Using a Non-invasive Micro-test Technique, flux profiles of Cd²⁺, Ca²⁺, and H⁺ were investigated in axenically grown cultures of two strains of Paxillus involutus (MAJ and NAU), ectomycorrhizae formed by these fungi with the woody Cd²⁺-hyperaccumulator, Populus × canescens, and non-mycorrhizal (NM) roots. The influx of Cd²⁺ increased in fungal mycelia, NM and ectomycorrhizal (EM) roots upon a 40-min shock, after short-term (ST, 24 h), or long-term (LT, 7 days) exposure to a hydroponic environment of 50 μM CdCl₂. Cd²⁺ treatments (shock, ST, and LT) decreased Ca²⁺ influx in NM and EM roots but led to an enhanced influx of Ca²⁺ in axenically grown EM cultures of the two P. involutus isolates. The susceptibility of Cd²⁺ flux to typical Ca²⁺ channel blockers (LaCl₃, GdCl₃, verapamil, and TEA) in fungal mycelia and poplar roots indicated that the Cd²⁺ entry occurred mainly through Ca²⁺-permeable channels in the plasma membrane (PM). Cd²⁺ treatment resulted in H₂O₂ production. H₂O₂ exposure accelerated the entry of Cd²⁺ and Ca²⁺ in NM and EM roots. Cd²⁺ further stimulated H⁺ pumping activity benefiting NM and EM roots to maintain an acidic environment, which favored the entry of Cd²⁺ across the PM. A scavenger of reactive oxygen species, DMTU, and an inhibitor of PM H⁺-ATPase, orthovanadate, decreased Ca²⁺ and Cd²⁺ influx in NM and EM roots, suggesting that the entry of Cd²⁺ through Ca²⁺-permeable channels is stimulated by H₂O₂ and H⁺ pumps. Compared to NM roots, EM roots exhibited higher Cd²⁺-fluxes under shock, ST, and LT Cd²⁺ treatments. We conclude that ectomycorrhizal P. × canescens roots retained a pronounced H₂O₂ production and a high H⁺-pumping activity, which activated PM Ca²⁺ channels and thus facilitated a high influx of Cd²⁺ under Cd²⁺ stress.

Cadmium (Cd²⁺) pollution occurring in salt-affected soils has become an increasing environmental concern in the world. Fast-growing poplars have been widely utilized for phytoremediation of soil contaminating heavy metals (HMs). However, the woody Cd²⁺-hyperaccumulator, Populus × canescens, is relatively salt-sensitive and therefore cannot be directly used to remediate HMs from salt-affected soils. The aim of the present study was to testify whether colonization of P. × canescens with ectomycorrhizal (EM) fungi, a strategy known to enhance salt tolerance, provides an opportunity for affordable remediation of Cd²⁺-polluted saline soils. Ectomycorrhization with Paxillus involutus strains facilitated Cd²⁺ enrichment in P. × canescens upon CdCl₂ exposures (50 μM, 30 min to 24 h). The fungus-stimulated Cd²⁺ in roots was significantly restricted by inhibitors of plasmalemma H⁺-ATPases and Ca²⁺-permeable channels (CaPCs), but stimulated by an activator of plasmalemma H⁺-ATPases. NaCl (100 mM) lowered the transient and steady-state Cd²⁺ influx in roots and fungal mycelia. Noteworthy, P. involutus colonization partly reverted the salt suppression of Cd²⁺ uptake in poplar roots. EM fungus colonization upregulated transcription of plasmalemma H⁺-ATPases (PcHA4, 8, 11) and annexins (PcANN1, 2, 4), which might mediate Cd²⁺ conductance through CaPCs. EM roots retained relatively highly expressed PcHAs and PcANNs, thus facilitating Cd²⁺ enrichment under co-occurring stress of cadmium and salinity. We conclude that ectomycorrhization of woody hyperaccumulator species such as poplar could improve phytoremediation of Cd²⁺ in salt-affected areas.

The potato (Solanum tuberosum L.) ranks among the most consumed agricultural products globally and is nutrient-rich. Exposure of potato tubers’ epidermal and subcutaneous tissues to light results in greening and the production of neurotoxic steroidal glycoalkaloids, which significantly reduces tuber quality, increases food safety risks, and leads to rejection by consumers and the processing industry. This review conducts an in-depth analysis of three key aspects: (1) the differences in various light conditions, namely, the disparities in light sources, wavelengths, intensities, and durations; (2) the characteristics of potato cultivars resistant to greening; and (3) the molecular mechanisms of light-induced biosynthesis of chlorophyll and steroidal glycoalkaloids (SGAs). This review is expected to provide technical support for potato food safety measures and a theoretical foundation for the molecular breeding of green-resistant potato varieties.

Potato tubers undergo greening and accumulate steroidal glycoalkaloids (SGAs) upon light exposure, posing potential food safety risks. In this study, six potato cultivars (“Favorita”, “Lucinda”, “Jizhangshu 12”, “Longshu 10”, “Qingshu 9”, and “Purple Potato”) were subjected to six light treatments (dark, UVA, blue, green, red, and white), and peel color, pigment content, SGAs, and the expression of genes related to light signaling, chlorophyll biosynthesis, and SGA biosynthesis was evaluated. Under green light, the contents of α-solanine and α-chaconine were 76.22 and 171.84 mg/kg fresh weight (FW), respectively; by contrast, their levels under blue and white light were approximately 60% higher. These effects may be mediated by the upregulation of HY5 and COP1 expression, which in turn could regulate the biosynthesis of chlorophyll-related genes (CHID, CHLI1) and SGA-related genes (HMGR, SGT1). Yellow-skinned cultivars exhibited pronounced light sensitivity (chlorophyll 18.47–18.52 mg/kg FW; SGAs up to 290.41 mg/kg FW), whereas red- and purple-skinned cultivars delayed greening through anthocyanin-mediated light attenuation. Collectively, these findings provide a framework for postharvest management and breeding, suggesting that reducing blue light while enhancing green light in spectral illumination, together with the development of anthocyanin-enriched cultivars, may serve as effective strategies to extend shelf life, mitigate food safety risks, and reduce postharvest losses.

Enzymatic browning markedly reduces the processing quality and economic value of potatoes. This study evaluated the effects of copper sulfate (CuSO₄) on potato growth, yield, and enzymatic browning. Quantitative analysis of browning-related enzymes, organic acids, free amino acids, and the browning index (BI) was conducted using high-performance liquid chromatography and non-contact colorimetric technology. Moderate Cu²⁺ (0.078–0.157 mmol·L⁻¹) supply enhanced photosynthetic capacity, biomass, and starch accumulation, whereas excessive Cu induced oxidative stress, increased PPO activity, phenolic accumulation, and BI. Metabolic profiling revealed that Cu²⁺ activates PPO via its copper-binding sites and reprograms amino acid and organic acid metabolism—upregulating arginine and proline while downregulating isoleucine, leucine, phenylalanine, lysine, citrate, and chlorogenic acid, all strongly correlated with BI. These findings highlight the dual role of copper in yield formation and enzymatic browning, introducing metabolic reprogramming as a potential mechanism for optimizing Cu fertilization to balance productivity and postharvest quality.

RING-zf E3 ligases play key roles in plant development and light signaling, but their genome-wide characterization and light-responsive functions in potatoes remain largely unexplored. In this study, we identified 291 StRING-zf genes containing complete RING domains in the potato genome and classified them into four major RING domain types, with RING-H2 being the predominant and structurally conserved group. Evolutionary analyses indicated that gene duplication contributed to the expansion of the StRING-zf genes, while promoter analysis revealed abundant cis-regulatory elements associated with light, hormones, and abiotic stress responses. Transcriptome analysis of the terminal leaflets of the third leaves of potato seedlings under different light qualities, combined with qRT-PCR validation, revealed diverse and gene-specific expression patterns among StRING-zf genes. Five candidate genes (Soltu.DM.01G022260.1, Soltu.DM.04G001050.1, Soltu.DM.10G023720.1, Soltu.DM.11G009040.1, and Soltu.DM.11G017440.1) exhibited distinct light-quality-dependent expression responses. These expression patterns provide preliminary evidence for their potential involvement in light-responsive regulatory processes and ubiquitin-mediated protein modification. Overall, this study provides a comprehensive genomic and transcriptomic resource for elucidating the evolutionary characteristics and potential functions of the StRING-zf genes and identifies candidate genes for further functional validation of light-responsive mechanisms in potatoes.