The BTB-BACK-TAZ domain protein MdBT2 reduces drought resistance by weakening the positive regulatory effect of MdHDZ27 on apple drought tolerance via ubiquitination.

Drought stress is one of the dominating challenges to the growth and productivity in crop plants. Elucidating the molecular mechanisms of plants responses to drought stress is fundamental to improve fruit quality. However, such molecular mechanisms are poorly understood in apple (Malus domestica Borkh.). In this study, we explored that the BTB-BACK-TAZ protein, MdBT2, negatively modulates the drought tolerance of apple plantlets. Moreover, we identified a novel Homeodomain-leucine zipper (HD-Zip) transcription factor, MdHDZ27, using a yeast two-hybrid (Y2H) screen with MdBT2 as the bait. Overexpression of MdHDZ27 in apple plantlets, calli, and tomato plantlets enhanced their drought tolerance by promoting the expression of drought tolerance-related genes [responsive to dehydration 29A (MdRD29A) and MdRD29B]. Biochemical analyses demonstrated that MdHDZ27 directly binds to and activates the promoters of MdRD29A and MdRD29B. Furthermore, in vitro and in vivo assays indicate that MdBT2 interacts with and ubiquitinates MdHDZ27, via the ubiquitin/26S proteasome pathway. This ubiquitination results in the degradation of MdHDZ27 and weakens the transcriptional activation of MdHDZ27 on MdRD29A and MdRD29B. Finally, a series of transgenic analyses in apple plantlets further clarified the role of the relationship between MdBT2 and MdHDZ27, as well as the effect of their interaction on drought resistance in apple plantlets. Collectively, our findings reveal a novel mechanism by which the MdBT2-MdHDZ27 regulatory module controls drought tolerance, which is of great significance for enhancing the drought resistance of apple and other plants.

Copper-catalyzed oxidative cyclization of 2-(1H-pyrrol-1-yl)aniline and alkylsilyl peroxides: a route to pyrrolo[1,2-a]quinoxalines.

An efficient method was developed for the one-pot construction of pyrrolo[1,2-a]quinoxalines via a Cu(II)-catalyzed domino reaction between 2-(1H-pyrrol-1-yl)anilines and alkylsilyl peroxides. This reaction proceeds through C-C bond cleavage and new C-C and C-N bond formation. A mechanistic study suggests that alkyl radical species participate in the cascade reaction.

Electrochemical oxidative dehydrogenative annulation of 1-(2-aminophenyl)pyrroles with cleavage of ethers to synthesize pyrrolo[1,2-a]quinoxaline derivatives.

An array of pyrrolo[1,2-a]quinoxaline derivatives were achieved with moderate to good yields via the electrochemical redox reaction, which includes the functionalization of C(sp3)-H bonds and the construction of C-C and C-N bonds. In this atom economic reaction, THF was used as both a reactant and a solvent, and H2 was the sole by-product.

HDAC inhibitors as a potential therapy for chemotherapy-induced neuropathic pain.

Cancer, a chronic disease characterized by uncontrolled cell development, kills millions of people globally. The WHO reported over 10 million cancer deaths in 2020. Anticancer medications destroy healthy and malignant cells. Cancer treatment induces neuropathy. Anticancer drugs cause harm to spinal cord, brain, and peripheral nerve somatosensory neurons, causing chemotherapy-induced neuropathic pain. The chemotherapy-induced mechanisms underlying neuropathic pain are not fully understood. However, neuroinflammation has been identified as one of the various pathways associated with the onset of chemotherapy-induced neuropathic pain. The neuroinflammatory processes may exhibit varying characteristics based on the specific type of anticancer treatment delivered. Neuroinflammatory characteristics have been observed in the spinal cord, where microglia and astrocytes have a significant impact on the development of chemotherapy-induced peripheral neuropathy. The patient's quality of life might be affected by sensory deprivation, loss of consciousness, paralysis, and severe disability. High cancer rates and ineffective treatments are associated with this disease. Recently, histone deacetylases have become a novel treatment target for chemotherapy-induced neuropathic pain. Chemotherapy-induced neuropathic pain may be treated with histone deacetylase inhibitors. Histone deacetylase inhibitors may be a promising therapeutic treatment for chemotherapy-induced neuropathic pain. Common chemotherapeutic drugs, mechanisms, therapeutic treatments for neuropathic pain, and histone deacetylase and its inhibitors in chemotherapy-induced neuropathic pain are covered in this paper. We propose that histone deacetylase inhibitors may treat several aspects of chemotherapy-induced neuropathic pain, and identifying these inhibitors as potentially unique treatments is crucial to the development of various chemotherapeutic combination treatments.

Ethylene inhibits malate accumulation in apple by transcriptional repression of aluminum-activated malate transporter 9 via the WRKY31-ERF72 network.

Malic acid accumulation in the vacuole largely determines acidity and perception of sweetness of apple. It has long been observed that reduction in malate level is associated with increase in ethylene production during the ripening process of climacteric fruits, but the molecular mechanism linking ethylene to malate reduction is unclear. Here, we show that ethylene-modulated WRKY transcription factor 31 (WRKY31)-Ethylene Response Factor 72 (ERF72)-ALUMINUM ACTIVATED MALATE TRANSPORTER 9 (Ma1) network regulates malate accumulation in apple fruit. ERF72 binds to the promoter of ALMT9, a key tonoplast transporter for malate accumulation of apple, transcriptionally repressing ALMT9 expression in response to ethylene. WRKY31 interacts with ERF72, suppressing its transcriptional inhibition activity on ALMT9. In addition, WRKY31 directly binds to the promoters of ERF72 and ALMT9, transcriptionally repressing and activating ERF72 and ALMT9, respectively. The expression of WRKY31 decreases in response to ethylene, lowering the transcription of ALMT9 directly and via its interactions with ERF72. These findings reveal that the regulatory complex WRKY31 forms with ERF72 responds to ethylene, linking the ethylene signal to ALMT9 expression in reducing malate transport into the vacuole during fruit ripening.

Glucose sensor MdHXK1 activates an immune response to the fungal pathogen Botryosphaeria dothidea in apple.

Sugars are essential regulatory molecules involved in plant growth and development and defense response. Although the relationship between sugars and disease resistance has been widely discussed, the underlying molecular mechanisms remain unexplored. Ring rot caused by Botryosphaeria dothidea (B. dothidea), which severely affects fruit quality and yield, is a destructive disease of apples (Malus domestica Borkh.). The present study found that the degree of disease resistance in apple fruit was closely related to glucose content. Therefore, the gene encoding a hexokinase, MdHXK1, was isolated from the apple cultivar 'Gala', and characterized during the defense response. Overexpression of MdHXK1 enhanced disease resistance in apple calli, leaves and fruits by increasing the expression levels of genes related to salicylate (SA) synthesis (PHYTOALEXIN DEFICIENT 4, PAD4; PHENYLALANINE AMMONIA-LYASE, PAL; and ENHANCED DISEASE SUSCEPTIBILITY 1, EDS1) and signaling (PR1; PR5; and NONEXPRESSER OF PR GENES 1, NPR1) as well as increasing the superoxide (O2- ) production rate and the hydrogen peroxide (H2 O2 ) content. Overall, the study provides new insights into the MdHXK1-mediated molecular mechanisms by which glucose signaling regulates apple ring rot resistance.

MdbHLH3 modulates apple soluble sugar content by activating phosphofructokinase gene expression.

Sugars are involved in plant growth, fruit quality, and signaling perception. Therefore, understanding the mechanisms involved in soluble sugar accumulation is essential to understand fruit development. Here, we report that MdPFPß, a pyrophosphate-dependent phosphofructokinase gene, regulates soluble sugar accumulation by enhancing the photosynthetic performance and sugar-metabolizing enzyme activities in apple (Malus domestica Borkh.). Biochemical analysis revealed that a basic helix-loop-helix (bHLH) transcription factor, MdbHLH3, binds to the MdPFPß promoter and activates its expression, thus promoting soluble sugar accumulation in apple fruit. In addition, MdPFPß overexpression in tomato influenced photosynthesis and carbon metabolism in the plant. Furthermore, we determined that MdbHLH3 increases photosynthetic rates and soluble sugar accumulation in apple by activating MdPFPß expression. Our results thus shed light on the mechanism of soluble sugar accumulation in apple leaves and fruit: MdbHLH3 regulates soluble sugar accumulation by activating MdPFPß gene expression and coordinating carbohydrate allocation.

The apple bHLH transcription factor MdbHLH3 functions in determining the fruit carbohydrates and malate.

Changes in carbohydrates and organic acids largely determine the palatability of edible tissues of horticulture crops. Elucidating the potential molecular mechanisms involved in the change in carbohydrates and organic acids, and their temporal and spatial crosstalk are key steps in understanding fruit developmental processes. Here, we used apple (Malus domestica Borkh.) as research materials and found that MdbHLH3, a basic helix-loop-helix transcription factor (bHLH TF), modulates the accumulation of malate and carbohydrates. Biochemical analyses demonstrated that MdbHLH3 directly binds to the promoter of MdcyMDH that encodes an apple cytosolic NAD-dependent malate dehydrogenase, activating its transcriptional expression, thereby promoting malate accumulation in apple fruits. Additionally, MdbHLH3 overexpression increased the photosynthetic capacity and carbohydrate levels in apple leaves and also enhanced the carbohydrate accumulation in fruits by adjusting carbohydrate allocation from sources to sinks. Overall, our findings provide new insights into the mechanism of how the bHLH TF MdbHLH3 modulates the fruit quality. It directly regulates the expression of cytosolic malate dehydrogenase MdcyMDH to coordinate carbohydrate allocation and malate accumulation in apple.

BTB-TAZ Domain Protein MdBT2 Modulates Malate Accumulation and Vacuolar Acidification in Response to Nitrate.

Excessive application of nitrate, an essential macronutrient and a signal regulating diverse physiological processes, decreases malate accumulation in apple (Malus domestica) fruit, but the underlying mechanism remains poorly understood. Here, we show that an apple BTB/TAZ protein, MdBT2, is involved in regulating malate accumulation and vacuolar pH in response to nitrate. In vitro and in vivo assays indicate that MdBT2 interacts directly with and ubiquitinates a bHLH transcription factor, MdCIbHLH1, via the ubiquitin/26S proteasome pathway in response to nitrate. This ubiquitination results in the degradation of MdCIbHLH1 protein and reduces the transcription of MdCIbHLH1-targeted genes involved in malate accumulation and vacuolar acidification, including MdVHA-A, which encodes a vacuolar H+-ATPase, and MdVHP1, which encodes a vacuolar H+-pyrophosphatase, as well as MdALMT9, which encodes an aluminum-activated malate transporter. A series of transgenic analyses in apple materials including fruits, plantlets, and calli demonstrate that MdBT2 controls nitrate-mediated malate accumulation and vacuolar pH at least partially, if not completely, via regulating the MdCIbHLH1 protein level. Taken together, these findings reveal that MdBT2 regulates the stability of MdCIbHLH1 via ubiquitination in response to nitrate, which in succession transcriptionally reduces the expression of malate-associated genes, thereby controlling malate accumulation and vacuolar acidification in apples under high nitrate supply.

Glycosides for Peripheral Neuropathic Pain: A Potential Medicinal Components.

Neuropathic pain is a refractory disease that occurs across the world and pharmacotherapy has limited efficacy and/or safety. This disease imposes a significant burden on both the somatic and mental health of patients; indeed, some patients have referred to neuropathic pain as being 'worse than death'. The pharmacological agents that are used to treat neuropathic pain at present can produce mild effects in certain patients, and induce many adverse reactions, such as sedation, dizziness, vomiting, and peripheral oedema. Therefore, there is an urgent need to discover novel drugs that are safer and more effective. Natural compounds from medical plants have become potential sources of analgesics, and evidence has shown that glycosides alleviated neuropathic pain via regulating oxidative stress, transcriptional regulation, ion channels, membrane receptors and so on. In this review, we summarize the epidemiology of neuropathic pain and the existing therapeutic drugs used for disease prevention and treatment. We also demonstrate how glycosides exhibit an antinociceptive effect on neuropathic pain in laboratory research and describe the antinociceptive mechanisms involved to facilitate the discovery of new drugs to improve the quality of life of patients experiencing neuropathic pain.

Auxin regulates anthocyanin biosynthesis through the auxin repressor protein MdIAA26.

Auxin plays an important role in plant growth and development; for example, it regulates the elongation and division of plant cells, the formation of plantlet's geotropism and phototropism, and the growth of main lateral roots and hypocotyl. IAA gene is associated with auxin and can response to biotic and abiotic stress in plants. However, the regulatory effect of auxin on anthocyanin accumulation has been rarely reported. In this study, we show that auxin inhibites the accumulation of anthocyanin and decreases the expression of genes related to anthocyanin synthesis in calli, leaves, and seedlings of apple. The expression levels of MdIAA family genes were determined, and we found that MdIAA26 significantly responded to auxin, which also induced MdIAA26 degradation. Functional analysis of MdIAA26 showed that overexpressing MdIAA26 in apple calli and Arabidopsis could promote the accumulation of anthocyanin and up-regulate the genes related to anthocyanin synthesis. Furthermore, the MdIAA26-overexpressing Arabidopsis could counteract auxin-induced inhibition on anthocyanin accumulation, which indicates that auxin inhibits the accumulation of anthocyanin in apple by degrading MdIAA26 protein.

Pre-mixed nitrous oxide/oxygen mixture treatment of pain induced by postoperative dressing change for perianal abscess: Study protocol for a randomized, controlled trial.

AIM: This study aims to evaluate the safety and analgesic efficacy of pre-mixed nitrous oxide/oxygen mixture treatment of pain induced by dressing change for perianal abscess. DESIGN: This protocol is a randomized, double-blind, placebo-controlled trial. METHODS: This study will be implemented in the Hospital of Traditional Chinese Medicine. Subjects enrolled in this study are hospitalized patients who suffered from moderate to severe pain due to dressing change after incision and drainage. Two hundred patients will be selected and randomly assigned to either an intervention or a control group. The intervention group will get routine pain treatment plus pre-mixed nitrous oxide/oxygen mixture treatment and the control group will be treated with routine pain management plus medical air treatment. All these patients, medical staff and investigators are blind to the nature of the gas in each cylinder, which is randomized. Data will be collected at baseline (T0), 5 min (T1) after the starting of intervention and 5 min post intervention (T2) for each group. The primary outcome is the level of pain relief at T1 and T2. The secondary outcomes cover physiological parameters, adverse events, satisfaction of patients and health professionals and the acceptance from patients. DISCUSSION: Results of this study will be discussed and the safety and effect of nitrous oxide/oxygen treatment of pain induced by dressing change will be proven. IMPACT: When the finding of this study has an active effect on the treatment of pain caused by dressing change, it may provide more options for nursing staff to choose nurse-led analgesia techniques and then improving the level and quality of pain care as well as patients' overall satisfaction with the Anorectal Department in China.

Matrine ameliorates cognitive deficits via inhibition of microglia mediated neuroinflammation in an Alzheimer's disease mouse model.

Amyloid ß (Aß) induced microglial activation and attendant neuroinflammation play pivotal roles in Alzheimer's disease (AD) pathogenesis. Matrine is a natural anti-inflammation compound from the Chinese herbal medicine Sophora flavescens Ait. (Kushen). This study aimed to investigate the effects of matrine on memory deficit and neuroinflammation in an oligomeric Aß (oAß)-induced AD mice model. Whether microglial activation and NADPH oxidase were involved in these effects were further studied. Different doses of matrine (10, 20, or 40 mg/kg) were intragastrically administered once a day after intracerebroventricular oAß injection (2.5 µg/µl, 4 µl). 15 days after the oAß injection, behavioral experiments including novel object recognition (NOR) test and Morris water maze (MWM) test were performed. 21 days after the oAß injection, concentration of ROS, TNF-α, IL-1ß and IL-6 as well as expression of NADPH oxidase subunits gp91phox and p47phox in mice hippocampal tissues were assessed, and microglial activation were evaluated by Iba-1 immunohistochemical staining. Results of NOR test and MWM test revealed that oAß injection could remarkably impair learning and memory function in AD mice, and matrine administration could significantly ameliorate the impairment. ROS, TNF-α, IL-1ß and IL-6 levels increased after oAß injection, while matrine could significantly reduce the concentrations of these inflammatory factors. OAß induced protein expression of NADPH oxidase subunits gp91phox and p47phox were also significantly reduced by matrine. Iba-1 immunohistochemistry results showed less activated microglia in matrine-treated mice brain. These results indicate that matrine could ameliorate learning and memory impairment and neuroinflammation induced by oAß injection. These effects were found to be mediated through inhibition of microglial activation and NADPH oxidase expression in hippocampal tissue. The results suggest that matrine may be a valuable natural compound with therapeutic potential against AD.

The apple U-box E3 ubiquitin ligase MdPUB29 contributes to activate plant immune response to the fungal pathogen Botryosphaeria dothidea.

MAIN CONCLUSION: MdPUB29 is a positive regulator of the defense response to the fungal pathogen Botryosphaeria dothidea possibly by directly regulating the salicylic acid (SA) content as well as SA synthesis-related and signaling-related gene transcription. In plants, ubiquitin E3 ligases containing a U-box domain (PUBs, Plant U-box E3 ubiquitin ligase) have been identified as key regulators of fundamental cellular processes, such as cellular growth, development, and apoptosis, as well as biotic and abiotic stress responses. However, the function of PUBs in apple ring rot remains elusive. Here, we isolated the U-box E3 ligase MdPUB29 from the apple cultivar 'Royal Gala' and characterized its function in plant pathogen defense against Botryosphaeria dothidea. qRT-PCR showed that the expression of MdPUB29 was significantly induced in apple fruits after B. dothidea infection. Overexpression of the MdPUB29 gene in apple calli increased the resistance to B. dothidea infection. In contrast, silencing MdPUB29 in apple calli resulted in reduced resistance. Ectopic expression of MdPUB29 in Arabidopsis also exhibited enhanced resistance to B. dothidea infection compared to that of the wild-type (Col) control. In addition, it was found that the increase of plant pathogen defense was correlated with the increased salicylic acid (SA) content, as well as SA synthesis-related and signaling-related gene transcription in comparison to the wild type. We elucidated the mechanism by which MdPUB29 elevates plant pathogen defense against B. dothidea possibly by regulating the SA pathway.

The regulatory module MdPUB29-MdbHLH3 connects ethylene biosynthesis with fruit quality in apple.

The plant hormone ethylene is critical for climacteric fruit ripening, while glucose and anthocyanins determine the fruit quality of climacteric fruits such as apple. Understanding the exact molecular mechanism for this process is important for elucidating the interconnection of ethylene and fruit quality. Overexpression of apple MdbHLH3 gene, an anthocyanin-related basic helix-loop-helix transcription factor (bHLH TF) gene, promotes ethylene production, and transgenic apple plantlets and trees exhibit ethylene-related root developmental abnormalities, premature leaf senescence, and fruit ripening. Biochemical analyses demonstrate that MdbHLH3 binds to the promoters of three genes that are involved in ethylene biosynthesis, including MdACO1, MdACS1, and MdACS5A, activating their transcriptional expression, thereby promoting ethylene biosynthesis. High glucose-inhibited U-box-type E3 ubiquitin ligase MdPUB29, the ortholog of Arabidopsis AtPUB29 in apple, influences the expression of ethylene biosynthetic genes and ethylene production by direct ubiquitination of the MdbHLH3 protein. Our findings provide new insights into the ubiquitination of MdbHLH3 by glucose-inhibited ubiquitin E3 ligase MdPUB29 in the regulation of ethylene biosynthesis as well as indicate that the regulatory module MdPUB29-MdbHLH3 connects ethylene biosynthesis with fruit quality in apple.

Echinacoside Alleviates Hypoxic-Ischemic Brain Injury in Neonatal Rat by Enhancing Antioxidant Capacity and Inhibiting Apoptosis.

Hypoxic-ischemic brain damage (HIBD) is a leading cause of death and disability in neonatal or perinatal all over the world, seriously affecting children, families and society. Unfortunately, only few satisfactory therapeutic strategies have been developed. It has been demonstrated that Echinacoside (ECH), the major active component of Cistanches Herba, exerts many beneficial effects, including antioxidative, anti-apoptosis, and neuroprotective in the traditional medical practice in China. Previous research has demonstrated that ECH plays a protective effect on ischemic brain injury. This study aimed to investigate whether ECH provides neuroprotection against HIBD in neonatal rats. We subjected 120 seven-day-old Sprague-Dawley rats to cerebral hypoxia-ischemia (HI) and randomly divided into the following groups: sham group, HI group and ECH (40, 80 and 160 mg/kg, intraperitoneal) post-administration group. After 48 h of HI, 2,3,5-Triphenyltetrazolium chloride, Hematoxylin-Eosin and Nissl staining were conducted to evaluate the extent of brain damage. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities, total antioxidant capacity (T-AOC), and malondialdehyde (MDA) production were assessed to determine the antioxidant capacity of ECH. TUNEL staining and Western blot analysis was performed to respectively estimate the extent of brain cell apoptosis and the expression level of the apoptosis-related proteins caspase-3, Bax, and Bcl-2. Results showed that ECH remarkably reduced the brain infarct volume and ameliorated the histopathological damage to neurons. ECH post-administration helped recovering the antioxidant enzyme activities and decreasing the MDA production. Furthermore, ECH treatment suppressed neuronal apoptosis in the rats with HIBD was by reduced TUNEL-positive neurons, the caspase-3 levels and increased the Bcl-2/Bax ratio. These results suggested that ECH treatment was beneficial to reducing neuronal damage by attenuating oxidative stress and apoptosis in the brain under HIBD.

Analgesic Effect of Nitrous Oxide/Oxygen Mixture for Traumatic Pain in the Emergency Department: A Randomized, Double-Blind Study.

BACKGROUND: Acute pain is the most common complaint in Emergency Department (ED) admissions, and options for analgesia are limited. Nitrous oxide/oxygen possesses many properties showing it may be an ideal analgesic in the ED. OBJECTIVES: The aim of this study is to evaluate the safety and analgesic effect of the fixed nitrous oxide/oxygen mixture for trauma patients in the ED. METHODS: We enrolled 60 patients in this double-blind, randomized study. The treatment group received conventional pain treatment plus a mixture of 65% nitrous oxide/oxygen. The control group received the conventional pain treatment plus oxygen. Primary outcome was the reduction in pain intensity at 5 and 15 min after the start of intervention. Secondary outcomes include adverse events, physiological parameters, and satisfaction from both patients and health care professionals. RESULTS: Initial pain scores for the nitrous oxide/oxygen group (6.0 [5.0-8.0]) and the oxygen group (6.75 [5.0-9.0]) were comparable (p = 0.57). The mean numerical rating scale scores at 5 min were 3.4 ± 1.8 and 7.0 ± 1.8 for nitrous oxide/oxygen and oxygen, respectively (p < 0.01). The mean pain intensity at 15 min in the treatment group was 3.0 ± 1.9, compared with 6.3 ± 2.2 in the control group (p < 0.01). Both patients' (8.0 [7.0-9.0] vs. 4.0 [2.0-6.0], p < 0.01) and physicians' (8.5 [8.0-9.0] vs. 4.0 [3.0-6.0], p < 0.01) satisfaction scores in the treatment group were significantly higher than the oxygen group. No serious adverse events were observed. CONCLUSIONS: This study gives supporting evidence for the safety and effectiveness of using self-administered nitrous oxide/oxygen mixture in the ED for moderate-to-severe traumatic pain.

Flowers of Astragalus membranaceus var. mongholicus as a Novel High Potential By-Product: Phytochemical Characterization and Antioxidant Activity.

The root of Astragalus membranaceus var. mongholicus is one of the most popular herbal medicines worldwide. In order to increase the yield of underground roots of A. membranaceus var. mongholicus, its flowers (AMF) have often been removed in their flowering stage, which produces the flowers as waste being discarded. To explore its phytochemicals and potential value for utilization, the antioxidant activities of extracts from AMF were evaluated by a free radical scavenging assay and reducing power assay. The total phenols and flavonoids, as well as the individual compounds, in different extracts of AMF were also investigated. The results showed that the extract ME obtained from AMF through macroporous resins separation exhibited strong antioxidant activities, which were close to those of positive control BHT. ME was rich in phenolic acids and flavonoids, and the contents reached 108.42 mg gallic acid equivalents/g and 265.70 mg rutin equivalents/g, respectively. A total of 31 compounds, including four phenolic acids, nineteen flavonoids, three isoflavones, two pterocarpans, and three saponins, were identified using UPLC-QTOF-MS in ME. Quantitative analysis of sixteen components in the extracts of AMF showed that flavonoids were the predominant constituents, especially for the compounds of hyperoside, rutin, and isorhamnetin-3-O-ß-d-glucoside.

The R2R3-MYB transcription factor MdMYB73 is involved in malate accumulation and vacuolar acidification in apple.

Malate, the predominant organic acid in many fruits, is a crucial component of the organoleptic quality of fruit, including taste and flavor. The genetic and environmental mechanisms affecting malate metabolism in fruit cells have been studied extensively. However, the transcriptional regulation of malate-metabolizing enzymes and vacuolar transporters remains poorly understood. Our previous studies demonstrated that MdMYB1 modulates anthocyanin accumulation and vacuolar acidification by directly activating vacuolar transporters, including MdVHA-B1, MdVHA-E, MdVHP1 and MdtDT. Interestingly, we isolated and identified a MYB transcription factor, MdMYB73, a distant relative of MdMYB1 in this study. It was subsequently found that MdMYB73 protein bound directly to the promoters of MdALMT9 (aluminum-activated malate transporter 9), MdVHA-A (vacuolar ATPase subunit A) and MdVHP1 (vacuolar pyrophosphatase 1), transcriptionally activating their expression and thereby enhancing their activities. Analyses of transgenic apple calli demonstrated that MdMYB73 influenced malate accumulation and vacuolar pH. Furthermore, MdCIbHLH1 interacted with MdMYB73 and enhanced its activity upon downstream target genes. These findings help to elucidate how MdMYB73 directly modulates the vacuolar transport system to affect malate accumulation and vacuolar pH in apple.

Ectopic expression of the apple nucleus-encoded thylakoid protein MdY3IP1 triggers early-flowering and enhanced salt-tolerance in Arabidopsis thaliana.

BACKGROUND: The roles in photosystem I (PSI) assembly of the nucleus-encoded thylakoid protein Y3IP1 who interacts with the plastid-encoded Ycf3 protein that has been well-characterized in plants. However, its function and potential mechanisms in other aspects remain poorly understood. RESULTS: We identified the apple MdY3IP1 gene, which encodes a protein highly homologous to the Arabidopsis Y3IP1 (AtY3IP1). Ectopic expression of MdY3IP1 triggered early-flowering and enhanced salt tolerance in Arabidopsis plants. MdY3IP1 controlled floral transition by accelerating sugar metabolism process in plant cells, thereby influencing the expression of flowering-associated genes. The increase in salt stress tolerance in MdY3IP1-expressing plants correlated with reduced reactive oxygen species (ROS) accumulation, and an increase in lateral root development by regulating both auxin biosynthesis and transport, as followed by enhancement of salt tolerance in Arabidopsis. Overall, these findings provide new evidences for additional functions of Y3IP1-like proteins and their underlying mechanisms of which Y3IP1 confers early-flowering and salt tolerance phenotypes in plants. CONCLUSIONS: These observations suggest that plant growth and stress resistance can be affected by the regulation of the MdY3IP1 gene. Further molecular and genetic approaches will accelerate our knowledge of MdY3IP1 functions in PSI complex formation and plants stress resistance, and inform strategies for creating transgenic crop varieties with early maturity and high-resistant to adverse environmental conditions.