Novel insights into the regulation of exosomal PD-L1 in cancer: From generation to clinical application.

Programmed cell death ligand 1 (PD-L1) interacts with programmed cell death 1 (PD-1), leading to T cell exhaustion and promoting tumor cell survival, ultimately mediating immunosuppression. While FDA-approved monoclonal antibodies targeting the PD-1/PD-L1 interaction have shown success in cancer treatment, some patients experience limited and short-lived therapeutic outcomes. Recent studies have identified PD-L1 expression not only on tumor cell surfaces but also on exosomes, with secretion pathways including both conventional and unconventional endocytosis routes, presenting a unique therapeutic opportunity. Emerging evidence suggests that exosomal PD-L1 contributes to systemic immunosuppression, potentially counteracting the effects of anti-PD-1 checkpoint therapies. However, the significance of exosomal PD-L1 in clinical cancer patients unresponsive to anti-PD-1/PD-L1 immunotherapy, as well as the factors regulating its generation, remain unclear. Moreover, the mechanisms underlying PD-L1 expression on exosomes and its regulation in cancer are yet to be fully elucidated. This review primarily focuses on the mechanisms modulating exosomal PD-L1 generation in cancer, while also outlining its involvement in immunosuppression, tumor proliferation, and response to cancer immunotherapy. Additionally, we explore the potential of exosomal PD-L1 as a cancer biomarker and therapeutic target, aiming to provide a comprehensive overview of this emerging field and its implications for cancer treatment and diagnosis.

A ratiometric fluorescence and colorimetry dual-signal sensing strategy based on o-phenylenediamine and AuNCs for determination of Cu2+ and glyphosate.

A ratiometric fluorescence sensing strategy has been developed for the determination of Cu2+ and glyphosate with high sensitivity and specificity based on OPD (o-phenylenediamine) and glutathione-stabilized gold nanoclusters (GSH-AuNCs). Water-soluble 1.75-nm size GSH-AuNCs with strong red fluorescence and maximum emission wavelength at 682 nm were synthesized using GSH as the template. OPD was oxidized by Cu2+, which produced the bright yellow fluorescence oxidation product 2,3-diaminophenazine (DAP) with a maximum fluorescence emission peak at 570 nm. When glyphosate existed in the system, the chelation between glyphosate and Cu2+ hindered the formation of DAP and reduced the fluorescence intensity of the system at the wavelength of 570 nm. Meanwhile, the fluorescence intensity at the wavelength of 682 nm remained basically stable. It exhibited a good linear relationship towards Cu2+ and glyphosate in water in the range 1.0-10 µM and 0.050-3.0 µg/mL with a detection limit of 0.547 µM and 0.0028 µg/mL, respectively. The method was also used for the semi-quantitative determination of Cu2+ and glyphosate in water by fluorescence color changes visually detected by the naked eyes in the range 1.0-10 µM and 0.30-3.0 µg/mL, respectively. The sensing strategy showed higher sensitivity, more obvious color changes, and better disturbance performance, satisfying with the detection demands of Cu2+ and glyphosate in environmental water samples. The study provides a reliable detection strategy in the environment safety fields.

Yolk-shell MOF-on-MOF hybrid solid-phase microextraction coatings for efficient enrichment and detection of pesticides: Structural regulation cause performance differences.

Metal-organic frameworks (MOFs) based composites with different structure-activity relationships have been widely used in the field of organic pollutant adsorption and extraction. Here, two MOF-on-MOF composites with different structures (yolk-shell and core-shell) from homologous sources were prepared by a simple in-situ growth synthesis method and structural regulation. In order to verify the effect of composite structure on the extraction capacity, the adsorption performance of the yolk-shell structure (YS-NH2-UiO-66@CoZn-ZIF) and the core-shell structured (NH2-UiO-66@CoZn-ZIF) material were compared by using them as coating material of direct immersion solid-phase microextraction (DI-SPME) to enrich six pesticides in five matrices. The results showed that because of the unique hollow hierarchical structure, high specific surface area (930.68 m2 g-1), abundant and open active sites, and synergistic and complementary adsorption forces, YS-NH2-UiO-66@CoZn-ZIF composites had the maximum adsorption amount of 36.01-66.31 mg g-1 under the same experiment condition, which was 6.81%-34.26 % higher than that of NH2-UiO-66@CoZn-ZIF. In addition, the adsorption mechanism of the prepared materials was verified and elaborated through theoretical simulations and material characterization. Under the optimized conditions, the YS-NH2-UiO-66@CoZn-ZIF-coated SPME-HPLC-UV method had a wide linear range (0.241-500 µg L-1), a good linear correlation coefficient (R2 > 0.9988), a low detection limits (0.072-0.567 µg L-1, S/N = 3) and low quantification limits (0.241-1.891 µg L-1, S/N = 10). The relative standard deviations of individual fibers and different batches of fibers were 0.47-6.20 % and 0.22-2.48 %, respectively, and individual fibers could be recycled more than 104 times. This work provided a good synthetic route and comparative ideas for exploring the in-situ growth synthesis of yolk-shell composites with reasonable structure-activity relationships.

MdARF3 switches the lateral root elongation to regulate dwarfing in apple plants.

Apple rootstock dwarfing and dense planting are common practices in apple farming. However, the dwarfing mechanisms are not understood. In our study, the expression of MdARF3 in the root system of dwarfing rootstock 'M9' was lower than in the vigorous rootstock from Malus micromalus due to the deletion of the WUSATAg element in the promoter of the 'M9' genotype. Notably, this deletion variation was significantly associated with dwarfing rootstocks. Subsequently, transgenic tobacco (Nicotiana tabacum) cv. Xanthi was generated with the ARF3 promoter from 'M9' and M. micromalus genotypes. The transgenic apple with 35S::MdARF3 was also obtained. The transgenic tobacco and apple with the highly expressed ARF3 had a longer root system and a higher plant height phenotype. Furthermore, the yeast one-hybrid, luciferase, electrophoretic mobility shift assays, and Chip-qPCR identified MdWOX4-1 in apples that interacted with the pMm-ARF3 promoter but not the pM9-ARF3 promoter. Notably, MdWOX4-1 significantly increased the transcriptional activity of MdARF3 and MdLBD16-2. However, MdARF3 significantly decreased the transcriptional activity of MdLBD16-2. Further analysis revealed that MdARF3 and MdLBD16-2 were temporally expressed during different stages of lateral root development. pMdLBD16-2 was mainly expressed during the early stage of lateral root development, which promoted lateral root production. On the contrary, pMmARF3 was expressed during the late stage of lateral root development to promote elongation. The findings in our study will shed light on the genetic causes of apple plant dwarfism and provide strategies for molecular breeding of dwarfing apple rootstocks.

Mitogen-activated protein kinase MxMPK3-2 mediated phosphorylation of MxZR3.1 participates in regulating iron homoeostasis in apple rootstocks.

The micronutrient iron plays a crucial role in the growth and development of plants, necessitating meticulous regulation for its absorption by plants. Prior research has demonstrated that the transcription factor MxZR3.1 restricts iron absorption in apple rootstocks; however, the precise mechanism by which MxZR3.1 contributes to the regulation of iron homoeostasis in apple rootstocks remains unexplored. Here, MxMPK3-2, a protein kinase, was discovered to interact with MxZR3.1. Y2H, bimolecular fluorescence complementation and pull down experiments were used to confirm the interaction. Phosphorylation and cell semi-degradation tests have shown that MxZR3.1 can be used as a substrate of MxMPK3-2, which leads to the MxZR3.1 protein being more stable. In addition, through tobacco transient transformation (LUC and GUS) experiments, it was confirmed that MxZR3.1 significantly inhibited the activity of the MxHA2 promoter, while MxMPK3-2 mediated phosphorylation at the Ser94 site of MxZR3.1 further inhibited the activity of the MxHA2 promoter. It is tightly controlled to absorb iron during normal growth and development of apple rootstocks due to the regulatory effect of the MxMPK3-2-MxZR3.1 module on MxHA2 transcription level. Consequently, this research has revealed the molecular basis of how the MxMPK3-2-MxZR3.1 module in apple rootstocks controls iron homoeostasis by regulating the MxHA2 promoter's activity.

Review of published 467 achondroplasia patients: clinical and mutational spectrum.

AIM: Achondroplasia is the most common of the skeletal dysplasias that cause fatal and disabling growth and developmental disorders in children, and is caused by a mutation in the fibroblast growth factor receptor, type 3 gene(FGFR3). This study aims to analyse the clinical characteristics and gene mutations of ACH to accurately determine whether a patient has ACH and to raise public awareness of the disease. METHODS: The database of Pubmed, Cochrane Library, Wanfang and CNKI were searched with terms of "Achondroplasias" or "Skeleton-Skin-Brain Syndrome" or "Skeleton Skin Brain Syndrome" or "ACH" and "Receptor, Fibroblast Growth Factor, Type 3" or "FGFR3". RESULTS: Finally, four hundred and sixty-seven patients with different FGFR3 mutations were enrolled. Of the 138 patients with available gender information, 55(55/138, 40%) were female and 83(83/138, 60%) were male. Among the patients with available family history, 47(47/385, 12%) had a family history and 338(338/385, 88%) patients were sporadic. The age of the patients ranged from newborn babies to 36 years old. The mean age of their fathers was 37 ± 7 years (range 31-53 years). Patients came from 12 countries and 2 continents, with the majority being Asian (383/432, 89%), followed by European (49/432, 11%). Short stature with shortened arms and legs was found in 112(112/112) patients, the abnormalities of macrocephaly in 94(94/112) patients, frontal bossing in 89(89/112) patients, genu valgum in 64(64/112) patients and trident hand were found in 51(51/112) patients. The most common mutation was p.Gly380Arg of the FGFR3 gene, which contained two different base changes, c.1138G > A and c.1138G > C. Ten rare pathogenic mutations were found, including c.831A > C, c.1031C > G, c.1043C > G, c.375G > T, c.1133A > G, c.1130T > G, c.833A > G, c.649A > T, c.1180A > T and c.970_971insTCTCCT. CONCLUSION: ACH was caused by FGFR3 gene mutation, and c.1138G > A was the most common mutation type. This study demonstrates the feasibility of molecular genetic testing for the early detection of ACH in adolescents with short stature, trident hand, frontal bossing, macrocephaly and genu valgum.

Active Targeted Janus Theranostic Nanoplatforms Enable Chemo-Photothermal Therapy to Inhibit the Growth of Breast Cancer.

Nanoscale structures have been developed to serve various functions in cancer therapy, encompassing areas such as diagnosis, biomedical visualization, tissue regeneration, and drug delivery. Based on biocompatible chitosan oligosaccharides (COS) and gold nanorods (GNRs), we designed the drug delivery systems (GNR@polyacrylic acid-Mn@COS Janus nanoparticles (JNPs)), which achieved paclitaxel (PTX) loaded on the side of GNRs, and the PAA-Mn domain served as magnetic resonance imaging contrast agents. This system was found to be effectively delivered to tumor sites through the enhanced permeability and retention (EPR) effect and the active target of the COS. The uniform JNPs selectively targeted cancer cells instead of normal cells through interacting with the COS on the surface of tumor cells, and the pH/NIR-responsive drug release behavior further enhanced their therapeutic effects. The in vivo effects of JNPs against tumors were evaluated using subcutaneous and orthotopic lung metastasis models, yielding promising outcomes for both tumor diagnosis and cancer treatment. In conclusion, the obtained JNPs hold great promise as a theranostic nanoplatform with synergistic chemotherapeutic and photothermal effects.

Synergistic effects of multitype carbon doping and oxygen vacancies in TiO2/CNTs composite fabricated via nonthermal plasma for formaldehyde removal.

Formaldehyde as one of the typical indoor pollutants has long been concerned as it can pose a threat to human health. TiO2/CNTs composite with oxygen vacancies and multitype carbon doping (C-TiO2/CNTs) was fabricated using nonthermal plasma for the photocatalytic degradation of formaldehyde. The maximum degradation rate of formaldehyde was 93% and 83% via the new catalyst (with 5% CNTs content) under solar and visible light, respectively. The characterization of the catalyst confirmed the in-situ multitype carbon doping and oxygen vacancies: interstitial carbon doping and oxygen vacancies could dramatically reduce the bandgap and contribute to the improved absorption capability of formaldehyde and electrons. Interfacial carbon doping in the form of C-O-Ti bonds provided a migration channel, whereby photogenerated electrons could efficiently transfer from CNTs to TiO2 and then quench the holes left in the VB of TiO2. Therefore, the multitype carbon doping and oxygen vacancies can expand the light response as well as promote the separation of photo-generated electron/hole pairs. EPR results and experiment section indicated that O2·- plays the most significant role in formaldehyde removal due to the reverse transfer of the electrons. This work advances the understanding of photo-degradation of TiO2/CNTs composite and provides a new route for the abatement of formaldehyde.

Calcium Orthophosphate in Liposomes for Co-Delivery of Doxorubicin Hydrochloride/Paclitaxel in Breast Cancer.

Nanoparticles (NPs) show great advantages in cancer treatment by enabling controlled and targeted delivery of payloads to tumor sites through the enhanced permeability and retention (EPR) effect. In this study, highly effective pH-responsive and biodegradable calcium orthophosphate@liposomes (CaP@Lip) NPs with a diameter of 110 ± 20 nm were designed and fabricated. CaP@Lip NPs loaded with hydrophobic paclitaxel and hydrophilic doxorubicin hydrochloride achieved excellent drug loading efficiencies of 70 and 90%, respectively. Under physiological conditions, the obtained NPs are negatively charged. However, they switched to positively charged when exposed to weak acidic environments by which internalization can be promoted. Furthermore, the CaP@Lip NPs exhibit an obvious structural collapse under acid conditions (pH 5.5), which confirms their excellent biodegradability. The "proton expansion" effect in endosomes and the pH-responsiveness of the NPs facilitate the release of encapsulated drugs from individual channels. The effectiveness and safety of the drug delivery systems were demonstrated through in vitro and in vivo experiments, with a 76% inhibition of tumor growth. These findings highlight the high targeting ability of the drug-loaded NPs to tumor sites through the EPR effect, effectively suppressing tumor growth and metastasis. By combining CaP NPs and liposomes, this study not only resolves the toxicity of CaP but also enhances the stability of liposomes. The CaP@Lip NPs developed in this study have significant implications for biomedical applications and inspire the development of intelligent and smart drug nanocarriers and release systems for clinical use.

MxMPK6-2-mediated phosphorylation enhances the response of apple rootstocks to Fe deficiency by activating PM H+ -ATPase MxHA2.

Iron (Fe) deficiency significantly affects the growth and development, fruit yield and quality of apples. Apple roots respond to Fe deficiency stress by promoting H+ secretion, which acidifies the soil. In this study, the plasma membrane (PM) H+ -ATPase MxHA2 promoted H+ secretion and root acidification of apple rootstocks under Fe deficiency stress. H+ -ATPase MxHA2 is upregulated in Fe-efficient apple rootstock of Malus xiaojinensis at the transcription level. Fe deficiency also induced kinase MxMPK6-2, a positive regulator in Fe absorption that can interact with MxHA2. However, the mechanism involving these two factors under Fe deficiency stress is unclear. MxMPK6-2 overexpression in apple roots positively regulated PM H+ -ATPase activity, thus enhancing root acidification under Fe deficiency stress. Moreover, co-expression of MxMPK6-2 and MxHA2 in apple rootstocks further enhanced PM H+ -ATPase activity under Fe deficiency. MxMPK6-2 phosphorylated MxHA2 at the Ser909 site of C terminus, Thr320 and Thr412 sites of the Central loop region. Phosphorylation at the Ser909 and Thr320 promoted PM H+ -ATPase activity, while phosphorylation at Thr412 inhibited PM H+ -ATPase activity. MxMPK6-2 also phosphorylated the Fe deficiency-induced transcription factor MxbHLH104 at the Ser169 site, which then could bind to the promoter of MxHA2, thus enhancing MxHA2 upregulation. In conclusion, the MAP kinase MxMPK6-2-mediated phosphorylation directly and indirectly regulates PM H+ -ATPase MxHA2 activity at the protein post-translation and transcription levels, thus synergistically enhancing root acidification under Fe deficiency stress.

The relationships between thyroid functions of short-term rapid hypothyroidism and blood lipid levels in post-thyroidectomy patients of differentiated thyroid cancer.

Objective: To explore the relationship between short-term rapid hypothyroidism and blood lipid levels in patients with differentiated thyroid cancer (DTC). Methods: Seventy-five DTC patients scheduled to receive radioactive iodine ablation were enrolled. Levels of thyroid hormone and serum lipids were tested at two time points: the euthyroid before thyroidectomy, and the hypothyroid (off thyroxine). Then the collected data were analyzed. Results: Totally 75 DTC patients enrolled, among them, 5o were female (66.67%) and 25 were male (33. 33%), with an average age of 52.24 ± 1.24 years old. The short-term rapid severe hypothyroidism induced by thyroid hormone withdrawal significantly aggravated dyslipidemia, particularly in patients with dyslipidemia before thyroidectomy (All P < 0.01). However, there was no significant differences between blood lipid levels with different thyroid stimulating hormone (TSH) levels. And our study showed significant negative correlations between free triiodothyronine levels and the changes from euthyjroidism to hypothyroidism in total cholesterol (r=-0.31, P=0.03), triglycerides (r=-0.39, P=0.006), high density lipoprotein-cholesterol (HDL-C) (r=-0.29, P=0.042), and significant positive correlations between free thyroxine and the changes of HDL-C (r=-0.32, P=0.027) were identified in females, however, which were not observed in males. Conclusion: Short-term rapids severe hypothyroidism caused by thyroid hormone withdrawal can lead to rapid significant changes in blood lipid levels. It is necessary to pay attention to dyslipidemia and its long-term effects after thyroid hormone withdrawal, especially in patients with dyslipidemia before thyroidectomy. Clinical trial registration: https://clinicaltrials.gov/ct2/show/NCT03006289?term=NCT03006289&draw=2&rank=1, identifier NCT03006289.

Kinase MxMPK4-1 and calmodulin-binding protein MxIQM3 enhance apple root acidification during Fe deficiency.

Iron (Fe) deficiency is a long-standing issue in plant mineral nutrition. Ca2+ signals and the mitogen-activated protein kinase (MAPK) cascade are frequently activated in parallel to perceive external cues, but their interplay under Fe deficiency stress remains largely unclear. Here, the kinase MxMPK4-1, which is induced during the response to Fe deficiency stress in apple rootstock Malus xiaojinensis, cooperates with IQ-motif containing protein3 (MxIQM3). MxIQM3 gene expression, protein abundance, and phosphorylation level increased under Fe deficiency stress. The overexpression of MxIQM3 in apple calli and rootstocks mitigated the Fe deficiency phenotype and improved stress tolerance, whereas RNA interference or silencing of MxIQM3 in apple calli and rootstocks, respectively, worsened the phenotype and reduced tolerance to Fe deficiency. MxMPK4-1 interacted with MxIQM3 and subsequently phosphorylated MxIQM3 at Ser393, and co-expression of MxMPK4-1 and MxIQM3 in apple calli and rootstocks enhanced Fe deficiency responses. Furthermore, MxIQM3 interacted with the central-loop region of the plasma membrane (PM) H+-ATPase MxHA2. Phospho-mimicking mutation of MxIQM3 at Ser393 inhibited binding to MxHA2, but phospho-abolishing mutation promoted interaction with both the central-loop and C terminus of MxHA2, demonstrating phosphorylation of MxIQM3 caused dissociation from MxHA2 and therefore increased H+ secretion. Moreover, Ca2+/MxCAM7 (Calmodulin7) regulated the MxMPK4-1-MxIQM3 module in response to Fe deficiency stress. Overall, our results demonstrate that MxMPK4-1-MxIQM3 forms a functional complex and positively regulates PM H+-ATPase activity in Fe deficiency responses, revealing a versatile mechanism of Ca2+/MxCAM7 signaling and MAPK cascade under Fe deficiency stress.

In situ anchor of multi-walled carbon nanotubes into iron-based metal-organic frameworks for enhanced adsorption of polycyclic aromatic hydrocarbons by magnetic solid-phase extraction.

In this work, a magnetic MIL-101(γ-Fe2O3)/MWCNTs composite derived from iron-based metal-organic frameworks (MIL-101(Fe)) with multi-walled carbon nanotubes (MWCNTs) was successfully synthesized by low-temperature calcination process. The composite was used as adsorbent of magnetic solid-phase extraction (MSPE) for enhanced and rapid enrichment of trace polycyclic aromatic hydrocarbons (PAHs) based on its strong π-π stacking interactions, hydrophobic and cationic-π stacking interactions. The pseudo-second-order kinetic model and Langmuir isotherm model could be applied to better describe the adsorption process. The maximum adsorption capacity for PAHs reached 93.9 mg g-1. In addition, the conditions of MSPE process were optimized by orthogonal array design (OAD). A MSPE-HPLC-UV method was established for the sensitive detection of PAHs in real water samples and exhibited wide linear range (0.05-1000 µg L-1), low detection limits (0.02-0.41 µg L-1) and high enrichment factors (44-169) for PAHs. The relative standard deviations (RSD) ranged from 0.8 to 4.0% and 1.2-7.2% for single batch and batch-to-batch, respectively, and the spiked recoveries at two levels of 10 and 50 µg L-1 ranged from 79.6 to 112% with RSD of less than 5.81%. The unique MWCNTs in situ anchor MIL-101(γ-Fe2O3) composite with an outstanding PAHs adsorption performance provides a new opportunity and promising application in removal of toxic pollutants.

Genome-wide identification of apple PPI genes and a functional analysis of the response of MxPPI1 to Fe deficiency stress.

Iron (Fe) deficiency affects plant growth and development. The proton pump interactor (PPI) in plants responds to multiple abiotic stresses, although it has not been well characterized under Fe deficiency stress. In this study, we systematically identified and analyzed the PPI gene family in apple. Three PPI candidate genes were found, and they contained 318-1349 amino acids and 3-7 introns. Under Fe deficiency stress, we analyzed the expression of all the PPI genes in roots of apple rootstock Malus xiaojinensis. Expression of the gene MD11G1247800, designated PPI1, is obviously induced by Fe deficiency treatment in M. xiaojinensis. We first cloned MxPPI1 from M. xiaojinensis and determined its subcellular localization, which indicated that it is localized in the cell membrane and nucleus in tobacco. We found that the level of expression of the MxPPI1 protein increased significantly under Fe deficiency stress in apple calli. Moreover, overexpressing MxPPI1 in apple calli enhanced the activities of ferric chelate reductase and H+-ATPase, H+ secretion, MxHA2 gene expression and total Fe content when compared with the wild type calli. We further found that MxPPI1 interacted with MxHA2 using bimolecular fluorescence complementation and luciferase complementation assays. Overall, we demonstrated that MxPPI1 interacts with MxHA2 to enhance the activity of H+-ATPase to regulate Fe absorption in M. xiaojinensis.

Nitrate transporter MdNRT2.4 interacts with rhizosphere bacteria to enhance nitrate uptake in apple rootstocks.

Plants have developed complex mechanisms to adapt to changing nitrate (NO3-) concentrations and can recruit microbes to boost nitrogen absorption. However, little is known about the relationship between functional genes and the rhizosphere microbiome in NO3- uptake of apple rootstocks. Here, we found that variation in Malus domestica NO3- transporter (MdNRT2.4) expression contributes to nitrate uptake divergence between two apple rootstocks. Overexpression of MdNRT2.4 in apple seedlings significantly improved tolerance to low nitrogen via increasing net NO3- influx at the root surface. However, inhibiting the root plasma membrane H+-ATPase activity abolished NO3- uptake and led to NO3- release, suggesting that MdNRT2.4 encodes an H+-coupled nitrate transporter. Surprisingly, the nitrogen concentration of MdNRT2.4-overexpressing apple seedlings in unsterilized nitrogen-poor soil was higher than that in sterilized nitrogen-poor soil. Using 16S ribosomal RNA gene profiling to characterize the rhizosphere microbiota, we found that MdNRT2.4-overexpressing apple seedlings recruited more bacterial taxa with nitrogen metabolic functions, especially Rhizobiaceae. We isolated a bacterial isolate ARR11 from the apple rhizosphere soil and identified it as Rhizobium. Inoculation with ARR11 improved apple seedling growth in nitrogen-poor soils, compared with uninoculated seedlings. Together, our results highlight the interaction of host plant genes with the rhizosphere microbiota for host plant nutrient uptake.

Siderophore production in pseudomonas SP. strain SP3 enhances iron acquisition in apple rootstock.

AIMS: The purpose of this study was to analyse the effects of siderophore-producing bacteria and bacterial siderophore on the iron nutrition of apple rootstocks under iron-deficient conditions. METHODS AND RESULTS: We isolated three Pseudomonas strains, SP1, SP2 and SP3 from the rhizosphere of the Fe-efficient apple rootstocks using the chrome azurol S agar plate assay. We found that all three strains had the ability to secrete indole acetic acid-like compounds and siderophores, especially SP3. When Fe-inefficient rootstocks treated with SP3 were grown in alkaline soil, an increase in the biomass, root development, and Fe concentration was observed in the plants. In addition, SP3 secreted pyoverdine, a siderophore that can chelate Fe3+ to enhance the bioavailability of Fe for plants. We purified the pyoverdine from the SP3 culture supernatant. Hydroponic experiments were conducted with a Fe-deficient solution supplemented with pyoverdine, resulting in a reduction in the chlorosis caused by Fe deficiency and marked improvement in Fe uptake. CONCLUSIONS: Under iron-deficient conditions, Pseudomonas sp. strain SP3 can effectively promote apple rootstock growth and improve plant iron nutrition by secreting siderophores that enhance Fe availability. SIGNIFICANCE AND IMPACT OF THE STUDY: This study showed that plant growth-promoting rhizobacteria from Fe-efficient plants have the potential to improve iron nutrition in Fe-inefficient plants, and Fe-siderophore chelates can be used as an effective source of iron for apple plants. Based on these findings, it may be possible to develop biological agents such as siderophore-producing bacteria for sustainable agricultural and horticultural production.

Long-distance mobile mRNA CAX3 modulates iron uptake and zinc compartmentalization.

Iron deficiency in plants can lead to excessive absorption of zinc; however, important details of this mechanism have yet to be elucidated. Here, we report that MdCAX3 mRNA is transported from the leaf to the root, and that MdCAX3 is then activated by MdCXIP1. Suppression of MdCAX3 expression leads to an increase in the root apoplastic pH, which is associated with the iron deficiency response. Notably, overexpression of MdCAX3 does not affect the apoplastic pH in a MdCXIP1 loss-of-function Malus baccata (Mb) mutant that has a deletion in the MdCXIP1 promoter. This deletion in Mb weakens MdCXIP1 expression. Co-expression of MdCAX3 and MdCXIP1 in Mb causes a decrease in the root apoplastic pH. Furthermore, suppressing MdCAX3 in Malus significantly reduces zinc vacuole compartmentalization. We also show that MdCAX3 activated by MdCXIP1 is not only involved in iron uptake, but also in regulating zinc detoxification by compartmentalizing zinc in vacuoles to avoid iron starvation-induced zinc toxicity. Thus, mobile MdCAX3 mRNA is involved in the regulation of iron and zinc homeostasis in response to iron starvation.

Ethylene response factor MdERF4 and histone deacetylase MdHDA19 suppress apple fruit ripening through histone deacetylation of ripening-related genes.

Histone deacetylase enzymes participate in the regulation of many aspects of plant development. However, the genome-level targets of histone deacetylation during apple (Malus domestica) fruit development have not been resolved in detail, and the mechanisms of regulation of such a process are unknown. We previously showed that the complex of ethylene response factor 4 (MdERF4) and the TOPLESS co-repressor (MdTPL4; MdERF4-MdTPL4) is constitutively active during apple fruit development (Hu et al., 2020), but whether this transcriptional repression complex is coupled to chromatin modification is unknown. Here, we show that a histone deacetylase (MdHDA19) is recruited to the MdERF4-MdTPL4 complex, thereby impacting fruit ethylene biosynthesis. Transient suppression of MdHDA19 expression promoted fruit ripening and ethylene production. To identify potential downstream target genes regulated by MdHDA19, we conducted chromatin immunoprecipitation (ChIP) sequencing of H3K9 and ChIP-quantitative polymerase chain reaction assays. We found that MdHDA19 affects ethylene production by facilitating H3K9 deacetylation and forms a complex with MdERF4-MdTPL4 to directly repress MdACS3a expression by decreasing the degree of acetylation. We demonstrate that an early-maturing-specific acetylation H3K9ac peak in MdACS3a and expression of MdACS3a were specifically up-regulated in fruit of an early-maturing, but not a late-maturing, cultivar. We provide evidence that a C-to-G mutation in the ethylene-responsive element binding factor-associated amphiphilic repression motif of MdERF4 reduces the repression of MdACS3a by the MdERF4-MdTPL4-MdHDA19 complex. Taken together, our results reveal that the MdERF4-MdTPL-MdHDA19 repressor complex participates in the epigenetic regulation of apple fruit ripening.

MxRop1-MxrbohD1 interaction mediates ROS signaling in response to iron deficiency in the woody plant Malus xiaojinensis.

Iron (Fe) deficiency affects crop production and quality. Rho of plants (ROPs) involves in multiple physiological processes in plants. While it has not been well characterized under Fe deficiency, especially in perennial woody plants. In our study, we cloned ROP homologous gene MxRop1 from Malus xiaojinenesis, then overexpressed it in Arabidopsis, showing enhanced plant tolerance to Fe deficiency, which demonstrated its gene function during this stress. Overexpression of MxRop1 also increased reactive oxygen species (ROS) levels. Moreover, active state of MxRop1 (CA-MxRop1) interacted with N-terminal region of MxrbohD1, one ROS synthesis gene. When MxrbohD1 was overexpressed in apple calli, it showed significantly increased H2O2 content, fresh weight and FCR activity, while ROS inhibitor application dramatically inhibited FCR activity, demonstrating ROS produced by MxrbohD1 regulated Fe deficiency responses. Furthermore, using Agrobacterium rhizogenes transformation, MxrbohD1 was overexpressed in apple roots, with increased expression of Fe deficiency-induced genes and increased root FCR activity. Under Fe deficiency, it exhibited slight leaf yellowing phenotype. Co-expression of CA-MxRop1 and MxrbohD1 significantly induced ROS generation. Finally, we proposed that MxRop1 interacted with MxrbohD1 to modulate ROS mediated Fe deficiency adaptive responses in Malus xiaojinensis, which will provide a guidance of cultivation of Fe-deficiency tolerant apple plant.

Codelivery of satraplatin and aminopyrrolic receptor with Pluronic F127-based polyaniline nanoparticles with NIR induced release for combined chemotherapy.

The acquired drug resistance of the platinum-based drug is a main obstacle in cancer therapy. Herein, an aminopyrrolic receptor 1 was synthesized to sensitize satraplatin for overcoming the drug resistance as well as improving tumor targeted ability. Thus, Pluronic F127-based polyaniline nanoparticles were designed to co-deliver satraplatin and aminopyrrolic receptor 1, which could control the drug release with the Near Infrared laser irradiation (808 nm) due to the polyaniline mediated photothermal conversion. Biological evaluation shows prepared nanoparticles (Pt-ARNPs) exhibited more effective cytotoxicity (IC50 = 2.7µM) against the tested cancer cell lines under laser irradiation, compared with free satraplatin or treatment without Near-infrared radiation. Moreover, Pt-ARNPs showed comparable cytotoxicity against A549 and A549/cis cells, implying that the combination of satraplatin and aminopyrrolic receptor 1 with nano carrier might be a promising strategy to reduce platinum resistance and improve therapeutic effect in cancer therapy.