Xingwang Liu

Editing the cucumber peroxidase gene CsPOD7 establishes a haploid inducer line capable of inducing maternal haploids.

Glandular trichomes (GTs) are epidermal outgrowths that function as “natural cell factories” for the synthesis of specialized metabolites. Beyond their traditional understanding, GTs on cucumber fruits can form an undesirable trait known as bloom, which negatively affects market value. However, the secretory process, metabolite profiles, and genetic regulation underlying GT development in cucumber remain largely unclear. In this study, we employed scanning electron microscopy (SEM), transmission electron microscopy (TEM), histochemical staining, multi-omics analyses, and liquid chromatography–mass spectrometry (LC-MS) to systematically investigate GT development. The secretory process was classified into four distinct stages via SEM observations: morphogenesis, active metabolism, head sunken, and metabolite release. TEM revealed progressive ultrastructural changes, including increased organelle abundance and expansion of the periplasmic space, which facilitate metabolite transport and release. This process occurs through an autonomous mechanism involving osmiophilic substances and eventual cell rupture. LC-MS analysis identified 744 metabolites belonging to 11 classes, with phenylpropanoids/polyketides—particularly flavonoids—being the most abundant. While metabolite classes are conserved between European greenhouse and North China ecotypes, specific metabolite contents vary significantly. Multi-transcriptome analysis identified 60 candidate genes associated with GT development. Among these, CsaV4_3G003418 was functionally validated through virus-induced gene silencing (VIGS) to be involved in early GT development. Collectively, this work elucidates the secretory mechanism and metabolic characteristics of cucumber GTs, providing a foundation for future functional studies and biotechnological applications of secondary metabolites.

Jasmonic acid (JA) and its derivatives, including methyl jasmonate, are well-known plant growth regulators that mediate a wide range of physiological and developmental processes. Although the role of JA in regulating fruit trichome density has been recognized, the specific mechanisms underlying this remain to be fully understood. This study investigated the effects of various JA concentrations on trichome density at different developmental stages in cucumber (Cucumis sativus L.). Our findings revealed a dose-dependent increase in trichome density following exogenous JA application, with 1.5 mM JA showing the most significant effect at all stages. Conversely, the use of a JA biosynthesis inhibitor resulted in reduced trichome density, further highlighting the pivotal role of JA in trichome formation. Through transcriptomic analysis, we identified the allene oxide synthase CsAOS gene, which encodes an allene oxide synthase, as a key regulator of the JA biosynthesis enzyme preferentially expressed in trichomes. To investigate its functional role, we used CRISPR/Cas9-mediated knockout and overexpression strategies. Knockout of CsAOS in wild-type plants lead to a significant reduction in trichome density, whereas CsAOS overexpression in wild-type plants resulted in an enhanced trichome phenotype. These results provide novel insights into the molecular mechanisms governing trichome development in cucumbers, establishing CsAOS as a critical mediator of JA signaling in regulating trichome density. This study not only sheds light on the intricate relationship between JA and trichome development but also paves the way for future applications in plant breeding and genetic modification to improve pest resistance and herbivore defense.

Skin color is a crucial quality trait in cucumber fruit, yet the regulatory mechanisms underlying cucumber skin color remain poorly understood. In this study, we characterized a cucumber natural mutant displaying yellow peel, and identified a key gene yellow peel (CsYP) through map-based cloning. CsYP encodes a rhodanese-like protein with a Rhod domain. A single-base insertion results in premature termination of protein translation, leading to the yellowing pericarp phenotype in the natural mutant. To further investigate the function of CsYP, two knockout lines, yp-1 and yp-2, were generated using CRISPR-Cas9 technology. Phenotypic investigation of yp-1 and yp-2 revealed a significant yellowing of the pericarp starting from 6 days after pollination, consistent with the natural mutant phenotype. Additionally, our study revealed an interaction between CsYP and Cscytb6f, a cytochrome b6-f complex iron–sulfur subunit, suggesting a collaborative role of CsYP and iron–sulfur proteins in regulating cucumber peel color. These findings provide novel insights into the regulatory mechanisms underlying cucumber peel color and broaden our understanding of this important trait.

The southern root-knot nematode ( Meloidogyne incognita , M. incognita ) poses a severe threat to cucurbit production, yet no resistant germplasm exists among cultivated species. Although Cucumis metuliferus ( C. metuliferus ), a wild Cucurbitaceae species, exhibits resistance to M. incognita and prior transcriptomic studies have identified key responsive genes and signaling pathways, an integrated understanding of the dynamic transcriptional and metabolic reprogramming is still lacking. Here, an integrated transcriptomic and metabolomic analysis was performed on resistant (CM064) and susceptible (CM083) C. metuliferus accessions during M. incognita infection. The resistant CM064 exhibited distinct temporal shifts in defense strategy: early-stage activation of defense pathways (hormone signaling and chitin response) coupled with repression of cell wall biogenesis, and late-stage upregulation of cell wall reinforcement, redox homeostasis, and restriction of phloem transport. In contrast, the susceptible CM083 showed progressive susceptibility, characterized by early-stage modulation of cytoskeletal activity and defense suppression, followed by late-stage upregulation of amino acid biosynthesis and downregulation of serine/threonine kinase signaling. Multi-omics integration revealed a sustained activation of the phenylpropanoid biosynthesis pathway during infection. Ectopic overexpression of Cinnamate 4-hydroxylase ( C4H ) was associated with significant resistance to M. incognita in cucumber. Collectively, this study provides insights into the multi-layered defense mechanism of C. metuliferus against M. incognita and supports the important role of phenylpropanoid pathway activation in nematode resistance, suggesting a potential strategy for crop improvement.

Cucumber (Cucumis sativus L.) is a Cucurbitaceae plant that often suffers from fruit drop and deformity caused by excessive fruiting, poor growth, and unfavorable environmental conditions during cultivation.Forchlorfenuron [N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU)] is a plant growth regulator that has been widely used in the production of cucumbers and other horticultural plants because of its significant effects in promoting fruit set and enlargement. However, the underlying mechanism through which CPPU regulates cucumber fruit development remains unclear. To verify the role of CPPU in regulating cucumber fruit development, field experiments were conducted in both spring and autumn. The results confirmed that CPPU application significantly promoted fruit enlargement, shortened the time from flowering to harvest of marketable fruits, reduced fruit curvature, and increased the marketable fruit rate. Interestingly, we found that environmental conditions influence the regulatory effect of CPPU on fruit expansion. To investigate the molecular basis underlying CPPU-mediated regulation of fruit development, transcriptome analysis was performed. Firstly, 44 cross-stage differentially expressed genes (DEGs) were identified through differential gene analysis. Subsequent Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional annotation revealed that plant hormone signaling pathways are the key pathways mediating CPPU-regulated fruit expansion. Furthermore, five key candidate genes (CsaWIP2, CsPILS7, CsJOX2, CsGIR1, and CsAAA18193) responding to the CPPU signal were screened and preliminarily validated using machine learning and real-time quantitative polymerase chain reaction techniques. This study clarified CPPU's effect on cucumber fruit development, and the selected genes provided theoretical support for molecular breeding of cucumber and high-quality, high-yield cultivation optimization.

Trichomes are found on almost all terrestrial plants and are derived from epidermal cells. Nonglandular trichomes (NGTs) protect plants from environmental stress, such as pest and pathogen invasion, reduce water loss, and increase resistance to abiotic stressors, including UV radiation, cold, and extreme temperatures. Trichomes provide an excellent model system for studying the growth and differentiation of plant cells. Although several such genes that govern the specification and patterning of trichomes have been molecularly characterized in a few model plants, including Arabidopsis thaliana , most aspects of trichome initiation remain unclear. In this review, we summarize the structural and morphological characteristics of NGTs in diverse crops as well as report recent investigations providing insights into the regulation of NGT formation in plants. We also discuss how NGTs help plants resist various abiotic factors that impose multiple stresses on plant life. This review provides a foundation for understanding the valuable role of NGTs in protecting plants from multiple stresses.

Silicon plays a vital role in plant physiology. Although the silicon transport mechanisms in monocots are well characterized, the molecular basis of silicon deposition in dicots remains elusive. Fruit bloom, an off-white substance covering the fruit surface and affecting its appearance, is crucial for the market-driven breeding and production of cucumbers (Cucumis sativus). However, the mechanisms regulating fruit bloom formation are not well understood. In this study, we aimed to elucidate the molecular mechanisms underlying silicon deposition in glandular trichomes (GTs) and GT's role in fruit bloom formation. Using map-based cloning, we identified a single-nucleotide polymorphism in CsaV3_3G017280, encoding a homolog of the rice (Oryza sativa) silicon efflux transporter Low Silicon Rice 2 (Lsi2), causing a premature translation termination mutation linked to the nonfruit-bloom phenotype. Knocking out CsLsi2 prevented silicon deposition on the fruit surface, leading to a nonfruit-bloom phenotype. The MYB transcription factor CsRAX3 directly activated CsLsi2, and the GT development–related factor TINY BRANCHED HAIR (TBH) regulated both CsRAX3 and CsLsi2, linking silicon deposition with GT development. Collectively, our observations establish a direct connection between Si deposition and GT development and provide a perspective on the mechanisms regulating fruit bloom formation.