ABA-mediated regulation of rice grain quality and seed dormancy via the NF-YB1-SLRL2-bHLH144 Module.

Abscisic acid (ABA) plays a crucial role in promoting plant stress resistance and seed dormancy. However, how ABA regulates rice quality remains unclear. This study identifies a key transcription factor SLR1-like2 (SLRL2), which mediates the ABA-regulated amylose content (AC) of rice. Mechanistically, SLRL2 interacts with NF-YB1 to co-regulate Wx, a determinant of AC and rice quality. In contrast to SLR1, SLRL2 is ABA inducible but insensitive to GA. In addition, SLRL2 exhibits DNA-binding activity and directly regulates the expression of Wx, bHLH144 and MFT2. SLRL2 competes with NF-YC12 for interaction with NF-YB1. NF-YB1 also directly represses SLRL2 transcription. Genetic validation supports that SLRL2 functions downstream of NF-YB1 and bHLH144 in regulating rice AC. Thus, an NF-YB1-SLRL2-bHLH144 regulatory module is successfully revealed. Furthermore, SLRL2 regulates rice dormancy by modulating the expression of MFT2. In conclusion, this study revealed an ABA-responsive regulatory cascade that functions in both rice quality and seed dormancy.

Itaconate protects ferroptotic neurons by alkylating GPx4 post stroke.

Neuronal ferroptosis plays a key role in neurologic deficits post intracerebral hemorrhage (ICH). However, the endogenous regulation of rescuing ferroptotic neurons is largely unexplored. Here, we analyzed the integrated alteration of metabolomic landscape after ICH using LC-MS and MALDI-TOF/TOF MS, and demonstrated that aconitate decarboxylase 1 (Irg1) and its product itaconate, a derivative of the tricarboxylic acid cycle, were protectively upregulated. Deficiency of Irg1 or depletion of neuronal Irg1 in striatal neurons was shown to exaggerate neuronal loss and behavioral dysfunction in an ICH mouse model using transgenic mice. Administration of 4-Octyl itaconate (4-OI), a cell-permeable itaconate derivative, and neuronal Irg1 overexpression protected neurons in vivo. In addition, itaconate inhibited ferroptosis in cortical neurons derived from mouse and human induced pluripotent stem cells in vitro. Mechanistically, we demonstrated that itaconate alkylated glutathione peroxidase 4 (GPx4) on its cysteine 66 and the modification allosterically enhanced GPx4's enzymatic activity by using a bioorthogonal probe, itaconate-alkyne (ITalk), and a GPx4 activity assay using phosphatidylcholine hydroperoxide. Altogether, our research suggested that Irg1/itaconate-GPx4 axis may be a future therapeutic strategy for protecting neurons from ferroptosis post ICH.

Simultaneous production of biosurfactant and extracellular unspecific peroxygenases by Moesziomyces aphidis XM01 enables an efficient strategy for crude oil degradation.

Crude oil is a hazardous pollutant that poses significant and lasting harm to human health and ecosystems. In this study, Moesziomyces aphidis XM01, a biosurfactant mannosylerythritol lipids (MELs)-producing yeast, was utilized for crude oil degradation. Unlike most microorganisms relying on cytochrome P450, XM01 employed two extracellular unspecific peroxygenases, MaUPO.1 and MaUPO.2, with preference for polycyclic aromatic hydrocarbons (PAHs) and n-alkanes respectively, thus facilitating efficient crude oil degradation. The MELs produced by XM01 exhibited a significant emulsification activity of 65.9% for crude oil and were consequently supplemented in an "exogenous MELs addition" strategy to boost crude oil degradation, resulting in an optimal degradation ratio of 72.3%. Furthermore, a new and simple "pre-MELs production" strategy was implemented, achieving a maximum degradation ratio of 95.9%. During this process, the synergistic up-regulation of MaUPO.1, MaUPO.1 and the key MELs synthesis genes contributed to the efficient degradation of crude oil. Additionally, the phylogenetic and geographic distribution analysis of MaUPO.1 and MaUPO.1 revealed their wide occurrence among fungi in Basidiomycota and Ascomycota, with high transcription levels across global ocean, highlighting their important role in biodegradation of crude oil. In conclusion, M. aphidis XM01 emerges as a novel yeast for efficient and eco-friendly crude oil degradation.

Structural insights into ion selectivity and transport mechanisms of Oryza sativa HKT2;1 and HKT2;2/1 transporters.

Plant high-affinity K+ transporters (HKTs) play a pivotal role in maintaining the balance of Na+ and K+ ions in plants, thereby influencing plant growth under K+-depleted conditions and enhancing tolerance to salinity stress. Here we report the cryo-electron microscopy structures of Oryza sativa HKT2;1 and HKT2;2/1 at overall resolutions of 2.5 Å and 2.3 Å, respectively. Both transporters adopt a dimeric assembly, with each protomer enclosing an ion permeation pathway. Comparison between the selectivity filters of the two transporters reveals the critical roles of Ser88/Gly88 and Val243/Gly243 in determining ion selectivity. A constriction site along the ion permeation pathway is identified, consisting of Glu114, Asn273, Pro392, Pro393, Arg525, Lys517 and the carboxy-terminal Trp530 from the neighbouring protomer. The linker between domains II and III adopts a stable loop structure oriented towards the constriction site, potentially participating in the gating process. Electrophysiological recordings, yeast complementation assays and molecular dynamics simulations corroborate the functional importance of these structural features. Our findings provide crucial insights into the ion selectivity and transport mechanisms of plant HKTs, offering valuable structural templates for developing new salinity-tolerant cultivars and strategies to increase crop yields.

Optimizing early neurological deterioration prediction in acute ischemic stroke patients following intravenous thrombolysis: a LASSO regression model approach.

Background: Acute ischemic stroke (AIS) remains a leading cause of disability and mortality globally among adults. Despite Intravenous Thrombolysis (IVT) with recombinant tissue plasminogen activator (rt-PA) emerging as the standard treatment for AIS, approximately 6-40% of patients undergoing IVT experience Early Neurological Deterioration (END), significantly impacting treatment efficacy and patient prognosis. Objective: This study aimed to develop and validate a predictive model for END in AIS patients post rt-PA administration using the Least Absolute Shrinkage and Selection Operator (LASSO) regression approach. Methods: In this retrospective cohort study, data from 531 AIS patients treated with intravenous alteplase across two hospitals were analyzed. LASSO regression was employed to identify significant predictors of END, leading to the construction of a multivariate predictive model. Results: Six key predictors significantly associated with END were identified through LASSO regression analysis: previous stroke history, Body Mass Index (BMI), age, Onset to Treatment Time (OTT), lymphocyte count, and glucose levels. A predictive nomogram incorporating these factors was developed, effectively estimating the probability of END post-IVT. The model demonstrated robust predictive performance, with an Area Under the Curve (AUC) of 0.867 in the training set and 0.880 in the validation set. Conclusion: The LASSO regression-based predictive model accurately identifies critical risk factors leading to END in AIS patients following IVT. This model facilitates timely identification of high-risk patients by clinicians, enabling more personalized treatment strategies and optimizing patient management and outcomes.

Adsorption of phosphate over a novel magnesium-loaded sludge-based biochar.

The production of sludge-based biochar to recover phosphorus (P) from wastewater and reuse the recovered phosphorus as agricultural fertilizer is a preferred process. This article mainly studied the removal of phosphate (PO4-P) from aqueous solution by synthesizing sludge-based biochar (MgSBC-0.1) from anaerobic fermentation sludge treated with magnesium (Mg)-loading-modification, and compared it with unmodified sludge-based biochar (SBC). The physicochemical properties, adsorption efficiency, and adsorption mechanism of MgSBC-0.1 were studied. The results showed that the surface area of MgSBC-0.1 synthesized increased by 5.57 times. The material surface contained MgO, Mg(OH)2, and CaO nanoparticles. MgSBC-0.1 can effectively remove phosphate in the initial solution pH range of 3.00-7.00, with a fitted maximum phosphorus adsorption capacity of 379.52 mg·g-1. The adsorption conforms to the pseudo second-order kinetics model and Langmuir isotherm adsorption curve. The characterization of the adsorbed composite material revealed the contribution of phosphorus crystal deposition and electrostatic attraction to phosphorus absorption.

Glycan-Imprinted Nanoparticle as Artificial Neutralizing Antibody for Efficient HIV-1 Recognition and Inhibition.

The HIV-1 envelope is a heavily glycosylated class 1 trimeric fusion protein responsible for viral entry into CD4+ immune cells. Developing neutralizing antibodies against the specific envelope glycans is an alternative method for antiviral therapies. This work presents the first-ever development and characterization of artificial neutralizing antibodies using molecular imprinting technology to recognize and bind to the envelope protein of HIV-1. The prepared envelope glycan-imprinted nanoparticles (GINPs) can successfully prevent HIV-1 from infecting target cells by shielding the glycans on the envelope protein. In vitro experiments showed that GINPs have strong affinity toward HIV-1 (Kd = 36.7 ± 2.2 nM) and possess high anti-interference and specificity. GINPs demonstrate broad inhibition activity against both tier 1 and tier 2 HIV-1 strains with a pM-level IC50 and exhibit a significant inhibitory effect on long-term viral replication by more than 95%. The strategy provides a promising method for the inhibition and therapy of HIV-1 infection.

Bioavailability and Metabolism of Bioactive Peptide IRW with Angiotensin-Converting Enzyme 2 (ACE2) Upregulatory Activity in Spontaneously Hypertensive Rats.

Peptide IRW is the first food-derived angiotensin-converting enzyme 2 (ACE2) upregulator. This study aimed to investigate the pharmacokinetic characteristics of IRW and identify the metabolites contributing to its antihypertensive activity in spontaneously hypertensive rats (SHRs). Rats were administered 100 mg of IRW/kg of the body weight via an intragastric or intravenous route. The bioavailability (F %) was determined to be 11.7%, and the half-lives were 7.9 ± 0.5 and 28.5 ± 6.8 min for gavage and injection, respectively. Interestingly, significant blood pressure reduction was not observed until 1.5 h post oral administration, or 2 h post injection, indicating that the peptide's metabolites are likely responsible for the blood pressure-lowering activity. Time-course metabolomics revealed a significant increase in the level of kynurenine, a tryptophan metabolite, in blood after IRW administration. Kynurenine increased the level of ACE2 in cells. Oral administration of tryptophan (W), but not dipeptide IR, lowered the blood pressure and upregulated aortic ACE2 in SHRs. Our study supports the key role of tryptophan and its metabolite, kynurenine, in IRW's blood pressure-lowering effects.

Structurally diverse oxygen-containing aromatic compounds with anti-inflammatory activity from Aspergillus sp. LY-1-2.

Three isocoumarins, ascoisocoumarin A (1), embeurekol (2), and sclerotinin A (3), and five biosynthetically related derivatives, ascospinols A-C (4, 6, and 7), and talaflavuols C and B (5 and 8), together with twelve polyketides or terpenes (9-20) were isolated from the fungus Aspergillus sp. LY-1-2 inhabited in a sample of Cordyceps sp. Most of them belong to the family of oxygen-containing aromatic compounds and compounds 1, 4, 6, and 7 are previously undescribed compounds. Their planar structures were established by a combined spectroscopic analysis of HRESIMS and NMR, and their stereochemistry was determined by 13C NMR calculations with sorted training set (STS) protocol analysis, and ECD calculations. New compounds 1 and 6 displayed potential anti-inflammatory effects in lipopolysaccharide (LPS)-induced BV2 microglia cells.

Stigmasterol: Remodeling gut microbiota and suppressing tumor growth through Treg and CD8+ T cells in hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC), the most primary malignant liver tumor and is ranked as the fifth most common malignancy worldwide. Despite various therapeutic approaches being used in clinical practice, the overall effectiveness remains insufficient. Stigmasterol, a compound known for its anti-tumor properties and ability to induce apoptosis in tumor cells, has been found to influenced the composition of the intestinal microbiota. However, the mechanism through which stigmasterol influences the intestinal microbial-host crosstalk in HCC remains elusive. PURPOSE: This study was to investigate whether stigmasterol can remodel gut microbiota, and suppress tumor volume by regulating Treg and IFN-γ+ CD8+ cell in the host with HCC. METHOD: Stigmasterol (at dosages of 0, 50, 100, or 200 mg/kg) was orally administered to Balb/c mice with subcutaneous tumor once every 2 days for 3 weeks. RESULTS: We first found that tumors volume in the group treated with 100 mg/kg stigmasterol were significantly decreased compared with those in the control group (P < 0.05), which exhibited a similar effect as the sorafenib treatment in mice with HCC. This resulted in a significant upregulation of Caspase3, Bax, and P53 expressions, as well as a decrease in Cyclin D1 expression, ultimately leading to a reduction in tumor volume. Additionally, stigmasterol can alter the α and ß diversity of the intestinal flora and significantly increase the abundance of Lactobacillus_johnsonii, Lactobacillus_murinus, and Lactobacillus_reuteri (P<0.05), which can lead to a decrease in the ratio of regulatory T cells (Tregs) to CD8+ T cells in the intestinal tract and tumor tissue, and consequently enhance immune response in the tumor microenvironment (TME) in the host with HCC. CONCLUSION: In this study, we initially utilized different dosages of stigmasterol to intervene in mice with HCC and confirmed its inhibitory effects on tumor growth in vivo, and discovered that stigmasterol affected Lactobacillus johnsonii, Lactobacillus murinus, and Lactobacillus reuteri, resulting in an increased proportion of IFN-γ+ CD8+ T cells and Treg cells in both the intestinal mucosa and tumor tissues, and ultimately leading to increased levels of apoptotic proteins and the subsequent death of tumor cells, which shed light on the effect of stigmasterol on host intestinal tissue and intratumoral immune cells by reshaping the intestinal microbiota, and provide a theoretical foundation for the potential clinical application of stigmasterol in the treatment of HCC.

Design of Vif-Derived Peptide Inhibitors with Anti-HIV-1 Activity by Interrupting Vif-CBFß Interaction.

One of the major functions of the accessory protein Vif of human immunodeficiency virus type 1 (HIV-1) is to induce the degradation of APOBEC3 (A3) family proteins by recruiting a Cullin5-ElonginB/C-CBFß E3 ubiquitin ligase complex to facilitate viral replication. Therefore, the interactions between Vif and the E3 complex proteins are promising targets for the development of novel anti-HIV-1 drugs. Here, peptides are designed for the Vif-CBFß interaction based on the sequences of Vif mutants with higher affinity for CBFß screened by a yeast surface display platform. We identified two peptides, VMP-63 and VMP-108, that could reduce the infectivity of HIV-1 produced from A3G-positive cells with IC50 values of 49.4 µM and 55.1 µM, respectively. They protected intracellular A3G from Vif-mediated degradation in HEK293T cells, consequently increasing A3G encapsulation into the progeny virions. The peptides could rapidly enter cells after addition to HEK293T cells and competitively inhibit the binding of Vif to CBFß. Homology modeling analysis demonstrated the binding advantages of VMP-63 and VMP-108 with CBFß over their corresponding wild-type peptides. However, only VMP-108 effectively restricted long-term HIV-1 replication and protected A3 functions in non-permissive T lymphocytes. Our findings suggest that competitive Vif-derived peptides targeting the Vif-CBFß interaction are promising for the development of novel therapeutic strategies for acquired immune deficiency syndrome.

Comparison of three-dimensional heads-up system versus traditional microscopic system in medical education for vitreoretinal surgeries: a prospective study.

BACKGROUND: To compare the value and efficiency of the three-dimensional (3D) heads-up surgical system and traditional microscopic (TM) system in teaching and learning vitreoretinal surgeries. METHODS: Twenty ophthalmologists and scrub nurses were recruited as teachers, and 45 junior ophthalmology residents and trainee doctors, trainee nurses, and medical students were recruited as observers. Each teacher and observer were assigned to both a 3D-assisted and TM-assisted vitreoretinal surgery and then asked to complete satisfaction questionnaires for both surgical systems at the end of each surgery. RESULTS: The 3D heads-up surgical system was rated significantly higher in most of the subscales and overall satisfaction score by both teachers and observers (P < 0.05). However, ratings for instrument adjustment were significantly higher in the TM group compared to the 3D group for junior ophthalmology residents and trainee doctors (6.1 ± 1.7 vs. 8.8 ± 1.1, P < 0.001). CONCLUSIONS: The 3D heads-up surgical system has great didactical value in the medical education of vitreoretinal surgeries, but it is important to consider the specific needs of different learners when choosing between the two systems. TRIAL REGISTRATION: Not applicable.

Iron-containing nanominerals for sustainable phosphate management: A comprehensive review and future perspectives.

Adsorption, which is a quick and effective method for phosphate management, can effectively address the crisis of phosphorus mineral resources and control eutrophication. Phosphate management systems typically use iron-containing nanominerals (ICNs) with large surface areas and high activity, as well as modified ICNs (mICNs). This paper comprehensively reviews phosphate management by ICNs and mICNs in different water environments. mICNs have a higher affinity for phosphates than ICNs. Phosphate adsorption on ICNs and mICNs occurs through mechanisms such as surface complexation, surface precipitation, electrostatic ligand exchange, and electrostatic attraction. Ionic strength influences phosphate adsorption by changing the surface potential and isoelectric point of ICNs and mICNs. Anions exhibit inhibitory effects on ICNs and mICNs in phosphate adsorption, while cations display a promoting effect. More importantly, high concentrations and molecular weights of natural organic matter can inhibit phosphate adsorption by ICNs and mICNs. Sodium hydroxide has high regeneration capability for ICNs and mICNs. Compared to ICNs with high crystallinity, those with low crystallinity are less likely to desorb. ICNs and mICNs can effectively manage municipal wastewater, eutrophic seawater, and eutrophic lakes. Adsorption of ICNs and mICNs saturated with phosphate can be used as fertilizers in agricultural production. Notably, mICNs and ICNs have positive and negative effects on microorganisms and aquatic organisms in soil. Finally, this study introduces the following: trends and prospects of machine learning-guided mICN design, novel methods for modified ICNs, mICN regeneration, development of mICNs with high adsorption capacity and selectivity for phosphate, investigation of competing ions in different water environments by mICNs, and trends and prospects of in-depth research on the adsorption mechanism of phosphate by weakly crystalline ferrihydrite. This comprehensive review can provide novel insights into the research on high-performance mICNs for phosphate management in the future.

MdPRX34L, a class III peroxidase gene, activates the immune response in apple to the fungal pathogen Botryosphaeria dothidea.

MAIN CONCLUSION: MdPRX34L enhanced resistance to Botryosphaeria dothidea by increasing salicylic acid (SA) and abscisic acid (ABA) content as well as the expression of related defense genes. The class III peroxidase (PRX) multigene family is involved in complex biological processes. However, the molecular mechanism of PRXs in the pathogen defense of plants against Botryosphaeria dothidea (B. dothidea) remains unclear. Here, we cloned the PRX gene MdPRX34L, which was identified as a positive regulator of the defense response to B. dothidea, from the apple cultivar 'Royal Gala.' Overexpression of MdPRX34L in apple calli decreased sensitivity to salicylic acid (SA) and abscisic acid（ABA). Subsequently, overexpression of MdPRX34L in apple calli increased resistance to B. dothidea infection. In addition, SA contents and the expression levels of genes related to SA synthesis and signaling in apple calli overexpressing MdPRX34L were higher than those in the control after inoculation, suggesting that MdPRX34L enhances resistance to B. dothidea via the SA pathway. Interestingly, infections in apple calli by B. dothidea caused an increase in endogenous levels of ABA followed by induction of ABA-related genes expression. These findings suggest a potential mechanism by which MdPRX34L enhances plant-pathogen defense against B. dothidea by regulating the SA and ABA pathways.

Unveiling Mechanistic Insights and Photocatalytic Advancements in Intramolecular Photo-(3 + 2)-Cycloaddition: A Comparative Assessment of Two Paradigmatic Single-Electron-Transfer Models.

The synthesis of 1-aminonorbornane (1-aminoNB), a potential aniline bioisostere, through photochemistry or photoredox catalysis signifies a remarkable breakthrough with implications in organic chemistry, pharmaceutical chemistry, and sustainable chemistry. However, an understanding of the underlying mechanisms involved in these reactions remains limited and ambiguous. Herein, we employ high-precision CASPT2//CASSCF calculations to elucidate the intricate mechanisms regulating the intramolecular photo-(3 + 2)-cycloaddition reactions for the synthesis of 1-aminoNB in the presence or absence of the Ir-complex-based photocatalyst. Our investigations delve into radical cascades, stereoselectivity, particularly single-electron-transfer (SET) events, etc. Furthermore, we innovatively introduce and compare two SET models integrating Marcus electron-transfer theory and transition-state theory. These models combined with kinetic data contribute to recognizing the critical control factors in diverse photocatalysis, thereby guiding the design and manipulation of photoredox catalysis as well as the improvement and modification of photocatalysts.

Central and Peripheral Changes in Retinal Vein Occlusion and Fellow Eyes in Ultra-Widefield Optical Coherence Tomography Angiography.

Purpose: To explore the central and peripheral retinal and choroidal changes in retinal vein occlusion (RVO) and fellow eyes using ultra-widefield swept-source optical coherence tomography angiography (UWF-SS-OCTA). Methods: Fifteen ischemic central RVO (CRVO), 15 branch RVO (BRVO), and 15 age-matched healthy controls were prospectively recruited. Retinal and choroidal parameters, including retinal vessel flow density (VFD) and vessel linear density (VLD), choroidal vascularity volume (CVV), choroidal vascularity index (CVI), and VFD in the large and medium choroidal vessels (LMCV-VFD), were measured in the central and peripheral regions of the 24 × 20-mm UWF-SS-OCTA images. Results: Ischemic CRVO and BRVO eyes showed increased foveal avascular zone area, perimeter, and acircularity index (AI) compared to their fellow eyes and healthy control eyes, and RVO fellow eyes also had larger AI values than controls (P < 0.05). For ischemic CRVO and BRVO eyes versus control eyes, VFD, VLD, CVV, CVI, and LMCV-VFD decreased, but retinal thickness and volume in the superficial capillary plexus, deep capillary plexus, and whole retina increased (P < 0.05). Moreover, RVO fellow eyes also showed significantly decreased retinal VFD, LMCV-VFD, and CVI, as well as increased retinal thickness and volume, compared with control eyes (P < 0.05). Alterations were not consistent throughout the retina, as they involved only the peripheral or central regions in some cases. Conclusions: The affected and unaffected fellow eyes of RVO patients both demonstrated central and/or peripheral structural and vascular alterations in the retina and choroid. Because UWF-SS-OCTA enables visualization and evaluation of the vasculature outside the posterior pole, it presents a promising approach to more fully characterize vascular alterations in RVO.

The XCL1-Mediated DNA Vaccine Targeting Type 1 Conventional Dendritic Cells Combined with Gemcitabine and Anti-PD1 Antibody Induces Potent Antitumor Immunity in a Mouse Lung Cancer Model.

With the advent of cancer immunotherapy, there is a growing interest in vaccine development as a means to activate the cellular immune system against cancer. Despite the promise of DNA vaccines in this regard, their effectiveness is hindered by poor immunogenicity, leading to modest therapeutic outcomes across various cancers. The role of Type 1 conventional dendritic cells (cDC1), capable of cross-presenting vaccine antigens to activate CD8+T cells, emerges as crucial for the antitumor function of DNA vaccines. To address the limitations of DNA vaccines, a promising approach involves targeting antigens to cDC1 through the fusion of XCL1, a ligand specific to the receptor XCR1 on the surface of cDC1. Here, female C57BL/6 mice were selected for tumor inoculation and immunotherapy. Additionally, recognizing the complexity of cancer, this study explored the use of combination therapies, particularly the combination of cDC1-targeted DNA vaccine with the chemotherapy drug Gemcitabine (Gem) and the anti-PD1 antibody in a mouse lung cancer model. The study's findings indicate that fusion antigens with XCL1 effectively enhance both the immunogenicity and antitumor effects of DNA vaccines. Moreover, the combination of the cDC1-targeted DNA vaccine with Gemcitabine and anti-PD1 antibody in the mouse lung cancer model demonstrates an improved antitumor effect, leading to the prolonged survival of mice. In conclusion, this research provides important support for the clinical investigation of cDC1-targeting DNA vaccines in combination with other therapies.

Beyond Spirometry: Linking Wasted Ventilation to Exertional Dyspnea in the Initial Stages of COPD.

Exertional dyspnea, a key complaint of patients with chronic obstructive pulmonary disease (COPD), ultimately reflects an increased inspiratory neural drive to breathe. In non-hypoxemic patients with largely preserved lung mechanics - as those in the initial stages of the disease - the heightened inspiratory neural drive is strongly associated with an exaggerated ventilatory response to metabolic demand. Several lines of evidence indicate that the so-called excess ventilation (high ventilation-CO2 output relationship) primarily reflects poor gas exchange efficiency, namely increased physiological dead space. Pulmonary function tests estimating the extension of the wasted ventilation and selected cardiopulmonary exercise testing variables can, therefore, shed unique light on the genesis of patients' out-of-proportion dyspnea. After a succinct overview of the basis of gas exchange efficiency in health and inefficiency in COPD, we discuss how wasted ventilation translates into exertional dyspnea in individual patients. We then outline what is currently known about the structural basis of wasted ventilation in "minor/trivial" COPD vis-à-vis the contribution of emphysema versus a potential impairment in lung perfusion across non-emphysematous lung. After summarizing some unanswered questions on the field, we propose that functional imaging be amalgamated with pulmonary function tests beyond spirometry to improve our understanding of this deeply neglected cause of exertional dyspnea. Advances in the field will depend on our ability to develop robust platforms for deeply phenotyping (structurally and functionally), the dyspneic patients showing unordinary high wasted ventilation despite relatively preserved FEV1.