Shikimic acid accelerates phase change and flowering in Chinese jujube

The juvenile-to-adult phase change with first flowering as the indicator plays a crucial role in the lifecycle of fruit trees. However, the molecular mechanisms underlying phase change in fruit trees remain largely unknown. Shikimic acid (ShA) pathway is a main metabolic pathway closely related to the synthesis of hormones and many important secondary metabolites participating in plant phase change. So,whether ShA regulates phase change in plants is worth clarifying. Here, the distinct morphological characteristics and the underlying mechanisms of phase change in jujube (Ziziphus jujuba Mill.), an important fruit tree native to China with nutritious fruit and outstanding tolerance abiotic stresses, were clarified. A combined transcriptome and metabolome analysis found that ShA is positively involved in jujube(Yuhong’×Xing 16’) phase change. The genes in the upstream of ShA synthesis pathway (ZjDAHPS, ZjDHQS and ZjSDH), the contents of ShA and the downstream secondary metabolites like phenols were significantly upregulated in the phase change period. Further, the treatment of spraying exogenous ShA verified that ShA at a very low concentration (60 mg·L^(-1)) can substantially speed up the phase change and flowering of jujube and other tested plants including Arabidopsis, tomato and wheat. The exogenous ShA (60 mg·L^(-1)) treatment in jujube seedlings could increase the accumulation of endogenous ShA, enhance leaf photosynthesis and the synthesis of phenols especially flavonoids and phenolic acids, and promote the expression of genes (ZjCOs, ZjNFYs and ZjPHYs) involved in flowering pathway. Basing on above results, we put forward a propose for the underlying mechanism of ShA regulating phase change, and a hypothesis that ShA could be considered a phytohormone-like substance because it is endogenous, ubiquitous, movable and highly efficient at very low concentrations. This study highlights the critical role of ShA in plant phase change and its phytohormone-like properties.

GST family genes in jujube actively respond to phytoplasma infection

Jujube witches’broom(JWB)caused by phytoplasma has a severely negative effect on multiple metabolisms in jujube.The GST gene family in plants participates in the regulation of a variety of biotic and abiotic stresses.This study aims to identify and reveal the changes in the jujube GST gene family in response to phytoplasma infection.Here,70 ZjGSTs were identified in the jujube genome and divided into 8 classes.Among them,the Tau-class,including 44 genes,was the largest.Phylogenetic analysis indicated that Tau-class genes were highly conserved among species,such as Arabidopsis,cotton,chickpea,and rice.Through chromosome location analysis,37.1%of genes were clustered,and 8 of 9 gene clusters were composed of Tau class members.Through RT-PCR,qRT-PCR and enzyme activity detection,the results showed that the expression of half(20/40)of the tested ZjGSTs was inhibited by phytoplasma infection in field and tissue culture conditions,and GST activity was also significantly reduced.In the resistant and susceptible varieties under phytoplasma infection,ZjGSTU49-ZjGSTU54 in the cluster IV showed opposite expression patterns,which may be due to functional divergence during evolution.Some upregulated genes(ZjGSTU45,ZjGSTU49,ZjGSTU59,and ZjGSTU70)might be involved in the process of jujube against JWB.The yeast two-hybrid results showed that all 6 Tauclass proteins tested could form homodimers or heterodimers.Overall,the comprehensive analysis of the jujube GST gene family revealed that ZjGSTs responded actively to phytoplasma infection.Furthermore,some screened genes(ZjGSTU24,ZjGSTU49-52,ZjGSTU70,and ZjDHAR10)will contribute to further functional studies of jujube-phytoplasma interactions.

The historical and current research progress on jujube–a superfruit for the future

Jujube(Ziziphus jujuba Mill.),or Chinese date,is the most important species of Rhamnaceae,a large cosmopolitan family,and is one of the oldest cultivated fruit trees in the world.It originates from the middle and lower reaches of the Yellow River,the‘mother river’of the Chinese people.It is distributed in at least 48 countries on all continents except Antarctica and is becoming increasingly important,especially in arid and semiarid marginal lands.Based on a systematic analysis of the unique characteristics of jujube,we suggest that it deserves to be recognized as a superfruit.We summarized historical research achievements from the past 3000 years and reviewed recent research advances since 1949 in seven fields,including genome sequencing and application,germplasm resources and systematic taxonomy,breeding and genetics,cultivation theory and techniques,pest control,postharvest physiology and techniques,and nutrition and processing.Based on the challenges facing the jujube industry,we discuss eight research aspects to be focused on in the future.

The regulatory pathways of distinct flowering characteristics in Chinese jujube

Flowering is the most important event in higher plants.Compared to most fruit tree species,Chinese jujube(Ziziphus jujuba Mill.),the most important member of the large,diverse Rhamnaceae family and a leading dry fruit-producing species,has unique characteristics that include a short juvenile phase and extremely fast flower bud differentiation.However,the distinct mechanism of flowering regulation in Chinese jujube is still unclear.The morphological and cytological development period of jujube flowering was first investigated,and the crucial developmental stages were defined.Flower bud differentiation in Chinese jujube took only approximately 11–13 days,which is a distinct characteristic of perennial fruit trees.Afterward,44 genes related to six flowering pathways were identified in the jujube genome and were found to be randomly distributed among 11 of the 12 chromosomes.Tissue-specific and spatiotemporal expression patterns showed that all these genes were expressed in the flowers.Overall,photoperiodrelated genes were highly expressed during flower bud differentiation.These genes were also positively responsive to photoperiod regulation and phase change processes,indicating that photoperiod-related genes play crucial roles in jujube flower bud differentiation.Under protected cultivation,ZjPIF4,a temperature-related gene,was expressed in the early stages of flowering and responded to increasing temperatures.Moreover,STRING analysis and yeast two-hybrid screening indicated that photoperiod-related(ZjCO)and temperature-related(ZjPIF4)proteins could interact with ZjFT,the key protein involved in the determination of flowering time,indicating crosstalk between photoperiodrelated pathways and ambient temperature-related pathways in jujube.This study is the first report to comprehensively analyze the flowering pathways in Chinese jujube and revealed that photoperiod-related and ambient temperature-related pathways are the main mechanisms regulating the distinct flowering process and that members of the ZjPHY family(ZjPIF4,ZjFT,and ZjCO5)are the key factors involved in the regulatory network.These results will increase our understanding of the molecular and genetic mechanisms of flowering in Chinese jujube and provide meaningful clues for the flowering regulation of other fruit tree species.

The regulation of cell wall lignification and lignin biosynthesis during pigmentation of winter jujube

Fruit lignification is due to lignin deposition in the cell wall during cell development.However,there are few studies on the regulation of cell wall lignification and lignin biosynthesis during fruit pigmentation.In this study,we investigated the regulation of cell wall lignification and lignin biosynthesis during pigmentation of winter jujube.The cellulose content decreased,while the lignin content increased in the winter jujube pericarp during pigmentation.Safranin O-fast green staining showed that the cellulose content was higher in the cell wall of winter jujube prior to pigmentation,whereas the lignin in the cell wall increased after pigmentation.The thickness of the epidermal cells decreased with pericarp pigmentation.A combined metabolomics and transcriptomics analysis showed that guaiacyl-syringyl(G-S)lignin was the main lignin type in the pericarp of winter jujube,and F5H(LOC107424406)and CCR(LOC107420974)were preliminarily identified as the key genes modulating lignin biosynthesis in winter jujube.Seventeen MYB and six NAC transcription factors(TFs)with potential regulation of lignin biosynthesis were screened out based on phylogenetic analysis.Three MYB and two NAC TFs were selected as candidate genes and further studied in detail.Arabidopsis ectopic expression and winter jujube pericarp injection of the candidate genes indicated that the MYB activator(LOC107425254)and the MYB repressor(LOC107415078)control lignin biosynthesis by regulating CCR and F5H,while the NAC(LOC107435239)TF promotes F5H expression and positively regulates lignin biosynthesis.These findings revealed the lignin biosynthetic pathway and associated genes during pigmentation of winter jujube pericarp and provide a basis for further research on lignin regulation.

Highly efficient nonuniform finite difference method for three-dimensional electrically stimulated liquid crystal photonic devices

Liquid crystal(LC)photonic devices have attracted intensive attention in recent decades,due to the merits of tunability,cost-effectiveness,and high efficiency.However,the precise and efficient simulation of large-scale three-dimensional electrically stimulated LC photonic devices remains challenging and resource consuming.Here we report a straightforward nonuniform finite difference method(NFDM)for efficiently simulating largescale LC photonic devices by employing a spatially nonuniform mesh grid.

Insights into the evolution and spatial chromosome architecture of jujube from an updated gapless genome assembly

Dear Editor,Jujube(Ziziphus jujuba Mill.),commonly called Chinese jujube,is a vital member of the Rhamnaceae family.It is famous for its tolerance to dry,barren,and saline-alkali soils,and its fruit has important nutritional and medicinal value.Recent fundamental research on jujube has involved assembly of draft genome sequences for the fresh-eating cultivar‘Dongzao’(Liu et al.,2014),dry-eating cultivar‘Junzao’(Huang et al.,2016),and wild sour jujube‘Suanzao’(Shen et al.,2021).

Expression profiles of genes and enzymes related to ascorbic acid metabolism in fruits of Ziziphus jujuba Mill.‘Jinsixiaozao’

The fruit of Chinese jujube(Ziziphus jujuba)possesses extremely high concentrations of ascorbic acid(As A).The accumulation of As A,the expression patterns of the nine genes related to As A metabolism as well as the activities of five enzymes involved in As A synthesis,oxidation and recycling were investigated during fruit development in Z.jujuba Mill.‘Jinsixiaozao'.The results showed that the high level of As A accumulation in jujube fruit is due to a contribution from both As A biosynthesis and As A recycling.It is suggested that L-galactono-1,4-lactone dehydrogenase,ascorbate peroxidase and monodehydro-ascorbate reductase are the crucial genes/enzymes of jujube As A synthesis,oxidization and recycling,respectively.These results provide useful new insights into the regulatory mechanisms of As A accumulation in Chinese jujube.

Liquid crystal-based optical aptasensor for the sensitive and selective detection of Gram-negative bacteria

The sensitive and differential detection of Gram-negative bacteria is essential in food processing,environmental monitoring,and the daily chemical industry.Herein,we propose and validate a liquid crystal(LC)-based aptasensor for the ultrasensitive detection of Escherichia coli(E.coli),a model of Gram-negative bacteria.The nematic liquid crystal of 4-cyano-4’-pentylbiphenyl(5 CB) molecules can be orderly or disorderly arranged at the LC-aqueous interface via different stimuli,causing changes in optical texture due to birefringence.Bright schlieren texture is observed when a mixture solution of aptamer and hexadecyl trimethyl ammonium bromide(CTAB) is dripped onto the segmented LC films on a copper mesh.The specific binding of aptamers with target bacteria biomarkers liberates the CTAB molecules,which then self-assemble at the LC-aqueous interface to induce the vertical alignment of LCs.An optical transition from bright to dark is therefore achieved via the LC molecular orientation and serves as an aptasensor.Given the prominent affinity and specificity of the aptamer,the established sensitive and selective E.coli assay shows an ultralow detection limit of 27 cfu/mL.The prepared aptasensor can also be applied for the sensitive and selective determination of E.coli in fruit juice,soft drink,and cosmetic products,and shows great promise for the on-site detection of Gram-negative bacteria with high sensitivity and specificity for environmental monitoring,food safety assessment,and household chemical inspection.