activity. Strain MAHUQ-68T hydrolysed casein, starch, aesculin and l-tyrosine. Based on the results of phylogenetic analysis using 16S rRNA gene and genome sequences, strain MAHUQ-68T clustered together within the genus Solitalea. The closest members were Solitalea longa HR-AVT (98.8 % sequence similarity), Solitalea canadensis DSM 3403T (96.9 %) and Solitalea koreensis R2A36-4T (94.0 %). The genome of strain MAHUQ-68 T was 4 250 173 bp long with 68 scaffolds and 3 570 protein-coding genes. The genomic DNA G+C content of the type strain was 38.0 mol%. The average nucleotide identity and in silico DNA-DNA hybridization values between strain MAHUQ-68T and its closest relatives were 72.0-81.4% and 19.8-24.3 %, respectively. The major cellular fatty acids were iso-C15 : 0 and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c). The main respiratory quinone was menaquinone-7. The polar lipids comprised phosphatidylethanolamine, an unidentified aminolipid and four unidentified lipids. Based on these data, strain MAHUQ-68T represents a novel species in the genus Solitalea, for which the name Solitalea agri sp. nov. is proposed. The type strain is MAHUQ-68T (=KACC 22249T=CGMCC 1.19062T).

Transcriptome Characterization of Pigment-Related Genes in Jujube (Ziziphus Jujuba Mill.) Peel at Different Growth Stages.

One of the most important qualities of jujube fruit is its color. Chlorophyll, carotenoid, and anthocyanin all play important roles in the coloring of jujube fruit. However, few studies have focused on the pigment molecular mechanism. In the present study, jujube peels of 'Sanbianhong' in three growth stages were evaluated for their gene expression characteristics and gene regulation related to pigment formation using the transcriptome sequencing analysis. A total of 84.86 Gb of clean data were obtained in the analysis. In the FS1 vs. FS3, FS1 vs. FS5, and FS3 vs. FS5, 4,530, 11,012, and 9,072 differentially expressed genes (DEGs) were identified, respectively. The inter-group screening among the three comparisons yielded 1430 common DEGs. Among these DEGs, 27, 16, and 28 genes were enriched in chlorophyll, carotenoid, and anthocyanin metabolic pathways, respectively. Twelve genes were chosen at random, and the accuracy of the transcriptome data were confirmed using qRT-PCR. The molecular mechanism underlying the pigmentation of jujube fruit was elucidated at the transcriptome level, which would provide a scientific basis for the subsequent functional studies on the color-regulating genes of jujube fruits.

Genome-wide characterization of the cellulose synthase gene family in Ziziphus jujuba reveals its function in cellulose biosynthesis during fruit development.

The cellulose synthase (Ces/Csl) is a key enzyme in plant cellulose synthesis. Jujube fruits are rich in cellulose. 29 ZjCesA/Csl genes were identified in jujube genome and showed tissue-specific expression. 13 genes highly expressed in jujube fruit exhibited obviously sequential expressions during the fruit development, indicating that they might play distinct roles during the process. Meanwhile, the correlation analysis showed the expressions of ZjCesA1 and ZjCslA1 were significant positive related to the cellulose synthase activities. Furthermore, transient overexpressions of ZjCesA1 or ZjCslA1 in jujube fruits significantly increased cellulose synthase activities and contents, whereas silencing of ZjCesA1 or ZjCslA1 in jujube seedlings obviously reduced cellulose levels. Moreover, the Y2H assays verified that ZjCesA1 and ZjCslA1 may participate in cellulose synthesis by forming protein complexes. The study not only reveals the bioinformatics characteristics and functions of cellulose synthase genes in jujube, but also provides clues for studying cellulose synthesis in other fruits.

Mixed infections with new emerging viruses associated with jujube mosaic disease.

BACKGROUND: Jujube is an economically important fruit tree and native to China. Viral disease is a new threat to jujube production, and several new viruses have been identified infecting jujube plants. During our field survey, jujube mosaic disease was widely distributed in Beijing, but the associated causal agents are still unknown. METHODS: Small RNA deep sequencing was conducted to identify the candidate viruses associated with jujube mosaic. Further complete genome sequences of the viruses were cloned, and the genomic characterization of each virus was analyzed. The field distribution of these viruses was further explored with PCR/RT-PCR detection of field samples. RESULTS: Mixed infection of four viruses was identified in a plant sample with the symptom of mosaic and leaf twisting, including the previously reported jujube yellow mottle-associated virus (JYMaV), persimmon ampelovirus (PAmpV), a new badnavirus tentatively named jujube-associated badnavirus (JaBV), and a new secovirus tentatively named jujube-associated secovirus (JaSV). PAmpV-jujube was 14,093 nt in length with seven putative open reading frames (ORFs) and shared highest (79.4%) nucleotide (nt) sequence identity with PAmpV PBs3. Recombination analysis showed that PAmpV-jujube was a recombinant originating from plum bark necrosis stem pitting-associated virus isolates nanjing (KC590347) and bark (EF546442). JaBV was 6449 bp in length with conserved genomic organization typical of badnaviruses. The conserved RT and RNAse H region shared highest 67.6% nt sequence identity with jujube mosaic-associated virus, which was below the 80% nt sequence identity value used as the species demarcation threshold in Badnavirus. The genome of JaSV composed of two RNA molecules of 5878 and 3337 nts in length, excluding the polyA tails. Each genome segment contained one large ORF that shared homology and phylogenetic identity with members of the family Secoviridae. Field survey showed JYMaV and JaBV were widely distributed in jujube trees in Beijing. CONCLUSION: Two new viruses were identified from jujube plants, and mixed infections of JYMaV and JaBV were common in jujube in Beijing.

Genome-wide screening of the RNase T2 gene family and functional analyses in jujube (Ziziphus jujuba Mill.).

BACKGROUND: Ribonuclease (RNase T2) plays crucial roles in plant evolution and breeding. However, there have been few studies on the RNase T2 gene family in Ziziphus jujuba Mill., one of important dried fruit tree species. Recently, the released sequences of the reference genome of jujube provide a good chance to perform genome-wide identification and characterization of ZjRNase gene family in the jujube. RESULTS: In this study, we identified four members of RNase T2 in jujube distributed on three chromosomes and unassembled chromosomes. They all contained two conserved sites (CASI and CASII). Analysis of the phylogenetic relationships revealed that the RNase T2 genes in jujube could be divided into two groups: ZjRNase1 and ZjRNase2 belonged to class I, while ZjRNase3 and ZjRNase4 belonged to class II. Only ZjRNase1 and ZjRNase2 expression were shown by the jujube fruit transcriptome analysis. So ZjRNase1 and ZjRNase2 were selected functional verification by overexpression transformation of Arabidopsis. The overexpression of these two genes led to an approximately 50% reduction in seed number, which deserve further attention. Moreover, the leaves of the ZjRNase1 overexpression transgenic lines were curled and twisted. Overexpression of ZjRNase2 resulted in shortened and crisp siliques and the production of trichomes, and no seeds were produced. CONCLUSION: In summary, these findings will provide new insights into the molecular mechanisms of low number of hybrid seeds in jujube and a reference for the future molecular breeding of jujube.