Evolutionary gain of oligosaccharide hydrolysis and sugar transport enhanced carbohydrate partitioning in sweet watermelon fruits.

How raffinose (Raf) family oligosaccharides, the major translocated sugars in the vascular bundle in cucurbits, are hydrolyzed and subsequently partitioned has not been fully elucidated. By performing reciprocal grafting of watermelon (Citrullus lanatus) fruits to branch stems, we observed that Raf was hydrolyzed in the fruit of cultivar watermelons but was backlogged in the fruit of wild ancestor species. Through a genome-wide association study, the alkaline alpha-galactosidase ClAGA2 was identified as the key factor controlling stachyose and Raf hydrolysis, and it was determined to be specifically expressed in the vascular bundle. Analysis of transgenic plants confirmed that ClAGA2 controls fruit Raf hydrolysis and reduces sugar content in fruits. Two single-nucleotide polymorphisms (SNPs) within the ClAGA2 promoter affect the recruitment of the transcription factor ClNF-YC2 (nuclear transcription factor Y subunit C) to regulate ClAGA2 expression. Moreover, this study demonstrates that C. lanatus Sugars Will Eventually Be Exported Transporter 3 (ClSWEET3) and Tonoplast Sugar Transporter (ClTST2) participate in plasma membrane sugar transport and sugar storage in fruit cell vacuoles, respectively. Knocking out ClAGA2, ClSWEET3, and ClTST2 affected fruit sugar accumulation. Genomic signatures indicate that the selection of ClAGA2, ClSWEET3, and ClTST2 for carbohydrate partitioning led to the derivation of modern sweet watermelon from non-sweet ancestors during domestication.

Comprehensive Profiling of Alternative Splicing and Alternative Polyadenylation during Fruit Ripening in Watermelon (Citrullus lanatus).

Fruit ripening is a highly complicated process that is accompanied by the formation of fruit quality. In recent years, a series of studies have demonstrated post-transcriptional control play important roles in fruit ripening and fruit quality formation. Till now, the post-transcriptional mechanisms for watermelon fruit ripening have not been comprehensively studied. In this study, we conducted PacBio single-molecule long-read sequencing to identify genome-wide alternative splicing (AS), alternative polyadenylation (APA) and long non-coding RNAs (lncRNAs) in watermelon fruit. In total, 6,921,295 error-corrected and mapped full-length non-chimeric (FLNC) reads were obtained. Notably, more than 42,285 distinct splicing isoforms were derived from 5,891,183 intron-containing full-length FLNC reads, including a large number of AS events associated with fruit ripening. In addition, we characterized 21,506 polyadenylation sites from 11,611 genes, 8703 of which have APA sites. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that fructose and mannose metabolism, starch and sucrose metabolism and carotenoid biosynthesis were both enriched in genes undergoing AS and APA. These results suggest that post-transcriptional regulation might potentially have a key role in regulation of fruit ripening in watermelon. Taken together, our comprehensive PacBio long-read sequencing results offer a valuable resource for watermelon research, and provide new insights into the molecular mechanisms underlying the complex regulatory networks of watermelon fruit ripening.

ClSnRK2.3 negatively regulates watermelon fruit ripening and sugar accumulation.

Watermelon (Citrullus lanatus) as non-climacteric fruit is domesticated from the ancestors with inedible fruits. We previously revealed that the abscisic acid (ABA) signaling pathway gene ClSnRK2.3 might influence watermelon fruit ripening. However, the molecular mechanisms are unclear. Here, we found that the selective variation of ClSnRK2.3 resulted in lower promoter activity and gene expression level in cultivated watermelons than ancestors, which indicated ClSnRK2.3 might be a negative regulator in fruit ripening. Overexpression (OE) of ClSnRK2.3 significantly delayed watermelon fruit ripening and suppressed the accumulation of sucrose, ABA and gibberellin GA4 . Furthermore, we determined that the pyrophosphate-dependent phosphofructokinase (ClPFP1) in sugar metabolism pathway and GA biosynthesis enzyme GA20 oxidase (ClGA20ox) could be phosphorylated by ClSnRK2.3 and thereby resulting in accelerated protein degradation in OE lines and finally led to low levels of sucrose and GA4 . Besides that, ClSnRK2.3 phosphorylated homeodomain-leucine zipper protein (ClHAT1) and protected it from degradation to suppress the expression of the ABA biosynthesis gene 9'-cis-epoxycarotenoid dioxygenase 3 (ClNCED3). These results indicated that ClSnRK2.3 negatively regulated watermelon fruit ripening by manipulating the biosynthesis of sucrose, ABA and GA4 . Altogether, these findings revealed a novel regulatory mechanism in non-climacteric fruit development and ripening.

ClZISO mutation leads to photosensitive flesh in watermelon.

KEY MESSAGE: The mutation of ClZISO identified in EMS-induced watermelon leads to photosensitive flesh in watermelon. Watermelon (Citrullus lanatus) has a colorful flesh that attracts consumers and benefits human health. We developed an ethyl-methanesulfonate mutation library in red-fleshed line '302' to create new flesh color lines and found a yellow-fleshed mutant which accumulated ζ-carotene. The initial yellow color of this mutant can be photobleached within 10 min under intense sunlight. A long-term light-emitting diode (LED) light treatment turned flesh color from yellow to pink. We identified this unique variation as photosensitive flesh mutant ('psf'). Using bulked segregant analysis, we fine-mapped an EMS-induced G-A transversion in 'psf' which leads to a premature stop codon in 15-cis-ζ-carotene isomerase (ClZISO) gene. We detected that wild-type ClZISO is expressed in chromoplasts to catalyze the conversion of 9,15,9'-tri-cis-ζ-carotene to 9,9'-di-cis-ζ-carotene. The truncated ClZISOmu protein in psf lost this catalytic function. Light treatment can partially compensate ClZISOmu isomerase activity via photoisomerization in vitro and in vivo. Transcriptome analysis showed that most carotenoid biosynthesis genes in psf were downregulated. The dramatic increase of ABA content in flesh with fruit development was blocked in psf. This study explores the molecular mechanism of carotenoid biosynthesis in watermelon and provides a theoretical and technical basis for breeding different flesh color lines in watermelon.

Natural variation in the NAC transcription factor NONRIPENING contributes to melon fruit ripening.

The NAC transcription factor NONRIPENING (NOR) is a master regulator of climacteric fruit ripening. Melon (Cucumis melo L.) has climacteric and non-climacteric fruit ripening varieties and is an ideal model to study fruit ripening. Two natural CmNAC-NOR variants, the climacteric haplotype CmNAC-NORS,N and the non-climacteric haplotype CmNAC-NORA,S , have effects on fruit ripening; however, their regulatory mechanisms have not been elucidated. Here, we report that a natural mutation in the transcriptional activation domain of CmNAC-NORS,N contributes to climacteric melon fruit ripening. CmNAC-NOR knockout in the climacteric-type melon cultivar "BYJH" completely inhibited fruit ripening, while ripening was delayed by 5-8 d in heterozygous cmnac-nor mutant fruits. CmNAC-NOR directly activated carotenoid, ethylene, and abscisic acid biosynthetic genes to promote fruit coloration and ripening. Furthermore, CmNAC-NOR mediated the transcription of the "CmNAC-NOR-CmNAC73-CmCWINV2" module to enhance flesh sweetness. The transcriptional activation activity of the climacteric haplotype CmNAC-NORS,N on these target genes was significantly higher than that of the non-climacteric haplotype CmNAC-NORA,S . Moreover, CmNAC-NORS,N complementation fully rescued the non-ripening phenotype of the tomato (Solanum lycopersicum) cr-nor mutant, while CmNAC-NORA,S did not. Our results provide insight into the molecular mechanism of climacteric and non-climacteric fruit ripening in melon.

A unique chromosome translocation disrupting ClWIP1 leads to gynoecy in watermelon.

To understand sex determination in watermelon (Citrullus lanatus), a spontaneous gynoecious watermelon mutant, XHBGM, was selected from the monoecious wild type XHB. Using map-based cloning, resequencing and fluorescence in situ hybridization analysis, a unique chromosome translocation between chromosome 2 and chromosome 3 was found in XHBGM. Based on the breakpoint location in chromosome 2, a putative C2H2 zinc finger transcription factor gene, ClWIP1 (gene ID Cla008537), an orthologue of the melon gynoecy gene CmWIP1, was disrupted. Using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated system 9 to edit ClWIP1, we obtained gynoecious watermelon lines. Functional studies showed that ClWIP1 is expressed specifically in carpel primordia and is related to the abortion of carpel primordia in early floral development. To identify the cellular and metabolic processes associated with ClWIP1, we compared the shoot apex transcriptomes of two gynoecious mutants and their corresponding wild types. Transcriptome analysis showed that differentially expressed genes related to the ethylene and cytokinin pathways were upregulated in the gynoecious mutants. This study explores the molecular mechanism of sex determination in watermelon and provides a theoretical and technical basis for breeding elite gynoecious watermelon lines.

Decreased Protein Abundance of Lycopene ß-Cyclase Contributes to Red Flesh in Domesticated Watermelon.

Red-fleshed watermelons (Citrullus lanatus) that accumulate lycopene in their flesh cells have been selected and domesticated from their pale-fleshed ancestors. However, the molecular basis of this trait remains poorly understood. Using map-based cloning and transgenic analysis, we identified a lycopene ß-cyclase (ClLCYB) gene that controls the flesh color of watermelon. Down-regulation of ClLCYB caused the flesh color to change from pale yellow to red, and ClLCYB overexpression in the red-fleshed line caused the flesh color to change to orange. Analysis of ClLCYB single-nucleotide polymorphisms using 211 watermelon accessions with different flesh colors revealed that two missense mutations between three haplotypes (ClLCYB red , ClLCYB white , and ClLCYB yellow ) were selected and largely fixed in domesticated watermelon. Proteins derived from these three ClLCYB haplotypes were localized in plastids to catalyze the conversion of lycopene to ß-carotene and showed similar catalytic abilities. We revealed that ClLCYB protein abundance, instead of ClLCYB transcript level, was negatively correlated with lycopene accumulation. Different amounts of ClLCYB protein degradation among the ClLCYB haplotypes were found in ClLCYB transgenic Arabidopsis (Arabidopsis thaliana) lines. After treatment with the proteasome inhibitor MG132, the concentration of ClLCYBred increased noticeably compared with other ClLCYB proteins. These results indicate that natural missense mutations within ClLCYB influence ClLCYB protein abundance and have contributed to the development of red flesh color in domesticated watermelon.

Localization shift of a sugar transporter contributes to phloem unloading in sweet watermelons.

Unloading sugar from sink phloem by transporters is complex and much remains to be understood about this phenomenon in the watermelon fruit. Here, we report a novel vacuolar sugar transporter (ClVST1) identified through map-based cloning and association study, whose expression in fruit phloem is associated with accumulation of sucrose (Suc) in watermelon fruit. ClVST197 knockout lines show decreased sugar content and total biomass, whereas overexpression of ClVST197 increases Suc content. Population genomic and subcellular localization analyses strongly suggest a single-base change at the coding region of ClVST197 as a major molecular event during watermelon domestication, which results in the truncation of 45 amino acids and shifts the localization of ClVST197 to plasma membranes in sweet watermelons. Molecular, biochemical and phenotypic analyses indicate that ClVST197 is a novel sugar transporter for Suc and glucose efflux and unloading. Functional characterization of ClVST1 provides a novel strategy to increase sugar sink potency during watermelon domestication.

Regulation of cotton (Gossypium hirsutum) drought responses by mitogen-activated protein (MAP) kinase cascade-mediated phosphorylation of GhWRKY59.

Drought is a key limiting factor for cotton (Gossypium spp.) production, as more than half of the global cotton supply is grown in regions with high water shortage. However, the underlying mechanism of the response of cotton to drought stress remains elusive. By combining genome-wide transcriptome profiling and a loss-of-function screen using virus-induced gene silencing, we identified Gossypium hirsutum GhWRKY59 as an important transcription factor that regulates the drought stress response in cotton. Biochemical and genetic analyses revealed a drought stress-activated mitogen-activated protein (MAP) kinase cascade consisting of GhMAP3K15-Mitogen-activated Protein Kinase Kinase 4 (GhMKK4)-Mitogen-activated Protein Kinase 6 (GhMPK6) that directly phosphorylates GhWRKY59 at residue serine 221. Interestingly, GhWRKY59 is required for dehydration-induced expression of GhMAPK3K15, constituting a positive feedback loop of GhWRKY59-regulated MAP kinase activation in response to drought stress. Moreover, GhWRKY59 directly binds to the W-boxes of DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN 2 (GhDREB2), which encodes a dehydration-inducible transcription factor regulating the plant hormone abscisic acid (ABA)-independent drought response. Our study identified a complete MAP kinase cascade that phosphorylates and activates a key WRKY transcription factor, and elucidated a regulatory module, consisting of GhMAP3K15-GhMKK4-GhMPK6-GhWRKY59-GhDREB2, that is involved in controlling the cotton drought response.

Increased abscisic acid levels in transgenic maize overexpressing AtLOS5 mediated root ion fluxes and leaf water status under salt stress.

Abscisic acid (ABA) is a vital cellular signal in plants, and effective ABA signalling is pivotal for stress tolerance. AtLOS5 encoding molybdenum cofactor sulphurase is a key regulator of ABA biosynthesis. Here, transgenic AtLOS5 plants were generated to explore the role of AtLOS5 in salt tolerance in maize. AtLOS5 overexpression significantly up-regulated the expression of ZmVp14-2, ZmAO, and ZmMOCO, and increased aldehyde oxidase activities, which enhanced ABA accumulation in transgenic plants under salt stress. Concurrently, AtLOS5 overexpression induced the expression of ZmNHX1, ZmCBL4, and ZmCIPK16, and enhanced the root net Na(+) efflux and H(+) influx, but decreased net K(+) efflux, which maintained a high cytosolic K(+)/Na(+) ratio in transgenic plants under salt stress. However, amiloride or sodium orthovanadate could significantly elevate K(+) effluxes and decrease Na(+) efflux and H(+) influx in salt-treated transgenic roots, but the K(+) effluxes were inhibited by TEA, suggesting that ion fluxes regulated by AtLOS5 overexpression were possibly due to activation of Na(+)/H(+) antiport and K(+) channels across the plasma membrane. Moreover, AtLOS5 overexpression could up-regulate the transcripts of ZmPIP1:1, ZmPIP1:5, and ZmPIP2:4, and enhance root hydraulic conductivity. Thus transgenic plants had higher leaf water potential and turgor, which was correlated with greater biomass accumulation under salt stress. Thus AtLOS5 overexpression induced the expression of ABA biosynthetic genes to promote ABA accumulation, which activated ion transporter and PIP aquaporin gene expression to regulate root ion fluxes and water uptake, thus maintaining high cytosolic K(+) and Na(+) homeostasis and better water status in maize exposed to salt stress.

Compressed sensing magnetic resonance imaging (CS-MRI) diagnosis of rotator cuff tears.

OBJECTIVE: The present prospective study was performed to evaluate the diagnostic efficiency of compressed sensing magnetic resonance imaging (CS-MRI) for rotator cuff tears. METHODS: Between December 1, 2021 and April 1, 2022, 62 patients with suspected rotator cuff tears were admitted to Affiliated Hospital of Jinggangshan University and received CS-MRI and arthroscopy to determine the diagnosis and the disease type of tears. Their medical data were obtained and analyzed to evaluate the clinical feasibility of CS-MRI in diagnosing rotator cuff tears. RESULTS: Of the 62 cases of suspected rotator cuff tears, 45 were confirmed by arthroscopy, including 31 cases of total tears and 14 partial tears. Using arthroscopic findings as the gold standard for the diagnosis of rotator cuff tears, the sensitivity of clinical signs to diagnose rotator cuff tears was 66.67%, the specificity was 70.59%, and the accuracy was 67.74%, while the sensitivity of CS-MRI in diagnosing rotator cuff tears was 84.44%, the specificity was 88.24%, and the accuracy was 81.54%. The accuracy of CS-MRI was significantly higher than that of clinical signs as determined by chi-square test within groups (P=0.019). CONCLUSION: CS-MRI provides high resolution for muscles, tendons, and soft tissues, significantly contributing to the diagnosis of soft tissue injuries. Although there were no significant differences in the sensitivity and specificity of CS-MRI for the clinical diagnosis of rotator cuff tears compared to the clinical signs, CS-MRI significantly improved the diagnostic accuracy.

Trends and risk factors for drug-resistant tuberculosis among children in Sichuan, China: A 10-year retrospective analysis, 2013-2022.

To investigate the status of the drug-resistant tuberculosis (DR-TB) among children in Sichuan, and to find out the risk factors and high-risk population related to drug resistance among children. The clinical data of tuberculosis patients ≤14 years old with culture-confirmed tuberculosis hospitalized in Chengdu Public Health Clinical Center from January 2013 through December 2022 were collected. Clinical data such as gender, age, ethnicity, history of anti-TB treatment, history of exposure to tuberculosis, nutritional status, and specific drug resistance of the children were collected and recorded. The drug resistance of children in different age groups (0-4 years old, 5-9 years old, 10-14 years old) and different periods (2013-2017 and 2018-2022) were grouped and compared. Logistic regression analysis was to analyze analysis of risk factors of drug resistance in children. A total of 438 children with culture-confirmed tuberculosis were screened. Among them, 26.19% (11/42) were 0 to 4 years old, 33.33% (22/66) were 5 to 9 years old, and 36.67% (121/330) were 10 to 14 years old among the resistant children. There was no statistically significant difference in the resistance rate among the 3 groups (P = .385). The proportions of DR-TB, monoresistant tuberculosis, polydrug-resistant tuberculosis were decreased during 2019 to 2022 compared with 2013 to 2017 (P < .0001). The resistance rates of drug resistant, monoresistant, polydrug-resistant, isoniazid-resistant, and rifampicin resistant during 2018 to 2022 were decreased compared with those from 2013 to 2017 (P < .05), but the multi-drug resistance rate was not decreased (P = .131, without statistical difference). The results of logistic regression analysis showed that male gender OR = 1.566 (95% CI 1.035-2.369), a history of antituberculosis therapy OR = 4.049 (95% CI 1.442-11.367), and pulmonary and extrapulmonary tuberculosis OR = 7.335 (95% CI 1.401-38.392) were risk factors for the development of drug resistance; but fever OR = 0.581 (95% CI 0.355-0.950) was Protective factor. The total drug resistance rate of children in Sichuan showed a downward trend, but the rate of multi-drug-resistant tuberculosis was still at a high level, and the form of drug resistance was still severe. Absence of fever, male, retreatment, and pulmonary concurrent with extrapulmonary tuberculosis are risk factors for DR-TB in children.

Design and Simulation of a 19-Electrode MEMS Piezoelectric Thin-Film Micro-Deformable Mirror for Ophthalmology.

This study presents a numerical simulation-based investigation of a MEMS (micro-electromechanical systems)technology-based deformable mirror employing a piezoelectric film for fundus examination in adaptive optics. Compared to the classical equal-area electrode arrangement model, we optimize the electrode array for higher-order aberrations. The optimized model centralizes electrodes around the mirror center, which realizes low-voltage driving with high-accuracy correction. The optimized models exhibited commendable correction abilities, achieving a unidirectional displacement of 5.74 µm with a driven voltage of 15 V. The voltage-displacement relationship demonstrated high linearity at 0.99. Furthermore, the deformable mirror's influence matrix was computed, aligning with the Zernike standard surface shape of the order 1-3. To quantify aberration correction capabilities, fitting residuals for both models were calculated. The results indicate an average removal of 96.8% of aberrations to the human eye. This underscores that the optimized model outperforms the classical model in correcting high-order aberrations.

Combining with volatilomic profiling and chemometrics to explore the volatile characteristics in five different dried Zanthoxylum bungeanum maxim.

Owing to the short picking period of the fresh Zanthoxylum bungeanum, the postharvest drying has become an essential operation before the storage and transportation of Z. bungeanum. To explore the effects of drying methods on volatile characteristics, the volatilomic profiling of five different dried Z. bungeanum was investigated by E-nose, HS-SPME-GC/MS, GC-IMS in combination with chemometrics. The results indicated that W1W, W2W and W5S sensors within E-nose analysis showed the strongest responses in both fresh and dried Z. bungeanum. According to the identification of volatile organic compounds (VOCs), terpenes, esters and alcohols played the major roles in the volatile formation of the fresh and dried Z. bungeanum. The samples derived from hot air drying showed the relatively similar features with the fresh sample based on the relative abundances of these major VOCs. According to the results of multiple factor analysis (MFA), GC-IMS showed the strongest ability in distinguishing the fresh and different dried samples. Compared with the high levels of terpenes in fresh group, the significant increasement of terpene alcohols and terpene esters from the degradation and transformation of bound terpenoids was the main characteristics of all dried Z. bungeanum. Using the GC-IMS datasets, a weighted correlation network analysis (WCNA) model was constructed to clarify the VOC characteristics in all detetected samples. Thereinto, 6 significantly correlated modules were identified in fresh and five different dried samples. Additionally, a total of 23 hub VOCs can be recognized as the potential biomarkers for better distinguishing the fresh and five different dried Z. bungeanum.

Facile low-temperature synthesis of ultralong monodisperse ZnSe quantum wires with the assistance of Ag2S.

A facile method for the low-cost and large-scale production of ultralong Ag(2)S (or Ag(2)Se)-ZnSe quantum wires has been developed. ZnSe quantum wires (diameter≈4 nm) with high uniformity in their crystal structure and diameter can be synthesized by using a catalyst-assisted growth approach with Ag(2)S nanoparticles as a catalyst. The influence of the growth temperature, time, and type of catalytic particle on the morphology of the ZnSe quantum wires was systematically explored. Besides Ag(2)S, Ag(2)Se nanoparticles can also be adopted as the catalyst for the growth of ZnSe wires. This method can also be applied to the fabrication of uniform CdSe nanorods. This method is convenient for the controllable fabrication of metal selenides and is of importance for exploring fundamental nanoscale semiconductor physics, as well as for affording technological devices with optimized characteristics.

Cotton GhBAK1 mediates Verticillium wilt resistance and cell death.

Virus-induced gene silencing (VIGS) offers a powerful approach for functional analysis of individual genes by knocking down their expression. We have adopted this approach to dissect gene functions in cotton resistant to Verticillium wilt, one of the most devastating diseases worldwide. We showed here that highly efficient VIGS was obtained in a cotton breeding line (CA4002) with partial resistance to Verticillium wilt, and GhMKK2 and GhVe1 are required for its resistance to Verticillium wilt. Arabidopsis AtBAK1/SERK3, a central regulator in plant disease resistance, belongs to a subfamily of somatic embryogenesis receptor kinases (SERKs) with five members, AtSERK1 to AtSERK5. Two BAK1 orthologs and one SERK1 ortholog were identified in the cotton genome. Importantly, GhBAK1 is required for CA4002 resistance to Verticillium wilt. Surprisingly, silencing of GhBAK1 is sufficient to trigger cell death accompanied with production of reactive oxygen species in cotton. This result is distinct from Arabidopsis in which AtBAK1 and AtSERK4 play redundant functions in cell death control. Apparently, cotton has only evolved SERK1 and BAK1 whereas AtSERK4/5 are newly evolved genes in Arabidopsis. Our studies indicate the functional importance of BAK1 in Verticillium wilt resistance and suggest the dynamic evolution of SERK family members in different plant species.

Antagonistic Activity of Streptomyces alfalfae 11F against Fusarium Wilt of Watermelon and Transcriptome Analysis Provides Insights into the Synthesis of Phenazine-1-Carboxamide.

Streptomyces alfalfa strain 11F has inhibitory effects on many phytopathogenic fungi and improves the establishment and biomass yield of switchgrass. However, the antagonistic effects of strain 11F on Fusarium wilt of watermelon and its secondary metabolites that contribute to its biocontrol activity are poorly understood. We evaluated the antagonistic and growth-promoting effects of strain 11F and conducted a transcriptome analysis to identify the metabolites contributing to antifungal activity. Strain 11F had marked inhibitory effects on six fungal pathogens. The incidence of Fusarium wilt of watermelon seedlings was decreased by 46.02%, while watermelon seedling growth was promoted, as indicated by plant height (8.7%), fresh weight (23.1%), and dry weight (60.0%). Clean RNA-sequencing data were annotated with 7553 functional genes. The 2582 differentially expressed genes (DEGs) detected in the Control vs. Case 2 comparison were divided into 42 subcategories of the biological process, cellular component, and molecular function Gene Ontology categories. Seven hundred and forty functional genes (55.47% of the DEGs) were assigned to Kyoto Encyclopedia of Genes and Genomes metabolic pathways, reflecting the complexity of the strain 11F metabolic regulatory system. The expression level of the gene phzF, which encodes an enzyme essential for phenazine-1-carboxylic acid (PCA) synthesis, was downregulated 3.7-fold between the 24 h and 48 h fermentation time points, suggesting that strain 11F can produce phenazine compounds. A phenazine compound from 11F was isolated and identified as phenazine-1-carboxamide (PCN), which contributed to the antagonistic activity against Fusarium oxysporum f. sp. niveum. PCA was speculated to be the synthetic precursor of PCN. The downregulation in phzF expression might be associated with the decrease in PCA accumulation and the increase in PCN synthesis in strain 11F from 24 to 48 h. Streptomyces alfalfae 11F protects watermelon seedlings from Fusarium wilt of watermelon and promotes seedling growth. The transcriptome analysis of strain 11F provides insights into the synthesis of PCN, which has antifungal activity against F. oxysporum f. sp. niveum of watermelon.