Alkali-assisted extraction, characterization and encapsulation functionality of enzymatic hydrolysis-resistant prolamin from distilled spirit spent grain.

Curcumin is a natural lipophilic polyphenol that exhibits significant various biological properties such as antioxidant and anti-inflammatory properties following oral administration. However, its uses have shown limitations concerning aqueous solubility, bioavailability and biodegradability that could be improved by prolamin-based nanoparticle. In this study, curcumin was encapsulated into prolamin from sorghum (SOP) and wheat (WHP) and distilled spirit spent grain (DSSGP), which was obtained after microbial proteolysis of the former two cereal grains. All the three prolamins showed clear variation of protein profiles and microstructure as confirmed by electrophoresis analysis, disulfide bond determination and Fourier-transform infrared spectroscopy (FTIR). For curcumin-loaded nanospheres (NPs) fabrication, three prolamin-based NPs shared features of spherical shape, uniform particle size, and smooth surface. The average size ranged from 122 to 193 nm depending on the prolamin variety and curcumin loading. In the experiments in vitro, curcumin showed significantly improved UV/thermal stability. Furthermore, DSSGP was more resistant to enzymatic digestion in vitro, hence achieving the controlled release of curcumin in gastrointestinal tract. Collectively, the results indicated the improved bioavailability and biodegradability of curcumin encapsulated by DSSGP, which would be an innovative potential encapsulant for effective protection and targeted delivery of hydrophobic compounds.

Biofunctional study on chemoresistance in esophageal squamous carcinoma cells induced by missense mutation of NOTCH1 p.E450K.

Background: Neoadjuvant chemotherapy (nCT) combined with surgery is one of the main strategies for the treatment of resectable locally advanced esophageal squamous cell carcinoma (ESCC). However, nearly 40% of patients did not benefit from nCT, and the detection rate of NOTCH1 missense mutation was significantly increased in patients who did not respond to chemotherapy, suggesting that the missense mutation may be related to tumor chemoresistance. We aim to explore the effect of a NOTCH1 missense mutation on cell phenotype, to interpret the biofunctional changes in cell lines with a NOTCH1 missense mutation and to analyze the effect of a NOTCH1 missense mutation on drug resistance in ESCC cell lines. Methods: Sanger sequencing was used to evaluate the exon mutations in the NOTCH1 ligand binding region of candidate ESCC cell lines. After screening, KYSE450 and KYSE140 cells were selected as the research objects, and point mutation cell lines [KYSE140-mutant-type (MT) and KYSE450-MT] were constructed by CRISPR/Cas9 technology. Then, functional experiments were performed with the four cell lines [KYSE450-MT/wild-type (WT) and KYSE140-MT/WT]. The drug resistance of ESCC cell lines was assessed with a drug sensitivity test, and the proliferation, invasion and migration of ESCC lines were evaluated by proliferation test, scratch test and Transwell test. The cell cycle status of ESCC cells was assessed using flow cytometry. Results: Drug sensitivity tests showed that the NOTCH1 p.E450K point mutation caused chemotherapy resistance in KYSE140 and KYSE450 ESCC cell lines. Cell proliferation, Wound scratch and Transwell assays showed that the NOTCH1 p.E450K point mutation enhanced the proliferation, invasion and migration abilities of KYSE140 and KYSE450 cells. Flow cytometry analysis showed that the NOTCH1 p.E450K point mutation caused an increase in KYSE140 and KYSE450 cells in S phase. Conclusions: The NOTCH1 p.E450K point mutation causes chemotherapy resistance in KYSE140 and KYSE450 ESCC cells. Cell functional experiments showed that the NOTCH1 p.E450K point mutation enhanced the proliferation, migration and invasion abilities of KYSE140 and KYSE450 cells and increased the number of cells in S phase.

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.

Searching for novel MDM2/MDMX dual inhibitors through a drug repurposing approach.

Disruption of p53-MDM2/MDMX interaction by smaller inhibitors is a promising therapeutic intervention gaining tremendous interest. However, no MDM2/MDMX inhibitors have been marketed so far. Drug repurposing is a validated, practical approach to drug discovery. In this regard, we employed structure-based virtual screening in a reservoir of marketed drugs and identified nintedanib as a new MDM2/MDMX dual inhibitor. The computational structure analysis and biochemical experiments uncover that nintedanib binds MDM2/MDMX similarly to RO2443, a dual MDM2/MDMX inhibitor. Furthermore, the mechanistic study reveals that nintedanib disrupts the physical interaction of p53-MDM2/MDMX, enabling the transcriptional activation of p53 and the subsequent cell cycle arrest and growth inhibition in p53+/+ cancer cells. Lastly, structural minimisation of nintedanib yields H3 with the equivalent potency. In summary, this work provides a solid foundation for reshaping nintedanib as a valuable lead compound for the further design of MDM2/MDMX dual inhibitors.

The Role of Adjuvant Chemotherapy in the Treatment of Esophageal Squamous Cell Carcinoma after Neoadjuvant Chemotherapy.

Background: The aim of this study was to compare the efficacy of adjuvant chemotherapy after neoadjuvant chemotherapy in patients with esophageal squamous cell carcinoma (ESCC). Methods: This retrospective study included patients diagnosed with ESCC at clinical stage T1N1-3M0 or T2-4N0-3M0. Six hundred and eleven patients underwent radical tumor surgical resection after neoadjuvant chemotherapy. Adjuvant chemotherapy was mainly a platinum-based combination regimen. Propensity score matching (PSM) was used to compare adjuvant chemotherapy (AC) vs. postoperative observation (POB) after surgery. Results: A total of 611 patients were eligible, with 381 in the POB group and 230 in the AC group. POB group patients were younger (P=0.046) and at a later stage (ypT3/4: 127 [55%] vs. 177 [46%]), P=0.036; yPN+: 117[51%] vs. 3428[37%], P=0.001) before PSM. After 1:1 PSM, 213 pairs of patients were included in analysis. The 5-year overall survival (OS) was 60.6% and 57.2% in the POB and AC groups, respectively (HR 1.10, 95% CI: 0.80-1.51, P=0.562), and adjuvant chemotherapy did not improve OS compared with postoperative observation. Conclusions: Postoperative adjuvant chemotherapy cannot improve the OS of patients with ESCC after neoadjuvant chemotherapy, but adjuvant chemotherapy tends to benefit ypN+ patients.

Improved Production of Anti-FGF-2 Nanobody Using Pichia pastoris and Its Effect on Antiproliferation of Keratinocytes and Alleviation of Psoriasis.

Fibroblast growth factor 2 (FGF-2) is not only an angiogenic factor, but also a mitogen for epidermal keratinocytes. FGF-2 has been shown to be positively immunoreactive in the basal layer of psoriatic lesions. In previous work, we used the Escherichia coli (E. coli) expression system to biosynthesize a biologically active anti-FGF-2 nanobody (Nb) screened by phage display technology, but the low yield limited its clinical application. In this study, we aimed to increase the yield of anti-FGF-2 Nb, and evaluate its therapeutic potential for psoriasis by inhibiting FGF-2-mediated mitogenic signaling in psoriatic epidermal keratinocytes. We demonstrated a 16-fold improvement in the yield of anti-FGF-2 Nb produced in the Pichia pastoris (P. pastoris) compared to the  E. coli expression system. In vitro, the FGF-2-induced HaCaT cell model (FHCM) was established to mimic the key feature of keratinocyte overproliferation in psoriasis. Anti-FGF-2 Nb was able to effectively inhibit the proliferation and migration of FHCM. In vivo, anti-FGF-2 Nb attenuated the severity of imiquimod (IMQ)-induced psoriatic lesions in mice, and also improved the inflammatory microenvironment by inhibiting the secretion of inflammatory cytokines (IL-1ß, IL-6, IL-23, and TNF-α), chemokines (CXCL1 and CCL20), and neutrophil infiltration in skin lesions. These were mainly related to the suppression of FGF-2-mediated mitogenic signaling in psoriatic keratinocytes. In conclusion, we have improved the production of anti-FGF-2 Nb and demonstrated the modality of attenuating the abnormal proliferative behavior of psoriatic keratinocytes by inhibiting FGF-2-mediated mitogenic signaling, which offers the possibility of treating psoriasis.

MdGRF11-MdARF19-2 module acts as a positive regulator of drought resistance in apple rootstock.

14-3-3 proteins play an important role in the response of plants to drought resistance. In this study, 14-3-3 protein MdGRF11 was cloned from Malus xiaojinensis, and its positive regulation of drought resistance was verified using Orin calli and M. xiaojinensis plants. The transcription factor MdARF19-2 was further screened for interaction with this protein in vitro and in vivo. We also conducted experiments using Orin calli and found that the overexpression of MdARF19-2 decreased the level of reactive oxygen species (ROS) and increased the activity of enzymes that scavenge ROS in plant materials. This indicates that MdARF19-2 is a positive regulator in the drought resistance of plants. The drought tolerance was further improved by the overexpression of both MdGRF11 and MdARF19-2 in the calli. In addition, we examined several genes related to ROS scavenging with auxin response factor binding elements in their promoters and found that their level of expression was regulated by the MdGRF11-MdARF19-2 module. In conclusion, the enhancement of plant drought resistance by MdGRF11 could be owing to its accumulation at the protein level in response to drought, which then combined with MdARF19-2, affecting the expression of MdARF19-2 downstream genes. Thus, it scavenges ROS, which ultimately improves the resistance of plant to drought stress.

Genome-wide analysis of the MdZR gene family revealed MdZR2.2-induced salt and drought stress tolerance in apple rootstock.

The DNL-type zinc finger protein constitutes a zinc ribbon protein (ZR) family, which belongs to a branch of zinc finger protein and plays an essential role in response to abiotic stress. Here, we identified six apple (Malus domestica) MdZR genes. Based on their phylogenetic relationship and gene structure, the MdZR genes were divided into three categories, including MdZR1, MdZR2, and MdZR3. Subcellular results showed that the MdZRs are located on the nuclear and membrane. The transcriptome data showed that MdZR2.2 is expressed in various tissues. The expression analysis results showed that MdZR2.2 was significantly upregulated under salt and drought treatments. Thus, we selected MdZR2.2 for further research. Overexpression of MdZR2.2 in apple callus improved their tolerance to drought and salt stress and ability to scavenge reactive oxygen species (ROS). In contrast, transgenic apple roots with silenced MdZR2.2 grew more poorly than the wild type when subjected to salt and drought stress, which reduced their ability to scavenge ROS. To our knowledge, this is the first study to analyze the MdZR protein family. This study identified a gene that responds to drought and salt stress. Our findings lay a foundation for a comprehensive analysis of the MdZR family members.

The feasibility of a "no tube, no fasting" fast-track recovery protocol after esophagectomy for esophageal cancer patients aged 75 and over.

Objective: For elderly patients aged ≥75 with esophageal cancer, whether surgical treatment is safe and effective and whether it is feasible to use a relatively radical "no tube, no fasting" fast-track recovery protocol remain topics of debate. We conducted a retrospective analysis to shed light on these two questions. Methods: We retrospectively collected the data of patients who underwent McKeown minimally invasive esophagectomy (MIE) combined with early oral feeding (EOF) on postoperative day 1 between April 2015 and December 2017 at Medical Group 1, Ward 1, Department of Thoracic Surgery of our hospital. Preoperative characteristics, postoperative complications, operation time, intraoperative blood loss, duration of anastomotic leakage (day), hospital stay, and survival were evaluated. Results: Twenty-three elderly patients with esophageal cancer underwent surgery with EOF. No significant difference was observed in intraoperative measures. The incidence of postoperative complications was 34.8% (8/23). Two patients (8.7%) were terminated early during the analysis of the feasibility of EOF. For all 23 patients, the mean hospital stay was 11.4 (5-42) days, and the median survival was 51 months. Conclusion: Patients aged ≥75 with resectable esophageal cancer can achieve long-term survival with active surgical treatment. Moreover, the "no tube, no fasting" fast-track recovery protocol is safe and feasible for elderly patients.

Neoadjuvant Chemotherapy Compared with Surgery for Oesophageal Carcinoma: A Retrospective Study and Missing Evidence.

Background: Negative evidence for the use of neoadjuvant chemotherapy (NAC) to treat oesophageal squamous cell carcinoma (ESCC) has been reported in Western countries in the past century. However, in China, most ESCC patients underwent paclitaxel and platinum-based NAC without evidence from local RCTs. Empiricism or a lack of evidence does not necessarily mean that the evidence is negative. However, there was no way to compensate for the missing evidence. The only way to obtain evidence is by conducting a retrospective study using propensity score matching (PSM) to compare the effects of NAC and primary surgery on overall survival (OS) and disease-free survival (DFS) among ESCC patients in China, which is the country with the highest prevalence of ESCC patients. Methods: From January 1, 2015, to December 31, 2018, a total of 5443 patients with oesophageal cancer/oesophagogastric junction carcinoma who underwent oesophagectomy were retrospectively identified at Henan Cancer Hospital. After PSM, 826 patients were selected for the retrospective study and divided into the NAC and primary surgery groups. The median follow-up period was 54.08 months. Toxicity and tumour responses to NAC, intraoperative and postoperative outcomes, recurrence, DFS and OS were analysed. Results: The postoperative complication rates were not significantly different between the two groups. The 5-year DFS rates were 57.48% (95% CI, 52.05% to 62.53%) for the NAC group and 49.93% (95% CI, 44.56% to 55.05%) for the primary surgery group (P=0.0129). The 5-year OS rates were 62.95% (95% CI, 57.63% to 67.79%) for the NAC group and 56.29% (95% CI, 50.99% to 61.25%) for the primary surgery group (P=0.0397). Conclusion: Compared with primary surgery, NAC with paclitaxel and platinum-based chemotherapy and two-field extensive mediastinal lymphadenectomy might be associated with long-term survival benefits among ESCC patients.

Anti-inflammation of hydrogenated isoflavones in LPS-stimulated RAW264.7 cells via inhibition of NF-κB and MAPK signaling pathways.

Isoflavones are commonly found in diets, such as soybean and clover. Their anti-inflammatory effects are due to the inhibition of the transcriptional regulation of NF-κB. Hydrogenated isoflavones are metabolites of isoflavones with higher bioavailability, however, there have been few studies on their anti-inflammatory effects. In this work, by using the LPS-stimulated RAW264.7 cell model, we investigated the anti-inflammatory effect and the underlying mechanism of hydrogenated isoflavones. Hydrogenated isoflavones reduced the production of LPS-stimulated pro-inflammatory mediators and enzymes, including TNF-α, IL-6, NO, iNOS and COX-2. The level of ROS was also diminished in LPS-stimulated RAW264.7 cells. Further mechanistic studies showcase that hydrogenated isoflavones block NF-κB and MAPK pathways via attenuation of p65 nuclear translocation and JNK, ERK, and p38 phosphorylation, respectively. In addition, we found that hydrogenated isoflavones display anti-proliferation effect in human colon cancer cells with wild-type p53. Together, hydrogenated isoflavones could be used as an adjuvant for the treatment of inflammation and cancer.

The Feasibility of Early Oral Feeding After Neoadjuvant Chemotherapy Combined With "Non-Tube No Fasting"-Enhanced Recovery.

BACKGROUND: This study aimed to investigate the feasibility of early oral feeding (EOF) after neoadjuvant chemotherapy (nCT) combined with "non-tube no fasting"-enhanced recovery after minimally invasive esophagectomy (MIE). METHODS: This retrospective study investigated patients who underwent nCT combined with non-tube no fasting-enhanced recovery after MIE in the Department of Thoracic Surgery, Ward I, of the authors' hospital from January 2014 to August 2017. These patients were divided into an early oral feeding (EOF) group (n = 112) and a late oral feeding (LOF) group (n = 69). The postoperative complications were compared between the two groups. RESULTS: The study enrolled 181 patients (112 patients in the EOF group and 69 patients in the LOF group). No significant differences were found between the two groups in the incidence rates of complications such as anastomotic leakage (P = 0.961), pneumonia (P = 0.450), respiratory failure (P = 0.944), heart failure (P = 1.000), acute respiratory distress syndrome (ARDS) (P = 0.856), and unplanned reoperation (P = 0.440), whereas the time to the first postoperative flatus/bowel movement (P < 0.001) and the postoperative length of stay (P < 0.001) were significantly better in the EOF group than in the LOF group.. CONCLUSIONS: In this study, EOF after nCT combined with non-tube no fasting-enhanced recovery after MIE did not significantly increase complications, but significantly shortened the time to the first postoperative flatus/bowel movement and the postoperative length of stay.

Abdominal heterotopic pregnancy after in vitro fertilization and embryo transfer following bilateral salpingectomy: A case report and literature review.

Background: Risk of heterotopic pregnancy following bilateral salpingectomy has increased considerably due to the widespread use of assisted reproductive technology. Poor understanding of this condition often causes delayed or missed diagnosis. Objective: In this report, we describe the case of a 30-year-old pregnant woman with lower abdominal pain lasting for half a day and a history of bilateral salpingectomy. Two embryos had been transferred 21 days preceding her presentation. Methods: Case report. Results: Laparoscopic surgery revealed intraperitoneal hemorrhage and proper ovarian ligament pregnancy confirmed by histopathology. Viable intrauterine pregnancy was verified 3 days later by ultrasound examination. Conclusion: Heterotopic pregnancy is a serious condition that may be life-threatening. Clinicians should be aware of the potential for heterotopic pregnancy in patients receiving in vitro fertilization and embryo transfer after bilateral salpingectomy.

Cytochemical and comparative transcriptome analyses elucidate the formation and ecological adaptation of three types of pollen coat in Zingiberaceae.

BACKGROUND: The pollen ornate surface of flowering plants has long fascinated and puzzled evolutionary biologists for their variety. Each pollen grain is contained within a pollen wall consisting of intine and exine, over which the lipoid pollen coat lies. The cytology and molecular biology of the development of the intine and exine components of the pollen wall are relatively well characterised. However, little is known about the pollen coat, which confers species specificity. We demonstrate three types of pollen coat in Zingiberaceae, a mucilage-like pollen coat and a gum-like pollen coat, along with a pollen coat more typical of angiosperms. The morphological differences between the three types of pollen coat and the related molecular mechanisms of their formation were studied using an integrative approach of cytology, RNA-seq and positive selection analysis. RESULTS: Contrary to the 'typical' pollen coat, in ginger species with a mucilage-like (Caulokaempferia coenobialis, Cco) or gum-like (Hornstedtia hainanensis, Hhn) pollen coat, anther locular fluid was still present at the bicellular pollen (BCP) stage of development. Nevertheless, there were marked differences between these species: there were much lower levels of anther locular fluid in Hhn at the BCP stage and it contained less polysaccharide, but more lipid, than the locular fluid of Cco. The set of specific highly-expressed (SHE) genes in Cco was enriched in the 'polysaccharide metabolic process' annotation term, while 'fatty acid degradation' and 'metabolism of terpenoids and polyketides' were significantly enriched in SHE-Hhn. CONCLUSIONS: Our cytological and comparative transcriptome analysis showed that different types of pollen coat depend on the residual amount and composition of anther locular fluid at the BCP stage. The genes involved in 'polysaccharide metabolism' and 'transport' in the development of a mucilage-like pollen coat and in 'lipid metabolism' and 'transport' in the development of a gum-like pollen coat probably evolved under positive selection in both cases. We suggest that the shift from a typical pollen coat to a gum-like or mucilage-like pollen coat in flowering plants is an adaptation to habitats with high humidity and scarcity of pollinators.

Shape-stabilized phase change material with high phase change enthalpy made of PEG compounded with lignin-based carbon.

Lignin-based porous carbon (LTC), lignin-based hierarchical porous carbon (LTCA) and lignin-based ordered porous carbon (MC) with different pore structures were prepared by template method and chemical activation method using lignin as raw material. The lignin-based carbon composite phase change materials were prepared by vacuum impregnation with polyethylene glycol (PEG) and porous carbon material. The results showed that LTCA has the largest loading capacity of Phase change Materials, which could load 85% of PEG; MC has the largest phase transition enthalpy value (ΔHm), which is 89.7 J·g-1. When the loading amount is the same as 60%, the thermal conductivity of LTCA/PEG is the largest, which is 0.5167 W/mK, 53.8% higher than that of pure PEG. Under constant heating at 70 °C, the pure cotton fabric and the polyurethane coated fabric reached 60 °C in the 4th and 10th second, The cotton fabric coated with composite phase change material reached 60 °C only at 16 s, and a significant slowdown in the temperature rise rate occurred between 50-60 °C. It showed that the cotton fabric coated with composite phase change material had good phase change temperature regulation performance.

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.

One-Pot Tandem Access to Phenothiazine Derivatives from Acetanilide and 2-Bromothiophenol via Rhodium-Catalyzed C-H Thiolation and Copper-Catalyzed C-N Amination.

A one-pot and step economic reaction involving Rh(III)-catalyzed C-H thiolation and relay Cu(II)-catalyzed C-N amination of acetanilide and 2-bromothiophenol is reported here, with several valuable phenothiazine products obtained. This synthesis protocol proceeds from easily starting materials, demonstrating high atom economy, broad substrate scope, and good yield. Furthermore, the directing group can be easily eliminated, and chlorpromazine is provided in a large scale; thus this synthesis protocol could be utilized to construct phenothiazine scaffolds.

MxMPK6-2-bHLH104 interaction is involved in reactive oxygen species signaling in response to iron deficiency in apple rootstock.

Iron (Fe) is a trace element necessary for plant growth. Many land plants have evolved a set of mechanisms associated with the Fe absorption process to deal with the problem of insufficient Fe supply in the soil. During Fe absorption, reactive oxygen species (ROS) can be used as a signal to initiate a response to stress caused by Fe deficiency. However, the molecular mechanisms underlying the involvement of ROS in the Fe deficiency stress response remains unclear. In this study, we have identified a kinase, MxMPK6-2, from Malus xiaojinensis, an apple rootstock that is highly efficient at Fe absorption. MxMPK6-2 has been shown to be responsive to ROS signals during Fe deficiency, and MxMPK6-2 overexpression in apple calli enhanced its tolerance to Fe deficiency. We further screened for proteins in the Fe absorption pathway and identified MxbHLH104, a transcription factor which interacts with MxMPK6-2. MxbHLH104 can be phosphorylated by MxMPK6-2 in vivo, and we confirmed that its phosphorylation increased Fe absorption in apple calli under Fe deficiency, with the presence of ROS promoting this process. Overall, we have demonstrated that MxMPK6-2 is responsive to ROS signaling during Fe deficiency, and is able to control its response by regulating MxbHLH104.

Ethylene Response Factors MbERF4 and MbERF72 Suppress Iron Uptake in Woody Apple Plants by Modulating Rhizosphere pH.

Iron (Fe) deficiency limits the yield of fruit trees. When subjected to Fe deficiency, H+ secretion increases in the rhizosphere of dicotyledonous plants and pH decreases. This leads to the acidification of the soil and promotes Fe3+ to Fe2+ conversion, which plants can better uptake. This study investigated the relationship between two inhibitory transcription factors (ethylene response factors MbERF4 and MbERF72) and the H+-ATPase gene MbHA2. Two species of apple woody plants were studied: the Fe-inefficient Malus baccata and the Fe-efficient Malus xiaojinensis. Yeast one-hybrid and electrophoretic mobility shift assays showed that both MbERF4 and MbERF72 bind to the GCC cassette (AGCCGCC) of the MbHA2 promoter. Moreover, yeast two-hybrid and bimolecular fluorescence complementation assays showed that MbERF4 interacts with MbERF72. Furthermore, ß-glucuronidase and luciferase reporter assays showed that the MbERF4- and MbERF72-induced repression of MbHA2 expression is synergistic. Virus-induced gene silencing of MbERF4 or MbERF72 increased MbHA2 expression, and thus lowered the rhizosphere pH in M. baccata. Consequently, the high expressions of MbERF4 and MbERF72 induced by Fe deficiency contributed to the Fe sensitivity of M. baccata. Moreover, the low expressions of MxERF4 and MxERF72 contributed to the Fe-deficiency tolerance of M. xiaojinensis via different binding conditions to the HA2 promoter. In summary, this study identified the relationship of two inhibitory transcription factors with the H+-ATPase gene and proposed a model in which ERF4 and ERF72 affect the rhizosphere pH in response to Fe deficiency.