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LATERAL ORGAN BOUNDARIES DOMAIN (LBD) genes encode plant specific transcription factors that regulate various developmental processes and abiotic stresses. In this study, we characterized RrLBD40 from Rosa rugosa as a nucleus-localized transcription factor harboring a conserved LOB domain. We generated RrLBD40-overexpressing Rosa rugosa plants and compared them with control plants in terms of physiological indices, root architecture, and Na+ homeostasis. The results showed that RrLBD40 overexpression significantly increased peroxidase activity and reduced malondialdehyde content in the roots, indicating enhanced antioxidant capacity under salt stress. Furthermore, RrLBD40 overexpression markedly promoted root growth and development, a similar phenotype consistently observed in RrLBD40 transgenic Arabidopsis plants. Propidium iodide staining and analysis of the Na+ flux rates of root tips revealed that the barrier function of the Casparian strip was compromised in both the RrLBD40-overexpression and control plants under salt stress. This disruption of endodermal selectivity permitted Na+ influx into the vascular cylinder. Furthermore, neither plants exhibited significant Na+ efflux capacity. Taken together, these findings demonstrate that RrLBD40 enhances salt tolerance in Rosa rugosa by primarily promoting root growth and development, rather than modulating Na+ homeostasis.

Background Fruit drop and quality deterioration are major constraints limiting date palm ( Phoenix dactylifera L.) productivity, particularly under environmental constraints. While plant growth regulators (PGRs), particularly synthetic auxins like 2,4-Dichlorophenoxyacetic acid (2,4-D), have demonstrated potential in managing these physiological limitations, cultivar-specific responses and optimal application protocols remain insufficiently characterized. Results This study evaluated the impact of foliar-applied 2,4-D at three concentrations (25, 50, and 75 mg/L) on fruit retention and quality traits in two date palm cultivars under field conditions. Application of 2,4-D, particularly at 50 mg/L during the kimri stage, significantly improved key agronomic parameters, including bunch weight, fruit and pulp weight, fruit length and width, and moisture content. Fruit quality parameters such as total soluble solids (TSS), total sugars, reducing and non-reducing sugars, ascorbic acid, and tannins were also enhanced. Furthermore, antioxidative enzymes peroxidase and catalase, flavonoids, and phenolic content were significantly higher compared to the untreated control. Among the tested cultivars, differential responses were observed, with one cultivar consistently showing superior outcomes in terms of fruit quality. Conclusion The exogenous application of 2,4-D demonstrated a positive effect on reducing fruit drop and enhancing both physical and quality traits in date palm cultivars. These findings suggest that 2,4-D can serve as an effective tool in sustainable date palm production by improving yield and fruit quality under stress conditions.

Vegetative propagation through stem cuttings represents the primary mode of reproduction in Rosa species. While numerous studies have reported physiological factors affecting cutting rooting, the genes regulating the formation of adventitious roots in roses have not yet been fully explored and studied. In this study, we demonstrate that Rosa rugosa ‘Feng Hua’ exhibits an indirect rooting pattern, requiring callus formation prior to root primordium differentiation. Phytohormone profiling revealed exceptionally high concentrations of auxin precursors, particularly tryptophan (Trp), in both callus and root tissues. Therefore, we identified and analyzed the members of the YUCCA family, which are the key rate-limiting enzymes in the tryptophan-dependent IAA biosynthesis pathway. A total of 11 RrYUCs family genes were identified, with RT-qPCR analysis showing that RrYUC10 was highly expressed in callus and root tissues. Functional studies confirmed its critical role in adventitious root formation: virus-induced gene silencing (VIGS) of RrYUC10 significantly inhibited AR development, whereas its overexpression enhanced rooting. Our findings have provided a molecular theoretical basis for the rooting of cuttings in roses.

Background Roses are widely used as garden ornamental plants and cut flowers. Rosa chinensis cv ‘Old Blush’ has been used as a model genotype in rose studies due to its contribution to recurrent flowering and tea scent traits of modern roses. The deficiency of efficient genetic transformation systems is a handicap limiting functional genetics studies of roses. Agrobacterium -mediated transient transformation offers a powerful tool for the characterization of gene function in plants. Results A convenient and highly efficient Agrobacterium mediated genetic transformation protocol using R. chinensis cv ‘Old Blush’ seedlings in vitro as an expression system is described in this paper. The most important factor affecting transformation efficiency in this system is seedling age; 3/4-week-old rose shoots with or without roots from sub-culturing are optimal for transformation, requiring no complicated inoculation media, supplements, or carefully tuned plant growth conditions. This transient expression system was successfully applied to analysis of the gene promoter activities, DNA binding capacity of transcription factors, protein–protein interaction in physiological contexts using luciferase as a reporter gene. Conclusions This transient transformation system was validated as a robust and efficient platform, thus providing a new option for gene function and signaling pathway investigation in roses and further extending the utility of R. chinensis cv ‘Old Blush’ as a model plant to study diverse gene function and signaling pathways in Rosaceae.

Rose (Rosa spp.) plants flower via two contrasting methods: once flowering (OF) and continuous flowering (CF). Purple branch is a rare continuously flowering variety of Rosa rugosa that is extensively cultivated in China. However, the genetic basis of its CF behavior is unknown. We demonstrated that Purple branch is heterozygous for the TFL1 homolog KSN. One KSN allele with a 9 kb Copia insertion was found to be identical to that from continuously flowering Rosa chinensis Old blush. The other allele was found to be a functional wild-type allele. The overall expression of KSN was closely linked to the floral transition, and it was significantly repressed in continuously flowering Purple branch compared with OF Plena. The promoter region of the normal KSN allele was hypermethylated, and histone methylation at H3H4, H3K9, and H3K27 of the KSN gene locus was modified in continuously flowering Purple branch. Silencing of the DNA methyltransferase genes MET1 and CMT3 and the histone methyltransferase gene SUVR5 in Purple branch led to enhanced KSN expression, but silencing of the histone demethylase gene JMJ12 suppressed KSN expression. Therefore, the CF habit of Purple branch may be due to reduced expression of KSN caused by the halved dose and may be associated with epigenetic modifications together with retrotransposon insertions along the chromosome. Our study revealed a novel mechanism underlying the CF behavior of rose plants.

Roses (Rosa spp.) are widely used as ornamental plants and cut flowers and in perfumes and cosmetics; therefore, they have extremely high ornamental and economic value. Improving ornamental qualities (color, aroma, flower shape, plant architecture, petal senescence), agronomic traits (disease resistance, stress tolerance), and other traits would add value to cultivated roses. However, the lack of an efficient genetic transformation system limits functional genetic studies of roses. Therefore, we aimed to develop a simple, high-throughput Agrobacterium rhizogenes-mediated hairy root transformation system to analyze gene function in rose. We explored the factors affecting the induction and transformation of hairy root cultures in rose by screening different types of explants, Rosa genotypes, Agrobacterium strains, media, and infection and co-cultivation times for genetic transformation under aseptic conditions. We established an A. rhizogenes-mediated hairy root transformation system in rose using A. rhizogenes strains MSU440 and Ar Qual, successfully obtained transgenic hairy roots, and conducted preliminary experiments to examine their regeneration by employing the ultraviolet light (UV)-visible reporter eYGFPuv as a marker. Finally, we established a simple hairy root transformation process under non-aseptic conditions. The rapid and efficient transformation system developed here will enable efforts to investigate gene function in roses and engineer improved rose varieties. Refining the transformation protocol to work under aseptic and non-aseptic conditions will allow researchers to use this system efficiently and broadly.

Rosa rugosa is highly regarded for its aesthetic and therapeutic qualities. In particular, R. rugosa’s flowers are known to produce essential oils containing a mixture of volatile terpenes, phenylpropanoids, and other compounds. Despite this, extensive research exists on volatile terpenes in flowers, while the knowledge of non-volatile terpenes in distinct tissues is still limited. Using UPLC–ESI–MS/MS, a comprehensive analysis of the terpene metabolites in five different tissues of R. rugosa was conducted. These metabolites accumulated in distinct tissues, and the majority of them were triterpenoids. Transcriptome data were collected from five tissues using RNA-seq. Transcriptomics and metabolomics were utilized to evaluate the triterpene biosynthesis pathway, resulting in new insights into its regulation and biosynthesis. The RrOSC10 was identified as a key enzyme in converting 2,3-oxidosqualene into α-amyrin, potentially contributing to the triterpene biosynthesis pathway. Furthermore, the expression of the RrOSC10 gene was upregulated by salinity for 0.5 h and 1 h, with subsequent downregulation at 2 h. This study lays a foundation for future research on the biosynthesis and accumulation of triterpenes in R. rugosa.

Photoperiodic flowering responses are classified into three major types: long day (LD), short day (SD), and day neutral (DN). The inverse responses to daylength of LD and SD plants have been partly characterized in Arabidopsis and rice; however, the molecular mechanism underlying the DN response is largely unknown. Modern roses are economically important ornamental plants with continuous flowering (CF) features, and are generally regarded as DN plants. Here, RcCO and RcCOL4 were identified as floral activators up-regulated under LD and SD conditions, respectively, in the CF cultivar Rosa chinensis ‘Old-Blush’. Diminishing the expression of RcCO or/and RcCOL4 by virus-induced gene silencing (VIGS) delayed flowering time under both SDs and LDs. Interestingly, in contrast to RcCO-silenced plants, the flowering time of RcCOL4-silenced plants was more delayed under SD than under LD conditions, indicating perturbed plant responses to day neutrality. Further analyses revealed that physical interaction between RcCOL4 and RcCO facilitated binding of RcCO to the CORE motif in the promoter of RcFT and induction of RcFT. Taken together, the complementary expression of RcCO in LDs and of RcCOL4 in SDs guaranteed flowering under favorable growth conditions regardless of the photoperiod. This finding established the molecular foundation of CF in roses and further shed light on the underlying mechanisms of DN responses.

Although the petals of Rosa rugosa are rich in flavonoids and their bioactivity has a significant impact on human health, the flavonoid content decreases during flower development. In this study, R. rugosa ‘Feng hua’ was used to investigate the effects of the melatonin foliar spray on enhancing the quality of rose by focusing on major flavonoids. The results showed that the contents of total flavonoids in rose petals at the full bloom stage induced by melatonin obeyed a bell-shaped curve, with a maximum at 0.3 mM, indicating the concentration-dependent up-regulation of flavonoid biosynthesis. In the treatment with 0.3 mM melatonin, metabolomic analyses showed that the concentrations of ten main flavonoids were identified to be increased by melatonin induction, with high levels and increases observed in three flavonols and two anthocyanins. KEGG enrichment of transcriptomic analysis revealed a remarkable enrichment of DEGs in flavonoid and flavonol biosynthesis, such as Rr4CL, RrF3H, and RrANS. Furthermore, functional validation using virus-induced gene silencing technology demonstrated that Rr4CL3 is the crucial gene regulating flavonoid biosynthesis in response to the stimulant of melatonin. This study provides insights into the exogenous melatonin regulation mechanism of biosynthesis of flavonoids, thereby offering potential industrial applications.

Rosa rugosa ( R. rugosa ), an economically important crop valued for its fragrance and medicinal properties, is highly susceptible to drought stress under open‐field cultivation. However, the molecular mechanisms underlying its drought response remain largely unexplored. Here, we identified RrMYB2, a transcription factor that positively regulates drought tolerance in R. rugosa . Overexpressing RrMYB2 in Arabidopsis thaliana and R. rugosa enhanced drought tolerance. Virus‐induced silencing of RrMYB2 plants exhibited impaired stomatal closure and reduced drought resistance. RNA‐seq of silenced plants revealed that protein phosphatases type 2C ( PP2C ) genes, including RrHAB1 , RrHAB2 and RrABI1 , were significantly up‐regulated. Biochemical analyses demonstrated that the negative regulation of PP2Cs by RrMYB2 was dependent on its interaction protein RrJMJ12, an H3K27me3 histone demethylase and genetic evidence indicated that RrJMJ12 acts downstream of RrMYB2 to negatively regulate drought resistance. Moreover, the RrMYB2‐RrJMJ12 protein complex reduced RrJMJ12 binding to the CTCTGYTY motifs in the promoters of PP2C genes, with this inhibitory effect further enhanced under drought conditions. Collectively, our findings reveal a novel molecular mechanism in which a transcription factor cooperates with an epigenetic modifier to regulate drought tolerance in R. rugosa .