Carotenoids are essential for photosynthesis and photoprotection; they also serve as precursors to signaling molecules that influence plant development and biotic/abiotic stress responses. With ...potential to improve plant yield and nutritional quality, carotenoids are targets for metabolic breeding/engineering, particularly in the Poaceae (grass family), which includes the major food crops. Depending on genetic background, maize (Zea mays) endosperm carotenoid content varies, and therefore breeding-enhanced carotenoid levels have been of ongoing interest. The first committed step in the plastid-localized biosynthetic pathway is mediated by the nuclear-encoded phytoene synthase (PSY). The gene family in maize and other grasses contains three paralogs with specialized roles that are not well understood. Maize endosperm carotenoid accumulation requires PSY1 expression. A maize antibody was used to localize PSY1 to amyloplast envelope membranes and to determine PSY1 accumulation in relation to carotenoid accumulation in developing endosperm. To test when and if PSY transcript levels correlated with carotenoid content, advantage was taken of a maize germplasm diversity collection that exhibits genetic and chemical diversity. Total carotenoid content showed statistically significant correlation with endosperm transcript levels at 20 d after pollination for PSY1 but not PSY2 or PSY3. Timing of PSY1 transcript abundance, previously unknown, provides critical information for choosing breeding alleles or properly controlling introduced transgenes. PSY1 was unexpectedly found to have an additional role in photosynthetic tissue, where it was required for carotenogenesis in the dark and for heat stress tolerance. Leaf carotenogenesis was shown to require phytochrome-dependent and phytochrome-independent photoregulation of PSY2 plus nonphotoregulated PSY1 expression.
Carotenoids are a diverse group of pigments found in plants, fungi, and bacteria. They serve essential functions in plants and provide health benefits for humans and animals. In plants, it was ...thought that conversion of the C40 carotenoid backbone, 15-cis-phytoene, to all-trans-lycopene, the geometrical isomer required by downstream enzymes, required two desaturases (phytoene desaturase and ζ-carotene desaturase ZDS) plus a carotene isomerase (CRTISO), in addition to light-mediated photoisomerization of the 15-cis-double bond; bacteria employ only a single enzyme, CRTI. Characterization of the maize (Zea mays) pale yellow9 (y9) locus has brought to light a new isomerase required in plant carotenoid biosynthesis. We report that maize Y9 encodes a factor required for isomerase activity upstream of CRTISO, which we term Z-ISO, an activity that catalyzes the cis- to trans-conversion of the 15-cis-bond in 9,15,9'-tri-cis-ζ-carotene, the product of phytoene desaturase, to form 9,9'-di-cis-ζ-carotene, the substrate of ZDS. We show that recessive y9 alleles condition accumulation of 9,15,9'-tri-cis-ζ-carotene in dark tissues, such as roots and etiolated leaves, in contrast to accumulation of 9,9'-di-cis-ζ-carotene in a ZDS mutant, viviparous9. We also identify a locus in Euglena gracilis, which is similarly required for Z-ISO activity. These data, taken together with the geometrical isomer substrate requirement of ZDS in evolutionarily distant plants, suggest that Z-ISO activity is not unique to maize, but will be found in all higher plants. Further analysis of this new gene-controlled step is critical to understanding regulation of this essential biosynthetic pathway.
Endosomal Sorting Complex Required for Transport (ESCRT)-III proteins mediate membrane remodeling and the release of endosomal intraluminal vesicles into multivesicular bodies. Here, we show that the ...ESCRT-III subunit paralogs CHARGED MULTIVESICULAR BODY PROTEIN1 (CHMP1A) and CHMP1B are required for autophagic degradation of plastid proteins in Arabidopsis thaliana. Similar to autophagy mutants, chmp1a chmp1b (chmp1) plants hyperaccumulated plastid components, including proteins involved in plastid division. The autophagy machinery directed the release of bodies containing plastid material into the cytoplasm, whereas CHMP1A and B were required for delivery of these bodies to the vacuole. Autophagy was upregulated in chmp1 as indicated by an increase in vacuolar green fluorescent protein (GFP) cleavage from the autophagic reporter GFP-ATG8. However, autophagic degradation of the stromal cargo RECA-GFP was drastically reduced in the chmp1 plants upon starvation, suggesting that CHMP1 mediates the efficient delivery of autophagic plastid cargo to the vacuole. Consistent with the compromised degradation of plastid proteins, chmp1 plastids show severe morphological defects and aberrant division. We propose that CHMP1 plays a direct role in the autophagic turnover of plastid constituents.
•The regulatory mechanism(s) of autophagy was uncovered by transcriptomic studies.•Proteomics approaches were used to analyze the dynamics of ATG Proteins.•The effects of autophagy on plant ...development were assessed by metabolomic analyses.•Integrative analysis of multi-omics data could provide a precise picture of plant autophagy.
Autophagy is a highly conserved pathway in eukaryotes that promotes nutrient recycling and cellular homeostasis through the degradation of excess or damaged cytoplasmic constituents. In plants, autophagy is increasingly recognized as a key contributor to development, reproduction, metabolism, leaf senescence, endosperm and grain development, pathogen defense, and tolerance to abiotic and biotic stresses. Characterizing the functional transcriptomic, proteomic, and metabolomic networks relating to autophagy in plants subjected to various extra- and intra-cellular stimuli may help to identify components associated with the pathway. As such, the integration of multi-omics approaches (i.e., transcriptomics, proteomics and metabolomics), along with cellular, genetic and functional analyses, could provide a global perspective regarding the effects of autophagy on plant metabolism, development and stress responses. In this mini-review, recent research progress in plant autophagy is discussed, highlighting the importance of high-throughput omics approaches for defining the underpinning molecular mechanisms of autophagy and understanding its associated regulatory network.
Display omitted
► Nafion/polytetrafluoroethylene (PTFE) blend membranes were prepared by solution casting method. ► The blend membranes were tested for vanadium redox flow battery (VRB) application. ...► The blend membranes show lower vanadium ion permeability than that of recast Nafion membrane. ► In VRB single cell test, the blend membrane shows superior performances than that of pure recast Nafion.
Solution casting method was adopted using Nafion and polytetrafluoroethylene (PTFE) solution to prepare Nafion/PTFE blend membranes for vanadium redox flow battery application. The physicochemical properties of the membranes were characterized by using water uptake, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal analysis (TA). The electrochemical properties of the membranes were examined by using electrochemical impedance spectroscopy (EIS) and single cell test. Despite the high miscibility of PTFE with Nafion, the addition of hydrophobic PTFE reduces the water uptake, ion exchange capacity (IEC) and conductivity of blend membranes. But PTFE can increase the crystallinity, thermal stability of Nafion/PTFE membranes and reduce the vanadium permeability. The blend membrane with PTFE (30wt%, N0.7P0.3) was chosen and investigated for VRB single cell test. The energy efficiency of this VRB with N0.7P0.3 membrane was 85.1% at current density of 50mAcm−2, which was superior to that of recast Nafion (r-Nafion) membrane (80.5%). Self-discharge test shows that the decay of open circuit potential of N0.7P0.3 membrane is much lower than that of r-Nafion membrane. More than 50 cycles charge–discharge test proved that the N0.7P0.3 membrane possesses high stability in long time running. Chemical stabilities of the chosen N0.7P0.3 membrane are further proved by soaking the membrane for 3 weeks in highly oxidative V(V) solution. All results suggest that the addition of PTFE is a simple and effective way to improve the performance of Nafion for VRB application.
The plant membrane-trafficking system plays a crucial role in maintaining proper cellular functions and responding to various developmental and environmental cues. Thus far, our knowledge of the ...maize membrane-trafficking system is still limited. In this study, we systematically identified 479 membrane-trafficking genes from the maize genome using orthology search and studied their functions by integrating transcriptome and evolution analyses. These genes encode the components of coated vesicles, AP complexes, autophagy, ESCRTs, retromers, Rab GTPases, tethering factors, and SNAREs. The maize genes exhibited diverse but coordinated expression patterns, with 249 genes showing elevated expression in reproductive tissues. Further WGCNA analysis revealed that five COPII components and four Rab GTPases had high connectivity with protein biosynthesis during endosperm development and that eight components of autophagy, ESCRT, Rab, and SNARE were strongly co-upregulated with defense-related genes and/or with secondary metabolic processes to confer basal resistance to
Fusarium graminearum
. In addition, we identified 39 membrane-trafficking genes with strong selection signals during maize domestication and/or improvement. Among them,
ZmSec23a
and
ZmVPS37A
were selected for kernel oil production during improvement and pathogen resistance during domestication, respectively. In summary, these findings will provide important hints for future appreciation of the functions of membrane-trafficking genes in maize.
The endosomal sorting complex required for transport (ESCRT) machinery is an ancient, evolutionarily conserved membrane remodeling complex that is essential for multivesicular body (MVB) biogenesis ...in eukaryotes. FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING 1 (FREE1), which was previously identified as a plant‐specific ESCRT component, modulates MVB‐mediated endosomal sorting and autophagic degradation. Although the basic cellular functions of FREE1 as an ESCRT component have been described, the regulators that control FREE1 turnover remain unknown. Here, we analyzed how FREE1 homeostasis is mediated by the RING‐finger E3 ubiquitin ligases, SINA of Arabidopsis thaliana (SINATs), in response to iron deficiency. Under iron‐deficient growth conditions, SINAT1‐4 were induced and ubiquitinated FREE1, thereby promoting its degradation and relieving the repressive effect of FREE1 on iron absorption. By contrast, SINAT5, another SINAT member that lacks ubiquitin ligase activity due to the absence of the RING domain, functions as a protector protein which stabilizes FREE1. Collectively, our findings uncover a hitherto unknown mechanism of homeostatic regulation of FREE1, and demonstrate a unique regulatory SINAT–FREE1 module that subtly regulates plant response to iron deficiency stress.
FREE1 is a plant‐specific protein essential for endosomal sorting, autophagic degradation and plant growth. FREE1 protein homeostasis is tightly regulated by the RING‐finger E3 ubiquitin ligases, SINA of Arabidopsis thaliana (SINATs), thereby relieving the repressive effect of FREE1 on metal absorption under iron deficient growth condition.
The article examines modern practical approaches to ensuring the safety of seaports as hubs of logistics centres for international trade and replacement points for ship crews under the conditions of ...the COVID-19 pandemic. The historical retrospective of the formation of anti-epidemic legal instruments to counteract the spread of particularly dangerous and rapidly spreading diseases is outlined. It is emphasized that the COVID-19 pandemic and the quarantine restrictions imposed by it in the states belong to the range of force majeure. The approaches of national legislations, international agreements, case law, and time charter pro-forma to the legal category of “safe port” are analyzed. Emphasis has been placed on shifting priorities in port security from those prevailing since the early 2000s to terrorist, technical and navigational threats to threats related to the spread of the COVID-19 and to take measures to prevent the spread of the disease. The study develops the concept of ensuring a universal approach to the formation of protocols and best practices to combat the spread of COVID-19 and the introduction of increased financial sanctions in case of violation of the established rules.
PDF
