MiR166, as an ancient and large family of plant microRNAs, has been demonstrated to participate in plant growth and development as well as responses to abi

Cadmium (Cd) is a highly toxic heavy metal that severely impairs plant growth and poses ecological and health risks. Chrysanthemum indicum (L.), a dominant species in Cd-contaminated regions, represents a valuable germplasm for phytoremediation. In this study, we cloned and characterized CiWRKY50, a WRKY transcription factor containing a conserved WRKY domain and C2H2-type zinc finger. CiWRKY50 was localized to the nucleus but lacked intrinsic transcriptional activation activity. Overexpression of CiWRKY50 in Arabidopsis thaliana and C. indicum significantly enhanced Cd tolerance, as shown by reduced root Cd accumulation, improved transport efficiency, lower ROS and MDA levels, and increased chlorophyll, proline, and soluble protein contents. Antioxidant enzyme activities and Cd-chelating compounds (GSH, NPT, PCs) were also upregulated. Furthermore, combined Cd and ABA treatments promoted Cd sequestration in roots and activated ABA-responsive genes (CiABF1, CiABF2, CiABF4), alleviating shoot toxicity. These findings indicate that CiWRKY50 enhances Cd tolerance in association with enhanced ABA-mediated signaling and redox homeostasis, providing new insights for breeding Cd-resistant plants and improving phytoremediation strategies.

To improve Chrysanthemum tolerance to low temperatures and its adaptability to low autumn temperatures in Northeast China, we conducted the first genome-wide identification of the heat shock transcription factors (Hsfs) in Chrysanthemum indicum under low-temperature stress. Based on genome-wide analyses, we identified 14 CiHsf genes in Chrysanthemum indicum. Based on structural characteristics, the genes were grouped into two subfamilies, comprising 10 HsfA and four HsfB members, with no representatives of the HsfC subfamily detected. CiHsf1~CiHsf14 were located on seven chromosomes, and their promoter regions harbored numerous cis-acting elements associated with responses to low temperature, hormones, and light. Tissue-specific expression profiling revealed that seven CiHsf genes were predominantly expressed in roots, two in stems, three in leaves, and two in flowers. The analysis of low-temperature expression characteristics showed that CiHsf2, CiHsf5, CiHsf8, and CiHsf10 were significantly upregulated following cold acclimation, indicating that these genes may participate in the low-temperature response mechanism of Chrysanthemum indicum. Here, we demonstrated that transient transformation of Chrysanthemum indicum with 35S:CiHsf10 reduced reactive oxygen species (ROS) accumulation under low-temperature stress, which may contribute to enhanced cold tolerance.

Iris setosa is a characteristic perennial wild herbaceous flower in the Changbai Mountain region of China, boasting significant ornamental and medicinal values. Given the increasing scarcity of its wild resources, this study developed an efficient in vitro regeneration system using shoot tips as explants via the direct organogenesis pathway. The optimal surface sterilization protocol was achieved with a treatment of 0.1% HgCl₂ for 8 min, resulting in an explant survival rate of 57.78%. The highest multiple shoot induction rate (88.89%) of shoot tips was achieved on MS medium supplemented with 2.0 mg·L⁻¹ 6-benzylaminopurine (6-BA), 0.5 mg·L⁻¹ naphthalene acetic acid (NAA), and 1.0 mg·L⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D). The optimal shoot differentiation and proliferation medium was MS + 2.0 mg·L⁻¹ 6-BA + 0.3 mg·L⁻¹ NAA, achieving a proliferation coefficient of 3.37. The optimal medium for rooting was confirmed to be 1/2 MS + 0.5 mg·L⁻¹ indole-3-butyric acid (IBA), exhibiting a high rooting rate reached 98.33%. During transplantation, plantlets exhibited high survival rates (over 90%) and vigorous growth across all three tested substrates, with no significant differences in survival rates among substrates. The key advance of this study lies in the development of a highly efficient and stable regeneration protocol for I. setosa derived from shoot tip explants, providing critical technical backing for the conservation and sustainable exploitation of its wild-type germplasm.

Hosta ‘So Sweet’, a shade-tolerant Asparagaceae species, displays remarkable high-light tolerance in open-field full-sun cultivation without photoinhibition symptoms. To clarify its growing-season photosynthetic dynamics and adaptive strategies, this study measured diurnal photosynthetic variations from May to September, determined chlorophyll fluorescence parameters and pigment contents in May, July and September, and analyzed the data alongside the light and CO₂ response curves for July. The results showed that the high temperatures combined with high-light conditions in July lowered P_n relative to May and September, but the light saturation point (LSP) reached 1508.99 μmol m⁻² s⁻¹, and the CO₂ compensation point (CCP) was 75.46 μmol mol⁻¹, highlighting the robust light energy utilization and carbon assimilation potential. Meanwhile, PSII maximum photochemical efficiency (Fv/Fm) remained stable under these conditions, indicating undamaged photosystems. Mechanistically, its photosynthetic limitation strategies showed seasonal plasticity: a tight coupling between P_n, stomatal conductance, and humidity in May shifted to a strong association between P_n and photoprotective dissipation (qN) in July, followed by an optimization of light capture linked to increased chlorophyll content and adjusted Chl a/b ratios in September. Taken together, H. ‘So Sweet’ synergistically adapts to growing-season light and temperature fluctuations by integrating light utilization potential, photosystem stability and pigment adjustment strategies. This study preliminarily delineated its photosynthetic physiological profile, revealed core light-adaptive strategies, and provided a theoretical basis for the ecological application of this excellent ornamental cultivar.

Low-temperature stress is a major factor limiting the development of the chrysanthemum industry. Chrysanthemum indicum L., wild germplasm with strong cold tolerance within the genus, is an ideal material for mining cold resistance genes. Through preliminary transcriptome analysis of C. indicum under low-temperature stress (PRJNA1391062), we found that multiple R2R3-MYB family members were significantly differentially expressed (|log₂FC| ≥ 1, p < 0.05), suggesting that this family may play important roles in cold stress responses. Within the C. indicum genome, we identified 63 R2R3-MYB members (CiMYBs) through HMMER and BLAST searches combined with domain validation. Phylogenetic analysis classified these genes into 19 subgroups, with most key nodes supported by bootstrap values > 80%. Promoter cis-element analysis revealed enrichment of elements related to light responsiveness, hormone signaling, and stress responses, including 41 low-temperature responsive elements distributed across 28 genes and 32 drought-induced MYB-binding sites present in 23 genes. Synteny analysis identified 13 duplicated gene pairs within the C. indicum genome and 41 collinear gene pairs between C. indicum and Arabidopsis thaliana L. Transcriptome data under low-temperature stress showed that 22 of the 63 CiMYB members were differentially expressed under 4 °C acclimation and −4 °C freezing stress, and they could be classified into three response patterns: acute stress-responsive (rapid upregulation upon initial stress), acclimation-induced (significant activation after 4 °C acclimation), and freezing-suppressed (downregulation after −4 °C freezing). Six differentially expressed genes were randomly selected for RT-qPCR validation, and the results showed consistent trends with the transcriptome data. This study provides a comprehensive identification of R2R3-MYB family members in C. indicum and reveals their expression divergence under low-temperature stress, offering candidate gene resources for deciphering the cold adaptation mechanisms of C. indicum and breeding new cold-resistant chrysanthemum cultivars.