Minghua Deng

Cadmium (Cd) contamination in agricultural soils poses a severe threat to food safety and human health through the food chain. This study investigated the efficacy of tobacco straw-derived biochar, applied at varying rates (0%, 1%, 2%, and 5% w/w), in mitigating Cd accumulation and modulating the growth and nutritional quality of two amaranth (Amaranthus tricolor L.) cultivars (red and green) grown in Cd-contaminated soil (initial total Cd of 2.18 mg/kg). The pot experiment revealed that biochar significantly reduced Cd uptake in both cultivars. Mechanistically, biochar elevated soil pH and drove the in-situ transformation of highly bioavailable exchangeable Cd into the more stable Fe-Mn oxide-bound fraction. Consequently, shoot Cd concentrations were notably suppressed, with the red cultivar exhibiting a superior response; the 2% biochar treatment optimally reduced its shoot Cd concentration by 37.6% compared to the control. Crucially, the amendments induced highly cultivar-specific growth responses. While biochar application simultaneously mitigated Cd toxicity and promoted biomass accumulation in red amaranth (yielding a 58.6% increase in shoot dry weight at the 2% rate), it exerted antagonistic, inhibitory effects on the growth of green amaranth. In conclusion, the incorporation of 2% tobacco straw biochar serves as a highly effective, dual-purpose strategy for significantly reduced health risks and enhancing the yield of red amaranth in Cd-contaminated fields. However, in green amaranth, biochar application induced a physiological trade-off, inhibiting growth despite successful Cd reduction. Furthermore, while Cd concentrations were significantly reduced on a dry-weight basis, future evaluations based on fresh-weight regulatory limits are required to fully confirm food safety.

Chrysanthemum is one of the world’s four main cut flowers. However, postharvest drought stress severely disrupts water homeostasis, triggering reactive oxygen species burst and membrane lipid peroxidation, thereby reducing its ornamental quality and vase life. Melatonin serves as a multifunctional antioxidant and stress regulator. This study demonstrated that 200 μmol L⁻¹ melatonin effectively alleviated drought-induced leaf wilting, maintained relative water content, decreased the accumulation of MDA, H₂O₂, and O₂^•−, and enhanced the activities of SOD, CAT, POD, and APX. Concurrently, non-enzymatic antioxidants (proline, GSH, ASA) accumulated to high levels. RNA-seq analysis revealed that drought affects pathways closely related to the production of antioxidant and osmoprotectant metabolites, while melatonin initiated extensive transcriptional reprogramming and responded to drought stress through distinct pathways at the early (12 h) and late (24 h) treatment stages. Melatonin also modulated key transcription factor families, including bHLH, NAC, ERF, MYB, and bZIP. Collectively, exogenous MT mitigates drought damage in chrysanthemum cut flowers by coordinating antioxidant systems and complex transcriptional regulatory networks. This study provides a theoretical foundation for improving postharvest drought tolerance and prolonging the vase life of cut flowers.

(1) Background: The bHLH (basic helix-loop-helix) transcription factor family is one of the most abundant in plants and is involved in plant growth, development, and abiotic stress responses. Notably, the functions of most bHLH family members remain poorly characterized. (2) Results: CmbHLH112, a nuclear-localized bHLH transcription factor from chrysanthemum, exhibits transcriptional activation activity. Overexpression of CmbHLH112 in Arabidopsis significantly promotes flowering and enhances drought resistance. qRT-PCR analysis revealed that CmbHLH112 regulates flowering time by affecting the expression of key flowering genes, including FT, SOC1, LFY, and FLC. Under drought stress, CmbHLH112 overexpression plants showed reduced ROS accumulation compared with wild-type plants, accompanied by elevated activities of key antioxidant enzymes and increased proline content. Moreover, transgenic plants exhibited lower MDA concentrations and reduced water loss rates under drought conditions, further indicating enhanced stress resilience. Overexpression of CmbHLH112 also upregulates ABA levels under drought stress, while simultaneously promoting the expression of genes involved in ABA biosynthesis and ABA signaling pathways. (3) Conclusions: Our results demonstrate that heterologous overexpression of CmbHLH112 in Arabidopsis enhances drought tolerance and promotes flowering. Thus, CmbHLH112 is proposed to play a dual role in modulating flowering time and drought tolerance, at least partly by regulating ABA biosynthesis.

Hybrid tea roses (Rosa hybrida) are economically important horticultural crops and highly susceptible to heat stress, which significantly impacts flower quality and yield. As a key member of the heat shock protein (HSP) family, HSP70 protein acts as a molecular chaperone and exhibits diverse abiotic stress response functions in plants. A total of 113 HSP70 transcription factors (TFs) with varying physical and chemical properties were identified in the genome of hybrid tea rose. Phylogenetic analysis showed that the identified TFs could classify into three (I, II, and III) subfamilies, with most members (51 TFs) falling in subfamily II. Wide gene structural variations were observed among the three subfamilies, with group I and II members lacking introns, while group III members only harbored 1~4 exons and introns. Numerous cis-acting elements associated with abiotic stress, hormone response, growth and development responses, as well as light response were detected in the HSP70 gene promoters. In addition, protein interaction networks predicted a wide range of interactions between different hybrid tea rose HSP70 subfamilies. Gene expression analysis revealed that 57 HSP70 genes had strong organ specificity and response to heat stress in the hybrid tea rose plants. Notably, the expression levels of two RhHSP70 genes, RhHSP70-69 and RhHSP70-88, were significantly increased after heat stress, indicating that these two genes might be crucial for plant heat stress response. Subcellular localization of RhHSP70-69 and RhHSP70-88 revealed that their proteins were located in the nucleus. Our results are not only useful for future evaluation of the regulatory roles of RhHSP70 genes in the hybrid tea rose growth and development, but also provides key genes for future molecular breeding of heat tolerant plants.

Cuticular wax is the first barrier between plants and the environment. Here, the densities of cuticular wax crystals on the petals of eight rose cultivars were determined to be sparse; the crystals were mostly granular and only a few rod-shaped crystals were observed in ‘Sweet’. The total contents and chemical compositions of waxes were significantly different among the rose varieties. The waxes were mainly composed of n-alkanes, iso-alananes and alkenes. Under water-loss stress, ‘Diana’ and ‘Carola’ cultivars, having high petal wax contents, had low water permeability levels, long vase lives, high relative water contents and low relative conductivity levels. However, the low wax contents of the ‘Jubilance’ and ‘Candy Avalanche’ cultivars resulted in high water permeability levels and short vase lives. Pearson correlation analyses showed the total wax content in petal epidermis was positively correlated with vase life. The data provide novel insights into the compositional variances in the cuticular waxes of rose petals and their impacts on cut rose vase lives.

The WRKY gene family is a key transcription factor family for plant development and the stress response. However, few studies have investigated the WRKY gene family in Chinese rose (Rosa chinensis). In this study, 68 RcWRKY genes were identified from the Chinese rose genome and classified into three primary groups and five subgroups based on the structural and phylogenetic characteristics. The analysis of the conserved domains, motifs, and gene structure revealed that the RcWRKY genes within the same group had the same exon–intron organization and composition. Chromosome mapping and gene duplication revealed that the RcWRKY genes were randomly dispersed across seven chromosomes. Fragment duplication and refined selection may have influenced the evolution of the WRKY gene family in Chinese rose. The cis-acting elements in the WRKY promoter region revealed that the RcWRKY genes contained numerous abiotic stress response elements. The results of qRT-PCR revealed that the expression of RcWRKY was tissue-specific, with high expression being observed under drought, heat, and salt stress. Notably, RcWRKY49′s expression increased more than fivefold following salt stress, indicating that it is a crucial gene mediating the salt stress response of Chinese rose. These findings shed light on the regulatory role of RcWRKY in the growth and development of Chinese rose, and they serve as a foundation for future molecular breeding programs and gene discovery.