Biosynthesis-related Genes Research Articles

Mechanism of abscisic acid in promoting softening of postharvest ‘Docteur Jules Guyot’ pear (Pyrus communis L.)

Abscisic acid (ABA) is a key hormone in plant growth and development, playing a central role in responses to various biotic and abiotic stresses as well as in fruit ripening. The present study examined the impact of ABA and nordihydroguaiaretic acid (NDGA) on various postharvest ‘Docteur Jules Guyot’ pear fruit characteristics, including firmness, pectinase activity, pectin content, volatile aromatic substances, and the expression of correlated genes. The results showed that ABA quickly reduced fruit firmness, increasing the activity of pectin degradation-related enzymes. The contents of water-soluble pectin (WSP) and ionic-soluble pectin (ISP) increased, and covalent binding pectin (CBP) decreased under ABA treatment. Among the detected volatile aromatic substances, the highest-level substance of the fruit was ester, and the ABA treatment significantly promoted the amount of ester substances. The cell wall disassembly-related genes PcPME3, PcPG1, PcPG2, PcPL, PcARF2, and PcGAL1, as well as ABA biosynthesis-related genes PcNCED1 and PcNCED2, were also significantly induced by ABA. Conversely, all these genes were repressed in the NDGA treatment group. Therefore, it was speculated that ABA may promote the softening of postharvest European pear fruit by affecting the activity of pectin degradation enzymes in fruit cell walls.

Identification of cepharanthine as an effective inhibitor of African swine fever virus replication

ABSTRACT African swine fever virus (ASFV) causes highly contagious swine disease, African swine fever (ASF), thereby posing a severe socioeconomic threat to the global pig industry and underscoring that effective antiviral therapies are urgently required. To identify safe and efficient anti-ASFV compounds, a natural compound library was screened by performing an established cell-based ELISA in an ASFV-infected porcine alveolar macrophage (PAM) model. In total, 6 effective anti-ASFV compounds with low cytotoxicity were identified. Cepharanthine (CEP), a bisbenzylisoquinoline alkaloid, was the most potent inhibitor effect with an IC50 of 0.3223 μM. To further investigate the mechanism through which CEP inhibits ASFV replication, transcriptome profiles were generated in PAMs treated with CEP and/or infected with ASFV. ASFV infection dramatically altered immune response-associated gene expression. CEP treatment upregulated the expression of cholesterol biosynthesis-related genes, regardless of infection status. According to time-of-addition experiments, CEP primarily exerts its antiviral effect during the early stages of ASFV infection, specifically by inhibiting viral entry. Transcriptomic analysis suggested that CEP blocks ASFV entry through the clathrin-mediated endocytosis pathway by increasing EHD2 gene expression in macrophages. Disrupting EHD2 with small interfering RNA promoted ASFV entry into clathrin-positive vesicles. Finally, the protective effect of CEP in vivo was evaluated using ASFV-infected pigs. CEP could provide partial protection against ASFV infection, as indicated by an increase in survival time from 9.67 days to 16.67 days. Our findings imply that CEP exhibits potential antiviral activity against ASFV infection in PAMs, positioning it as a promising therapeutic strategy for ASF.

Study on the changes of miRNAs and their target genes in regulating anthocyanin synthesis during purple discoloration of cauliflower curd under low temperature stress.

Cauliflower is widely cultivated all over the world is attributed to its palatable flavor, high levels of anti-cancer compounds, and diverse array of nutrients. Exposure to extremely cold stress during production can result in a more frequent occurrence of purple discoloration in cauliflower curds. In response to cold stress, plants naturally produce anthocyanins to eliminate reactive oxygen species (ROS) generated as a defense mechanism. This research involved conducting mRNA sequencing analysis on cauliflower curds both before and after exposure to cold stress treatment. It was determined that the up-regulation of anthocyanin biosynthesis-related genes CHS, CHI, DFR, ANS, UGFT, PAP1/2, and MYBL2 occurred significantly in response to cold stress, resulting in a significant increase in total anthocyanin content. Subsequently, miRNA sequencing was employed to identify miRNAs in cauliflower curds, followed by differential expression analysis. The results showed that Bna-miR289 and Ath-miR157a may play a key role in regulating the accumulation of anthocyanin in cauliflower curds. Furthermore, we utilized degradome sequencing data to predict the target genes of the identified miRNAs, resulting in the identification of BolK_3g48940.1, BolK_9g11680.1, BolK_7g41780.1, BolK_3g68050.1, and BolK_3g729700.1 as targets. Subsequently, the expression patterns of the miRNAs and their target genes were validated using qRT-PCR, the results showed that Ath-miR157a and its target genes BolK_3g68050.1 and BolK_3g72970.1 may be the key to the purple of cauliflower curds under cold stress. Our preliminary findings identified key miRNAs and their target genes that may be involved in regulating anthocyanin synthesis, thereby enhancing the cold tolerance of cauliflower through mRNA, miRNA, and degradome sequencing. Overall, our study sheds light on the activation of anthocyanin synthesis in flower curds under cold stress conditions as a mechanism to enhance resilience to adverse environmental conditions.

Full-length transcriptome sheds light into the molecular mechanism of tea leaf yellowing induced by red light

Light, as an energy source for plant photosynthesis, can not only affect the growth and development of plants, but also affect their leaf color. This study used white (WL), red (RL), and blue light (BL) to treat tea cuttings, aiming to investigate the effect of light quality on the color of tea leaves. The results showed that tea leaves turned yellow under red light, the SPAD and Fv/Fm values were significantly lower than WL and BL. Full-length transcriptome was analyzed, photosynthesis and chlorophyll biosynthesis related genes such as PsbS, Psb28, HemL, and POR had the lowest expression levels under RLCarotenoid biosynthesis related genes ZEP, ABA2, and CRTISO had the higher expression levels under RL. This study revealed the molecular mechanism of RL induced leaf yellowing in tea plants, providing new insights for the application of light quality in tea plants.

Whole genome analysis of Stenotrophomonas geniculata MK2 and antagonism against Botrytis cinerea in strawberry.

A novel strain isolated from soil identified as Stenotrophomonas geniculata MK2 could control strawberries' postharvest disease gray mold. An in vitro investigation showed that MK2 had significant bioactivity against Botrytis cinerea, with an observed zone of inhibition of 85%. The strain MK2 was 88% effective in controlling gray mold on detached fruits. De novo whole genome sequencing analysis showed that strain MK2 has a single circular chromosome with a genome size of 736,465bp, a G + C content of 66.34%, a coding ratio of 89.80%, and a protein-coding gene of 442. The NR database identified about 4284 genes among Stenotrophomonas spp. and S. geniculata, sharing the maximum number of 1277 genes with the MK2 strain. In COG annotation, most gene percentage was linked to general functions. In KEGG annotations, the majority of genes are associated with metabolism. According to the GO analysis, the maximum number of genes involved in the molecular process was linked to catalytic and transporter activity. CAZymes (carbohydrate-active enzymes) showed that enzymes related to glycosyl transferases (48), carbohydrate esterases (54), and glycoside hydrolases (51) are involved in the non-ribosomal synthesis of secondary metabolites. The PHI database showed that in strain MK2, the reduced virulence was 68 protein counts, and similarly unaffected pathogenicity protein counts were 52. AntiSMASH analysis for biosynthesis-related gene clusters involved in the production of secondary metabolites showed ten gene clusters coded for 2,3-dihydroxybenzoylserine, griseobactin, fuscachelin, benarthin, mirubactin, myxochelin, and bacillibactin. The MK2 strain could be a potent biocontrol agent for postharvest diseases.

Spätzle Regulates Developmental and Immune Trade-Offs Induced by Bacillus thuringiensis Priming in Rhynchophorus ferrugineus

The red palm weevil (RPW) is an invasive pest that causes devastating damage to a variety of palm plants, which exhibit specific immune priming to Bacillus thuringiensis (Bt). However, immune priming in RPW may incur a high fitness cost, and its molecular signaling pathways have not yet been reported. Here, we investigated the effect of Bt priming on RPW development and subsequently analyzed the hormonal and immune-related molecular pathways influencing the fitness cost induced by Bt priming. Bt priming delayed the body weight gain of fifth-instar larvae and prolonged their developmental duration. Bt priming significantly reduced the 20-hydroxyecdysone (20E) content in RPW hemolymph, and the expression levels of the 20E biosynthesis-related genes SHADOW and SHADE were significantly downregulated. Furthermore, we analyzed Toll pathway genes influencing Bt priming and found that only Spätzle (SPZ) transcription was significantly activated under Bt priming. After silencing SPZ expression, the negative effects of Bt priming on development, SHADOW expression, and 20E synthesis were eliminated, thereby suggesting that SPZ is a key molecular signal mediating developmental and immune trade-offs induced by Bt priming. Our results elucidate the molecular cascade pathway of immune priming and provide new targets for improving the efficiency of RPW biological controls.

Maternally expressed OsFERTILIZATION INDEPENDENT ENDOSPERM1 regulates seed dormancy and aleurone development in rice.

Seed dormancy, an essential trait for plant adaptation, is determined by the embryo itself and the surrounding tissues. Here, we found that rice (Oryza sativa) FERTILIZATION INDEPENDENT ENDOSPERM1 (OsFIE1) regulates endosperm-imposed dormancy and the dorsal aleurone thickness in a manner dependent on the parent of origin. Maternally expressed OsFIE1 suppresses gibberellin (GA) biosynthesis in the endosperm by depositing trimethylation of lysine 27 on histone H3 (H3K27me3) marks on GA biosynthesis-related genes, thus inhibiting germination and aleurone differentiation. Knockout of rice GA 20-oxidase1 (OsGA20ox1) alleviated the phenotypic defects in osfie1. The aleurone-positive determinant Crinkly 4 (OsCR4) is another target of the OsFIE1-containing Polycomb repressive complex 2 (PRC2). We found that OsFIE1 plays an important role in genomic imprinting in the endosperm of germinating seeds, particularly for paternally expressed genes associated with H3K27me3. The increased aleurone thickness of osfie1 substantially improved grain nutritional quality, indicating that the osfie1 gene may be utilized for breeding nutrient-enriched rice. The findings provide insights into the essential roles of PRC2-mediated H3K27me3 methylation in the acquisition of seed dormancy and endosperm cell differentiation in rice.

Yeast Synthesis and Herbicidal Activity Evaluation of Aspterric Acid.

Aspterric acid (AA) is a novel natural product herbicide that targets dihydroxyacid dehydratase in plants. In this study, we introduced two distinct AA biosynthesis-related gene clusters into Saccharomyces cerevisiae and screened the core biosynthetic enzyme, sesquiterpene cyclase, from various fungi. The combination of sesquiterpene cyclase from Aspergillus taichungensis IBT 19404 and two cytochrome P450s from Penicillium brasilianum resulted in the optimal AA synthesis efficiency in yeast, with the highest titer of 33.21 mg/L achieved by optimizing fermentation conditions in shake flasks. Moreover, the herbicidal effects of AA on weed germination and growth were evaluated. Notably, AA strongly inhibited the germination of Amaranthus tricolor, Portulaca oleracea, Bidens pilosa, Lolium perenne, and Leptochloa chinensis. Furthermore, AA could also inhibit the shoot and root growth of weeds with a superior inhibitory effect on roots relative to shoots. Our work not only provides a sustainable method for the biosynthesis of AA in yeast but also paves the way for the application of AA as a preemergence herbicide.

Molecular cloning and characterization of a brassinosteriod biosynthesis-related gene PtoCYP90D1 from Populus tomentosa

Brassinosteroids (BRs), one of the major classes of phytohormones are essential for various processes of plant growth, development, and adaptations to biotic and abiotic stresses. In Arabidopsis, AtCYP90D1 acts as a bifunctional cytochrome P450 monooxygenase, catalyzing C-23 hydroxylation in the brassinolide biosynthetic pathway. The present study reports the functional characterizations of PtoCYP90D1, one of the AtCYP90D1 homologous genes from Populus tomentosa. The qRT-PCR analysis showed that PtoCYP90D1 was highly expressed in roots and old leaves. Overexpression of PtoCYP90D1 (PtoCYP90D1-OE) in poplar promoted growth and biomass yield, as well as increased xylem area and cell layers. Transgenic plants exhibited a significant increase in plant height and stem diameter as compared to the wild type. In contrast, the CRISPR/Cas9-generated mutation of PtoCYP90D1 (PtoCYP90D1-KO) resulted in significantly decreased biomass production in transgenic plants. Further studies revealed that cell wall components increased significantly in PtoCYP90D1-OE lines but not in PtoCYP90D1-KO lines, as compared to wild-type plants. Overall, the findings indicate a positive role of PtoCYP90D1 in improving growth rate and elevating biomass production in poplar, which will have positive implications for its versatile industrial or agricultural applications.

Genomic insights into the cold adaptation and secondary metabolite potential of Pseudoalteromonas sp. WY3 from Antarctic krill.

In the Antarctic marine ecosystem, krill play a pivotal role, yet the intricate microbial community intertwined with these diminutive crustaceans remains largely unmapped. In this study, we successfully isolated and characterized a unique bacterial strain, Pseudoalteromonas sp. WY3, from Antarctic krill. Genomic analysis revealed that WY3 harbors a multitude of genes associated with cold shock proteins, oxidoreductases, and enzymes involved in the osmotic stress response, equipping it with a robust molecular arsenal to withstand frigid Antarctic conditions. Furthermore, the presence of two distinct biosynthesis-related gene clusters suggests that WY3 has the potential to synthesize diverse secondary metabolites, including aryl polyenes and ribosomally synthesized and post-translationally modified peptides. Notably, the identification of genes encoding enzymes crucial for biological immunity pathways, such as apeH and ubiC, hints at a complex symbiotic relationship between WY3 and its krill host. This comprehensive study highlights the robust potential of WY3 for secondary metabolite production and its remarkable ability to thrive at extremely low temperatures in the Antarctic ecosystem, shedding light on the interplay between culturable microorganisms and their hosts in harsh environments, and providing insights into the underexplored microbial communities associated with Antarctic marine organisms and their role in environmental adaptation and biotechnological applications.

Transcriptome and Expression Analysis of Glycerol Biosynthesis-Related Genes in Glenea cantor Fabricius (Cerambycidae: Lamiinae).

Glenea cantor Fabricius (Cerambycidae: Lamiinae) is an important pest that damages kapok trees in Southeast Asia with a wide adaptability to temperature. Glycerol is a protectant and energy source for insects in low-temperature environments. However, glycerol biosynthesis-related genes at the molecular level are limited in G. cantor. In this study, the supercooling points and freezing points at different stages were measured, and the cold hardiness of male and female pupae significantly differed. Moreover, a full-length transcriptome of G. cantor was established; glycerol kinase (GK) and glycerol-3-phosphate dehydrogenase (GPDH) genes, which are related to glycerol metabolism, were identified, with a special focus on their expression profiles. A total of 24,476 isoforms stemmed from the full-length transcriptome, along with 568 lncRNAs, 56 transcription factor (TF) families, and 1467 alternative splicing (AS) events. The KEGG pathway enrichment analysis revealed that the isoforms associated with AS were enriched primarily in glycerolipid and glycerophospholipid metabolism. In total, three GK genes and one GPDH gene were identified, and GcGK1 and GcGK3 presented differential sex expression during the pupal stage, which may play a role in thermal adaptability. This study provides a valuable transcriptional database of G. cantor and helps to elucidate the function of glycerol in the thermal adaptation mechanism of longhorn beetles.

Transcriptome and WGCNA Analyses Reveal Key Genes Regulating Anthocyanin Biosynthesis in Purple Sprout of Pak Choi (Brassica rapa L. ssp. chinensis).

Chinese cabbage is rich in vitamins, fibre, and nutrients and is one of the primary vegetables consumed in autumn and winter in South Asia. 'Purple pak choi' sprouts are particularly rich in anthocyanins and are favoured by consumers. However, reports on the regulation of anthocyanin synthesis in purple pak choi sprouts do not exist. In this study, we examined the phenotypic development of purple pak choi sprouts after germination. The total anthocyanin content increased from 0.02 to 0.52 mg/g FW from days 0 to 6. RNA-seq data analysis revealed an increase in differentially expressed genes corresponding to the development of purple pak choi sprouts. Expression pattern analysis of genes associated with the anthocyanin biosynthesis pathway revealed a significant upregulation of structural genes during the purple phase, suggesting that the transcription factors PAP2 and MYBL2 may play crucial regulatory roles. BraPAP2.A03, BraTT8.A09, and BraMYBL2.A07 exhibited strong interactions with key genes in the anthocyanin biosynthesis pathway, specifically BraDFR.A09. Furthermore, the expression of BraPAP2.A03 aligned with the expression patterns of most anthocyanin biosynthesis-related genes, whereas those of BraTT8.A09 and BraMYBL2.A07 corresponded with the expression pattern of BraDFR.A09. These results provide valuable insights into regulatory mechanisms underlying anthocyanin synthesis in purple pak choi sprouts.

PbAGL7-PbNAC47-PbMYB73 complex coordinately regulates PbC3H1 and PbHCT17 to promote the lignin biosynthesis in stone cells of pear fruit.

Lignification of the cell wall in pear (Pyrus) fruit results in the formation of stone cells, which affects the texture and quality of the fruit. However, it is still unclear that how different transcription factors (TFs) work together to coordinate the synthesis and deposition of lignin. Here, we examined the transcriptome of pear varieties with different stone cell contents and found a key TF (PbAGL7) that can promote the increase of stone cell contents and secondary cell wall thicknesses. In addition, PbAGL7 can facilitate the expression level of lignin biosynthesis-related genes and accelerate the lignin biosynthesis in pear fruit and Arabidopsis. However, PbAGL7 did not directly bind to the promoters of PbC3H1 and PbHCT17 which are crucial genes involved in lignin biosynthesis. On the other hand, yeast two-hybrid (Y2H) library showed that PbNAC47 and PbMYB73 interacted with PbAGL7 in the nucleus. PbNAC47 and PbMYB73 also increased the stone cell and lignin contents, and upregulated the expressions of PbC3H1 and PbHCT17 by binding to the SNBE and AC elements, respectively. Moreover, PbNAC47 also interacted with PbMYB73 to form PbAGL7-PbNAC47-PbMYB73 complex. This complex significantly activated the expression levels of PbC3H1 and PbHCT17 and promoted lignin biosynthesis to form stone cells in pear fruit. Overall, our study provides new insights into the molecular mechanism of TFs that coordinately regulate the stone cell formation in pear fruit and extend our knowledge to understand cell wall lignification in plants.

Sustained carbon import supports sugar accumulation and anthocyanin biosynthesis during fruit development and ripening in blueberry (Vaccinium ashei)

Fruit ripening is a highly coordinated process involving molecular and biochemical changes that collectively determine fruit quality. The underlying metabolic programs and their transitions leading to fruit ripening remain largely under-characterized in blueberry (Vaccinium sp.), which exhibits atypical climacteric behavior. In this study, we focused on sugar, acid and anthocyanin metabolism in two rabbiteye blueberry cultivars, Premier and Powderblue, during fruit development and ripening. Concentrations of the three major sugars, sucrose (Suc), glucose (Glc), and fructose (Fru) increased steadily during fruit development leading up to ripening, and increased dramatically by around 2-fold in ‘Premier’ and 2- to 3-fold in ‘Powderblue’ during the final stage of fruit ripening. Starch concentration was very low throughout fruit development in both cultivars indicating that it does not serve the role of a major transitory carbon (C) storage form in blueberry fruit. Together, these patterns indicate continued import of C, likely in the form of Suc, throughout blueberry fruit development. Concentrations of the predominant acids, malate and quinate, decreased during ripening, and may contribute to increased shikimate biosynthesis which, in-turn, allows for downstream phenylpropanoid metabolism leading to anthocyanin synthesis. Consistently, anthocyanin concentrations were highest in fully ripened blue fruit. Weighted gene co-expression network analysis (WGCNA) was performed using a ‘Powderblue’ fruit ripening transcriptome and targeted fruit metabolite concentration data. A ‘dark turquoise’ module positively correlated with sugars and anthocyanins, and negatively correlated with acids (malate, quinate), was identified. Gene Ontology (GO) enrichment analysis of this module identified transcripts related to sugar, acid, and phenylpropanoid metabolism pathways. Among these, increased transcript abundance of a VACUOLAR INVERTASE during ripening was consistent with sugar storage in the vacuole. In general, transcript abundance of the glycolysis pathway genes was upregulated during ripening. The transcript abundance of PHOSPHOENOLPYRUVATE (PEP) CARBOXYKINASE increased during fruit ripening and was negatively correlated with malate concentration, suggesting increased malate conversion to PEP, which supports anthocyanin production during fruit ripening. This was further supported by the co-upregulation of several anthocyanin biosynthesis-related genes. Together, this study provides insights into important metabolic programs, and their underlying gene expression patterns during fruit development and ripening in blueberry.

Dimethyl trisulfide reduces postharvest anthracnose and enhances mango quality, and a potential molecular mechanism against Colletotrichum gloeosporioides

Mango anthracnose, mainly caused by Colletotrichum gloeosporioides, is the major destructive postharvest disease of mango during storage and transport. Dimethyl trisulfide (DMTS), an organic volatile found in some microorganisms or plants, inhibited growth of C. gloeosporioides in vitro, but its effects on mango anthracnose and its molecular mechanisms of action have not been well characterized. In this study, the EC50 of DMTS against Colletotrichum spp. from mango mainly ranged from 2.3 to 20.0 μL/L. In vivo, the fumigation rates of 20 μL/L of DMTS for 24 h, or 80 μL/L for 3 h or 6 h could effectively reduce severity of anthracnose (natural inoculum) on postharvest mangoes with inhibitory effects of 61.7 %, 65.7 %, and 69.4 %, respectively, as observed 10 days after treatment. Furthermore, there was no detectable DMTS residue in mango skin or flesh, and an overall improvement in the quality of the fruit with higher soluble solids, total sugars, vitamin c, and β-carotene, and lower titratable acidity than the non-treated control. In addition, DMTS could significantly reduce ergosterol content in mycelia of C. gloeosporioides, and gene expression analysis showed DMTS significantly suppressed expression of ergosterol biosynthesis-related genes Cgerg6 and Cgerg11 after mycelia were exposed to DMTS. Knock-out mutants for each of these two genes showed reduced sensitivity to DMTS. After gene complementation in situ, the sensitivity of complementary transformants to DMTS was restored to that of the parental strain. Therefore, we concluded that the genes Cgerg6 and Cgerg11 are involved in an interaction with the antifungal activity of DMTS. This is the first study to demonstrate a control effect of DMTS on mango postharvest anthracnose resulting in reduced disease severity and enhanced fruit quality. Transformant studies also revealed some potential molecular mechanisms of the antifungal activity of DMTS that may lead to improved management of mango postharvest anthracnose.

Genomic insights into Aspergillus tamarii TPD11: enhancing polyphyllin production and uncovering potential therapeutic applications.

The excavation and utilization of endophytic fungi from medicinal plants is highly important for the development of new drugs. The endophytic fungus Aspergillus tamarii TPD11, which was isolated and obtained by the authors in the previous stage, can produce a variety of polyphyllins with important potential applications in hemostasis, inflammation and antitumor activities; however, the genomic information of TPD11 is still unknown. In this study, we sequenced and assembled the whole genome of the endophytic fungus A. tamarii TPD11, resolved the genome evolutionary relationships of 24 Aspergillus strains, and phylogenetic analysis of the genomes of 16 strains revealed the evolutionary differences between Aspergillus and Penicillium and the mechanisms of genome expansion and contraction. CAZy annotation analysis revealed that TPD11 obtains nutrients mainly by ingesting starch from the host plant. TPD11 has a biosynthesis-related gene cluster for the synthesis of squalestatin S1, and the silencing of this biosynthesis-related gene cluster might increase the content of polyphyllin. Annotation of 11 UDP-glycosyltransferase genes helps to further reveal the biosynthetic pathway of polyphyllin. In addition, secondary metabolism gene cluster and CAZy analyses confirmed the potential probiotic, insecticidal and antimicrobial activities of TPD11 on host plants. This study reveals the intrinsic mechanism by which endophytic fungi increase the content of polyphyllin, which provides a basis for the synthetic synthesis of the natural product polyphyllin.

Promotion of gentiopicroside production and transcriptional responses of biosynthetic genes in adventitious root cultures of Gentiana scabra Bunge by elicitation with methyl jasmonate

Abiotic elicitors play a crucial role in regulating various aspects of plant growth, development, and specialized metabolism. This study aimed to further increase the gentiopicroside content by screening elicitor types, optimizing elicitation conditions, and estimating transcriptional responses of biosynthetic genes in the adventitious roots of Gentiana scabra. The results showed that methyl jasmonate (MeJA) was the most effective inducer for biomass accumulation in the adventitious roots of G. scabra among tested elicitors, with fresh weight (FW) and dry weight (DW) of 13.26 ± 0.57 g flask−1 and 1.31 ± 0.25 g flask−1, respectively. The effects of the induction time and concentration of MeJA on the biomass and gentiopicroside content in the adventitious roots of G. scabra were investigated. The maximum FW (15.73 ± 0.41 g flask−1) and DW (1.51 ± 0.19 g flask−1) were obtained when the roots were cultured for 6 days in MS liquid medium containing 3.0 mg L−1 1-naphthlcetic acid (NAA) and 1.0 mg L−1 kinetin (KT) at MeJA concentration of 100 μM L−1. Also, the gentiopicroside content significantly increased to 62.62 ± 0.27 mg g−1 DW, and was 2.49 times higher than that for the nontreated control. The expression levels of 12 candidate gentiopicroside biosynthesis–related genes involved in the mevalonic acid (MVA), methyl erythritol phosphate (MEP), and secoiridoid pathways were estimated in the adventitious roots of G. scabra to further understand the transcriptional response to MeJA elicitation. Among these, 10 genes (ACCT1, HMGR1, MCK1, MVD1, GPPS4, G10H, IS3, DL7H1, DXS5, and ISPH5) were upregulated whereas DXR1 and IDI1 genes were downregulated in the adventitious roots of G. scabra compared with nontreated control, with significant differences having threshold P value ≤0.05. The transcriptional analyses revealed that 12 candidate genes were the key regulated genes in the gentiopicroside biosynthetic pathway. Overall, the findings provided a promising, feasible, and stable approach to utilizing MeJA elicitation to increase the production of valuable gentiopicroside. Additionally, they provided a foundation for future gentiopicroside biosynthesis through metabolic engineering strategies in the adventitious roots of G. scabra.

Exogenous Melatonin Reinforces Photosynthesis, Antioxidant Defense and Gene Expression to Ameliorate Na2CO3 Stress in Maize.

Salt stress can seriously affect the growth and development of maize (Zea mays L.), resulting in a great yield loss. Melatonin (MT), an indole hormone, is a potential enhancer of plant tolerance against salt stress. However, the complex mechanisms of MT application in enhancing maize salt tolerance are still unclear. Herein, three-leaf seedlings of salt-susceptible P138 and its salt-resistant ethyl methane sulfonate (EMS)-104 mutant were cultured with or without 150 μM MT application under 0 and 100 mM Na2CO3 treatments for seven days, to systematically explore the response mechanisms of exogenous MT in improving the salt tolerance of maize. The results showed that salt stress triggered an escalation in reactive oxygen species production, enhanced multiple antioxidant enzymes' activities, impaired cellular membrane permeability, inhibited photosynthetic pigment accumulation, and ultimately undermined the vigor and photosynthetic prowess of the seedlings. While suitable MT application counteracted the detrimental impacts of Na2CO3 on seedlings' growth and photosynthetic capacity, the seedling length and net photosynthetic rate of P138 and EMS-104 were increased by 5.5% and 18.7%, and 12.7% and 54.5%, respectively. Quantitative real-time PCR (qRT-PCR) analysis further showed that MT application activated the expression levels of antioxidant enzyme-related genes (Zm00001d025106, Zm00001d031908, Zm00001d027511, and Zm00001d040364) and pigment biosynthesis-related genes (Zm00001d011819 and Zm00001d017766) in both maize seedlings under Na2CO3 stress; they then formed a complex interaction network of gene expression, multiple physiological metabolisms, and phenotype changes to influence the salt tolerance of maize seedlings under MT or Na2CO3 stress. To sum up, these observations underscore that 150 μM MT can alleviate salt injury of maize seedlings, which may provide new insights for further investigating MT regulation mechanisms to enhance maize seedlings' salt resistance.

Phenotypic, genetic, variation, and molecular function of CaMYB113 in pepper (Capsicum annuum L.).

Pepper (Capsicum annuum L.) is widely consumed vegetables worldwide, and F1 hybrids are highly sought after in the pepper seed industry. However, studies on gene mutations affecting the color of cotyledon are rare, and the same is true for peppers. In this study, a segregating population was developed by crossing the pepper accession 21C1344 with purple cotyledon and accession 21C912 with green cotyledon. Initially, a target genomic region was identified by screening polymorphic SSR markers distributed across 12 chromosomes. Subsequently, polymorphic markers were developed based on resequencing data from the two parental lines, and genetic linkage analysis was performed. This approach ultimately identified Capana10g001433 (CaMYB113) as the candidate gene responsible for the purple cotyledons. The gene mutation type in 21C912 represents a new mutation type distinct from the reported missense mutation types, and this mutation affects the biosynthesis of anthocyanins. Virus-induced gene silencing (VIGS) of CaMYB113 substantially decreased anthocyanin accumulation in the cotyledons. Subsequent overexpression of CaMYB113 resulted in purple callus and leaves of pepper, and changed the expression levels of downstream genes involved in anthocyanin synthesis. Yeast one-hybrid and dual-luciferase transient expression assays demonstrated the binding of CaMYB113 to anthocyanin biosynthesis-related genes, thereby regulating anthocyanin accumulation in pepper cotyledons.

Investigation of the preharvest arginine spraying mechanism on antioxidant system in postharvest broccoli via transcriptomics and metabolomics

According to our previous study, preharvest spraying of arginine for 1 day enhanced the antioxidant capacity of postharvest broccoli, but the underlying molecular mechanisms remain unclear. We here performed a comprehensive transcriptome and metabolome analysis to investigate the effects of arginine sprayed 1 day before harvest on the antioxidant capacity and yellowing of broccoli as well as the related action mechanisms. In total, 67 differentially expressed genes and 12 key differentially accumulated metabolites were identified in broccoli at 4 and 8 days during storage. Herein, the gene expression of superoxide dismutase, catalase, and the corresponding peroxisome protein Mpv17 (MPV17) was upregulated, consequently enhancing the scavenging of reactive oxygen species. Genes encoding glucosinolate synthesis- and metabolism-related enzymes were upregulated, and among them, the gene ST5b_c was upregulated by 8.23-fold, which promoted the accumulation of its metabolites. Expression of lignin- and flavonoid biosynthesis-related genes (CAD, POD, CHI, and CHS) was elevated. Flavonoid and lignin accumulation was promoted, with a greater antioxidant capacity at 4 and 8 days, respectively, in the arginine-sprayed broccoli. Additionally, the ascorbate–glutathione cycle was promoted in broccoli at 4 days, GLCAK and APX genes were upregulated by more than 2-fold, and broccoli exhibited a higher tolerance level because of the notably stimulated ascorbic acid and glutathione accumulation. This study offers new insights into the mechanisms through which preharvest spraying of arginine regulates the antioxidant capacity of postharvest broccoli.