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Cucurbit Leaf Crumple Virus: An Important Pathogen of Cucurbit and Snap Bean Crops.

TAXONOMY: Cucurbit leaf crumple virus (CuLCrV); Begomovirus cucurbitae; Geminiviridae; Geplafuvirales. GEOGRAPHICAL DISTRIBUTION: The presence of CuLCrV is exclusively limited to North America, mainly Mexico and the United States. PHYSICAL PROPERTIES: CuLCrV is a bipartite begomovirus comprising two circular single-stranded DNA molecules (DNA-A and DNA-B), encapsidated within geminate icosahedral particles. GENOME AND ORGANIZATION: CuLCrV possesses a bipartite genome of DNA-A (2632 nucleotides) and DNA-B (2600 nucleotides). DNA-A contains five open reading frames (ORFs): AV1 (coat protein), AC1 (replication-associated protein), AC2 (transcriptional activator protein), AC3 (replication enhancer protein) and AC4. DNA-B contains two ORFs: BV1 (nuclear shuttle protein) and BC1 (movement protein). TRANSMISSION: CuLCrV is transmitted by the sweetpotato whitefly, Bemisia tabaci, in a persistent, circulative and non-propagative manner. HOSTS: CuLCrV primarily infects crop members of the Cucurbitaceae and snap bean (Phaseolus vulgaris, Fabaceae). Multiple weed species belonging to Brassicaceae, Convolvulaceae, Cucurbitaceae and Verbenaceae act as persistent virus reservoir hosts. SYMPTOMS: Symptom expression varies with host and infection timing. In cucurbits, infection induces leaf crumpling, thickening and downward curling of leaves, with green streaks and distortion of fruits. In snap bean, symptoms include leaf distortion, chlorosis and malformed pods. CONTROL: No commercial cultivars with resistance to CuLCrV are available for cucurbit crops, although some resistance has been reported in snap bean cultivars. Therefore, management relies primarily on integrated disease management.

Plant Diseases

Development of a highly efficient prime editing platform for cucurbits enables breeding of multi-disease-resistant cucumber.

The prime editing (PE) system is a precise genome editing technology that works efficiently in monocots; however, its application is limited by low editing efficiency in dicots, particularly Cucurbitaceae and Solanaceae plants. Here, we first significantly improved the transformation efficiency by introducing spectinomycin in cucurbits, then used the tomato elongation factor 1-alpha (SlEF1α) promoter to enhance PE protein expression, and incorporated the Csy4 ribonuclease to process pegRNAs, collectively addressing multiple constraints limiting PE efficiency in cucurbits. The optimized PE systems, particularly Csy4-PE6d, achieved an average desired editing frequency of 80.83% at targeted loci in cucumber via stable genetic transformation, with frequencies reaching up to 100% at certain sites. Moreover, Csy4-PE6d generated homozygous edits in 36.43% of transgenic lines and demonstrated robust editing activity in melon, pumpkin, and potato. Using the Csy4-PE6d tool, we generated heritable edited cucumber lines with dual resistance to bacterial angular leaf spot and downy mildew by targeting the CsSGR gene. Collectively, this optimized system substantially enhances PE efficiency in Cucurbit crops, providing an effective solution to common challenges such as low editing efficiency and limited heritability in these species.

Disease Resistance

Tandem Duplication-Driven Neofunctionalization of UDP-Glycosyltransferases Shapes the Diversification of Triterpenoid Saponins in the Cucurbitaceae.

Tandem duplication of tailoring enzymes allows evolutionary innovation that diversifies plant specialized metabolism. Here, we present an interesting example of how tandem duplicated UDP-glycosyltransferases undergo neofunctionalization and shape the chemical diversity of triterpenoid saponins in the Cucurbitaceae family. A chromosome-level genome of Siraitia grosvenorii was assembled and aligned with multiple cucurbit genomes, revealing a specific UGT73AM tandem duplication responsible for regio-selective glycosylation (e.g. the rare 1,4-linked disaccharide) of diverse saponins such as mogrosides, ginsenosides, and momordicines. Comparative genomics depicted the evolutionary trajectory of a universal saponin-biosynthesizing UGT73 tandem arrays syntenously preserved across core eudicots, where lineage-specific UGT copies contribute to distinct metabolic phenotypes. A crystal structure of SgUGT73AM30 (mogrol 25-O-glycosyltransferase) in complex with UDP and mogrol was obtained to elucidate the molecular basis of the regio-specific decoration on vicinal diol of the substrates. Altogether, these findings provide insights into tandem duplication-driven diversification of glycosyltransferases and lay the foundation for engineered glycosylation of valuable triterpenoid saponins.

Saponins

Recent advances in supramolecular macrocycle-based artificial light-harvesting systems.

Artificial light-harvesting systems (ALHSs) inspired by the antenna function of natural photosynthesis provide molecular platforms for collecting excitation energy and directing it to emissive or reactive acceptors. In many supramolecular ALHSs, however, practical performance is limited by poorly defined donor-acceptor orientation, aggregation-caused quenching (ACQ), interfacial defects, and limited stability in aqueous or complex media. Supramolecular macrocycles-particularly pillar[n]arenes (PAs), cucurbit[n]urils (CBs), calixarenes (CAs), cyclodextrins (CDs), and supramolecular coordination complexes (SCCs)-offer a useful design space because their cavities, pre-organized scaffolds, and reversible non-covalent interactions can confine chromophores, tune local donor/acceptor ratios, and modulate Förster resonance energy transfer (FRET). This Review systematically examines the unique structural advantages and assembly mechanisms of the five macrocyclic families, with an emphasis on their use in constructing ALHSs-from single-step to cascaded FRET-and in advancing aqueous photocatalysis, near-infrared bioimaging, panchromatic fluorescence modulation, and singlet oxygen generation. The resulting structure-property-application framework is intended to guide the rational design of macrocycle-assisted photofunctional materials while avoiding overextension of the photosynthesis analogy.

Journal Article

Pleiotropic mutation in a tendril TCP gene underlies the yield-enhancing multiple-flowering trait in summer squash (Cucurbita pepo).

Crop yield is a focal point in plant breeding. Regulation of lateral budding through apical dominance was a central target of crop domestication, directly affecting crop production. The young fruits of Cucurbita pepo, summer squash, are produced on plants characterized by apical dominance and differentiation of a single flower bud per leaf axil. A single recessive mutation, mf, results in differentiation of more than one flower per leaf axil, thereby directly increasing production because of the continual day-to-day harvest of the summer squash crop. Positional cloning of the Cucurbita pepo mf (Cpmf) gene denoted a frameshift mutation in a TCP transcription factor, Cp4.1LG13g07780, as causative for the increase in axillary flowering. Cpmf is an ortholog of a tendril-development TCP gene in other cucurbits, and likewise, the recessive allele of Cpmf is associated with distorted tendril development. Gene function is context dependent, and we propose that multiple flowering is a unique pleiotropic attribute of mutation in a tendril-development gene of C. pepo. Characterization of a C. pepo collection confirmed a significant association of the Cpmf mutation with multiple flowering and showed that the mutant allele is absent in ancestral C. pepo and one of its two cultivated subspecies. The beneficial mutation occurred and was selected after the domestication of the other subspecies, during its cultivation for young fruit production. We demonstrate the discovery of a causative yield-increasing sequence variant and its practical utilization in breeding. Our findings provide a molecular target for creation of high-yielding, multiple-flowering summer squash cultivars through marker-assisted breeding or precise genome editing.

Cucurbita

Cucurbitacins in Plant-Insect Interactions: Biosynthesis, Regulation, Ecological Functions, and Prospects for Crop Protection.

Cucurbitacins are highly oxygenated tetracyclic triterpenoids characterized by intense bitterness, substantial structural diversity, and important consequences for plant-herbivore interactions. Although best known from Cucurbitaceae, cucurbitacins and related cucurbitane-type metabolites also occur in phylogenetically distant herbaceous and woody plants. Genetic and biochemical studies have validated several core biosynthetic steps, including cucurbitadienol formation by oxidosqualene cyclases and subsequent modification by cytochrome P450 monooxygenases, acyltransferases, and glycosyltransferases. Tissue-preferential basic helix-loop-helix transcription factors constitute the best-characterized regulatory layer, whereas the evidence supporting accessory regulators, transporters, and environmental responses varies from functional validation to transcriptomic or genomic prediction. From the plant perspective, cucurbitacins deter feeding or impair performance in many generalist and non-adapted herbivores. By contrast, their use as host-recognition cues and feeding stimulants by specialist diabroticite beetles reflects evolved herbivore adaptations involving perception, tolerance, metabolism, or sequestration rather than a second defensive function of the plant trait. Herbivore-induced cucurbitacin accumulation has been demonstrated in particular systems, although its regulatory mechanisms and ecological generality remain unresolved. Unlike previous reviews centered primarily on cucurbitacin chemistry, pharmacological activity, or individual biosynthetic pathways, this review integrates evidence-graded pathway reconstruction and molecular regulation with taxonomic distribution, insect adaptation, domestication, and agroecological consequences. Mechanistically, this review traces how scaffold formation, oxidative tailoring, conjugation, tissue-specific regulation, and transport give rise to contrasting ecological outcomes through herbivore-specific perception, tolerance, metabolism, and sequestration. We conclude that uniformly increasing or eliminating cucurbitacins is unlikely to provide broadly effective crop resistance because either direction may favor a different herbivore group. Future priorities include functional validation of candidate genes, spatially resolved metabolite analysis, comparative investigation of non-cucurbit lineages, and field evaluation involving generalist and specialist herbivores, crop quality, and non-target organisms. These advances will support context-specific fruit-quality improvement, behavioral pest control, and integrated pest management strategies rather than cucurbitacin manipulation as a stand-alone resistance approach.

agroecology

Strain Diversity and Resistance to Cucumber Green Mottle Mosaic Virus (CGMMV) in Cucumber.

Cucumber green mottle mosaic virus (CGMMV) is a tobamovirus that causes disease in cucumber crops worldwide, leading to significant economic losses. To study the variability of CGMMV in southeastern Spain, partial genome sequences were obtained from isolates collected in 2017 and 2020 from cucumber crops. Phylogenetic analyses revealed that isolates clustered into two major groups, Asian (AS)-like and European (EU)-like CGMMV isolates. These two groups coexisted in the same area, crops, and even individual plants, although the AS type predominated. The accumulation and symptom expression of molecularly cloned isolates from these two groups were assessed in two cucumber cultivars (resistant and susceptible) under both summer and winter conditions. An in planta antagonistic interaction was detected between the AS and EU isolates, in which the accumulation of CGMMV-EU was suppressed during mixed infections. A multivariate analysis did not identify statistically significant differences because of variations in environmental conditions. Unlike CGMMV-EU, CGMMV-AS did not show significant differences in accumulation based on the plant genotype. To further investigate this, the response to CGMMV-AS infection was analyzed in additional susceptible and resistant cultivars. All cultivars appeared to be similarly susceptible to CGMMV-AS, in contrast to CGMMV-EU, which accumulated to a much lower extent in resistant compared with susceptible plants. These results reinforce the need to continue epidemiological surveillance, identify new sources of resistance, and implement strict control of infected seed trade, given the growing threat that CGMMV-AS isolates pose to cucumber cultivation.

agroinfectious clone