Flower color polymorphism of a wild Iris on the Qinghai-Tibet plateau.

BACKGROUND: Flower color plays a crucial role in attracting pollinators and facilitating environmental adaptation. Investigating the causes of flower color polymorphism and understanding their potential effects on both ecology and genetics can enhance our understanding of flower color polymorphism in wild plant. RESULTS: In this study, we examined the differences of potential male and female fitness between purple- and yellow- flower individuals in Iris potaninii on the Qinghai-Tibet Plateau, and screened key genes and positively selective genes involved in flower color change. Our results showed that yellow flower exhibited a higher pollen-to-ovule ratio. Yellow flowers were derived from purple flowers due to the loss of anthocyanins, and F3H could be an essential gene affecting flower color variation though expression regulation and sequence polymorphism in this species. Furthermore, our findings suggest that genes positively selected in yellow-flowered I. potaninii might be involved in nucleotide excision repair and plant-pathogen interactions. CONCLUSIONS: These results suggest that F3H induces the flower color variation of Iris potaninii, and the subsequent ecological and additive positive selection on yellow flowers may further enhance plant adaptations to alpine environments.

Iris lactea var. chinensis plant drought tolerance depends on the response of proline metabolism, transcription factors, transporters and the ROS-scavenging system.

BACKGROUND: Iris lactea var. chinensis, a perennial herbaceous species, is widely distributed and has good drought tolerance traits. However, there is little information in public databases concerning this herb, so it is difficult to understand the mechanism underlying its drought tolerance. RESULTS: In this study, we used Illumina sequencing technology to conduct an RNA sequencing (RNA-seq) analysis of I. lactea var. chinensis plants under water-stressed conditions and rehydration to explore the potential mechanisms involved in plant drought tolerance. The resulting de novo assembled transcriptome revealed 126,979 unigenes, of which 44,247 were successfully annotated. Among these, 1187 differentially expressed genes (DEGs) were identified from a comparison of the water-stressed treatment and the control (CK) treatment (T/CK); there were 481 upregulated genes and 706 downregulated genes. Additionally, 275 DEGs were identified in the comparison of the rehydration treatment and the water-stressed treatment (R/T). Based on Quantitative Real-time Polymerase Chain Reaction (qRT-PCR) analysis, the expression levels of eight randomly selected unigenes were consistent with the transcriptomic data under water-stressed and rehydration treatment, as well as in the CK. According to Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, proline metabolism-related DEGs, including those involved in the 'proline catabolic process', the 'proline metabolic process', and 'arginine and proline metabolism', may play important roles in plant drought tolerance. Additionally, these DEGs encoded 43 transcription factors (TFs), 46 transporters, and 22 reactive oxygen species (ROS)-scavenging system-related proteins. Biochemical analysis and histochemical detection showed that proline and ROS were accumulated under water-stressed conditions, which is consistent with the result of the transcriptomic analysis. CONCLUSIONS: In summary, our transcriptomic data revealed that the drought tolerance of I. lactea var. chinensis depends on proline metabolism, the action of TFs and transporters, and a strong ROS-scavenging system. The related genes found in this study could help us understand the mechanisms underlying the drought tolerance of I. lactea var. chinensis.

Response characteristics of rhizosphere microbial community and metabolites of Iris tectorum to Cr stress.

Chromium (Cr) is a toxic heavy element that interferes with plant metabolite biosynthesis and modifies the plant rhizosphere microenvironment, affecting plant growth. However, the interactions and response mechanisms between plants and rhizosphere bacteria under Cr stress still need to be fully understood. In this study, we used Iris tectorum as a research target and combined physiology, metabolomics, and microbiology to reveal the stress response mechanism of I. tectorum under heavy metal chromium stress. The results showed that Cr stress-induced oxidative stress inhibited plant growth and development and increased malondialdehyde and oxygen free radicals content. Also, it increased ascorbate peroxidase, peroxidase activity, and superoxide dismutase activity, as well as glutathione and soluble sugar content. Microbiome analysis showed that Cr stress changed the rhizosphere bacterial community diversity index by 33.56%. Proteobacteria, Actinobacteriota, and Chloroflexi together accounting for 71.21% of the total sequences. Meanwhile, the abundance of rhizosphere dominant and plant-promoting bacteria increased significantly with increasing time of Cr stress. The improvement of the soil microenvironment and the recruitment of bacteria by I. tectorum root secretions were significantly enhanced. By metabolomic analysis, five vital metabolic pathways were identified, involving 89 differentially expressed metabolites, divided into 15 major categories. In summary, a multi-omics approach was used in this study to reveal the interaction and stress response mechanisms between I. tectorum and rhizosphere bacterial communities under Cr stress, which provided theoretical basis for plant-microbial bioremediation of Cr-contaminated soils in constructed wetlands. This may provide more valuable information for wetland remediation of heavy metal pollution.

Association Analysis of Transcriptome and Targeted Metabolites Identifies Key Genes Involved in Iris germanica Anthocyanin Biosynthesis.

The anthocyanin biosynthetic pathway is the main pathway regulating floral coloration in Iris germanica, a well-known ornamental plant. We investigated the transcriptome profiles and targeted metabolites to elucidate the relationship between genes and metabolites in anthocyanin biosynthesis in the bitone flower cultivar 'Clarence', which has a deep blue outer perianth and nearly white inner perianth. In this study, delphinidin-, pelargonidin-, and cyanidin-based anthocyanins were detected in the flowers. The content of delphinidin-based anthocyanins increased with the development of the flower. At full bloom (stage 3), delphinidin-based anthocyanins accounted for most of the total anthocyanin metabolites, whereas the content of pelargonidin- and cyanidin-based anthocyanins was relatively low. Based on functional annotations, a number of novel genes in the anthocyanin pathway were identified, which included early biosynthetic genes IgCHS, IgCHI, and IgF3H and late biosynthetic genes Ig F3'5'H, IgANS, and IgDFR. The expression of key structural genes encoding enzymes, such as IgF3H, Ig F3'5'H, IgANS, and IgDFR, was significantly upregulated in the outer perianth compared to the inner perianth. In addition, most structural genes exhibited their highest expression at the half-color stage rather than at the full-bloom stage, which indicates that these genes function ahead of anthocyanins synthesis. Moreover, transcription factors (TFs) of plant R2R3-myeloblastosis (R2R3-MYB) related to the regulation of anthocyanin biosynthesis were identified. Among 56 R2R3-MYB genes, 2 members belonged to subgroup 4, with them regulating the expression of late biosynthetic genes in the anthocyanin biosynthetic pathway, and 4 members belonged to subgroup 7, with them regulating the expression of early biosynthetic genes in the anthocyanin biosynthetic pathway. Quantitative real-time PCR (qRT-PCR) analysis was used to validate the data of RNA sequencing (RNA-Seq). The relative expression profiles of most candidate genes were consistent with the FPKM of RNA-seq. This study identified the key structural genes encoding enzymes and TFs that affect anthocyanin biosynthesis, which provides a basis and reference for the regulation of plant anthocyanin biosynthesis in I. germanica.

Effect of enhanced UV-B radiation on growth and photosynthetic physiology of Iris tectorum maxim.

Iris tectorum Maxim. is an important plant that plays a very crucial role in the ecological welfare of wetlands. In this study, the effects of different intensities of UV-B radiation on the growth, photosynthetic pigment content, chlorophyll fluorescence characteristics, chloroplast ultrastructure, and gas exchange parameters of Iris tectorum Maxim. were studied. The results showed that enhanced UV-B radiation had a significant influence on the above-mentioned parameters of iris. Compared with the control, enhanced UV-B radiation caused certain damage to the leaf appearance. With the increasing intensity of radiation, the apparent damage degree became more serious. Enhanced UV-B radiation significantly decreased leaf chlorophyll contents, and the effect accumulated with the exposure time. Enhanced UV-B radiation increased Fo, significantly increased the non-photochemical quenching coefficient NPQ, reduced PSII and Qp, and significantly decreased the Fm, Fv/Fm, and Fv/Fo in leaves. The effect of UV-B radiation on PSII destruction of Iris tectorum Maxim. increased as the radiation intensity increased and the exposure time prolonged. The chloroplast structure was damaged under the enhanced UV-B radiation. More specifically, thylakoid lamellae were distorted, swelling and even blurred, and a large number of starch granules appeared. The effect of the high intensity of radiation on chloroplast ultrastructure was greater than that of lower intensity. Enhanced UV-B radiation reduced significantly the net photosynthetic rate, stomatal conductance, and transpiration rate, and the degree of degradation increased with the increasing irradiation intensity. However, the intercellular CO2 content increased, which suggests that the main reason for the decrease of photosynthetic rate was the non-stomatal factors.

MADS-box transcription factors determine the duration of temporary winter dormancy in closely related evergreen and deciduous Iris spp.

Winter dormancy (WD) is a crucial strategy for plants coping with potentially deadly environments. In recent decades, this process has been extensively studied in economically important perennial eudicots due to changing climate. However, in evergreen monocots with no chilling requirements, dormancy processes are so far a mystery. In this study, we compared the WD process in closely related evergreen (Iris japonica) and deciduous (I. tectorum) iris species across crucial developmental time points. Both iris species exhibit a 'temporary' WD process with distinct durations, and could easily resume growth under warm conditions. To decipher transcriptional changes, full-length sequencing for evergreen iris and short read RNA sequencing for deciduous iris were applied to generate respective reference transcriptomes. Combining results from a multipronged approach, SHORT VEGETATIVE PHASE and FRUITFULL (FUL) from MADS-box was associated with a dormancy- and a growth-related module, respectively. They were co-expressed with genes involved in phytohormone signaling, carbohydrate metabolism, and environmental adaptation. Also, gene expression patterns and physiological changes in the above pathways highlighted potential abscisic acid and jasmonic acid antagonism in coordinating growth and stress responses, whereas differences in carbohydrate metabolism and reactive oxygen species scavenging might lead to species-specific WD durations. Moreover, a detailed analysis of MIKCCMADS-box in irises revealed common features described in eudicots as well as possible new roles for monocots during temporary WD, such as FLOWERING LOCUS C and FUL. In essence, our results not only provide a portrait of temporary WD in perennial monocots but also offer new insights into the regulatory mechanism underlying WD in plants.

Identification of MADS-Box Transcription Factors in Iris laevigata and Functional Assessment of IlSEP3 and IlSVP during Flowering.

Iris laevigata is ideal for gardening and landscaping in northeast China because of its beautiful flowers and strong cold resistance. However, the short length of flowering time (2 days for individual flowers) greatly limits its applications. Molecular breeding and engineering hold high potential for producing I. laevigata of desirable flowering properties. A prerequisite is to identify and characterize key flowering control genes, the identity of which remains largely unknown in I. laevigata due to the lack of genome information. To fill this knowledge gap, we used sequencing data of the I. laevigata transcriptome to identify MADS-box gene-encoding transcription factors that have been shown to play key roles in developmental processes, including flowering. Our data revealed 41 putative MADS-box genes, which consisted of 8 type I (5 Mα and 3 Mß, respectively) and 33 type II members (2 MIKC* and 31 MIKCC, respectively). We then selected IlSEP3 and IlSVP for functional studies and found that both are localized to the nucleus and that they interact physically in vitro. Ectopic expression of IlSEP3 in Arabidopsis resulted in early flowering (32 days) compared to that of control plants (36 days), which could be mediated by modulating the expression of FT, SOC1, AP1, SVP, SPL3, VRN1, and GA20OX. By contrast, plants overexpressing IlSVP were phenotypically similar to that of wild type. Our functional validation of IlSEP3 was consistent with the notion that SEP3 promotes flowering in multiple plant species and indicated that IlSEP3 regulates flowering in I. laevigata. Taken together, this work provided a systematic identification of MADS-box genes in I. laevigata and demonstrated that the flowering time of I. laevigata can be genetically controlled by altering the expression of key MADS-box genes.

Performance and bacterial community dynamics of hydroponically grown Iris pseudacorus L. during the treatment of antibiotic-enriched wastewater at low/normal temperature.

Antibiotics are widely detected in the water environment, posing a serious threat to the health of humans and animals. The effect of levofloxacin (LOFL) on pollutant removal and the difference in the influence mechanisms at normal and low temperatures in constructed wetlands are worth discussing. A hydroponic culture experiment was designed with Iris pseudacorus L. at low and normal temperatures. LOFL (0-100 µg/L) was added to the systems. The results indicated that the removal of pollutants was affected most by temperature, followed by LOFL concentration. At the same concentration of LOFL, the pollutant removal rate was significantly higher at normal temperature than at low temperature. Low concentrations of LOFL promoted the degradation of pollutants except TN under normal-temperature conditions. Compared with the results at low temperature, the bacterial community richness was higher and the diversity of bacterial communities was lower under normal-temperature conditions. The genera and the function of bacteria were greatly affected by antibiotic concentration, temperature and test time. A series of microorganisms resistant to antibiotics and low temperature were identified in this study. The results will provide valuable information and a reference for our understanding of the ecological effects of LOFL.

Genome-Wide Identification and Expression Analysis of BBX Transcription Factors in Iris germanica L.

The family of B-box (BBX) transcription factors contains one or two B-BOX domains and sometimes also features a highly conserved CCT domain, which plays important roles in plant growth, development and stress response. Nevertheless, no systematic study of the BBX gene family in Iris germanica L. has been undertaken. In this study, a set of six BBX TF family genes from I. germanica was identified based on transcriptomic sequences, and clustered into three clades according to phylogenetic analysis. A transient expression analysis revealed that all six BBX proteins were localized in the nucleus. A yeast one-hybrid assay demonstrated that IgBBX3 has transactivational activity, while IgBBX1, IgBBX2, IgBBX4, and IgBBX5 have no transcriptional activation ability. The transcript abundance of IgBBXs in different tissues was divided into two major groups. The expression of IgBBX1, IgBBX2, IgBBX3 and IgBBX5 was higher in leaves, whereas IgBBX4 and IgBBX6 was higher in roots. The stress response patterns of six IgBBX were detected under phytohormone treatments and abiotic stresses. The results of this study lay the basis for further research on the functions of BBX gene family members in plant hormone and stress responses, which will promote their application in I. germanica breeding.

Phytoremediation of potentially toxic elements using constructed wetlands in coastal areas with a mining influence.

This paper proposes the use of wetlands as a phytoremediation strategy for areas of mining and maritime influence in the southeast of Spain. Potentially toxic elements (PTEs) tolerant and salinity-resistant macrophytes (Phragmites australis, Juncus effusus and Iris pseudacorus) have been used. The experiment is carried out in an aerobic artificial wetland using representative sediments affected by mining activities in the study area. Selected species were placed in pots containing substrates made with different mixtures of topsoil and/or peat, mining residues (black or yellow sand). After six months, rhizosphere, root and aerial parts were collected. A transfer study of As, Pb, Zn and Cu is performed, determining contents in rhizosphere and plant (aerial and underground part). From these data, the TF and BCF were calculated for each plant in 15 different substrates. The work is complemented by an initial study of scanning electron microscopy (SEM-EDX) of plants. The obtained results indicate a tolerance of the metallophytes to these PTEs, which may favour the obtaining of a naturalized habitat that acts as an effective protective barrier to the ecosystem, that is easy to maintain and that avoid the risk of transfer to the trophic chain. The use of these species can be a complement to the chemical stabilization proposed for the whole area and carried out in experimental plots. Because they are perennial plants, it is necessary to continue with the experiments and obtain results in a longer period of time that allows to evaluate yield and stabilization.

Formation of iron plaque on roots of Iris pseudacorus and its consequence for cadmium immobilization is impacted by zinc concentration.

The impact of iron plaque (IP) on bioavailability of heavy metals to plants has been well documented, but the role of zinc (Zn) in modulating the associated processes remains elusive. We took Iris pseudacorus used in wetland for remediating Cd-contaminated water as an example and systematically studied the combined influence of Cd and Zn concentration on formation of IP and its consequence for immobilization and plant uptake of Cd. The experiment was conducted in hydroponic culture and in each treatment, we measured the physiological traits, activity of antioxidant enzymes (SOD, POD, CAT), mass of the IP, as well as the Cd content in both plant tissues and IP. The results showed that increasing Cd concentration resulted in a steady reduction in IP while the impact of zinc on IP was complicated and appeared to be coupled with Cd. When the Cd concentration was low (0.5 mg L-1 measured as CdCl2 2·5H2O) increasing Zn concentration reduced IP, while when the Cd concentration was increased to 5 mg L-1 increasing zinc concentration led to an increase in IP mass first followed by a decline after Zn concentration exceeded 100 mg L-1 (measured as ZnSO4·7H2O). The change in IP as affected by Zn had a strong consequence for immobilization and plant uptake of Cd. When Cd concentration was low, the IP was comparatively abundant and hence adsorbed most Cd. In contrast, when Cd concentration was high, the IP reduced and the amount of Cd taken up by plant roots and translocated to shoots and leaves increased. Both Cd immobilization and its plant uptake were modulated by Zn concentration. At low Cd concentration the combined Cd immobilized and taken up by plant peaked when the Zn concentration was 50 mg L-1, while at high Cd concentration the combined Cd reached maxima when theZn concentration was 100 mg L-1. The activity of the antioxidant enzymes changed significantly with Zn rather than with Cd. Regardless of Cd concentration, the activity of all three antioxidant enzymes increased first with zinc concentration before declining when the Zn concentration exceeded approximately 100 mg L-1 in all treatments, comparable with the change in immobilization and plant uptake of Cd as the Zn concentration increased. SEM analysis did prove the formation and variation of IP on the root surface of Iris pseudacorus in different treatments. We also found that the plant developed a survival strategy by scarifying its leaves with high Cd content. The results presented in this paper has wide implications as it revealed that care needs to be taken in applying Zn to enhance Cd immobilization and its plant uptake as exceeding the optimal application rate might reduce remediating efficiency rather than increase it.

Antioxidative systems, metal ion homeostasis and cadmium distribution in Iris lactea exposed to cadmium stress.

Iris lactea is a perennial halophyte and is tolerant to Cd. However, the mechanisms underlying this Cd tolerance are still poorly understood. In this study, morphological, physiological and biochemical responses of I. lactea to a 21 d exposure to different concentrations of Cd (0-150mgL-1) were investigated. I. lactea plants showed no toxicity symptoms except for a small reduction in growth at 100 and 150mgL-1 Cd, along with the enhancement of H2O2 and MDA content in comparison to the control. The activities of SOD and POD were significantly enhanced and Ca accumulated with increasing Cd concentrations. Moreover, most Cd was retained in roots and only a small amount was transported to the shoots with increasing external Cd concentrations. Cd content had a negative correlation with content of K, Fe, Zn, and Mn and a positive correlation with Mg content in shoots and roots, which had no influence on these contents of mineral nutrients in shoots and chlorophyll levels with the increase of Cd concentrations. The Cd translocation factors were always less than 1 and bioaccumulation factors ranged from 3.43 to 15.6 across all treatments, suggesting that I. lactea might be effectively used in phytostabilization of Cd contaminated soils. Overall, the findings suggest that I. lactea could reduce photoinhibition and oxidative damage and maintain metal ion homeostasis in plant tissue by limiting translocation of Cd from roots to shoots and enhancing induction of antioxidant enzyme activities, thereby improving its Cd tolerance.

De novo characterization of the Iris lactea var. chinensis transcriptome and an analysis of genes under cadmium or lead exposure.

Iris lactea var. chinensis (I. lactea var. chinensis) is tolerant to accumulations of cadmium (Cd) and lead (Pb). In this study, the transcriptome of I. lactea var. chinensis was investigated under Cd or Pb stresses. Using the gene ontology database, 31,974 unigenes were classified into biological process, cellular component and molecular function. In total, 13,132 unigenes were involved in enriched Encyclopedia of Genes and Genomes (KEGG) metabolic pathways, and the expression levels of 5904 unigenes were significantly changed after exposure to Cd or Pb stresses. Of these, 974 were co-up-regulated and 1281 were co-down-regulated under the two stresses. The transcriptome expression profiles of I. lactea var. chinensis under Cd or Pb stresses obtained in this study provided a resource for identifying common mechanisms in the detoxification of different heavy metals. Furthermore, the identified unigenes may be used for the genetic breeding of heavy-metal tolerant plants.

Phytoremediation of petroleum hydrocarbon-contaminated saline-alkali soil by wild ornamental Iridaceae species.

As a green remediation technology, phytoremediation is becoming one of the most promising methods for treating petroleum hydrocarbons (PHCs)-contaminated soil. Pot culture experiments were conducted in this study to investigate phytoremediation potential of two representative Iridaceae species (Iris dichotoma Pall. and Iris lactea Pall.) in remediation of petroleum hydrocarbon-contaminated saline-alkali soil from the Dagang Oilfield in Tianjin, China. The results showed that I. lactea was more endurable to extremely high concentration of PHCs (about 40,000 mg/kg), with a relatively high degradation rate of 20.68%.The degradation rate of total petroleum hydrocarbons (TPHs) in soils contaminated with 10,000 and 20,000 mg/kg of PHCs was 30.79% and 19.36% by I. dichotoma, and 25.02% and 19.35% by I. lactea, respectively, which improved by 10-60% than the unplanted controls. The presence of I. dichotoma and I. lactea promoted degradation of PHCs fractions, among which saturates were more biodegradable than aromatics. Adaptive specialization was observed within the bacterial community. In conclusion, phytoremediation by I. dichotoma should be limited to soils contaminated with ≤20,000 mg/kg of PHCs, while I. lactea could be effectively applied to phytoremediation of contaminated soils by PHCs with at least 40,000 mg/kg.

The heterologous expression of the Iris lactea var. chinensis type 2 metallothionein IlMT2b gene enhances copper tolerance in Arabidopsis thaliana.

Iris lactea var. chinensis (I. lactea var. chinensis) is a widely adapted perennial species with a high level of copper tolerance. To evaluate the role of metallothioneins (MTs) in copper tolerance in I. lactea var. chinensis, a full-length cDNA homologue of MT2, designated IlMT2b (GenBank accession No. AB907788), was cloned using the RACE-PCR method. The expression level of IlMT2b in the leaves and roots of I. lactea var. chinensis was induced in response to copper (Cu) treatment. Ectopic expression of IlMT2b in Arabidopsis thaliana increased the Cu concentration and reduced H2O2 production in the transgenic plants. After treatment with 50 and 100 µM Cu, the root length of two transgenic seedlings was respectively about 1.5- and 3-fold longer than that of the wild-type. Together, these results suggested that IlMT2b may represent a useful target gene for the phytoremediation of Cu-polluted soil.

Cadmium Toxicity and Alleviating Effects of Exogenous Salicylic Acid in Iris hexagona.

Cadmium (Cd) toxictity and possible role of salicylic acid (SA) in alleviating Cd-induced toxicity were investigated on ornamental hydrophyte Iris hexagona. Compared to the control, treatments with 100 and 500 µM Cd for 7 days significantly decreased dry weight, the contents of chlorophyll, photosynthetic parameters, and increased the content of thiobarbituric acid reactive substance. Pretreatment of the roots of I. hexagona seedlings with 1 µM SA before Cd exposure may increase dry weight, photosynthetic rate, activities of antioxidant enzymes, improve the cell ultrastructure and protect plants from Cd-induced oxidative stress damage. However, SA pretreatment had no significant effect on Cd concentrations in the leaves and roots. It is suggested that SA-induced Cd tolerances in I. hexagona are likely associated with increases in antioxidant enzyme activities and vacuolar compartmentation, rather than Cd uptake.

The effects of polypropylene microplastics on the removal of nitrogen and phosphorus from water by Acorus calamus, Iris tectorum and functional microorganisms.

Polypropylene microplastics (PP-MPs), an emerging pollutant, adversely affect the ability of aquatic plants to restore water bodies, thereby compromising the functionality and integrity of wetland ecosystems. This study examines the effects of microplastic stress on the nitrogen and phosphorus removal capacities of Acorus calamus and Iris tectorum, as well as on functional microorganisms within the aquatic system. The findings indicate that under PP-MP stress, the nitrogen and phosphorus absorption capabilities of both plants were diminished. Additionally, there was a significant reduction in the metabolic enzyme activities related to nitrogen and phosphorus in the plants, alongside a notable decrease in leaf nitrogen content. PP-MPs hinder the nutrient uptake of plants, affecting their growth and indirectly reducing their ability to utilize nitrogen and phosphorus. Specifically, in the 10 mg L-1 treatment group, A. calamus and I. tectorum showed reductions in leaf nitrogen content by 23.1% and 31.0%, respectively, and by 14.8% and 27.7% in the 200 mg L-1 treatment group. Furthermore, I. tectorum had higher leaf nitrogen levels than A. calamus. Using fluorescent tagging, the distribution of PP-MPs was traced in the roots, stems, and leaves of the plants, revealing significant growth impairment in both species. This included a considerable decline in photosynthetic pigment synthesis, enhanced oxidative stress responses, and increased lipid peroxidation in cell membranes. PP-MP exposure also significantly reduced the abundance of functional microorganisms involved in denitrification and phosphorus removal at the genus level in aquatic systems. Ecological function predictions revealed a notable decrease in nitrogen cycling functions such as nitrogen respiration and nitrite denitrification among water microorganisms in both treatment groups, with a higher ecological risk potential in the A. calamus treatment group. This study provides new insights into the potential stress mechanisms of PP-MPs on aquatic plants involved in water body remediation and their impacts on wetland ecosystems.

Spatiotemporal dynamics of reactive oxygen species and its effect on beta-blockers' degradation in aquatic plants' rhizosphere.

The pathway for pollutant degradation involving reactive oxygen species (ROS) in the rhizosphere is poorly understood. Herein, a rootchip system was developed to pinpoint the ROS hotspot along the root tip of Iris tectorum. Through mass balance analysis and quenching experiment, we revealed that ROS contributed significantly to rhizodegradation for beta-blockers, ranging from 22.18 % for betaxolol to 83.83 % for atenolol. The identification of degradation products implicated ROS as an important agent to degrade atenolol into less toxic transformation products during phytoremediation. Moreover, an active production of ROS in rhizosphere was identified by mesocosm experiment. Across three root-associated regions aquatic plants inhabiting the rhizosphere accumulated the highest •OH of ∼1200 nM after 3 consecutive days, followed by rhizoplane (∼230 nM) and bulk environment (∼60 nM). ROS production patterns were driven by rhizosphere chemistry (Fe and humic substances) and microbiome variations in different rhizocompartments. These findings not only deepen understanding of ROS production in aquatic plants rhizosphere but also shed light on advancing phytoremediation strategies.

Influence of initial pesticide concentrations in water on chlorpyrifos toxicity and removal by Iris pseudacorus.

For understanding the influence of initial concentrations of pesticides in the water body on removal efficiency of the contaminant by aquatic plants, one hydroponics experiment was used to investigate the influence of initial concentration (1-16 mg L(-1)) on toxicity and chlorpyrifos removal potential of Iris pseudacorus for 20 days under greenhouse conditions. An increased sensitivity to and reduced removal rate for chlorpyrifos were observed with increasing chlorpyrifos concentration. The relative growth rate (RGR) of I. pseudacorus was significantly inhibited in the presence of 4, 8 and 16 mg L(-1) chlorpyrifos, and a negative relationship was also found between RGR and initial pesticide concentration. The half-life of chlorpyrifos was shortened in the hydroponic system with plants, indicating that I. pseudacorus accelerated chlorpyrifos removal from water. But the contribution of the plant to chlorpyrifos removal in the hydroponic phytoremediation system decreased with the increase of initial concentration of chlorpyrifos. The results also indicated that I. pseudacorus can efficiently eliminate chlorpyrifos and may ultimately serve as phytoremediation agents in the natural water body.

IlNRAMP5 is required for cadmium accumulation and the growth in Iris lactea under cadmium exposures.

Iris lactea is potentially applied for remediating Cd-contaminated soils due to the strong ability of Cd uptake and accumulation. However, its molecular mechanism underlying Cd uptake pathway remains unknown. Here, we report a member of NRAMP (Natural Resistance-Associated Macrophage Protein) family, IlNRAMP5, is involved in Cd/Mn uptake and the growth in I. lactea response to Cd. IlNRAMP5 was localized onto the plasma membrane, and was induced by Cd. It was expressed in the root cortex rather than the central vasculature, and in leaf vascular bundle and mesophyll cells. Heterologous expression in yeast showed that IlNRAMP5 could transport Cd and Mn, but not Fe. Knockdown of IlNRAMP5 triggered a significant reduction in Cd uptake, further diminishing the accumulation of Cd. In addition, silencing IlNRAMP5 disrupted Mn homeostasis by lowering Mn uptake and Mn allocation, accompanied by remarkably inhibiting photosynthesis under Cd conditions. Overall, the findings suggest that IlNRAMP5 plays versatile roles in Cd accumulation by mediating Cd uptake, and contributes to maintain the growth via modulating Mn homeostasis in I. lactea under Cd exposures. This would provide a mechanistic understanding Cd phytoremediation efficiency in planta.