The chromosome-scale genome assembly of Jasminum sambac var. unifoliatum provides insights into the formation of floral fragrance

Jasmine [Jasminum sambac(L.) Ait.], a tropical and subtropical plant emits a sweet, heady fragrance during flower opening. However, the molecular mechanisms underlying this phenomenon remain largely unknown. In the present study, integrated Illumina sequencing, Pacbio sequencing, and high-throughput chromatin conformation capture(Hi-C) scaffolding was used to generate a 495.60 Mb genome assembly of J.sambac var. unifoliatum cultivar ‘Fuzhou Single-petal’(JSU-FSP), with contig N50 of 16.88 Mb;96.23% of the assembly was assigned to 13 pseudochromosomes. The genome harbors 30 989 protein-coding genes, and 49.47% of the assembled sequences are repetitive sequences. The analysis of duplication modes showed that 51% of genes were duplicated through dispersed duplication, and expanded gene families are mainly involved in photosynthesis, which may be responsible for the light-loving characteristic specific to jasmine. Transcriptome analysis revealed that at least 35 structural genes involved in the biosynthesis of volatile terpenes(VTs), volatile phenylpropanoid/benzenoids(VPBs),fatty acid-derived volatiles(FADVs), and indole were highly expressed in the flower-opening stage, both preharvest and postharvest, and are proposed to be important in endowing flower aroma. Additionally, at least 28 heat shock protein(HSP) and 11 β-glucosidase(BGLU) genes may be involved in the formation of floral fragrance. These findings provide insights into the formation of the floral fragrance of jasmine and will promote germplasm utilization for breeding improved jasmine varieties.

Effects of 2, 4-Dichlorophenoxy Acetic Acid andLight on Growth of Gerbera (Gerbera jamesoniicv. Daxueju) Callus

This study was conducted to determine effects of 2,4-dichlorophenoxy acetic acid(2,4-D) and light on growth of gerbera(Gerbera jamesonii cv. Daxueju) callus. Callus was induced from both petiole and leaf explants of gerbera on Murashige and Skoog medium supplemented with 3% sucrose and various concentrations of 2,4-D and placed under light and dark. Callus induction percentage, callus size and callus fresh and dry weights were efficiently higher when using petiole as explant. MS medium supplemented with 1.5 mg/L 2,4-D showed the highest callus induction percentage of 96.70%. Callus induced under light had larger weight mass. It was indicated that 1.5 mg/L 2,4-D and light could promote growth of gerbera callus from petiole explant.

AFLP and MSAP Analysis of ‘Lane Late’ Navel Orange and Its Bud Sport Pumpkin-like Navel Orange

[Objectives]The paper was to analyze the differences of genes and genome methylation between‘lane late’navel orange and it’s bud sport pumpkin-like navel orange,and to reveal the causes of bud sport.[Methods]Amplification fragment length polymorphism(AFLP)and methylation sensitive amplification polymorphism(MSAP)were used to analyze the differences in genes and genome methylation of‘lane late’navel orange and its bud sport pumpkin-like navel orange.[Results]Gene mutation occurred between the‘lane late’navel orange and its bud sport pumpkin-like navel orange.A total of 15 differential bands were obtained by AFLP markers,and the percentage of polymorphic bands was 6.0000%.Meantime,10 differential bands were obtained by MSAP markers,and the percentage of polymorphic bands was 5.4645%.The semimethylation rate and permethylation rate of‘lane late’navel orange were higher than that of pumpkin-like navel orange,that is,pumpkin-like navel orange had demethylation(demethylation ratio was 1.6393%).[Conclusions]It is proved at the DNA level that the emergence of bud sport pumpkin-like navel orange is due to gene mutation,and the DNA methylation level of the bud sport material has also changed.This study lays a foundation for further exploring the mechanism of bud sport.

Cloning and Characterization of a Tyrosine Aminotransferase( TAT)Gene in Gerbera hybrida

In our previous study,a gene predicted to encode a Tyrosine aminotransferase( TAT) was found to be significantly up-regulated in root rot diseased Gerbera by transcriptome sequencing. To confirm the genes and investigate the function,we cloned the gene by RT-PCR and then conduct bioinformatic analyses. In this study,a 1 537 bp long c DNA sequence of this gene( named as Gh TAT) was firstly cloned,which contained a coding region of 1 233 bp,which was predicted to encode a protein of 410 amino acids. Bioinformatic analysis showed that the Gh TAT was a stable hydrophobic protein without signal peptide. Subcellular location prediction result indicated that this protein located in chloroplast,which is the biosynthesis position of tyrosine and the derived products of tyrosine biosynthesis pathway. Moreover,typical Tyrosine aminotransferase domain was found in this protein,indicating that it is a TAT. According to the TAT-based phylogenetic analysis and similarity analysis,the closest relationship and highest similarity was found between Gh TAT and Halianthus annuus TAT,which again verified the TAT property of Gh TAT. Tyrosine aminotransferase( TAT) is the first enzyme in tyrosine biosynthesis pathway,whose products include many antioxidant substances such as tocopherols and tocotrienols. The up-regulation of Gh TAT in root rot diseased gerbera suggests that it may play an important role in response to the root rot pathogen infection. In addition,60 phosphorylation sites( accounting for 14. 6%) were found in this protein,suggesting that the expression of this protein and its encoding gene were greatly influenced by the phosphorylation reactions.

U(VI) adsorption behavior onto polypyrrole coated 3R-MoS2 nanosheets prepared with the molten salt electrolysis method

To improve the separation capacity of uranium in aqueous solutions, 3R-MoS2 nanosheets were prepared with molten salt electro- lysis and further modified with polypyrrole (PPy) to synthesize a hybrid nanoadsorbent (PPy/3R-MoS2). The preparation conditions of PPy/3R- MoS2 were investigated and the obtained nanosheets were characterized with scanning electron microscope (SEM), high resolution transmis- sion electron microscope (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectro- scopy (XPS). The results showed that PPy/3R-MoS2 exhibited enhanced adsorption capacity toward U(VI) compared to pure 3R-MoS2 and PPy;the maximum adsorption was 200.4 mg/g. The adsorption mechanism was elucidated with XPS and FTIR: (1) negatively charged PPy/3R-MoS2 nanosheets attracted by an electrostatic interaction;(2) exposed C, N, Mo, and S atoms complexed with U(VI) through co- ordination;(3) Mo in the complex partly reduced the adsorbed U(VI) to U(IV), which further regenerated the adsorption point and continu- ously adsorbed U(VI). The design of the PPy/3R-MoS2 composite with a high adsorption capacity and chemical stability provides a new direc- tion for the removal of radionuclide.

Effects of Different Vase Solutions on Fresh-keeping Effects of Fresh-cut Rose

[Objective]The paper was to explore the effects of different vase solutions on fresh-keeping effects of fresh-cut rose,and to provide reference for fresh-keeping activities of fresh-cut rose.[Method]Acid oxidiation-potential water(AOW,p H 2-3,redox potential ORP≥1100 mv effective chlorine concentration 50 mg/L),melatonin solution(MT,45 mg/L),sodium hypochlorite solution(NaClO,95 mg/L),acidic oxidiation-potential aqueous solution+melatonin solution(50 mg/L AOW+45 mg/L MT),acidic oxidiation-potential aqueous solution+sodium hypochlorite solution(50 mg/L AOW+95 mg/L NaClO)and melatonin solution+sodium hypochlorite solution(45 mg/L MT+95 mg/L NaClO)were used as vase solutions to explore their fresh-keeping effects on fresh-cut rose.[Result]Compared with the control group of distilled water,all the six kinds of vase solutions had fresh-keeping effects on fresh-cut rose.AOW showed obvious fresh-keeping effects on fresh-cut rose,and the vase life could be extended by 1-4 d.Melatonin,AOW+melatonin,melatonin+sodium hypochlorite had the second best preservation effects,which could prolong the vase life by 1-3 d.The fresh-keeping effects of sodium hypochlorite and AOW+sodium hypochlorite had no significant difference with that of the control group,and the vase life could be prolonged by 1-2 d.[Conclusion]The study provides a certain theoretical basis for the application of fresh-cut flower preservative on rose.

Hidden players in the regulation of secondary metabolism in tea plant:focus on non-coding RNAs

Non-coding RNAs(ncRNAs)are functional transcripts with minimal or no protein-coding capacity that comprise a large portion of the plant transcriptome.Among them,the microRNAs(miRNAs),linear long ncRNAs(lncRNAs),and circular long ncRNAs(circRNAs)have been widely proven to play essential regulatory roles in the biosynthesis of secondary metabolites(SMs)by modulating the expression of key synthesisrelated genes in plants.Tea boasts numerous characteristic SMs,such as catechins,theanine,caffeine,volatile compounds,etc.,which have distinguished health properties and largely determine the pleasant flavor quality.Thus,understanding how the tea plant produces these specialized metabolites is of great research interest.With the innovation and progress of biotechnologies in recent years,significant progress has been made in research on the regulation mechanism of SMs in tea plants at the DNA,mRNA,protein and metabolite levels.The release of the genome sequences of tea plants paves a path for precisely exploring ncRNAs and their functions in tea,and their huge potential for the biosynthesis regulation of SMs has gradually received attention.We herein summarize recent progress on miRNAs,lncRNAs,and circRNAs in tea plants and discuss their regulatory roles in the accumulation of SMs to enlighten the development of novel agronomic tools to enhance the quality of tea.

RNA Methylome Reveals the m^(6)A-mediated Regulation of Flavor Metabolites in Tea Leaves under Solar-withering

The epitranscriptomic mark N6-methyladenosine(m^(6)A),which is the predominant internal modification in RNA,is important for plant responses to diverse stresses.Multiple environmental stresses caused by the tea-withering process can greatly influence the accumulation of specialized metabolites and the formation of tea flavor.However,the effects of the m^(6)A-mediated regulatory mechanism on flavor-related metabolic pathways in tea leaves remain relatively uncharacterized.We performed an integrated RNA methylome and transcriptome analysis to explore the m^(6)Amediated regulatory mechanism and its effects on flavonoid and terpenoid metabolism in tea(Camellia sinensis)leaves under solar-withering conditions.Dynamic changes in global m^(6)A level in tea leaves were mainly controlled by two m^(6)A erasers(CsALKBH4A and CsALKBH4B)during solar-withering treatments.Differentially methylated peak-associated genes following solarwithering treatments with different shading rates were assigned to terpenoid biosynthesis and spliceosome pathways.Further analyses indicated that CsALKBH4-driven RNA demethylation can directly affect the accumulation of volatile terpenoids by mediating the stability and abundance of terpenoid biosynthesis-related transcripts and also indirectly influence the flavonoid,catechin,and theaflavin contents by triggering alternative splicing-mediated regulation.Our findings revealed a novel layer of epitranscriptomic gene regulation in tea flavor-related metabolic pathways and established a link between the m^(6)A-mediated regulatory mechanism and the formation of tea flavor under solar-withering conditions.