In most higher plants, sucrose is the significant form of carbohydrate for long-distance transportation. Sucrose transporters/sucrose carriers (SUTs/SUCs) are involved in the loading and unloading of sucrose in phloem and play an important role in the growth and development of plants. In this study, 12 RsSUC genes were first identified from the radish genome, and their phylogenetic relationships, gene structure, and conserved motifs were further analyzed. RT-qPCR results indicated that RsSUC genes exhibited various expression patterns in different tissues and development stages of the radish. Overexpression of RsSUC1b in Arabidopsis significantly improved the uptake efficiency of exogenous sucrose, and promoted leaves and lateral root growth. In addition, the transgenic plants flowered significantly earlier than wild-type (WT) plants, and the soluble sugar contents (SSCs) including sucrose, glucose, and fructose in the mature leaves and pods were increased. It could be inferred that RsSUC1b is a plasma membrane sucrose transporter and plays a vital role in sucrose transportation and sugar accumulation during plant growth and development. These findings provided novel insights into the biological function of RsSUC genes and facilitate dissecting the molecular mechanism underlying sugar transport during radish development.

SWEET (Sugars Will Eventually be Exported Transporter) genes play essential roles in various biological processes, including phloem loading, sugar efflux, plant development and stress response. In this study, a total of 33 RsSWEET gene members were identified in the radish genome. They could be divided into four subfamilies and are distributed on eight radish chromosomes. Cis-acting regulatory element analysis indicated that these RsSWEET genes were potentially involved in the radish growth and development and stress response process, including circadian control and light response and responses to numerous stresses, including low-temperature and drought stress. Transcriptome data analysis revealed that a number of RsSWEET genes exhibited specific expression patterns in different tissues and developmental stages of radish. Moreover, several RsSWEET genes (e.g., RsSWEET2a, RsSWEET3a, RsSWEET16b and RsSWEET17) showed differential expression profiles under various abiotic stresses, including cold, heat, salt, Cd and Pb stress. Remarkably, the RsSWEET17 was specifically expressed in the cambium of radish. RsSWEET17 was heterologously expressed in yeast strain EBY.VW4000, which suggested that it has the ability to transport sugar. Notably, RsSWEET17-overexpressing Arabidopsis plants exhibited excessive root length, greater fresh weight and higher soluble sugar content (SSC) accumulation compared with wild-type (WT) plants, indicating that RsSWEET17 might positively regulate radish taproot development by strategically manipulating sugar accumulation. Collectively, these results clarify the molecular mechanisms underlying RsSWEET-mediated sugar accumulation and root growth and development in radish.

The RNA-directed DNA methylation (RdDM) pathway is a crucial epigenetic mechanism governing plant responses to environmental stress. While the RdDM pathway has been extensively studied in Arabidopsis thaliana, the comprehensive understanding of its components in cucumber (Cucumis sativus L.) remains lacking. In this study, we performed a genome-wide identification and characterization of RdDM pathway genes in cucumber, followed by an analysis of their expression patterns across various tissues and under multiple abiotic stress conditions. A total of 67 putative CsRdDM genes were identified, which are unevenly distributed across the cucumber’s chromosomes. Phylogenetic and gene structure analyses revealed considerable evolutionary divergence, particularly within the key Argonaute gene family (CsAGO). Crucially, the promoter regions of CsRdDM genes were found to contain cis-regulatory elements associated with abiotic stress, light signaling, and development, suggesting their potential involvement in complex regulatory networks. RT-qPCR assays confirmed that CsRdDM genes exhibit distinct and stress-specific transcriptional patterns. Notably, several genes such as CsAGO4 and CsIDN2 showed antagonistic expression between roots and leaves under drought (PEG-6000) stress, implying a sophisticated, tissue-specific defense mechanism. Among them, CsAGO4 emerged as a candidate gene responsive to abiotic stress. Those findings provide new insights into the regulatory roles of CsRdDM genes under abiotic stress and highlight candidate genes for the genetic improvement of stress tolerance in cucumber.

Carotenoid cleavage oxygenases (CCOs) constitute a pivotal enzyme family that catalyze the oxidative cleavage of carotenoids to produce apocarotenoids, which are important signaling molecules involved in plant development, stress adaptation, and immunity responses. Notably, several CCOs, particularly NCED members, contribute to pathogen resistance by mediating abscisic acid (ABA) biosynthesis and apocarotenoid-derived defense signaling. While this gene family has been characterized in diverse plant species, its composition and functions in radish (Raphanus sativus L.) remain poorly understood. This study presents the comprehensive, genome-wide identification of the CCO gene family in radish, revealing 19 putative RsCCO members. A combination of phylogenetic, gene structure, chromosomal localization, and synteny analyses revealed conserved evolutionary patterns and species-specific diversification of the RsCCO family within the Brassicaceae. Promoter analysis identified an abundance of cis-acting regulatory elements related to phytohormone signaling, light perception, and stress responses, suggesting complex transcriptional regulation. Crucially, transcriptomic profiling following infection with Fusarium oxysporum revealed that two genes, RsNCED6 and RsNCED9b, were significantly upregulated in a resistant radish inbred line (‘T5’) compared to a susceptible line (‘T24’), identifying them as key candidate genes involved in ABA-mediated defense responses. This work provides a foundational characterization of the radish CCO gene family, offering novel insights into its role in carotenoid metabolism and pathogen defense.

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.

Clubroot disease, caused by the soil-borne pathogen Plasmodiophora brassicae, poses a severe threat to the global production of Brassicaceae crops, including radish (Raphanus sativus L.). Although resistance breeding is an important method for sustainable disease management, the molecular mechanism underlying clubroot resistance remains elusive in radish compared to other Brassicaceae species. In this study, 52 radish inbred lines were screened for disease responses following P. brassicae inoculation, with the resistant line T6 and the susceptible line T14 selected for transcriptome analysis. RNA-Seq was performed at 10, 20, and 30 days post inoculation (DPI) to elucidate transcriptional responses. The susceptible line T14 exhibited a higher number of differentially expressed genes (DEGs) and persistent upregulation across all time points, indicating ineffective defense responses and metabolic hijacking by the pathogen. In contrast, the resistant line T6 displayed temporally coordinated defense activation marked by rapid induction of core immune mechanisms: enhanced plant–pathogen interaction recognition, MAPK cascade signaling, and phytohormone transduction pathways, consistent with effector-triggered immunity priming and multilayered defense orchestration. These findings indicate that resistance in T6 could be mediated by the rapid activation of multilayered defense mechanisms, including R gene-mediated recognition, MAPK-Ca²⁺-ROS signaling, and jasmonic acid (JA) pathway modulation. The outcomes of this study would not only facilitate clarifying the molecular mechanism underlying clubroot resistance, but also provide valuable resources for genetic improvement of clubroot resistance in radish.