Contributions To Physiology Research Articles

A cell wall–localized cytokinin/purine riboside nucleosidase is involved in apoplastic cytokinin metabolism in Oryza sativa

In the final step of cytokinin biosynthesis, the main pathway is the elimination of a ribose-phosphate moiety from the cytokinin nucleotide precursor by phosphoribohydrolase, an enzyme encoded by a gene named LONELY GUY (LOG). This reaction accounts for most of the cytokinin supply needed for regulating plant growth and development. In contrast, the LOG-independent pathway, in which dephosphorylation and deribosylation sequentially occur, is also thought to play a role in cytokinin biosynthesis, but the gene entity and physiological contribution have been elusive. In this study, we profiled the phytohormone content of chromosome segment substitution lines of Oryza sativa and searched for genes affecting the endogenous levels of cytokinin ribosides by quantitative trait loci analysis. Our approach identified a gene encoding an enzyme that catalyzes the deribosylation of cytokinin nucleoside precursors and other purine nucleosides. The cytokinin/purine riboside nucleosidase 1 (CPN1) we identified is a cell wall-localized protein. Loss-of-function mutations (cpn1) were created by inserting a Tos17-retrotransposon that altered the cytokinin composition in seedling shoots and leaf apoplastic fluid. The cpn1 mutation also abolished cytokinin riboside nucleosidase activity in leaf extracts and attenuated the trans-zeatin riboside-responsive expression of cytokinin marker genes. Grain yield of the mutants declined due to altered panicle morphology under field-grown conditions. These results suggest that the cell wall-localized LOG-independent cytokinin activating pathway catalyzed by CPN1 plays a role in cytokinin control of rice growth. Our finding broadens our spatial perspective of the cytokinin metabolic system.

New insights into the physiology and pathophysiology of the atypical sodium leak channel NALCN.

Cell excitability and its modulation by hormones and neurotransmitters involve the concerted action of a large repertoire of membrane proteins, especially ion channels. Unique complements of coexpressed ion channels are exquisitely balanced against each other in different excitable cell types, establishing distinct electrical properties that are tailored for diverse physiological contributions, and dysfunction of any component may induce a disease state. A crucial parameter controlling cell excitability is the resting membrane potential (RMP) set by extra- and intracellular concentrations of ions, mainly Na+, K+, and Cl-, and their passive permeation across the cell membrane through leak ion channels. Indeed, dysregulation of RMP causes significant effects on cellular excitability. This review describes the molecular and physiological properties of the Na+ leak channel NALCN, which associates with its accessory subunits UNC-79, UNC-80, and NLF-1/FAM155 to conduct depolarizing background Na+ currents in various excitable cell types, especially neurons. Studies of animal models clearly demonstrate that NALCN contributes to fundamental physiological processes in the nervous system including the control of respiratory rhythm, circadian rhythm, sleep, and locomotor behavior. Furthermore, dysfunction of NALCN and its subunits is associated with severe pathological states in humans. The critical involvement of NALCN in physiology is now well established, but its study has been hampered by the lack of specific drugs that can block or agonize NALCN currents in vitro and in vivo. Molecular tools and animal models are now available to accelerate our understanding of how NALCN contributes to key physiological functions and the development of novel therapies for NALCN channelopathies.

Quantifying physiological contributions to nitrogen-induced yield variation in field-grown cotton

The effect of nitrogen (N) application rate on lint yield and yield components have been studied extensively in cotton. However, reports quantifying contributions to N-induced yield loss and the response of intra-boll yield components to N deficiency are far less common. The objectives of this study were to 1) determine the effect of N application rate on lint yield biomass and fiber quality in cotton, 2) assess the contributions of intercepted photosynthetically active radiation (IPAR), radiation use efficiency (RUE), and harvest index (HI) to N-induced yield loss in cotton, and 3) characterize the effect of N application rate on yield component responses in cotton. An experiment was conducted at a field site near Tifton, Georgia, USA during the 2021 and 2022 growing seasons. The experiment was arranged as a randomized complete block design with five replications and five nitrogen application rates (0, 44, 89, 134, and 179 kg N ha−1). The studied parameters were lint yield, IPAR, RUE, HI, fiber quality, yield components, and yield loss contributions. Lint yield was significantly affected by N application rate, with yields ranging from 1452 to 1848 kg ha−1. Similarly, total IPAR was 23% lower for the 0 kg N ha−1 treatment than the 134 kg N ha−1 treatment, and IPAR contributed significantly to yield loss, with a 427 kg ha−1 loss attributable to IPAR under N deficiency. RUE was 37% higher for the 179 kg N ha−1 treatment than the 0 kg N ha−1 treatment and contributed positively to yield in the highest N rates (179 kg N ha−1). However, yield improvements due to RUE were mitigated by low HI values in the highest N application rate. Boll density was the most strongly and positively associated yield component parameter with N-induced variability in lint yield, whereas lint percent and lint production per seed were negatively associated with lint yield. Among the three physiological yield-driving parameters, light interception by the canopy was the primary contributor to N-induced yield loss. Boll density was the primary yield component governing N-induced variation in lint yield. Increased N application rate promotes greater dry matter partitioning to seeds than fiber, resulting in more seeds per boll and lower lint percent, lint weight per seed, and individual fiber weight. The results contained here identify the most important functional traits for determining lint yield response to N application rate.

Acetylated α-Tubulin and α-Synuclein: Physiological Interplay and Contribution to α-Synuclein Oligomerization.

Emerging evidence supports that altered α-tubulin acetylation occurs in Parkinson's disease (PD), a neurodegenerative disorder characterized by the deposition of α-synuclein fibrillary aggregates within Lewy bodies and nigrostriatal neuron degeneration. Nevertheless, studies addressing the interplay between α-tubulin acetylation and α-synuclein are lacking. Here, we investigated the relationship between α-synuclein and microtubules in primary midbrain murine neurons and the substantia nigra of post-mortem human brains. Taking advantage of immunofluorescence and Proximity Ligation Assay (PLA), a method allowing us to visualize protein-protein interactions in situ, combined with confocal and super-resolution microscopy, we found that α-synuclein and acetylated α-tubulin colocalized and were in close proximity. Next, we employed an α-synuclein overexpressing cellular model and tested the role of α-tubulin acetylation in α-synuclein oligomer formation. We used the α-tubulin deacetylase HDAC6 inhibitor Tubacin to modulate α-tubulin acetylation, and we evaluated the presence of α-synuclein oligomers by PLA. We found that the increase in acetylated α-tubulin significantly induced α-synuclein oligomerization. In conclusion, we unraveled the link between acetylated α-tubulin and α-synuclein and demonstrated that α-tubulin acetylation could trigger the early step of α-synuclein aggregation. These data suggest that the proper regulation of α-tubulin acetylation might be considered a therapeutic strategy to take on PD.

P-785 Promising Reproductive Outcomes In Patients With Refractory Thin Endometrium After Autologous Bone Marrow Regenerative Cell Therapy (ABM-RCT) – A Case Series

Abstract Study question Does Autologous Bone Marrow Regenerative Cell Therapy (ABM-RCT) improve endometrial thickness and receptivity and restoration of fertility in refractory cases of thin endometrium? Summary answer Selective Autologous Bone Marrow Regenerative Cell Therapy from Seragen (ABM-RCT) improves endometrial thickness, pregnancy, and live birth rate in refractory cases of thin endometrium. What is known already The impaired endometrial function can limit implantation due to insufficient tissue regeneration. Clinical investigation has proved that stem cells existing in the endometrium might originate from bone marrow and provides evidence that bone marrow-derived cells have a non-hematopoietic physiologic contribution to decidual stroma and play a vital role in implantation and pregnancy maintenance and non-hematopoietic BMSCs are able to impact decidual molecular milieu and overcome implantation defects. ABM-RCT is the most commonly used cell therapy and its safety and efficacy are well-established and documented. This forms the basis for exploring and standardizing ABM-RCT in the management of refractory thin endometrium. Study design, size, duration Eleven patients (from age 29 to 43 with refractory thin endometrium resistant to conventional treatment modalities were recruited and obtained informed consent with detailed explanation that the therapy is still experimental and the risk of failure was given to the couple as part of gynec-oncology treatment. Five patients had asherman’s syndrome, two patients had genital tuberculosis, two patients had thin endometrium hypo-responsive/unresponsive to estrogens, with RIF and two patients underwent chemo and radiotherapy Participants/materials, setting, methods BM aspiration was performed under local anesthesia, from the iliac crest using a disposable BM aspiration needle (Jamshidi, 11 G) and collected in heparinized syringes. Progenitor cell enrichment was done by Seragen’s Selective Enrichment Protocol. Peripheral blood was collected to enrich growth factor concentrate. A 2.9mm Hysteroscope was used with an operating channel and egg pickup needle attached to it and cells were implanted in subendometrial zone in all four walls of the uterine cavity. Main results and the role of chance All patients presented to us with refractory thin endometrium in HRT cycle despite giving all possible medications. Hence the decision was taken for Autologous Bone Marrow Cell Concentrate Therapy.Post ABM-RCT, endometrial thickness showed increase 100% (11/11) of more than 8 mm in all cases on day of embryo transfer with average endometrial thickness improvement was 1.8 mm than previous cycles, with uniform triple layer pattern.10 out of 11 (91%) patients conceived after autologous stem cell injection. 9 Out of 10 (90%) patients conceived had delivered healthy babies and 1 patient (9%) had a miscarriage at 12th week of pregnancy. 1 patient did not conceive will be assessed for immunoprofiling and one more rejuvenation cycle. Limitations, reasons for caution Our study outcomes are consistent with several previous studies and the feasibility of treatment at an IVF setup and encouraging results. Well-planned study with more patients is warranted to evaluate safety, effectiveness, and cost of this modality before it becomes integrated in treatment of this frustrating condition during IVF procedures Wider implications of the findings Our results demonstrates selectively enriched ABM-RCT enhances endometrial thickness, tissue remodeling, uneventful gestation, improved pregnancy and live birth rate. Need for Surrogacy in Non-Responsive Thinendometrium May Be Re-Evaluated. Role of hematopoetic stem cell research and knowledge generated is representing reliable strategy in IVF that may be routinely used in clinicalpractice. Trial registration number Not applicable

Generation of a new Adar1p150-/- mouse demonstrates isoform-specific roles in embryonic development and adult homeostasis.

The RNA editing enzyme Adenosine deaminase acting on RNA 1 (ADAR1) is an essential regulator of innate immune activation by both cellular and viral dsRNA. Adenosine-to-Inosine (A-to-I) editing by ADAR1 modifies the sequence and structure of endogenous dsRNA and masks it from the cytoplasmic dsRNA sensor melanoma differentiation-associated protein 5 (MDA5), preventing innate immune activation. Loss of function mutations in ADAR are associated with rare autoinflammatory disorders including Aicardi-Goutieres Syndrome (AGS), defined by a constitutive systemic upregulation of type I interferon (IFN). The murine Adar gene encodes two protein isoforms with distinct functions: ADAR1p110 is constitutively expressed and localizes to the nucleus, whereas ADAR1p150 is primarily cytoplasmic and is inducible by IFN. Recent studies have demonstrated the critical requirement for ADAR1p150 to suppress innate immune activation by self dsRNAs, however, detailed in vivo characterization of the role of ADAR1p150 during development and in adult mice is lacking. We developed a new ADAR1p150-specific knockout mouse mutant based on a single nucleotide deletion that resulted in the loss of the ADARp150 protein without affecting ADAR1p110 expression. The Adar1p150-/- died embryonically at E11.5-E12.5 due to cell death in the fetal liver accompanied by an activated IFN response. Somatic loss of ADAR1p150 in adults was lethal and caused rapid hematopoietic failure, demonstrating an ongoing requirement for ADAR1p150 in vivo. The generation and characterization of this mouse model demonstrates the essential role of ADAR1p150 in vivo and provides a new tool for dissecting the functional differences between ADAR1 isoforms and their physiological contributions.

A unique small RNA, sSp_p4 governs nutrition stress response and plant-growth promoting traits in Azospirillum baldaniorum Sp245

Azospirillum baldaniorum Sp245 is a well-studied plant growth-promoting bacterium and has recently been shown to possess ∼468 small, non-coding RNAs (sRNA), many of which exhibited differential expression under nutrient stress conditions. Plant-microbe interactions are usually a part of a multigenic response involving a multitude of regulators such as sRNAs and their associated mRNA targets. We report the functional characterization of the sRNA, sSp_p4, from A. baldaniorum Sp245 and confirm its differential expression in nutrient stress conditions. sSp_p4 was overexpressed, knocked down and complemented to characterize its physiological functions and contribution to plant growth promoting (PGP) traits of strain Sp245. Expression analysis of sSp_p4 confirmed that it influenced and regulates PGP traits such as polyhydroxybutyrate synthesis, indole acetic acid production, and biofilm formation. sSp_p4 is likely involved in the regulation of essential bacterial biological networks in this agriculturally relevant bacterial strain and may impact plant growth.

Lipid mediators in the regulation of innate and adaptive immunity.

Lipid mediators in the regulation of innate and adaptive immunity.

Evaluation of Short Chain Fatty Acids (SCFAs) intestinal absorption, following digestion and fermentation of a novel medical device containing partially-hydrolyzed Guar gum plus simethicone

Irritable Bowel Syndrome (IBS) is a common disease characterized by alternate symptoms (diarrhea and constipation) and intestinal gas overproduction. A new medical device (Fibergone®), containing Partially Hydrolyzed Guar Gum (PHGG) and Simethicone (SM) has been proposed for managing patients with bowel disorders. PHGG acts also as a prebiotic so increasing the Short-Chain Fatty Acid (SCFA) production, useful for intestinal physiology. This in vitro study investigated the effects exerted by PHGG+SM on SCFA production and their intestinal absorption following in vitro digestive process and fermentation model. An in vitro model evaluated the digestive process and fermentation using simulated digestive fluids and a human intestinal epithelium in vitro model derived from based on intestinal adenocarcinoma Caco-2 cells (ATCC, HTB-37TM) and organized as a functional monolayer on Transwell® inserts. PHGG+SM was added in experiments and compared with a control (non-treated). SCFA production and absorption were assessed. Viability and barrier integrity of the intestinal epithelium model were also evaluated. PHGG+SM significantly (p<0.05) increased SCFAs content after fermentation, indicating that this medical device is effectively fermented at the large intestine level. However, in relation to SCFAs bioavailability, their absorption did not increase compared to the non-treated condition in the light of the physiological contribution of SCFAs resulting from the microflora. PHGG+SM did not affect intestinal epithelium apparent permeability (Papp) and viability. This in vitro study documented that partially hydrolyzed guar gum combined with simethicone significantly affects short-chain fatty acids production and consequently could be fruitfully employed in managing patients with intestinal disorders.

Best practice for wildlife gut microbiome research: A comprehensive review of methodology for 16S rRNA gene investigations.

Extensive research in well-studied animal models underscores the importance of commensal gastrointestinal (gut) microbes to animal physiology. Gut microbes have been shown to impact dietary digestion, mediate infection, and even modify behavior and cognition. Given the large physiological and pathophysiological contribution microbes provide their host, it is reasonable to assume that the vertebrate gut microbiome may also impact the fitness, health and ecology of wildlife. In accordance with this expectation, an increasing number of investigations have considered the role of the gut microbiome in wildlife ecology, health, and conservation. To help promote the development of this nascent field, we need to dissolve the technical barriers prohibitive to performing wildlife microbiome research. The present review discusses the 16S rRNA gene microbiome research landscape, clarifying best practices in microbiome data generation and analysis, with particular emphasis on unique situations that arise during wildlife investigations. Special consideration is given to topics relevant for microbiome wildlife research from sample collection to molecular techniques for data generation, to data analysis strategies. Our hope is that this article not only calls for greater integration of microbiome analyses into wildlife ecology and health studies but provides researchers with the technical framework needed to successfully conduct such investigations.

SsrA and SmpB have multifaceted physiological roles in the black rot pathogen Xanthomonas campestris pathovar campestris.

SsrA and SmpB are known to play important roles in translational quality control and are essential for virulence in many human and animal pathogenic bacteria. The physiological roles and contribution of SsrA and SmpB to plant pathogen are unclear. Here, we present evidence to show that ssrA and smpB are involved in pathogenesis of Xanthomonas campestris pathovar campestris, the cause of black rot diseases in crucifers. The ssrA and smpB mutants exhibited defects in bacterial attachment, cell motility, and extracellular enzyme activity. The mutation of ssrA and smpB also resulted in a reduction in temperature tolerance. These altered phenotypes of the ssrA and smpB mutants could be complemented to wild-type levels by the intact ssrA and smpB genes. This is the first demonstration of the roles of SsrA and SmpB in phytopathogen.

Photoablation at single cell resolution and its application in the Drosophila epidermis and peripheral nervous system.

Tissues contain diverse cell populations that, together, make up physiologically functional units. A remarkable example is the animal epidermis, where neuronal and non-neuronal cells intermingle to allow somatosensory perception. In the peripheral nervous system (PNS), the tight association between heterogenous cell types poses challenges when the structural and physiological contributions of neuronal and surrounding cells need to be dissected with suitable precision. When genetic tools for cell-specific, spatiotemporally controlled gene expression are not available, targeted cell ablation represents a considerable obstacle. Here, we describe an efficient method to overcome this limitation and demonstrate its application to the study of the differentiating Drosophila epidermis and PNS. This methodology relies on the use of near infrared (NIR) femtosecond (fs) laser pulses for ablation of the desired cells at the desired time. We show how to confine the photodamage to the targeted cell to induce its death, without harming neighbouring tissues or structures. We validated our approach in the Drosophila PNS by studying the responses of photo-ablated neurons, non-neuronal cells, and the surrounding epidermis. Diverse cellular behaviours including cell extrusion, cell rearrangements and cell shape changes can be monitored in vivo immediately after damage, as well as for several hours post-ablation with high optical resolution using confocal microscopy. This methodology provides a flexible tool to ablate individual cells with high precision and study morphological responses to cell loss in targeted areas or neighbouring structures. We anticipate that this protocol can be easily adapted to other model systems and tissues.

How can physiology best contribute to wildlife conservation in a warming world?

Global warming is now predicted to exceed 1.5°C by 2033 and 2°C by the end of the 21st century. This level of warming and the associated environmental variability are already increasing pressure on natural and human systems. Here we emphasize the role of physiology in the light of the latest assessment of climate warming by the Intergovernmental Panel on Climate Change. We describe how physiology can contribute to contemporary conservation programmes. We focus on thermal responses of animals, but we acknowledge that the impacts of climate change are much broader phylogenetically and environmentally. A physiological contribution would encompass environmental monitoring, coupled with measuring individual sensitivities to temperature change and upscaling these to ecosystem level. The latest version of the widely accepted Conservation Standards designed by the Conservation Measures Partnership includes several explicit climate change considerations. We argue that physiology has a unique role to play in addressing these considerations. Moreover, physiology can be incorporated by institutions and organizations that range from international bodies to national governments and to local communities, and in doing so, it brings a mechanistic approach to conservation and the management of biological resources.

Hindbrain insulin controls feeding behavior

ObjectivePancreatic insulin was discovered a century ago, and this discovery led to the first lifesaving treatment for diabetes. While still controversial, nearly one hundred published reports suggest that insulin is also produced in the brain, with most focusing on hypothalamic or cortical insulin-producing cells. However, specific function for insulin produced within the brain remains poorly understood. Here we identify insulin expression in the hindbrain's dorsal vagal complex (DVC), and determine the role of this source of insulin in feeding and metabolism, as well as its response to diet-induced obesity in mice. MethodsTo determine the contribution of Ins2-producing neurons to feeding behavior in mice, we used the cross of transgenic RipHER-cre mouse and channelrhodopsin-2 expressing animals, which allowed us to optogenetically stimulate neurons expressing Ins2 in vivo. To confirm the presence of insulin expression in Rip-labeled DVC cells, in situ hybridization was used. To ascertain the specific role of insulin in effects discovered via optogenetic stimulation a selective, CNS applied, insulin receptor antagonist was used. To understand the physiological contribution of insulin made in the hindbrain a virogenetic knockdown strategy was used. ResultsInsulin gene expression and presence of insulin-promoter driven fluorescence in rat insulin promoter (Rip)-transgenic mice were detected in the hypothalamus, but also in the DVC. Insulin mRNA was present in nearly all fluorescently labeled cells in DVC. Diet-induced obesity in mice altered brain insulin gene expression, in a neuroanatomically divergent manner; while in the hypothalamus the expected obesity-induced reduction was found, in the DVC diet-induced obesity resulted in increased expression of the insulin gene. This led us to hypothesize a potentially divergent energy balance role of insulin in these two brain areas. To determine the acute impact of activating insulin-producing neurons in the DVC, optic stimulation of light-sensitive channelrhodopsin 2 in Rip-transgenic mice was utilized. Optogenetic photoactivation induced hyperphagia after acute activation of the DVC insulin neurons. This hyperphagia was blocked by central application of the insulin receptor antagonist S961, suggesting the feeding response was driven by insulin. To determine whether DVC insulin has a necessary contribution to feeding and metabolism, virogenetic insulin gene knockdown (KD) strategy, which allows for site-specific reduction of insulin gene expression in adult mice, was used. While chow-fed mice failed to reveal any changes of feeding or thermogenesis in response to the KD, mice challenged with a high-fat diet consumed less food. No changes in body weight were identified, possibly resulting from compensatory reduction in thermogenesis. ConclusionsTogether, our data suggest an important role for hindbrain insulin and insulin-producing cells in energy homeostasis.

Selenoprotein P – Selenium transport protein, enzyme and biomarker of selenium status

The habitual intake of selenium (Se) varies strongly around the world, and many people are at risk of inadequate supply and health risks from Se deficiency. Within the human organism, efficient transport mechanisms ensure that organs with a high demand and relevance for reproduction and survival are preferentially supplied. To this end, selenoprotein P (SELENOP) is synthesized in the liver and mediates Se transport to essential tissues such as the endocrine glands and the brain, where the "SELENOP cycle" maintains a privileged Se status. Mouse models indicate that SELENOP is not essential for life, as supplemental Se supply was capable of preventing the development of severe symptoms. However, knockout mice died under limiting supply, arguing for an essential role of SELENOP in Se deficiency. Many clinical studies support this notion, pointing to close links between health risks and low SELENOP levels. Accordingly, circulating SELENOP concentrations serve as a functional biomarker of Se supply, at least until a saturated status is achieved and SELENOP levels reach a plateau. Upon toxic intake, a further increase in SELENOP is observed, i.e., SELENOP provides information about possible selenosis. The SELENOP transcripts predict an insertion of ten selenocysteine residues. However, the decoding is imperfect, and not all these positions are ultimately occupied by selenocysteine. In addition to the selenocysteine residues near the C-terminus, one selenocysteine resides central within an enzyme-like environment. SELENOP proved capable of catalyzing peroxide degradation in vitro and protecting e.g. LDL particles from oxidation. An enzymatic activity in the intact organism is unclear, but an increasing number of clinical studies provides evidence for a direct involvement of SELENOP-dependent Se transport as an important and modifiable risk factor of disease. This interaction is particularly strong for cardiovascular and critical disease including COVID-19, cancer at various sites and autoimmune thyroiditis. This review briefly highlights the links between the growing knowledge of Se in health and disease over the last 50 years and the specific advances that have been made in our understanding of the physiological and clinical contribution of SELENOP to the current picture.

The Pierre Wertheimer Neurological and Neurosurgical Hospital in Lyon: history of its development and contributions to neurosurgery.

At the end of the 1950s, at the direction of Pierre Wertheimer, the first French professor of neurosurgery, the treatment of neurological and neurosurgical diseases for Lyon's 2 million people was concentrated in a single center functioning as not only a hospital but also a campus for neuroscience. The ideas behind the structure revolve around concepts such as spatial unity, comprehensive specialized fields, a critical mass of patients, a structured training program, and essential cross-communication between areas in the same field. Through several generations of doctors, researchers, and professors, the Pierre Wertheimer Neurological and Neurosurgical Hospital in Lyon (NHL) has had an important impact on clinical practice, fundamental neuroscientific research, and specialist training. Under Wertheimer's stewardship, functional neurosurgery became one of the fields of excellence at the NHL with contributions in pain surgery and physiology but also epilepsy surgery and surgery for spasticity. Typically, these contributions were the result of the collaboration of separate teams, ultimately laying the groundwork for a neuroscientific doctoral school. The large mass of patients treated at the NHL provided opportunities for other, more isolated insights, such as the classification of pineal tumors and contributions to interventional neuroradiology. The present work endeavors to illustrate the contributions of the NHL to neuroscience and discuss the background allowing for their occurrence.

Divergence in digestive and metabolic strategies matches habitat differentiation in juvenile salmonids.

Divergent energy acquisition and processing strategies associated with using different microhabitats may allow phenotypes to specialize and coexist at small spatial scales. To understand how ecological specialization affects differentiation in energy acquisition and processing strategies, we examined relationships among digestive physiology, growth, and energetics by performing captive experiments on juveniles of wild coho salmon (Oncorhynchus kisutch) and steelhead trout (O. mykiss) that exploit adjacent habitats along natural low‐to‐high energy flux gradients (i.e., pools versus riffles) in coastal streams. We predicted that: (i) the specialization of steelhead trout to high‐velocity, high‐energy habitats would result in elevated food intake and growth at the cost of lower growth efficiency relative to coho salmon; (ii) the two species would differentiate along a rate‐maximizing (steelhead trout) versus efficiency‐maximizing (coho salmon) axis of digestive strategies matching their ecological lifestyle; and (iii) the higher postprandial metabolic demand (i.e., specific dynamic action, SDA) associated with elevated food intake would occupy a greater fraction of the steelhead trout aerobic budget. Relative to coho salmon, steelhead trout presented a pattern of faster growth and higher food intake but lower growth efficiency, supporting the existence of a major growth versus growth efficiency trade‐off between species. After accounting for differences in ration size between species, steelhead trout also presented higher SDA than coho salmon, but similar intestinal transit time and lower assimilation efficiency. Both species presented similar aerobic budgets since the elevated SDA of steelhead trout was largely compensated by their higher aerobic scope relative to coho salmon. Our results illustrate the key contribution of digestive physiology to the adaptive differentiation of juvenile growth, energetics, and overall performance of taxa with divergent habitat specializations along a natural productivity gradient.

Factors affecting firmness loss in apples during postharvest handling and cold/controlled atmosphere storage in India: A review

Apples attract humans with their dominant appeal and eating quality. The most dominant properties are color and texture. This review paper discusses the scientifically published results of apple texture through understanding internal properties like structural, physiological, physical, mechanical, water and cell wall contributions and post-harvest handling and storage methods. A critical appraisal is made of factors responsible for inner texture and sustenance during post-harvest and storage periods. The status of research data available is discussed from a firmness point of view of Indian apple varieties vis-à-vis those grown in other countries. Most of the research work on Indian apples reported physico-chemical parameters like weight, diameter, firmness, bio-chemical and nutrient components. The latest literature did not find data for the long term behaviour in CAS (6 to 10 months). The research data on factors responsible for texture loss is also very limited for Indian-origin apples. There are still large gaps in research on firmness loss in apple. Hence, suggestions are made on the scope for future research on apples grown in India for the benefit of farmers, traders, and consumers.

Physiological dynamics dominate the response of canopy far-red solar-induced fluorescence to herbicide treatment

Solar-induced chlorophyll fluorescence (SIF) has shown great potential for detecting changes in vegetation function under herbicide stress. However, how physiological (ΦF, canopy SIF emission efficiency) and non-physiological (e.g., structure and illumination) dynamics regulate canopy SIF, and the coupling between SIF and gross primary production (GPP) under herbicide stress remains unclear. Here, we conducted continuous eddy covariance flux and far-red SIF measurements during the early stage of maize in an herbicide-resistant maize field, where herbicide exclusively affects weeds. We investigated the performance of SIF, GPP, and vegetation indices (VIs) in capturing herbicide stress and then explored the sensitivity of SIF to the effects of herbicide treatments by disentangling canopy SIF into the physiological (ΦF) and non-physiological components (NIRvP). We found that SIF rapidly increased in response to the herbicide and that GPP decreased, and that both were more responsive than VIs in capturing the early effects of herbicides. Thus, the opposing responses in SIF and GPP disrupted their otherwise linear relationship during herbicide treatment. More importantly, we found that the increased ΦF dominated the variation of SIF during the early stages of herbicide stress, while the influence of NIRvP was prominent in the variability of SIF in the absence of herbicide. By unraveling its physiological and non-physiological contributions, our findings advance our understanding of how SIF responds to herbicide stress in heterogeneous cropland and will improve our interpretation of SIF as a tool for monitoring photosynthesis.

Chemical inhibition of the auxin inactivation pathway uncovers the roles of metabolic turnover in auxin homeostasis

The phytohormone auxin, indole-3-acetic acid (IAA), plays a prominent role in plant development. Auxin homeostasis is coordinately regulated by auxin synthesis, transport, and inactivation; however, the physiological contribution of auxin inactivation to auxin homeostasis has not been determined. The GH3 IAA-amino acid conjugating enzymes play a central role in auxin inactivation. Chemical inhibition of GH3 proteins in planta is challenging because the inhibition of these enzymes leads to IAA overaccumulation that rapidly induces GH3 expression. Here, we report the characterization of a potent GH3 inhibitor, kakeimide, that selectively targets IAA-conjugating GH3 proteins. Chemical knockdown of the auxin inactivation pathway demonstrates that auxin turnover is very rapid (about 10 min) and indicates that both auxin biosynthesis and inactivation dynamically regulate auxin homeostasis.