Search Results (338)

Background: C2H2 zinc finger proteins (C2H2-ZFPs) are one of the largest transcription factor families in plants and play vital roles in plant organ development and patterning, seed germination, and fruit ripening, as well as responses to biotic and abiotic stresses. Although widely studied in many species, the genome-wide characterization of the C2H2-ZFP family in watermelon (Citrullus lanatus) remains lacking. Methods: In this study, we identified 96 ClZFP genes in the watermelon genome and analyzed their chromosomal positions, gene structures, conserved motifs, and expression profiles. A tissue-specific expression analysis of 12 representative ClZFP genes revealed diverse and organ-preferential expression profiles, indicating functional differentiation during development. Results: Under abiotic stress treatments, four genes were significantly downregulated under drought, while one gene was strongly induced; six genes were inhibited and three genes were activated under low temperature; and most tested genes were upregulated at 72 h under salt stress, with one gene continuously induced throughout the treatment period. Key ClZFP members such as ClZFP36 and ClZFP72 showed specific and strong induction under drought and salt stress, respectively. Conclusions: These results indicate that ClZFPs may be involved in the tolerance of watermelon to various abiotic stresses. This study not only clarifies the evolutionary and expression characteristics of the ClZFP family in watermelon but also provides candidate genes for the genetic improvement of stress tolerance in cucurbit crops. Full article

Sechium edule (Cucurbitaceae), commonly known as chayote, which is a cucurbit of economic relevance, has experienced higher incidence of wilting from Phytophthora capsici in Mexican commercial fields during heavy rainfall. The infection process of this oomycete on chayote stems at the anatomical level had not been documented. This study characterized histological changes in chayote stems infected with P. capsici. Plants were inoculated at the stem base with P. capsici mycelial plugs, while controls received sterile plugs. Stem samples collected at 8, 12, 16, 22, and 30 days post-inoculation were processed and stained using safranin O–fast green. Microscopic observations showed progressive anatomical alterations. At 8 dpi, hyphae appeared in cortical parenchyma and epidermis, with phenolic compound accumulation. By 12 dpi, stromata and sporangia were visible in vascular and cortical tissues, with tyloses formation. At 16 dpi, cell wall collapse and xylem colonization became evident. These effects intensified at 22 and 30 dpi, with tissue degradation and an abundance of hyphae. Control stems maintained intact structures. Macroscopically, plants remained asymptomatic until 12 dpi, when brown lesions appeared. By 22 dpi, leaf yellowing and stem necrosis were observed, leading to plant death by 30 dpi. The results demonstrate the rapid colonization of chayote tissues by P. capsici, and its impact on vascular integrity. This study provides knowledge for future research on host resistance and disease management in chayote crops. Full article

Background: PYR/PYL/RCAR proteins are core abscisic acid (ABA) receptors that play essential roles in ABA signal transduction, plant growth and development, and abiotic stress responses. However, the PYL gene family in watermelon (Citrullus lanatus) has not been systematically characterized, limiting our understanding of ABA-mediated stress adaptation in this economically important crop. Methods: A genome-wide analysis was performed to identify ClPYL genes in watermelon using a hidden Markov model search. Phylogenetic relationships were reconstructed using the maximum likelihood method. Segmental duplication events were analyzed using synteny analysis. Conserved motifs, gene structures, and promoter cis-acting elements were characterized using MEME and PlantCARE. Expression profiles under drought, salt, and cold stresses were examined by quantitative real-time PCR (qRT-PCR) with three biological replicates. Results: In this study, 15 ClPYL genes were identified in watermelon through genome-wide analysis. Phylogenetic reconstruction classified these genes into four subfamilies, with subfamily II being exclusively present in cucurbits—a lineage-specific feature not observed in Arabidopsis. Synteny analysis revealed eight segmental duplication events involving members of subfamilies I, III, and IV, while subfamily II members were not associated with these duplications. Members within the same subfamily share similar exon-intron structures and conserved motifs. Promoter analysis revealed that ClPYL genes are enriched with various cis-acting elements associated with hormone signaling and abiotic stress responses. Expression profiling demonstrated that ClPYL genes exhibit diverse and dynamic expression patterns under drought, high-salinity, and cold stresses. Notably, genes such as ClPYL5 under drought, ClPYL02 under salt, and ClPYL15 under cold stress displayed persistent stress-responsive expression. Conclusions: These findings reveal the evolutionary conservation and diversification of the PYL family in watermelon and provide a set of candidate genes for functional studies aimed at dissecting ABA-mediated stress adaptation. This work establishes a genomic framework for developing stress-resilient watermelon varieties through molecular breeding. Full article

Zucchini tigre mosaic virus (ZTMV; Potyvirus pepotigris), which infects wax gourd (Benincasa hispida), was first identified in Taiwan in 2017 and designated ZTMV-TW. In this study, mild strains of ZTMV-TW were generated by modifying the pathogenicity factor HC-Pro to develop cross-protection strategies for cucurbit crops. A full-length infectious cDNA clone of ZTMV-TW was cloned in pCAMBIA1304 under the control of the CaMV 35S promoter (ZTMV-TWic). ZTMV-TWic induced typical potyvirus particles, cytoplasmic inclusion bodies, and severe symptoms in wax gourd, pumpkin, and zucchini plants. Conserved motifs of HC-Pro were mutated to generate four single mutants (F7I, R181I, F206L, and D397N) and three double mutants (F7I+F206L, R181I+D397N, and F206L+D397N). Mutants R181I and R181I+D397N caused mild or no symptoms in zucchini, while D397N and F206L+D397N were mild in wax gourd. Cross-protection assays showed that R181I and R181I+D397N provided complete protection against ZTMV-GFP in zucchini, whereas D397N and F206L+D397N conferred high protection in wax gourd. These results demonstrate the feasibility of host-specific mild strain selection for effective ZTMV cross-protection. Full article

The Lateral Organ Boundaries Domain (LBD) gene family encodes plant-specific transcription factors that play pivotal roles in growth, development, and stress responses. However, a comprehensive genome-wide analysis of the LBD family in watermelon (Citrullus lanatus) has not been conducted until now. In this study, we identified 39 ClLBD genes using the latest watermelon reference genome and systematically analyzed the function of ClLBD2 in root development. These ClLBDs are unevenly distributed across 10 chromosomes except Chr4. Evolutionary analysis grouped the gene family members into six subgroups: Class I (a–e) and Class II. Physicochemical properties and gene structure analysis showed that the ClLBD protein members are tightly conserved. In the promoter regions of ClLBD genes, we identified abundant cis-acting regulatory elements related to abiotic stress and hormone responses. Through RNA-seq analysis from a cucurbit database, we found that several ClLBD genes showed high relative expression in roots, with ClLBD2 being the most highly expressed. Since its subfamily includes AtLBD25, a known root development-related gene, we hypothesized that ClLBD2 might be involved in root development. To validate this, ClLBD2-edited roots were generated using the CRISPR-Cas9 system and Agrobacterium rhizogenes-mediated transformation. Compared to the wild type, the ClLBD2 edited roots exhibited significant reduction in taproot length and lateral root numbers, indicating that ClLBD2 may regulate root development. This study provides the first comprehensive analysis of the LBD gene family in watermelon, offering valuable insights for evolutionary and further functional studies of ClLBD genes. Full article

Cucurbitaceous plants comprise a wide range of economically important vegetable and fruit crops. In this study, Alternaria species associated with Cucurbitaceae were investigated using an integrative approach combining multilocus phylogenetic analyses and morphological characterization. Two novel species, Alternaria charantiicola sp. nov. and A. cucumicola sp. nov., were identified from Momordica charantia and Cucumis sp., respectively. In addition, five Alternaria species, namely A. zeae, A. lycopersici, A. sanguisorbae, A. pulvinifungicola, and A. solanicola, are reported for the first time from cucurbitaceous hosts. These findings expand the known species diversity of Alternaria associated with Cucurbitaceae in China and provide a taxonomic basis for the accurate diagnosis of Alternaria-related diseases in cucurbit crops. Full article

The melon fly, Zeugodacus cucurbitae (Coquillett), is recognized as a globally significant quarantine pest, and it ranks among the most destructive insect species infesting cucurbit and solanaceous crops. However, the molecular mechanisms governing reproductive regulation in female Z. cucurbitae remain poorly characterized, particularly those underlying the reproductive processes mediated by microRNAs (miRNAs). In this study, we firstly identified the ovary-specific gene ZcCTL-S1 in Z. cucurbitae via transcriptomic analysis, and subsequently predicted its targeted miRNAs using bioinformatics approaches. Among these miRNAs, overexpression or inhibition of miR-971-1 and miR-let-7 led to corresponding inverse changes in the transcriptional level of ZcCTL-S1. Notably, only miR-let-7 displayed markedly elevated expression levels in Z. cucurbitae ovaries. Further analyses confirmed that miR-let-7 exhibited a direct targeting relationship with ZcCTL-S1, via a combinatorial approach involving in vivo RNA immunoprecipitation, in vitro dual-luciferase reporter assays, and site-directed mutagenesis techniques. Phenotypic analyses showed that both knockdown of ZcCTL-S1 and overexpression of miR-let-7 significantly inhibited egg hatchability, ultimately compromising the female reproductive capacity of Z. cucurbitae. Collectively, these findings identify a novel miRNA-gene regulatory module in the reproductive development of Z. cucurbitae, and provide novel insights for the development of gene- or miRNA-based pest control strategies. Full article

Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite begomovirus (family Geminiviridae) originally isolated from tomatoes and later evolved to cross-infect cucurbit crops, causing severe economic damage in Asia and Europe. In this study, we sequenced and characterized complete genomes of two ToLCNDV isolates collected from Hebei (ToLCNDV-HB) and Jiangsu (ToLCNDV-JS) provinces of China infecting melon. We constructed infectious clones for ToLCNDV-HB and ToLCNDV-JS, which could systemically infect Nicotiana benthamiana, tomato, and four species of cucurbitaceous plants. Notably, ToLCNDV-HB induced more severe symptoms and accumulated higher viral DNA and protein accumulation than ToLCNDV-JS in N. benthamiana, melon, and bottle gourd. Sequence analysis showed that sequence variations are present only in AV2, AC1, and AC4. However, only the AV2 ORF from ToLCNDV-HB was more efficient than that from that ToLCNDV-JS in enhancing potato X virus’s pathogenicity and suppressing post-transcriptional gene silencing (PTGS). An AV2-swapping experiment between ToLCNDV-HB and ToLCNDV-JS confirmed its vital role in determining the differential pathogenicity. Further evidence shows that virions from both clones are mechanically transmissible. This is the first report comparing the differential pathogenicity of two Chinese ToLCNDV isolates in cucurbits. The AV2 protein, a key pathogenicity determinant, represents a potential target for breeding ToLCNDV-resistant cucurbit varieties. Full article

Phytophthora capsici, an invasive oomycete pathogen causing blight in crops like cucurbits, tomatoes, and peppers, has led to significant economic losses. Due to the limitations of conventional control methods, research has focused on effective and eco-friendly biocontrol alternatives. The bacterial strain LT-22, identified as Bacillus velezensis, exhibits broad-spectrum antifungal activity and plant growth-promoting potential. This study investigated the biocontrol efficacy of volatile organic compounds (VOCs) from strain LT-22. LT-22 VOCs strongly inhibited P. capsici PC153 growth in vitro and reduced disease symptoms in pepper fruits. Microscopic observations showed that LT-22 VOCs caused significant morphological changes in P. capsici PC153 mycelium by disrupting cell wall and membrane integrity. The treatment increased malondialdehyde (MDA) levels and reduced cellulose content, further indicating that LT-22 VOCs compromise cell integrity to exert antifungal effects. Furthermore, 2-methylbutanoic acid was identified as the primary antifungal VOC, with an EC₅₀ value of 0.095 µL/mL against P. capsici PC153, lower than the reported plant-derived compounds. Together, these results indicate that strain LT-22 and its VOCs, especially 2-methylbutanoic acid, have significant potential as an effective biocontrol agent for managing Phytophthora blight. Full article

Climate warming has facilitated the expansion of insect vectors and plant viral pathogens, leading to increased incidence of viral diseases in crops. Cucurbit crops, including cucumber (Cucumis sativus), melon (Cucumis melo), squash (Cucurbita pepo), and watermelon (Citrullus lanatus), are of major economic importance worldwide, but their production is severely threatened by viral infections. Among the most damaging viruses are zucchini yellow mosaic virus (ZYMV; genus Potyvirus), transmitted by aphids, and melon yellow spot virus (MYSV; genus Orthotospovirus), transmitted by thrips, both of which cause significant yield losses in Asia, including Taiwan. Previously, an attenuated ZYMV mutant, ZAC, was shown to confer effective cross-protection against ZYMV in several cucurbit species. In the present study, we engineered a recombinant virus, ZAC-MYnp, by inserting the nucleocapsid protein (NP) open reading frame of MYSV into the ZAC genome. ZAC-MYnp retained the attenuated phenotype of ZAC and remained effective in protecting against ZYMV infection, with protection rates of 70.4% and 87.0% in zucchini and muskmelon plants, respectively. In addition, under both mechanical and thrips-mediated challenge conditions, ZAC-MYnp significantly reduced MYSV symptom severity in muskmelon, with a protection rate of 66.7% and a protective efficacy of 79.0%, respectively. These results demonstrate that ZAC-derived recombinant viruses can function as a bivalent viral vaccine, offering dual protection against an aphid-borne potyvirus and a thrips-borne orthotospovirus. Our study highlights the feasibility of using a bivalent recombinant vaccine to manage two distinct insect-borne viruses in cucurbit crops. Full article

Insects’ gut microbiota and their hosts share a mutually dependent symbiotic relationship. However, how insect dietary breadth relates to microbial diversity remains unclear. This study compared the gut bacterial communities of the polyphagous Aulacophora indica and the oligophagous Aulacophora lewisii. Using an integrated approach of cultivation, 16S rRNA high-throughput sequencing, and bioinformatic analyses, we assessed their composition, diversity, and functional potential. Using cultivation-based methods revealed that A. indica showed a greater abundance and diversity of culturable bacteria, dominated by Proteobacteria and Actinobacteria, compared to A. lewisii (Proteobacteria and Firmicutes). In contrast, high-throughput sequencing revealed the opposite pattern: A. lewisii exhibited significantly higher overall species richness and diversity. This apparent paradox highlights the methodological complementarity between cultivation and sequencing. Furthermore, the community composition differed notably at the genus level. Functional prediction via PICRUSt2 v2.2.0 indicated that core metabolic pathways, including carbohydrate metabolism, amino acid metabolism, and energy metabolism, were more enriched in A. indica. In summary, this study reveals systematic multi-dimensional differences in the gut microbiomes of these beetles, providing a theoretical foundation and microbial resources for understanding ecological adaptation and developing targeted control strategies based on gut microbiota. Full article

It has been well established that biofilm formation plays a critical role in the pathogenesis of various plant pathogenic bacteria. However, research on this process in Paracidovorax citrulli, the causal agent of bacterial fruit blotch (BFB) in cucurbits, remains limited. Through screening of the infection pathways of P. citrulli in sweet melon leaves, observing biofilm formation morphology at bacterial colonization sites, and detecting the activities of pathogenicity-related enzymes, this study revealed that P. citrulli readily colonizes Hami melon vascular tissues following inoculation via petiole immersion, petiole dipping, or vine injection. Dense biofilms were observed within the vascular bundles of symptomatic leaf veins. Furthermore, P. citrulli was confirmed to secrete cellulase and pectinase, with enzymatic activities increasing progressively as disease severity intensified. These findings suggest that BFB development in Hami melon is likely associated with the synergistic action of P. citrulli, biofilm-mediated occlusion of xylem vessels and hydrolytic degradation of plant cell walls, which may contribute to initial water-soaked lesions and subsequent vein-associated necrosis in leaf tissues. This study provides a theoretical foundation for further elucidation of the pathogenic mechanisms of P. citrulli. Full article

Drought is one of the most limiting abiotic stresses for agricultural production, especially in horticultural crops grown in arid and semi-arid areas. In the present study, we evaluated the potential of bacterial isolates obtained from coastal environments in Chile to improve drought tolerance in Lagenaria siceraria, a plant species increasingly used as a rootstock for cucurbit cropping. Rhizosphere bacteria were isolated from Sicyos baderoa, the only native cucurbit species of the Chilean coast, from which four isolates with plant growth-promoting traits, such as indole-3-acetic acid production, phosphorus solubilization, nitrogen fixation, and siderophore production, were selected. These isolates were inoculated on two L. siceraria genotypes, Illapel and Osorno, under both normal irrigation and water deficit conditions. The results showed that Peribacillus frigoritolerans showed a clearer positive effect on biomass and net photosynthesis under water deficit in the Illapel genotype, increasing shoot biomass by up to ~75% and restoring net photosynthetic rates by up to ~260% relative to non-inoculated drought-stressed plants. In contrast, responses associated with Staphylococcus succinus and those observed in the Osorno genotype were mainly expressed as trait- and tissue-specific adjustments, consistent with a more stabilizing response rather than broad growth stimulation. Additionally, malondialdehyde levels were reduced by up to ~25%, while free proline accumulation increased by more than 100% under water deficit. In contrast, total phenolic compounds showed more variable responses, indicating genotype- and strain-specific adjustment of antioxidant metabolism. Overall, the observed responses were heterogeneous and strongly dependent on the specific strain–genotype–trait combination and, therefore, should be interpreted as preliminary evidence supporting the potential value of native rhizobacteria for improving early drought-related traits in cucurbit rootstocks. Among the tested strains, Peribacillus frigoritolerans emerged as the most promising candidate for enhancing early drought tolerance in responsive genotypes such as Illapel, while highlighting the need for follow-up studies under replicated nursery and field conditions, including grafted plants, multiple drought intensities and combined inoculant strategies. Full article

In Saudi Arabia, cucurbit crops such as zucchini (Cucurbita pepo) and snake gourd (Trichosanthes cucumerina) are major vegetables and key dietary components, yet their associated viral threats remain poorly understood. We surveyed symptomatic cucurbit samples from greenhouses and open fields in the Al-Ahsa and Qatif regions. The detection methods employed included PCR, RCA, and Illumina NGS. Based on nucleotide sequence comparisons and maximum-likelihood phylogenetic analysis, we identified three viruses, i.e., TYLCV, WmCSV, and ToLCPalV, present as both single and mixed infections. Sequence analyses revealed a novel strain, TYLCV-Hasa, representing a distinct lineage of TYLCV. Analysis revealed that recombination occurred solely in the DNA-A components of the identified viruses, while DNA-B segments showed no evidence of recombination. Notably, no DNA satellites were detected, suggesting cucurbits may act as independent reservoirs of begomovirus diversity. These results provide a comprehensive genomic insight into cucurbit-infecting begomoviruses in Eastern Saudi Arabia. The discovery of TYLCV-Hasa and evidence of recombination raise concerns about the emergence of novel viral variants that could pose risks to cucurbit cultivation. The results establish a foundation for advanced molecular surveillance and breeding strategies, contributing to improved food security and supporting Saudi Arabia’s Vision 2030 goals for sustainable agriculture. Full article

The calmodulin-binding protein 60 (CBP60) family comprises essential Ca²⁺-responsive transcription factors that orchestrate salicylic acid (SA)-mediated immunity and broader stress responses. Despite being extensively characterized in model species, the CBP60 family remains poorly understood in watermelon (Citrullus lanatus), a globally significant cucurbit crop highly susceptible to aphid infestation and fusarium wilt. In this study, we performed a comprehensive genome-wide identification and characterization of the CBP60 gene family in watermelon, identifying 16 putative ClaCBP60 members, all of which harbor the conserved calmodulin-binding domain. These genes are non-randomly distributed across chromosomes, featuring a prominent cluster of 10 members on chromosome 3. Phylogenetic analysis across seven cucurbit species categorized the CBP60 proteins into four distinct subfamilies, revealing both evolutionary conservation and lineage-specific diversification. Gene structure and conserved motif analyses revealed shared core domains with subfamily-specific variations, indicative of functional divergence. Furthermore, synteny analysis showed strong collinearity with cucumber and melon, reflecting the evolutionary stability of key CBP60 loci. Transcriptional profiling under F. oxysporum infection and aphid infestation revealed dynamic expression patterns, with ClaCBP60_01 and ClaCBP60_16 exhibiting rapid and robust induction during the early stages of both stresses. These findings indicated that ClaCBP60 genes operate in a coordinated yet diversified manner to modulate defense signaling against F. oxysporum and aphid attack. This study provides a systematic insight into CBP60 family members in watermelon, establishing a foundation for validation and molecular breeding aimed at enhancing biotic tolerance. Full article