Lytic Vacuole Research Articles

Identification of Biomarkers and Mechanisms Associated with Apoptosis in Recurrent Pregnancy Loss.

In this study, we employed bioinformatics techniques to identify genes associated with apoptosis in recurrent pregnancy loss (RPL). We retrieved the RPL expression profile datasets GSE165004 and GSE73025 from the Gene Expression Omnibus (GEO) database. We also obtained data from the Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway of Apoptosis (hsa04210) to identify apoptosis-related genes. In addition, we performed Friends analysis to explore the interactions between differential apoptosis genes and other genes in the functional pathway. We identified six differentially expressed genes related to apoptosis, including CTSZ, BCL2, PIK3CD, KRAS, GADD45G, and CASP8, with GADD45G as the most gene. Functional fertility analysis revealed that differentially expressed genes primarily regulated protein stability, cell number homeostasis, myeloid cell homeostasis, hematopoietic progenitor cell differentiation, lytic vacuole and lysosome functions, vacuolar and lysosomal membranes, transmembrane transporter binding, protein domain-specific binding, G-protein beta-subunit binding, phospholipid binding, and were involved in pathways such as Rap1 signaling, regulation of actin cytoskeleton, and NOD-like receptor signaling. KRAS exhibited the highest mutation rate in RPL-related cancer CESC. There was also a positive correlation between differentially expressed genes and B cell memory, CD4 memory resting T cells, follicular helper T cells, naïve B cells, and resting dendritic cells. We identified six differentially expressed genes related to apoptosis in RPL, with GADD45G as the most important. NOD-like receptor signaling pathway and regulation of actin cytoskeleton could be therapeutic targets for RPL.

Contrasting Retromer with a Newly Described Retriever in Arabidopsis thaliana.

The tight regulation of protein composition within the plasma membranes of plant cells is crucial for the proper development of plants and for their ability to respond to a changing environment. Upon being endocytosed, integral membrane proteins can be secreted, sorted into multivesicular bodies/late endosomes, and degraded in the lytic vacuole, or recycled back to the plasma membrane to continue functioning. The evolutionarily conserved retromer complex has attracted the interest of plant cell biologists for over a decade as it has emerged as a key regulator of the trafficking of endocytosed integral plasma membrane proteins. Recently, a related recycling complex that shares a subunit with retromer was described in metazoan species. Named "retriever", homologs to the proteins that comprise this new recycling complex and its accessory proteins are found within plant lineages. Initial experiments indicate that there is conservation of function between metazoan and plant retriever proteins, suggesting that it is prudent to re-evaluate the available plant retromer data with the added potential of a plant retriever complex.

Advancing Sustainable Malting Practices: Aquaporins as Potential Breeding Targets for Improved Water Uptake during Controlled Germination of Barley (Hordeum vulgare L.).

The conversion of raw barley (Hordeum vulgare L.) to malt requires a process of controlled germination, where the grain is submerged in water to raise the moisture content to >40%. The transmembrane proteins, aquaporins, influence water uptake during the initial stage of controlled germination, yet little is known of their involvement in malting. With the current focus on sustainability, understanding the mechanisms of water uptake and usage during the initial stages of malting has become vital in improving efficient malting practices. In this study, we used quantitative proteomics analysis of two malting barley genotypes demonstrating differing water-uptake phenotypes in the initial stages of malting. Our study quantified 19 transmembrane proteins from nine families, including seven distinct aquaporin isoforms, including the plasma intrinsic proteins (PIPs) PIP1;1, PIP2;1, and PIP2;4 and the tonoplast intrinsic proteins (TIPs) TIP1;1, TIP2;3, TIP3;1, and TIP3;2. Our findings suggest that the presence of TIP1;1, TIP3;1, and TIP3;2 in the mature barley grain proteome is essential for facilitating water uptake, influencing cell turgor and the formation of large central lytic vacuoles aiding storage reserve hydrolysis and endosperm modification efficiency. This study proposes that TIP3s mediate water uptake in malting barley grain, offering potential breeding targets for improving sustainable malting practices.

Key molecules regulating the blood meals of Rhipicephalus sanguineus (Acari: Ixodidae) revealed by transcriptomics.

Rhipicephalus sanguineus, a repulsive obligate blood feeder, is a three-host tick inflicting tremendous damage. Blood-sucking initiates tick-pathogen-host interactions along with alterations in the expression levels of numerous bioactive ingredients. Key molecules regulating blood meals were identified using the transcriptomic approach. A total number of 744 transcripts showed statistically significantly differential expression including 309 significantly upregulated transcripts and 435 significantly downregulated transcripts in semiengorged female ticks compared to unfed ticks, all collected in 2021. The top 10 differentially upregulated transcripts with explicit functional annotations included turripeptide OL55-like protein, valine tRNA ligase-like protein and ice-structuring glycoprotein-like protein. The top 10 differentially down-regulated transcripts were uncharacterized proteins. Gene Ontology (GO) enrichment analysis revealed four associated terms in the cellular component category and 16 in the molecular function category among the top 20 terms. Differentially expressed genes (DEGs) were enriched in GO terms ID 0000323 (lytic vacuole) and ID 0005773 (vacuole). The top 20 enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways included metabolism, cellular processes, organismal systems and human diseases. The DEGs were enriched in the KEGG term ID: ko-04142 (lysosome pathway) associated with intracellular digestion in the tick midgut epithelium. Molecular markers annotated via comparative transcriptomic profiling were expected to be candidate markers for the purpose of tick control.

Screening of four lysosome-related genes in sepsis based on RNA sequencing technology

PurposeScreening of lysosome-related genes in sepsis patients to provide direction for lysosome-targeted therapy.MethodsPeripheral blood samples were obtained from 22 patients diagnosed with sepsis and 10 normal controls for the purpose of RNA sequencing and subsequent analysis of differential gene expression. Concurrently, lysosome-related genes were acquired from the Gene Ontology database. The intersecting genes between the differential genes and lysosome-related genes were then subjected to PPI, GO and KEGG analyses. Core genes were identified through survival analysis, and their expression trends in different groups were determined using meta-analysis. Single-cell RNA sequencing was used to clarify the cellular localization of core genes.ResultsThe intersection of 1328 sepsis-differential genes with 878 lysosome-related genes yielded 76 genes. PPI analysis showed that intersecting genes were mainly involved in Cellular process, Response to stimulus, Immune system process, Signal transduction, Lysosome. GO and KEGG analysis showed that intersecting genes were mainly involved in leukocyte mediated immunity, cell activation involved in immune response, lytic vacuole, lysosome. Survival analysis screened four genes positively correlated with sepsis prognosis, namely GNLY, GZMB, PRF1 and RASGRP1. The meta-analysis revealed that the expression levels of these four genes were significantly higher in the normal control group compared to the sepsis group, which aligns with the findings from RNA sequencing data. Furthermore, single-cell RNA sequencing demonstrated that T cells and NK cells exhibited high expression levels of GNLY, GZMB, PRF1, and RASGRP1.ConclusionGNLY, GZMB, PRF1, and RASGRP1, which are lysosome-related genes, are closely linked to the prognosis of sepsis and could potentially serve as novel research targets for sepsis, offering valuable insights for the development of lysosome-targeted therapy. The clinical trial registration number is ChiCTR1900021261, and the registration date is February 4, 2019.

A tyrosine phospho-switch within the Longin domain of VAMP721 modulates SNARE functionality.

The final step in secretion is membrane fusion facilitated by SNARE proteins that reside in opposite membranes. The formation of a trans-SNARE complex between one R and three Q coiled-coiled SNARE domains drives the final approach of the membranes providing the mechanical energy for fusion. Biological control of this mechanism is exerted by additional domains within some SNAREs. For example, the N-terminal Longin domain (LD) of R-SNAREs (also called Vesicle-associated membrane proteins, VAMPs) can fold back onto the SNARE domain blocking interaction with other cognate SNAREs. The LD may also determine the subcellular localization via interaction with other trafficking-related proteins. Here, we provide cell-biological and genetic evidence that phosphorylation of the Tyrosine57 residue regulates the functionality of VAMP721. We found that an aspartate mutation mimics phosphorylation, leading to protein instability and subsequent degradation in lytic vacuoles. The mutant SNARE also fails to rescue the defects of vamp721vamp722 loss-of-function lines in spite of its wildtype-like localization within the secretory pathway and the ability to interact with cognate SNARE partners. Most importantly, it imposes a dominant negative phenotype interfering with root growth, normal secretion and cytokinesis in wildtype plants generating large aggregates that mainly contain secretory vesicles. Non-phosphorylatable VAMP721Y57F needs higher gene dosage to rescue double mutants in comparison to native VAMP721 underpinning that phosphorylation modulates SNARE function. We propose a model where short-lived phosphorylation of Y57 serves as a regulatory step to control VAMP721 activity, favoring its open state and interaction with cognate partners to ultimately drive membrane fusion.

The journey of cardosin A in young Arabidopsis seedlings leads to evidence of a Golgi-independent pathway to the protein storage vacuole.

The aspartic proteinase cardosin A is a vacuolar enzyme found to accumulate in protein storage and lytic vacuoles in the flowers and protein bodies in the seeds of the native plant cardoon. Cardosin A was first isolated several decades ago and has since been extensively characterized, both in terms of tissue distribution and enzyme biochemistry. In the native system, several roles have been attributed to cardosin A, such as reproduction, reserve mobilization, and membrane remodeling. To participate in such diverse events, cardosin A must accumulate and travel to different compartments within the cell: protein storage vacuoles, lytic vacuoles, and the cytoplasmic membrane (and eventually outside the cell). Several studies have approached the expression of cardosin A in Arabidopsis thaliana and Nicotiana tabacum with promising results for the use of these systems to study of cardosin A trafficking. A poly-sorting mechanism has been uncovered for this protein, as two different vacuolar sorting determinants, mediating different vacuolar routes, have been described. The first is a conventional C-terminal domain, which delivers the protein to the vacuole via the Golgi, and the second is a more unconventional signal-the plant-specific insert (PSI)-that mediates a Golgi-independent route. The hypothesis that these two signals are activated according to cell needs and in organs with high metabolic activity is investigated here. An Arabidopsis line expressing cardosin A under an inducible promoter was used to understand the dynamics of cardosin A regarding vacuolar accumulation during seed germination events. Using antibodies against different regions of the protein and combining them with immunofluorescence and immunocytochemistry assays in different young seedling tissues, cardosin A was detected along the secretory pathway to the protein storage vacuole, often associated with the endoplasmic reticulum. More interestingly, upon treatment with the drug Brefeldin A, cardosin A was still detected in protein storage vacuoles, indicating that the intact protein can bypass the Golgi in this system, contrary to what was observed in N. tabacum. This study is a good starting point for further research involving the use of fluorescent fusions and exploring in more detail the relationship between cardosin A trafficking and plant development.

Transcriptomic profiles reveal differences in gene expression between the testes and epididymis in stallions

Spermatogenesis and sperm maturation take place in the testes and epididymis, respectively. These complex physiological processes are regulated by multiple genes, which have not been studied in the stallion. In this study, Illumina sequencing was used to analyze the transcriptomes of the testes, head, body and tail of the epididymis from three reproductively normal stallions. The mRNA was extracted and the libraries were generated using Next Generation Sequencing (NGS). The expression patterns of differentially expressed genes (DEGs) in the testes and epididymis were determined by bioinformatics analysis. Gene Ontology (GO) enrichment analysis of DEGs was implemented and gene length bias was corrected. Differentially expressed genes were compared between the different segments of the epididymis and the testis (control tissue). GO-terms with adjusted p < 0.05 were considered significantly enriched. Among the four libraries, 18,732 genes were identified. Of those, 6,574 genes (39.1%) were tissue-specific. The distribution of tissue-specific genes was 14.2 % in the testes, 2.2 % in the epididymal head, 1.1 % in the epididymal body, and 1.4 % in the epididymal tail. Compared with testicular tissue, there were 13,349 DEGs (5,595 up-regulated and 7,754 down-regulated) in the epidydimal head, 14,207 DEGs (5,884 up-regulated and 8,323 down-regulated) in the epididymal body, and 14,822 DEGs (5,842 up-regulated and 8,980 down regulated) in the epididymal tail. In the epididymal head,the main downregulated terms were male gamete generation (224 DEGs), spermatogenesis (224 DEGs), organelle fission (264 DEGs), sexual reproduction (343 DEGs) and nuclear division (233 DEGs). The main upregulated terms were associated with the ribosome (322 DEGs), lymphocyte activation (226 DEGs), and cytosolic part (104 DEGs). In the epididymal body, the most significantly downregulated terms were male gamete generation (232 DEGs), spermatogenesis (232 DEGs), sexual reproduction (358 DEGs), cilium morphogenesis (151 DEGs) and cilium (235 DEGs). The most significantly upregulated terms were lysosome (150 DEGs), lytic vacuole (150 DEGs), positive regulation of locomotion (197 DEGs), cytosolic ribosome (71 DEGs), vacuole (182 DEGs). In the epididymal tail, the most significantly downregulated terms were male gamete generation (239 DEGs), spermatogenesis (193 DEGs), cilium (253 DEGs), ciliary part (186 DEGs), cilium morphogenesis (158 DEGs). The most significantly upregulated terms were associated with the ribosome (438 DEGs) and cytosolic part (109 DEGs). In summary, we found decreased expression of genes involved in gamete production, and increased expression of genes involved in protein synthesis, immunity and sperm transport in different segments of the epididymis. These findings provide genome-wide mRNA expression profiles for the horse epididymis and testes, providing a biological basis for future research on stallion fertility.

Identification of key upregulated genes involved in foam cell formation and the modulatory role of statin therapy

We aimed to investigate the possible effect of statins on important genes/proteins involved in foam cell formation. The gene expression profile of the GSE9874, GSE54666, and GSE7138from the Omnibus database were usedto identify genes involved in foam cell formation. The protein-protein interaction (PPI) network and MCODE analysis of the intersection of three databases were analyzed. We used molecular docking analysis to investigate the possible interaction of different statins with the overexpressed hub genes obtained from PPI analysis. The intersection among the three datasets showed 54 upregulated and 26 down-regulated genes. The most critical overexpressed genes/proteins obtained as hub genes included: G6PD, NPC1, ABCA1, ABCG1, PGD, PLIN2, PPAP2B, and TXNRD1 based on PPI analysis. Functional enrichment analysis of 81 intersection DEGs at the biological process level focusing on the cholesterol metabolic process, secondary alcohol biosynthetic process and the cholesterol biosynthetic process. Under cellular components, the analysis confirmed that these 81 intersection DEGs were mainly applied in endoplasmic reticulum membrane, lysosome and lytic vacuole. The molecular functions were identified as sterol binding, oxidoreductase activity and NADP binding. The molecular docking showed that all statins appear to affect important protein targets overexpressed in foam cell formation. However, lipophilic statins, especially pitavastatin and lovastatin, had a greater effect than hydrophilic statins. The most significant protein target of all the overexpressed genes interacting with all statin types was ABCA1. The effect of lipophilic statins was shown for several critical proteins in foam cell formation.

K63-linked ubiquitin chains are a global signal for endocytosis and contribute to selective autophagy in plants

In contrast to other eukaryotic model organisms, the closely related ubiquitin (Ub)-conjugating enzymes UBC35 and UBC36 are the main sources of K63-linked Ub chains in Arabidopsis.1 Although K63-linked chains have been associated with the regulation of vesicle trafficking, definitive proof for their role in endocytosis was missing. We show that the ubc35 ubc36 mutant has pleiotropic phenotypes related to hormone and immune signaling. Specifically, we reveal that ubc35-1 ubc36-1 plants have altered turnover of integral membrane proteins including FLS2, BRI1, and PIN1 at the plasma membrane. Our data indicates that K63-Ub chains are generally required for endocytic trafficking in plants. In addition, we show that in plants K63-Ub chains are involved in selective autophagy through NBR1, the second major pathway delivering cargoes to the vacuole for degradation. Similar to autophagy-defective mutants, ubc35-1 ubc36-1 plants display an accumulation of autophagy markers. Moreover, autophagy receptor NBR1 interacts with K63-Ub chains, which are required for its delivery to the lytic vacuole.2 Together, we show that K63-Ub chains act as a general signal required for the two main pathways delivering cargo to the vacuole and thus, to maintain proteostasis.

In vitro reconstitution of COPII vesicles from Arabidopsis thaliana suspension-cultured cells.

Transport vesicles mediate protein traffic between endomembrane organelles in a highly selective and efficient manner. In vitro reconstitution systems have been widely used for studying mechanisms of vesicle formation, polar trafficking, and cargo specificity in mammals and yeast. However, this technique has not yet been applied to plants because of the large lytic vacuoles and rigid cell walls. Here, we describe an Arabidopsis-derived in vitro vesicle formation system to reconstitute, purify and characterize plant-derived coat protein complex II (COPII) vesicles. In this protocol, we provide a detailed method for the isolation of microsomes and cytosol from Arabidopsis thaliana suspension-cultured cells (7-8 h), in vitro COPII vesicle reconstitution and purification (4-5 h) and biochemical and microscopic analysis using specific antibodies against COPII cargo molecules for reconstitution efficiency evaluation (2 h). We also include detailed sample-preparation steps for analyzing vesicle morphology by cryogenic electron microscopy (1 h) and vesicle cargoes by quantitative proteomics (4 h). Routinely, the whole procedure takes ~18-20 h of operation time and enables plant researchers without specific expertise to achieve organelle purification or vesicle reconstitution for further characterization.

Role of pericytes in the development of cerebral cavernous malformations.

Cerebral cavernous malformation (CCM) is caused by loss-of-function mutations in CCM1, CCM2, or CCM3 genes of endothelial cells. It is characterized by pericyte deficiency. However, the role of pericytes in CCMs is not yet clarified. We found pericytes in Cdh5Cre ERT2 ;Ccm1 fl/fl (Ccm1 ECKO ) mice had a high expression of PDGFRβ. The inhibition of pericyte function by CP-673451 aggravated the CCM lesion development. RNA-sequencing analysis revealed the molecular traits of pericytes, such as highly expressed ECM-related genes, especially Fn1. Furthermore, KLF4 coupled with phosphorylated SMAD3 (pSMAD3) promoted the transcription of fibronectin in the pericytes of CCM lesions. RGDS peptide, an inhibitor of fibronectin, decreased the lesion area in the cerebella and retinas of Ccm1 ECKO mice. Also, human CCM lesions had abundant fibronectin deposition, and pSMAD3- and KLF4-positive pericytes. These findings indicate that pericytes are essential for CCM lesion development, and fibronectin intervention may provide a novel target for therapeutic intervention in such patients.

Phosphatidylinositol-4-phosphate controls autophagosome formation in Arabidopsis thaliana

Autophagy is an intracellular degradation mechanism critical for plant acclimation to environmental stresses. Central to autophagy is the formation of specialized vesicles, the autophagosomes, which target and deliver cargo to the lytic vacuole. How autophagosomes form in plant cells remains poorly understood. Here, we uncover the importance of the lipid phosphatidylinositol-4-phosphate in autophagy using pharmacological and genetical approaches. Combining biochemical and live-microscopy analyses, we show that PI4K activity is required for early stages of autophagosome formation. Further, our results show that the plasma membrane-localized PI4Kα1 is involved in autophagy and that a substantial portion of autophagy structures are found in proximity to the PI4P-enriched plasma membrane. Together, our study unravels critical insights into the molecular determinants of autophagy, proposing a model whereby the plasma membrane provides PI4P to support the proper assembly and expansion of the phagophore thus governing autophagosome formation in Arabidopsis.

Effects of Immunoglobulins G From Systemic Sclerosis Patients in Normal Dermal Fibroblasts: A Multi-Omics Study.

Autoantibodies (Aabs) are frequent in systemic sclerosis (SSc). Although recognized as potent biomarkers, their pathogenic role is debated. This study explored the effect of purified immunoglobulin G (IgG) from SSc patients on protein and mRNA expression of dermal fibroblasts (FBs) using an innovative multi-omics approach. Dermal FBs were cultured in the presence of sera or purified IgG from patients with diffuse cutaneous SSc (dcSSc), limited cutaneous SSc or healthy controls (HCs). The FB proteome and transcriptome were explored using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and microarray assays, respectively. Proteomic analysis identified 3,310 proteins. SSc sera and purified IgG induced singular protein profile patterns. These FB proteome changes depended on the Aab serotype, with a singular effect observed with purified IgG from anti-topoisomerase-I autoantibody (ATA) positive patients compared to HC or other SSc serotypes. IgG from ATA positive SSc patients induced enrichment in proteins involved in focal adhesion, cadherin binding, cytosolic part, or lytic vacuole. Multi-omics analysis was performed in two ways: first by restricting the analysis of the transcriptomic data to differentially expressed proteins; and secondly, by performing a global statistical analysis integrating proteomics and transcriptomics. Transcriptomic analysis distinguished 764 differentially expressed genes and revealed that IgG from dcSSc can induce extracellular matrix (ECM) remodeling changes in gene expression profiles in FB. Global statistical analysis integrating proteomics and transcriptomics confirmed that IgG from SSc can induce ECM remodeling and activate FB profiles. This effect depended on the serotype of the patient, suggesting that SSc Aab might play a pathogenic role in some SSc subsets.

Hydroxyproline-O-Galactosyltransferases Synthesizing Type II Arabinogalactans Are Essential for Male Gametophytic Development in Arabidopsis.

In flowering plants, male reproductive function is determined by successful development and performance of stamens, pollen grains, and pollen tubes. Despite the crucial role of highly glycosylated arabinogalactan-proteins (AGPs) in male gamete formation, pollen grain, and pollen tube cell walls, the underlying mechanisms defining these functions of AGPs have remained elusive. Eight partially redundant Hyp-galactosyltransferases (named GALT2-GALT9) genes/enzymes are known to initiate Hyp-O-galactosylation for Hyp-arabinogalactan (AG) production in Arabidopsis thaliana. To assess the contributions of these Hyp-AGs to male reproductive function, we used a galt2galt5galt7galt8galt9 quintuple Hyp-GALT mutant for this study. Both anther size and pollen viability were compromised in the quintuple mutants. Defects in male gametogenesis were observed in later stages of maturing microspores after meiosis, accompanied by membrane blebbing and numerous lytic vacuoles. Cytological and ultramicroscopic observations revealed that pollen exine reticulate architecture and intine layer development were affected such that non-viable collapsed mature pollen grains were produced, which were devoid of cell content and nuclei, with virtually no intine. AGP immunolabeling demonstrated alterations in cell wall architecture of the anther, pollen grains, and pollen tube. Specifically, the LM2 monoclonal antibody (which recognized β-GlcA epitopes on AGPs) showed a weak signal for the endothecium, microspores, and pollen tube apex. Pollen tube tips also displayed excessive callose deposition. Interestingly, expression patterns of pollen-specific AGPs, namely AGP6, AGP11, AGP23, and AGP40, were determined to be higher in the quintuple mutants. Taken together, our data illustrate the importance of type-II AGs in male reproductive function for successful fertilization.

Vacuoles in Bryophytes: Properties, Biogenesis, and Evolution.

Vacuoles are the most conspicuous organelles in plants for their indispensable functions in cell expansion, solute storage, water balance, etc. Extensive studies on angiosperms have revealed that a set of conserved core molecular machineries orchestrate the formation of vacuoles from multiple pathways. Usually, vacuoles in seed plants are classified into protein storage vacuoles and lytic vacuoles for their distinctive morphology and physiology function. Bryophytes represent early diverged non-vascular land plants, and are of great value for a better understanding of plant science. However, knowledge about vacuole morphology and biogenesis is far less characterized in bryophytes. In this review, first we summarize known knowledge about the morphological and metabolic constitution properties of bryophytes' vacuoles. Then based on known genome information of representative bryophytes, we compared the conserved molecular machinery for vacuole biogenesis among different species including yeast, mammals, Arabidopsis and bryophytes and listed out significant changes in terms of the presence/absence of key machinery genes which participate in vacuole biogenesis. Finally, we propose the possible conserved and diverged mechanism for the biogenesis of vacuoles in bryophytes compared with seed plants.

Autophagy and the Energy Status of Plant Cells

In plant cells the homeostatic control of energy balance involves the production and recycling of adenylates with macroergic bonds, ATP and ADP. The maintenance of anabolic processes requires the relative saturation of the adenylate pool with high energy phosphoanhydride bonds. The bulk of ATP synthesis is carried out both in mitochondria and in chloroplasts while optimal ATP levels within other cell compartments are maintained by adenylate kinases (AK). AK activity was recently found in cytosol, mitochondria, plastids and the nucleus. ATP synthesis in energy-producing organelles, as well as redistribution of nutrients among cellular compartments, requires fine-tuned regulation of ion homeostasis. A special role in energy metabolism is played by autophagy, a process of active degradation of unwanted and/or damaged cell components and macromolecules within the central lytic vacuole. So-called constitutive autophagy controls the quality of cellular contents under favorable conditions, i.e., when the cellular energy status is high. Energy depletion can lead to the activation of the pro-survival process of autophagic removal and utilization of damaged structures; the breakdown products are then used for ATP regeneration and de novo synthesis of macromolecules. Mitophagy and chlorophagy maintain the populations of healthy and functional energy-producing “stations”, preventing accumulation of defective mitochondria and chloroplasts as potential sources of dangerous reactive oxygen species. However, the increase of autophagic flux above a threshold level can lead to the execution of the vacuolar type of programmed cell death (PCD). In this case autophagy also contributes to preservation of energy through support of the outflow of nutrients from dying cells to healthy neighboring tissues. In plants, two central protein kinases, SnRK1 (Snf1-related protein kinase 1) and TOR (target of rapamycin), are responsible for the regulation of the metabolic switch between anabolic and catabolic pathways. TOR promotes the energy-demanding metabolic reactions in response to nutrient availability and simultaneously suppresses catabolism including autophagy. SnRK1, the antagonist of TOR, senses a decline in cellular energy supply and reacts by inducing autophagy through several independent pathways. Here, we provide an overview of the recent knowledge about the interplay between SnRK1 and TOR, autophagy and PCD in course of the regulation of energy balance in plants.

Rhesus macaques self-curing from a schistosome infection can display complete immunity to challenge

The rhesus macaque provides a unique model of acquired immunity against schistosomes, which afflict >200 million people worldwide. By monitoring bloodstream levels of parasite-gut-derived antigen, we show that from week 10 onwards an established infection with Schistosoma mansoni is cleared in an exponential manner, eliciting resistance to reinfection. Secondary challenge at week 42 demonstrates that protection is strong in all animals and complete in some. Antibody profiles suggest that antigens mediating protection are the released products of developing schistosomula. In culture they are killed by addition of rhesus plasma, collected from week 8 post-infection onwards, and even more efficiently with post-challenge plasma. Furthermore, cultured schistosomula lose chromatin activating marks at the transcription start site of genes related to worm development and show decreased expression of genes related to lysosomes and lytic vacuoles involved with autophagy. Overall, our results indicate that enhanced antibody responses against the challenge migrating larvae mediate the naturally acquired protective immunity and will inform the route to an effective vaccine.

Abiotic Stress Triggers the Expression of Genes Involved in Protein Storage Vacuole and Exocyst-Mediated Routes.

Adverse conditions caused by abiotic stress modulate plant development and growth by altering morphological and cellular mechanisms. Plants’ responses/adaptations to stress often involve changes in the distribution and sorting of specific proteins and molecules. Still, little attention has been given to the molecular mechanisms controlling these rearrangements. We tested the hypothesis that plants respond to stress by remodelling their endomembranes and adapting their trafficking pathways. We focused on the molecular machinery behind organelle biogenesis and protein trafficking under abiotic stress conditions, evaluating their effects at the subcellular level, by looking at ultrastructural changes and measuring the expression levels of genes involved in well-known intracellular routes. The results point to a differential response of the endomembrane system, showing that the genes involved in the pathway to the Protein Storage Vacuole and the exocyst-mediated routes are upregulated. In contrast, the ones involved in the route to the Lytic Vacuole are downregulated. These changes are accompanied by morphological alterations of endomembrane compartments. The data obtained demonstrate that plants’ response to abiotic stress involves the differential expression of genes related to protein trafficking machinery, which can be connected to the activation/deactivation of specific intracellular sorting pathways and lead to alterations in the cell ultrastructure.

Arabidopsis PAP17 is a dual-localized purple acid phosphatase up-regulated during phosphate deprivation, senescence, and oxidative stress

A 35 kDa monomeric purple acid phosphatase (APase) was purified from cell wall extracts of Pi starved (-Pi) Arabidopsis thaliana suspension cells and identified as AtPAP17 (At3g17790) by mass spectrometry and N-terminal microsequencing. AtPAP17 was de novo synthesized and dual-localized to the secretome and/or intracellular fraction of -Pi or salt-stressed plants, or senescing leaves. Transiently expressed AtPAP17-green fluorescent protein localized to lytic vacuoles of the Arabidopsis suspension cells. No significant biochemical or phenotypical changes associated with AtPAP17 loss of function were observed in an atpap17 mutant during Pi deprivation, leaf senescence, or salinity stress. Nevertheless, AtPAP17 is hypothesized to contribute to Pi metabolism owing to its marked up-regulation during Pi starvation and leaf senescence, broad APase substrate selectivity and pH activity profile, and rapid repression and turnover following Pi resupply to -Pi plants. While AtPAP17 also catalyzed the peroxidation of luminol, which was optimal at pH 9.2, it exhibited a low Vmax and affinity for hydrogen peroxide relative to horseradish peroxidase. These results, coupled with absence of a phenotype in the salt-stressed or -Pi atpap17 mutant, do not support proposals that the peroxidase activity of AtPAP17 contributes to the detoxification of reactive oxygen species during stresses that trigger AtPAP17 up-regulation.